WorldWideScience

Sample records for helicopter tail rotor

  1. Tail Rotor Airfoils Stabilize Helicopters, Reduce Noise

    Science.gov (United States)

    2010-01-01

    Founded by former Ames Research Center engineer Jim Van Horn, Van Horn Aviation of Tempe, Arizona, built upon a Langley Research Center airfoil design to create a high performance aftermarket tail rotor for the popular Bell 206 helicopter. The highly durable rotor has a lifetime twice that of the original equipment manufacturer blade, reduces noise by 40 percent, and displays enhanced performance at high altitudes. These improvements benefit helicopter performance for law enforcement, military training, wildfire and pipeline patrols, and emergency medical services.

  2. COMPUTATIONAL STUDY OF AERODYNAMIC CHARACTERISTICS OF SINGLE-ROTOR HELICOPTER TAIL ROTOR UNDER THE INFLUENCE OF VORTICAL WAKE OF MAIN ROTOR AT THE HOVER WITH CROSSWIND

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available For single-rotor helicopters there are special flight modes, when tail rotor (TR is under significant inductive influ- ence of vortical wake of main rotor (MR. Inductive influence of vortical wake of MR can provoke essential changes in flowing of TR and its aerodynamic characteristics comparing to isolated rotor. In this case increase of tail rotor pitch, nec- essary for helicopter controlling, is possible.The article contains computational modelling of TR work with vortical wake of MR at the example of MIL Mi-171 helicopter. The modelling has been made on the base of non-linear blade (free wake vortical model of rotor, pro- duced at Helicopter Design Department of MAI.Helicopter hovering modes with crosswind of various intensity Vz was considered. Thrust-time relationship forisolated TR and TR with vortical wake of MR for equal flight modes was obtained. Flow around the rotors was analyzed, its vortical wake was considered.The results make it possible to clarify the peculiarities of TR work on considered modes and MR influence on its work. It was found out that vortical wake of MR has a more significant impact on TR work with crosswind on the right, when TR falls into vortex ring state mode. Inductive influence of vortical wake of MR leads to vortexring state mode for TR on lower speeds (Vz :: 5 m/s than in case of isolated work of TR (Vz :: 12,5 m/s. In that case,the required tail rotor pitch has increased by 13% for Vz = 5 m/s. The results of modelling and flight tests led to good agreement.

  3. HELICOPTER ROTOR DESIGN

    Directory of Open Access Journals (Sweden)

    IONESCU Cristian Andrei

    2011-06-01

    Full Text Available The objective of this paper is to analyze the role of helicopter rotor, to classify them by type, and to imagine new types of helicopter rotors that can equip future helicopters. Finally, the author shows a coaxial rotor 3D model such a best alternative to equip the new helicopters.

  4. An experimental investigation of the chopping of helicopter main rotor tip vortices by the tail rotor. Part 2: High speed photographic study

    Science.gov (United States)

    Cary, Charles M.

    1987-01-01

    The interaction of a free vortex and a rotor was recorded photographically using oil smoke and stroboscopic illumination. The incident vortex is normal to the plane of the rotor and crosses the rotor plane. This idealized aerodynamic experiment most nearly corresponds to helicopter flight conditions in which a tip vortex from the main rotor is incident upon the tail rotor while hovering. The high speed photographs reveal important features not observed using conventional photography where the image is the time average of varying instantaneous images. Most prominent is the strong interaction between the rotor tip vortex system and the incident vortex, resulting in the roll-up of the incident vortex around the (stronger) tip vortices and the resulting rapid destabilization of the deformed incident vortex. The viscous interaction is clearly shown also. Other forms of instabilities or wave-like behavior may be apparent from further analysis of the photographs.

  5. Charts for Estimating Tail-rotor Contribution to Helicopter Directional Stability and Control in Low-Speed Flight

    Science.gov (United States)

    Amer, Kenneth B; Gessow, Alfred

    1955-01-01

    Theoretically derived charts and equations are presented by which tail-rotor design studies of directional trim and control response at low forward speed can be conveniently made. The charts can also be used to obtain the main-rotor stability derivatives of thrust with respect to collective pitch and angle of attack at low forward speeds. The use of the charts and equations for tail-rotor design studies is illustrated. Comparisons between theoretical and experimental results are presented. The charts indicate, and flight tests confirm, that the region of vortex roughness which is familiar for the main rotor is also encountered by the tail rotor and that prolonged operation at the corresponding flight conditions would be difficult.

  6. Helicopter Rotor Blade Monitoring using Autonomous Wireless Sensor Network

    NARCIS (Netherlands)

    Sanchez Ramirez, Andrea; Loendersloot, Richard; Tinga, Tiedo; Basu, B.

    2013-01-01

    The advancement on Wireless Sensor Networks for vibration monitoring presents important possibilities for helicopter rotor health and usage monitoring. While main rotor blades account for the main source of lift for helicopters, rotor induced vibration establishes an important source for

  7. 14 CFR 29.1565 - Tail rotor.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Tail rotor. 29.1565 Section 29.1565 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS....1565 Tail rotor. Each tail rotor must be marked so that its disc is conspicuous under normal daylight...

  8. 14 CFR 27.1565 - Tail rotor.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Tail rotor. 27.1565 Section 27.1565 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Tail rotor. Each tail rotor must be marked so that its disc is conspicuous under normal daylight ground...

  9. Optical Shaft-Angle Encoder For Helicopter Rotor

    Science.gov (United States)

    Golub, Robert A.; Fitzpatrick, Fred; Dennis, Dale V.; Taylor, Bryant D.

    1993-01-01

    Angular position of helicopter rotor blade determined precisely. Accomplished by use of optical shaft-angle encoder called "256 Ring" on rotor swashplate. Each 360 degree rotation of helicopter main rotor broken down into 256 reflective segments. As rotor rotates, beam of light reflected in turn from each segment into optoelectronic system. One of 256 segments reflects larger pulse than others do. Position of rotor determined by counting number of pulses after this reference pulse. While swashplate mounting requirements unique to each type of helicopter, concept applicable to all types of rotorcraft.

  10. A VORTEX MODEL OF A HELICOPTER ROTOR

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    Valentin BUTOESCU

    2009-06-01

    Full Text Available A vortex model of a helicopter rotor is presented. Each blade of the rotor has three degrees of freedom: flapping, lagging and feathering. The motions after each degree of freedom are also known for all blades. The blade is modelled as a thin vortex surface. The wakes are free fluid surfaces. A system of five equations are obtained: the first one is the integral equation of the lifting surface (rotor, the next three describe the wakes motion, and the last one relates the vortex strength on the wakes and the variation of vorticity on the rotor. A numerical solution of this system is presented. To avoid the singularities that can occur due to the complexity of vortex system, a desingularized model of the vortex core was adopted. A Mathcad worksheet containing the method has been written.The original contribution of the work. The calculation method of the motion of the wakes free vortex system, the development of the vortex cores in time and a new method to approximate the aerodynamic influence of remoted wake regions.

  11. Helicopter rotor noise investigation during ice accretion

    Science.gov (United States)

    Cheng, Baofeng

    An investigation of helicopter rotor noise during ice accretion is conducted using experimental, theoretical, and numerical methods. This research is the acoustic part of a joint helicopter rotor icing physics, modeling, and detection project at The Pennsylvania State University Vertical Lift Research Center of Excellence (VLRCOE). The current research aims to provide acoustic insight and understanding of the rotor icing physics and investigate the feasibility of detecting rotor icing through noise measurements, especially at the early stage of ice accretion. All helicopter main rotor noise source mechanisms and their change during ice accretion are discussed. Changes of the thickness noise, steady loading noise, and especially the turbulent boundary layer - trailing edge (TBL-TE) noise due to ice accretion are identified and studied. The change of the discrete frequency noise (thickness noise and steady loading noise) due to ice accretion is calculated by using PSU-WOPWOP, an advanced rotorcraft acoustic prediction code. The change is noticeable, but too small to be used in icing detection. The small thickness noise change is due to the small volume of the accreted ice compared to that of the entire blade, although a large iced airfoil shape is used. For the loading noise calculation, two simplified methods are used to generate the loading on the rotor blades, which is the input for the loading noise calculation: 1) compact loading from blade element momentum theory, icing effects are considered by increasing the drag coefficient; and 2) pressure loading from the 2-D CFD simulation, icing effects are considered by using the iced airfoil shape. Comprehensive rotor broadband noise measurements are carried out on rotor blades with different roughness sizes and rotation speeds in two facilities: the Adverse Environment Rotor Test Stand (AERTS) facility at The Pennsylvania State University, and The University of Maryland Acoustic Chamber (UMAC). In both facilities the

  12. A Computational Tool for Helicopter Rotor Noise Prediction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR project proposes to develop a computational tool for helicopter rotor noise prediction based on hybrid Cartesian grid/gridless approach. The uniqueness of...

  13. Ice Shapes on a Tail Rotor

    Science.gov (United States)

    Kreeger, Richard E.; Tsao, Jen-Ching

    2014-01-01

    Testing of a thermally-protected helicopter rotor in the Icing Research Tunnel (IRT) was completed. Data included inter-cycle and cold blade ice shapes. Accreted ice shapes were thoroughly documented, including tracing, scanning and photographing. This was the first time this scanning capability was used outside of NASA. This type of data has never been obtained for a rotorcraft before. This data will now be used to validate the latest generation of icing analysis tools.

  14. Recent developments in rotor wake modeling for helicopter noise prediction

    Science.gov (United States)

    Poling, D.; Dadone, L.; Althoff, S.

    1991-01-01

    A preliminary test/theory correlation evaluation is conducted for wake measurement test results obtained by LDV for a B360 helicopter rotor, at conditions critical to the understanding of wake-rollup and blade-vortex interaction phenomena. The LDV data were complemented by acoustic, blade pressure, rotor performance, and blade/control load measurements.

  15. Flow Structures within a Helicopter Rotor Hub Wake

    Science.gov (United States)

    Elbing, Brian; Reich, David; Schmitz, Sven

    2015-11-01

    A scaled model of a notional helicopter rotor hub was tested in the 48'' Garfield Thomas Water Tunnel at the Applied Research Laboratory Penn State. The measurement suite included total hub drag and wake velocity measurements (LDV, PIV, stereo-PIV) at three downstream locations. The main objective was to understand the spatiotemporal evolution of the unsteady wake between the rotor hub and the nominal location of the empennage (tail). Initial analysis of the data revealed prominent two- and four-per-revolution fluid structures linked to geometric hub features persisting into the wake far-field. In addition, a six-per-revolution fluid structure was observed in the far-field, which is unexpected due to the lack of any hub feature with the corresponding symmetry. This suggests a nonlinear interaction is occurring within the wake to generate these structures. This presentation will provide an overview of the experimental data and analysis with particular emphasis on these six-per-revolution structures.

  16. Comparison of calculated and measured helicopter rotor lateral flapping angles

    Science.gov (United States)

    Johnson, W.

    1980-01-01

    Calculated and measured values of helicopter rotor flapping angles in forward flight are compared for a model rotor in a wind tunnel and an autogiro in gliding flight. The lateral flapping angles can be accurately predicted when a calculation of the nonuniform wake-induced velocity is used. At low advance ratios, it is also necessary to use a free wake geometry calculation. For the cases considered, the tip vortices in the rotor wake remain very close to the tip-path plane, so the calculated values of the flapping motion are sensitive to the fine details of the wake structure, specifically the viscous core radius of the tip vortices.

  17. MODELING, CONTROL AND NAVIGATION OF AN AUTONOMOUS QUAD-ROTOR HELICOPTER

    Directory of Open Access Journals (Sweden)

    Damir Šoštarić

    2016-06-01

    Full Text Available Autonomous outdoor quad-rotor helicopters increasingly attract the attention of potential researchers. Several structures and configurations have been developed to allow 3D movements. The quadrotor helicopter is made of a rigid cross frame equipped with four rotors. The autonomous quad-rotor architecture has been chosen for this research for its low dimension, good manoeuvrability, simple mechanics and payload capability. This article presents the modelling, control and navigation of an autonomous outdoor quad-rotor helicopter.

  18. Automatic shearography inspection system for helicopter rotor blades

    Science.gov (United States)

    Walz, Thomas; Ettemeyer, Andreas

    1998-03-01

    Helicopter rotor blades are highly sophisticated products composed of a variety of materials and components and therefore, 100 percent quality control has to be assured. Therefore, the French helicopter producer, Eurocopter S.A., Paris, has installed a system for automatic and 100 percent inspection of rotor blades on structural defects. In this system, laser shearography is used as an inspection technique. The rotor blades are mounted in a vacuum chamber and loaded with a relative pressure difference. At this load, bonding and structural defects show up as tiny deformations of the surface and are recorded with two shearography cameras, positioned on both sides of the rotor blade. After each measurement, they are automatically moved to the next inspection position. In this way, the entire rotor blade is automatically inspected in several measuring steps. As this helicopter blade inspection system is the first automatic production control system based on laser shearography in Europe, this application is an important step in bringing shearography techniques into production control. In this paper, the complete inspection system is presented.

  19. Lift capability prediction for helicopter rotor blade-numerical evaluation

    Science.gov (United States)

    Rotaru, Constantin; Cîrciu, Ionicǎ; Luculescu, Doru

    2016-06-01

    The main objective of this paper is to describe the key physical features for modelling the unsteady aerodynamic effects found on helicopter rotor blade operating under nominally attached flow conditions away from stall. The unsteady effects were considered as phase differences between the forcing function and the aerodynamic response, being functions of the reduced frequency, the Mach number and the mode forcing. For a helicopter rotor, the reduced frequency at any blade element can't be exactly calculated but a first order approximation for the reduced frequency gives useful information about the degree of unsteadiness. The sources of unsteady effects were decomposed into perturbations to the local angle of attack and velocity field. The numerical calculus and graphics were made in FLUENT and MAPLE soft environments. This mathematical model is applicable for aerodynamic design of wind turbine rotor blades, hybrid energy systems optimization and aeroelastic analysis.

  20. Optimal Aerodynamic Design of Conventional and Coaxial Helicopter Rotors in Hover and Forward Flight

    Science.gov (United States)

    2015-12-28

    SECURITY CLASSIFICATION OF: This dissertation investigates the optimal aerodynamic performance and design of conventional and coaxial helicopters...Approved for public release; distribution is unlimited. Optimal Aerodynamic Design of Conventional andCoaxial Helicopter Rotors in Hover and ForwardFlight...Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 rotor aerodynamics , optimal aerodynamics , hover, compund helicopters REPORT

  1. Helicopter rotor induced velocities theory and experiment

    Science.gov (United States)

    Berry, John D.; Hoad, Danny R.; Elliott, Joe W.; Althoff, Susan L.

    1987-01-01

    An investigation has been performed to assess methods used for rotor inflow modeling. A key element of this assessment has been the recent acquisition of high quality experimental measurements of inflow velocities taken in the proximity of a lifting rotor in forward flight. Widely used rotor performance predictive methods are based on blade element strip theory coupled with an inflow model. The inflow prediction models assessed in this paper include the uniform inflow based on momentum, a skewed disk model, and two methods based on a vortex wake structure.

  2. Aeroelastic optimization of a helicopter rotor

    Science.gov (United States)

    Lim, Joon W.; Chopra, Inderjit

    1988-01-01

    Structural optimization of a hingeless rotor is investigated to reduce oscillatory hub loads while maintaining aeroelastic stability in forward flight. Design variables include spanwise distribution of nonstructural mass, chordwise location of blade center of gravity and blade bending stiffnesses (flap, lag and torsion). A comprehensive aeroelastic analysis of rotors, based on a finite element method in space and time, is linked with optimization algorithms to perform optimization of rotor blades. Sensitivity derivatives of blade response, hub loads, and eigenvalues with respect to the design variables are derived using a direct analytical approach, and constitute an integral part of the basic blade response and stability analyses. This approach reduces the computation time substantially; an 80 percent reduction of CPU time to achieve an optimum solution, as compared to the widely adopted finite difference approach. Through stiffness and nonstructural mass distributions, a 60-90 percent reduction in all six 4/rev hub loads is achieved for a four-bladed soft-inplane rotor.

  3. Stability Analysis of the Slowed-Rotor Compound Helicopter Configuration

    Science.gov (United States)

    Floros, Matthew W.; Johnson, Wayne

    2007-01-01

    The stability and control of rotors at high advance ratio are considered. Teetering, articulated, gimbaled, and rigid hub types are considered for a compound helicopter (rotor and fixed wing). Stability predictions obtained using an analytical rigid flapping blade analysis, a rigid blade CAMRAD II model, and an elastic blade CAMRAD II model are compared. For the flapping blade analysis, the teetering rotor is the most stable, showing no instabilities up to an advance ratio of 3 and a Lock number of 18. A notional elastic blade model of a teetering rotor is unstable at an advance ratio of 1.5, independent of pitch frequency. Analysis of the trim controls and blade flapping shows that for small positive collective pitch, trim can be maintained without excessive control input or flapping angles.

  4. Flap motion of helicopter rotors with novel, dynamic stall model

    Directory of Open Access Journals (Sweden)

    Han Wei

    2016-01-01

    Full Text Available In this paper, a nonlinear flapping equation for large inflow angles and flap angles is established by analyzing the aerodynamics of helicopter blade elements. In order to obtain a generalized flap equation, the Snel stall model was first applied to determine the lift coefficient of the helicopter rotor. A simulation experiment for specific airfoils was then conducted to verify the effectiveness of the Snel stall model as it applies to helicopters. Results show that the model requires no extraneous parameters compared to the traditional stall model and is highly accurate and practically applicable. Based on the model, the relationship between the flapping angle and the angle of attack was analyzed, as well as the advance ratio under the dynamic stall state.

  5. Quad-Rotor Unmanned Aerial Vehicle Helicopter Modelling & Control

    Directory of Open Access Journals (Sweden)

    Yogianandh Naidoo

    2011-09-01

    Full Text Available This paper presents the investigation of the modelling and control of a quad-rotor helicopter and forms part of research involving the development of an unmanned aerial vehicle (UAV to be used in search and rescue applications. Quad-rotor helicopters consist of two pairs of counter rotating rotors situated at the ends of a cross, symmetric about the centre of gravity, which coincides with the origin of the reference system used. These rotors provide the predominant aerodynamic forces which act on the rotorcraft, and are modelled using momentum theory as well as blade element theory. From this, one can determine the expected payload capacity and lift performance of the rotorcraft. The Euler-Lagrange method has been used to derive the defining equations of motion of the six degree-of-freedom system. The Lagrangian was obtained by modelling the kinetic and potential energy of the system and the external forces obtained from the aerodynamic analysis. Based on this model, a control strategy was developed using linear PD controllers. A numerical simulation was then conducted using MATLAB® Simulink®. First, the derived model was simulated to investigate the behaviour of the rotorcraft, and then a second investigation was conducted to determine the effectiveness of the implemented control system. The results and findings of these investigations are then presented and discussed.

  6. Smart helicopter rotors optimization and piezoelectric vibration control

    CERN Document Server

    Ganguli, Ranjan; Viswamurthy, Sathyamangalam Ramanarayanan

    2016-01-01

    Exploiting the properties of piezoelectric materials to minimize vibration in rotor-blade actuators, this book demonstrates the potential of smart helicopter rotors to achieve the smoothness of ride associated with jet-engined, fixed-wing aircraft. Vibration control is effected using the concepts of trailing-edge flaps and active-twist. The authors’ optimization-based approach shows the advantage of multiple trailing-edge flaps and algorithms for full-authority control of dual trailing-edge-flap actuators are presented. Hysteresis nonlinearity in piezoelectric stack actuators is highlighted and compensated by use of another algorithm. The idea of response surfaces provides for optimal placement of trailing-edge flaps. The concept of active twist involves the employment of piezoelectrically induced shear actuation in rotating beams. Shear is then demonstrated for a thin-walled aerofoil-section rotor blade under feedback-control vibration minimization. Active twist is shown to be significant in reducing vibra...

  7. Calculated hovering helicopter flight dynamics with a circulation-controlled rotor

    Science.gov (United States)

    Johnson, W.; Chopra, I.

    1979-01-01

    The flight dynamics of a hovering helicopter with a circulation-controlled rotor are analyzed. The influence of the rotor blowing coefficient on the calculated eigenvalues of the helicopter motion is examined for a range of values of the rotor lift and the blade flap frequency. The control characteristics of a helicopter with a circulation-controlled rotor are discussed. The principal effect of the blowing is a reduction in the rotor speed stability derivative. Above a critical level of blowing coefficient, which depends on the flap frequency and rotor lift, negative speed stability is produced and the dynamic characteristics of the helicopter are radically altered. The handling qualities of a helicopter with negative speed stability are probably unacceptable without a stability augmentation system.

  8. Separation of Main and Tail Rotor Noise Sources from Ground-Based Acoustic Measurements Using Time-Domain De-Dopplerization

    Science.gov (United States)

    Greenwood, Eric II; Schmitz, Fredric H.

    2009-01-01

    A new method of separating the contributions of helicopter main and tail rotor noise sources is presented, making use of ground-based acoustic measurements. The method employs time-domain de-Dopplerization to transform the acoustic pressure time-history data collected from an array of ground-based microphones to the equivalent time-history signals observed by an array of virtual inflight microphones traveling with the helicopter. The now-stationary signals observed by the virtual microphones are then periodically averaged with the main and tail rotor once per revolution triggers. The averaging process suppresses noise which is not periodic with the respective rotor, allowing for the separation of main and tail rotor pressure time-histories. The averaged measurements are then interpolated across the range of directivity angles captured by the microphone array in order to generate separate acoustic hemispheres for the main and tail rotor noise sources. The new method is successfully applied to ground-based microphone measurements of a Bell 206B3 helicopter and demonstrates the strong directivity characteristics of harmonic noise radiation from both the main and tail rotors of that helicopter.

  9. Modeling and simulation of coaxial helicopter rotor aerodynamics

    Science.gov (United States)

    Gecgel, Murat

    A framework is developed for the computational fluid dynamics (CFD) analyses of a series of helicopter rotor flowfields in hover and in forward flight. The methodology is based on the unsteady solutions of the three-dimensional, compressible Navier-Stokes equations recast in a rotating frame of reference. The simulations are carried out by solving the developed mathematical model on hybrid meshes that aim to optimally exploit the benefits of both the structured and the unstructured grids around complex configurations. The computer code is prepared for parallel processing with distributed memory utilization in order to significantly reduce the computational time and the memory requirements. The developed model and the simulation methodology are validated for single-rotor-in-hover flowfields by comparing the present results with the published experimental data. The predictive merit of different turbulence models for complex helicopter aerodynamics are tested extensively. All but the kappa-o and LES results demonstrate acceptable agreement with the experimental data. It was deemed best to use the one-equation Spalart-Allmaras turbulence model for the subsequent rotor flowfield computations. First, the flowfield around a single rotor in forward flight is simulated. These time---accurate computations help to analyze an adverse effect of increasing the forward flight speed. A dissymmetry of the lift on the advancing and the retreating blades is observed for six different advance ratios. Since the coaxial rotor is proposed to mitigate the dissymmetry, it is selected as the next logical step of the present investigation. The time---accurate simulations are successfully obtained for the flowfields generated by first a hovering then a forward-flying coaxial rotor. The results for the coaxial rotor in forward flight verify the aerodynamic balance proposed by the previously published advancing blade concept. The final set of analyses aims to investigate if the gap between the

  10. Damping augmentation of helicopter rotors using magnetorheological dampers

    Science.gov (United States)

    Zhao, Yongsheng

    This dissertation describes an investigation exploring the use of magnetorheological (MR) dampers to augment the stability of helicopter rotors. Helicopters with advanced soft in-plane rotors are susceptible to ground resonance instabilities due to the coupling of the lightly damped rotor lag modes and fuselage modes. Traditional passive lag dampers, such as hydraulic or elastomeric dampers, can be used to alleviate these instabilities. However, these passive dampers suffer from the disadvantages that they produce large damper loads in forward flight conditions. These damper forces increase fatigue loads and reduce component life. Thus, it is desirable to have lag dampers controllable or adaptable, so that the damper can apply loads only when needed. MR fluid based dampers have recently been considered for helicopter lag damping augmentation because the forces generated by these dampers can be controlled by an applied magnetic field. In this dissertation, control schemes to integrate MR dampers with helicopters are developed and the influences of the MR dampers on rotorcraft ground resonance are studied. Specifically, the MR dampers are incorporated into the ground resonance model in two ways: using a linear equivalent viscous damping and using a nonlinear damper model. The feasibility of using MR dampers to stabilize ground resonance is studied. The open loop on-off control is utilized where MR dampers are turned on over RPM where ground resonance occurs, and turned off otherwise. To further explore the damping control ability of MR dampers, the nonlinear semi-active closed loop feedback control strategies are developed: feedback linearization control and sliding mode control. The performance of the two control strategies is evaluated using two examples: to stabilize an unstable rotor and to augment the stability of a marginally stable rotor. In addition, the robustness of the closed loop control strategies is studied using two cases: damper degradation and

  11. Quad-Rotor Helicopter Autonomous Navigation Based on Vanishing Point Algorithm

    Directory of Open Access Journals (Sweden)

    Jialiang Wang

    2014-01-01

    Full Text Available Quad-rotor helicopter is becoming popular increasingly as they can well implement many flight missions in more challenging environments, with lower risk of damaging itself and its surroundings. They are employed in many applications, from military operations to civilian tasks. Quad-rotor helicopter autonomous navigation based on the vanishing point fast estimation (VPFE algorithm using clustering principle is implemented in this paper. For images collected by the camera of quad-rotor helicopter, the system executes the process of preprocessing of image, deleting noise interference, edge extracting using Canny operator, and extracting straight lines by randomized hough transformation (RHT method. Then system obtains the position of vanishing point and regards it as destination point and finally controls the autonomous navigation of the quad-rotor helicopter by continuous modification according to the calculated navigation error. The experimental results show that the quad-rotor helicopter can implement the destination navigation well in the indoor environment.

  12. Multidisciplinary Aerodynamic Design of a Rotor Blade for an Optimum Rotor Speed Helicopter

    Directory of Open Access Journals (Sweden)

    Jiayi Xie

    2017-06-01

    Full Text Available The aerodynamic design of rotor blades is challenging, and is crucial for the development of helicopter technology. Previous aerodynamic optimizations that focused only on limited design points find it difficult to balance flight performance across the entire flight envelope. This study develops a global optimum envelope (GOE method for determining blade parameters—blade twist, taper ratio, tip sweep—for optimum rotor speed helicopters (ORS-helicopters, balancing performance improvements in hover and various freestream velocities. The GOE method implements aerodynamic blade design by a bi-level optimization, composed of a global optimization step and a secondary optimization step. Power loss as a measure of rotor performance is chosen as the objective function, referred to as direct power loss (DPL in this study. A rotorcraft comprehensive code for trim simulation with a prescribed wake method is developed. With the application of the GOE method, a DPL reduction of as high as 16.7% can be achieved in hover, and 24% at high freestream velocity.

  13. Contributions to the dynamics of helicopters with active rotor controls

    Science.gov (United States)

    Malpica, Carlos A.

    This dissertation presents an aeromechanical closed loop stability and response analysis of a hingeless rotor helicopter with a Higher Harmonic Control (HHC) system for vibration reduction. The analysis includes the rigid body dynamics of the helicopter and blade flexibility. The gain matrix is assumed to be fixed and computed off-line. The discrete elements of the HHC control loop are rigorously modeled, including the presence of two different time scales in the loop. By also formulating the coupled rotor-fuselage dynamics in discrete form, the entire coupled helicopter-HHC system could be rigorously modeled as a discrete system. The effect of the periodicity of the equations of motion is rigorously taken into account by converting the system into an equivalent system with constant coefficients and identical stability properties using a time lifting technique. The most important conclusion of the present study is that the discrete elements in the HHC loop must be modeled in any HHC analysis. Not doing so is unconservative. For the helicopter configuration and HHC structure used in this study, an approximate continuous modeling of the HHC system indicates that the closed loop, coupled helicopter-HHC system remains stable for optimal feedback control configurations which the more rigorous discrete analysis shows can result in closed loop instabilities. The HHC gains must be reduced to account for the loss of gain margin brought about by the discrete elements. Other conclusions of the study are: (i) the HHC is effective in quickly reducing vibrations, at least at its design condition, although the time constants associated with the closed loop transient response indicate closed loop bandwidth to be 1 rad/sec on average, thus overlapping with FCS or pilot bandwidths, and raising the issue of potential interactions; (ii) a linearized model of helicopter dynamics is adequate for HHC design, as long as the periodicity of the system is correctly taken into account, i

  14. Navier-Stokes Simulation of a Heavy Lift Slowed-Rotor Compound Helicopter Configuration

    Science.gov (United States)

    Allan, Brian G.; Jenkins, Luther N.; Yao, Chung-Sheng; Bartram, Scott M.; Hallissy, Jim B.; Harris, Jerome; Noonan, Kevin W.; Wong, Oliver D.; Jones, Henry E.; Malovrh, Brendon D.; hide

    2009-01-01

    Time accurate numerical simulations were performed using the Reynolds-averaged Navier-Stokes (RANS) flow solver OVERFLOW for a heavy lift, slowed-rotor, compound helicopter configuration, tested at the NASA Langley 14- by 22-Foot Subsonic Tunnel. The primary purpose of these simulations is to provide support for the development of a large field of view Particle Imaging Velocimetry (PIV) flow measurement technique supported by the Subsonic Rotary Wing (SRW) project under the NASA Fundamental Aeronautics program. These simulations provide a better understanding of the rotor and body wake flows and helped to define PIV measurement locations as well as requirements for validation of flow solver codes. The large field PIV system can measure the three-dimensional velocity flow field in a 0.914m by 1.83m plane. PIV measurements were performed upstream and downstream of the vertical tail section and are compared to simulation results. The simulations are also used to better understand the tunnel wall and body/rotor support effects by comparing simulations with and without tunnel floor/ceiling walls and supports. Comparisons are also made to the experimental force and moment data for the body and rotor.

  15. Exploratory wind-tunnel investigation of the effect of the main rotor wake on tail rotor noise. [langley anechoic noise facility

    Science.gov (United States)

    Pegg, R. J.; Shidler, P. A.

    1978-01-01

    Approaches to minimizing the noise generated by the interaction of the tail rotor blades with the wake of the main rotor considered include repositioning of the tail rotor with respect to the main rotor, changes in the rotational direction of the tail rotor, and modification of the main rotor tip vortex. A variable geometry model was built which had the capability of varying tail rotor position relative to the main rotor as well as direction of tail rotor rotation. Acoustic data taken from the model in the Langley anechoic noise facility indicates interaction effects due to both main rotor shed vortex and the main rotor turbulence.

  16. The investigation of a variable camber blade lift control for helicopter rotor systems

    Science.gov (United States)

    Awani, A. O.

    1982-01-01

    A new rotor configuration called the variable camber rotor was investigated numerically for its potential to reduce helicopter control loads and improve hover performance. This rotor differs from a conventional rotor in that it incorporates a deflectable 50% chord trailing edge flap to control rotor lift, and a non-feathering (fixed) forward portion. Lift control is achieved by linking the blade flap to a conventional swashplate mechanism; therefore, it is pilot action to the flap deflection that controls rotor lift and tip path plane tilt. This report presents the aerodynamic characteristics of the flapped and unflapped airfoils, evaluations of aerodynamics techniques to minimize flap hinge moment, comparative hover rotor performance and the physical concepts of the blade motion and rotor control. All the results presented herein are based on numerical analyses. The assessment of payoff for the total configuration in comparison with a conventional blade, having the same physical characteristics as an H-34 helicopter rotor blade was examined for hover only.

  17. Design of a Slowed-Rotor Compound Helicopter for Future Joint Service Missions

    Science.gov (United States)

    Silva, Christopher; Yeo, Hyeonsoo; Johnson, Wayne R.

    2010-01-01

    A slowed-rotor compound helicopter has been synthesized using the NASA Design and Analysis of Rotorcraft (NDARC) conceptual design software. An overview of the design process and the capabilities of NDARC are presented. The benefits of trading rotor speed, wing-rotor lift share, and trim strategies are presented for an example set of sizing conditions and missions.

  18. Aeroelastic effects on stability and control of hingeless rotor helicopters

    Science.gov (United States)

    Celi, Roberto

    1988-01-01

    The combined effect of torsional flexibility and offset of the aerodynamic center relative to the elastic axis on the stability and control of a hingeless rotor helicopter in forward flight is studied in this paper. The aeroelastic model of the blade is based on fully coupled flap-lag-torsion equations of motion, which include kinematic nonlinearities due to moderate deflections. The equations are discretized using a finite element Galerkin method in space, and a classical Galerkin method in time. The vehicle trim calculations are coupled to the blade aeroelastic response calculations. Quasilinearization is used to compute aeroelastic stability. Reducing torsional stiffness and moving the elastic axis ahead of the aerodynamic center strongly stabilizes the phugoid mode without reducing control sensitivity. Aeroelastic stability calculations must accompany flight dynamics calculations to prevent aeroelastic instabilities that might easily go undetected.

  19. Advances in transitional flow modeling applications to helicopter rotors

    CERN Document Server

    Sheng, Chunhua

    2017-01-01

    This book provides a comprehensive description of numerical methods and validation processes for predicting transitional flows based on the Langtry–Menter local correlation-based transition model, integrated with both one-equation Spalart–Allmaras (S–A) and two-equation Shear Stress Transport (SST) turbulence models. A comparative study is presented to combine the respective merits of the two coupling methods in the context of predicting the boundary-layer transition phenomenon from fundamental benchmark flows to realistic helicopter rotors. The book will of interest to industrial practitioners working in aerodynamic design and the analysis of fixed-wing or rotary wing aircraft, while also offering advanced reading material for graduate students in the research areas of Computational Fluid Dynamics (CFD), turbulence modeling and related fields.

  20. Nonlinear Characteristics of Helicopter Rotor Blade Airfoils: An Analytical Evaluation

    Directory of Open Access Journals (Sweden)

    Constantin Rotaru

    2013-01-01

    Full Text Available Some results are presented about the study of airloads of the helicopter rotor blades, the aerodynamic characteristics of airfoil sections, the physical features, and the techniques for modeling the unsteady effects found on airfoil operating under nominally attached flow conditions away from stall. The unsteady problem was approached on the basis of Theodorsen's theory, where the aerodynamic response (lift and pitching moment is considered as a sum of noncirculatory and circulatory parts. The noncirculatory or apparent mass accounts for the pressure forces required to accelerate the fluid in the vicinity of the airfoil. The apparent mass contributions to the forces and pitching moments, which are proportional to the instantaneous motion, are included as part of the quasi-steady result.

  1. Dynamics Modeling and Control of a Quad-rotor Helicopter

    Science.gov (United States)

    Hossain, Mohammed Raju

    Unmanned Aerial Vehicles (UAVs) have become a promising field of research due to the enormous potential for both military and civilian applications. This thesis focuses on increasing the autonomy of one type of rotary wing UAV; namely a Quad-rotor Helicopter. In this work a detailed mathematical model was introduced for simulation of the dynamics and control of this system. The dynamic model evolved from a simple set of equations, valid only for hovering, to a complex mathematical model with more realistic aerodynamic factors like thrust factor and drag factor. A simple yet precise tool was developed to measure these aerodynamic factors. An intelligent vision based control technique has been proposed for the critical, near-hovering flight of the vehicle. Finally, a platform was developed and a PD controller was implemented with inertial sensors in order to prepare the platform for implementing the vision-based control in the future.

  2. Development of an analysis for the determination of coupled helicopter rotor/control system dynamic response. Part 2: Program listing

    Science.gov (United States)

    Sutton, L. R.

    1975-01-01

    A theoretical analysis is developed for a coupled helicopter rotor system to allow determination of the loads and dynamic response behavior of helicopter rotor systems in both steady-state forward flight and maneuvers. The effects of an anisotropically supported swashplate or gyroscope control system and a deformed free wake on the rotor system dynamic response behavior are included.

  3. Power harvesting in a helicopter rotor using a piezo stack in the lag damper

    NARCIS (Netherlands)

    de Jong, Pieter; de Boer, Andries; Loendersloot, Richard; van der Hoogt, Peter

    2012-01-01

    A piezoelectrically augmented helicopter lag damper has been simulated for the purpose of harvesting electrical energy within the rotor of the aircraft. This energy can then be consumed locally for sensing, processing and transmission of data to the cockpit. An 8.15m radius rotor is considered and

  4. Mach number scaling of helicopter rotor blade/vortex interaction noise

    Science.gov (United States)

    Leighton, Kenneth P.; Harris, Wesley L.

    1985-01-01

    A parametric study of model helicopter rotor blade slap due to blade vortex interaction (BVI) was conducted in a 5 by 7.5-foot anechoic wind tunnel using model helicopter rotors with two, three, and four blades. The results were compared with a previously developed Mach number scaling theory. Three- and four-bladed rotor configurations were found to show very good agreement with the Mach number to the sixth power law for all conditions tested. A reduction of conditions for which BVI blade slap is detected was observed for three-bladed rotors when compared to the two-bladed baseline. The advance ratio boundaries of the four-bladed rotor exhibited an angular dependence not present for the two-bladed configuration. The upper limits for the advance ratio boundaries of the four-bladed rotors increased with increasing rotational speed.

  5. Performance of Swashplateless Ultralight Helicopter Rotor with Trailing-edge Flaps for Primary Flight Control

    Science.gov (United States)

    Shen, Jin-Wei; Chopra, Inderjit

    2003-01-01

    The objective of present study is to evaluate the rotor performance, trailing-edge deflections and actuation requirement of a helicopter rotor with trailing-edge flap system for primary flight control. The swashplateless design is implemented by modifying a two-bladed teetering rotor of an production ultralight helicopter through the use of plain flaps on the blades, and by replacing the pitch link to fixed system control system assembly with a root spring. A comprehensive rotorcraft analysis based on UMARC is carried out to obtain the results for both the swashplateless and a conventional baseline rotor configuration. The predictions show swashplateless configuration achieve superior performance than the conventional rotor attributed from reduction of parasite drag by eliminating swashplate mechanic system. It is indicated that optimal selection of blade pitch index angle, flap location, length, and chord ratio reduces flap deflections and actuation requirements, however, has virtually no effect on rotor performance.

  6. The Effects of Ambient Conditions on Helicopter Rotor Source Noise Modeling

    Science.gov (United States)

    Schmitz, Frederic H.; Greenwood, Eric

    2011-01-01

    A new physics-based method called Fundamental Rotorcraft Acoustic Modeling from Experiments (FRAME) is used to demonstrate the change in rotor harmonic noise of a helicopter operating at different ambient conditions. FRAME is based upon a non-dimensional representation of the governing acoustic and performance equations of a single rotor helicopter. Measured external noise is used together with parameter identification techniques to develop a model of helicopter external noise that is a hybrid between theory and experiment. The FRAME method is used to evaluate the main rotor harmonic noise of a Bell 206B3 helicopter operating at different altitudes. The variation with altitude of Blade-Vortex Interaction (BVI) noise, known to be a strong function of the helicopter s advance ratio, is dependent upon which definition of airspeed is flown by the pilot. If normal flight procedures are followed and indicated airspeed (IAS) is held constant, the true airspeed (TAS) of the helicopter increases with altitude. This causes an increase in advance ratio and a decrease in the speed of sound which results in large changes to BVI noise levels. Results also show that thickness noise on this helicopter becomes more intense at high altitudes where advancing tip Mach number increases because the speed of sound is decreasing and advance ratio increasing for the same indicated airspeed. These results suggest that existing measurement-based empirically derived helicopter rotor noise source models may give incorrect noise estimates when they are used at conditions where data were not measured and may need to be corrected for mission land-use planning purposes.

  7. Power harvesting using piezoelectric materials: applications in helicopter rotors

    NARCIS (Netherlands)

    de Jong, Pieter

    2013-01-01

    The blades of helicopters are heavily loaded and are critical components. Failure of any one blade will lead to loss of the aircraft. Currently, the technical lifespan of helicopter blades is calculated using a worst-case operation scenario. The consequence is that a blade that may be suitable for,

  8. Wireless Sensor Network for Helicopter Rotor Blade Vibration Monitoring: Requirements Definition and Technological Aspects

    NARCIS (Netherlands)

    Sanchez Ramirez, Andrea; Das, Kallol; Loendersloot, Richard; Tinga, Tiedo; Havinga, Paul J.M.; Basu, Biswajit

    The main rotor accounts for the largest vibration source for a helicopter fuselage and its components. However, accurate blade monitoring has been limited due to the practical restrictions on instrumenting rotating blades. The use of Wireless Sensor Networks (WSNs) for real time vibration monitoring

  9. Reduction of Helicopter Blade-Vortex Interaction Noise by Active Rotor Control Technology

    Science.gov (United States)

    Yu, Yung H.; Gmelin, Bernd; Splettstoesser, Wolf; Brooks, Thomas F.; Philippe, Jean J.; Prieur, Jean

    1997-01-01

    Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor blade vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations, Published by Elsevier Science Ltd.

  10. Loads and Performance Data from a Wind-Tunnel Test of Generic Model Helicopter Rotor Blades

    Science.gov (United States)

    Yeager, William T., Jr.; Wilbur, Matthew L.

    2005-01-01

    An investigation was conducted in the NASA Langley Transonic Dynamics Tunnel to acquire data for use in assessing the ability of current and future comprehensive analyses to predict helicopter rotating-system and fixed-system vibratory loads. The investigation was conducted with a generic model helicopter rotor system using blades with rectangular planform, no built-in twist, uniform radial distribution of mass and stiffnesses, and a NACA 0012 airfoil section. Rotor performance data, as well as mean and vibratory components of blade bending and torsion moments, fixed-system forces and moments, and pitch link loads were obtained at advance ratios up to 0.35 for various combinations of rotor shaft angle-of-attack and collective pitch. The data are presented without analysis.

  11. Analysis and Prediction of Ice Shedding for a Full-Scale Heated Tail Rotor

    Science.gov (United States)

    Kreeger, Richard E.; Work, Andrew; Douglass, Rebekah; Gazella, Matthew; Koster, Zakery; Turk, Jodi

    2016-01-01

    When helicopters are to fly in icing conditions, it is necessary to consider the possibility of ice shed from the rotor blades. In 2013, a series of tests were conducted on a heated tail rotor at NASA Glenn's Icing Research Tunnel (IRT). The tests produced several shed events that were captured on camera. Three of these shed events were captured at a sufficiently high frame rate to obtain multiple images of the shed ice in flight that had a sufficiently long section of shed ice for analysis. Analysis of these shed events is presented and compared to an analytical Shedding Trajectory Model (STM). The STM is developed and assumes that the ice breaks off instantly as it reaches the end of the blade, while frictional and viscous forces are used as parameters to fit the STM. The trajectory of each shed is compared to that predicted by the STM, where the STM provides information of the shed group of ice as a whole. The limitations of the model's underlying assumptions are discussed in comparison to experimental shed events.

  12. Prediction of sand particle trajectories and sand erosion damage on helicopter rotor blades

    Science.gov (United States)

    Shin, Bong Gun

    Therefore, in this dissertation, accurate and time-efficient methodologies were developed for performing sand particle tracking and predicting sand erosion damage on actual helicopter rotor blades under realistic hover and vertical lift conditions. In this dissertation, first, injection (release) conditions of solid particles with new injection parameter, sand particle mass flow rate (SPmFR), were specified to deal with the effect of non-uniform and unsteady flow conditions surrounding at each injection point from which solid particles are released. The SPmFR defines the number of solid particles released from the same injection position per unit time. Secondly, a general definition of erosion rate, "mass or volume loss from the metal surface due to the impact of a unit "mass" of solid particles" was also modified by multiplying with SPmFR in order to solve the limitation for predicting erosion damage on actual helicopter rotor blade. Next, a suitable empirical particle rebound model and an erosion damage model for spherical sand particles with diameters ranging from 10 microm to 500 microm impacting on the material Ti-6A1-4V, the material of helicopter rotor blade, were developed. Finally, C++ language based codes in the form of User Defined Functions (UDFs) were developed and implemented into the commercially available multi-dimensional viscous flow solver ANSYS-FLUENT in order to develop and integrate with the general purpose flow solver, ANSYS-FLUENT, for a specific Lagrangian particle trajectory computing algorithm and rebound and erosion quantification purposes. In the erosion simulation, a reasonably accurate fluid flow solution is necessary. In order to validate the numerical results obtained in this dissertation, computations for flow-only around 2D RAE2822 airfoil and 3D rotating rotor blade (NACA0012) without any sand particle were performed. In the comparison of these results with experimental results, it is found that the flow solutions are in good

  13. Development of an analysis for the determination of coupled helicopter rotor/control system dynamic response. Part 1: Analysis and applications

    Science.gov (United States)

    Sutton, L. R.; Rinehart, S. A.

    1975-01-01

    A theoretical analysis is developed for a coupled helicopter rotor system to allow determination of the loads and dynamic response behavior of helicopter rotor systems in both steady-state forward flight and maneuvers. The effects of an anisotropically supported swashplate or gyroscope control system and a deformed free wake on the rotor system dynamic response behavior are included in the analysis.

  14. 76 FR 20490 - Special Conditions: Eurocopter France Model AS350B Series, AS350D, and EC130 Helicopters...

    Science.gov (United States)

    2011-04-13

    ... operation. These helicopter models are capable of carrying up to six passengers with one pilot, and have a... features include a 3- blade, fully articulated main rotor, an anti-torque tail rotor system, a skid landing...

  15. Identification of Flap Motion Parameters for Vibration Reduction in Helicopter Rotors with Multiple Active Trailing Edge Flaps

    Directory of Open Access Journals (Sweden)

    Uğbreve;ur Dalli

    2011-01-01

    Full Text Available An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.

  16. Optimal Aerodynamic Design of Conventional and Coaxial Helicopter Rotors in Hover and Forward Flight

    Science.gov (United States)

    Giovanetti, Eli B.

    This dissertation investigates the optimal aerodynamic performance and design of conventional and coaxial helicopters in hover and forward flight using conventional and higher harmonic blade pitch control. First, we describe a method for determining the blade geometry, azimuthal blade pitch inputs, optimal shaft angle (rotor angle of attack), and division of propulsive and lifting forces among the components that minimize the total power for a given forward flight condition. The optimal design problem is cast as a variational statement that is discretized using a vortex lattice wake to model inviscid forces, combined with two-dimensional drag polars to model profile losses. The resulting nonlinear constrained optimization problem is solved via Newton iteration. We investigate the optimal design of a compound vehicle in forward flight comprised of a coaxial rotor system, a propeller, and optionally, a fixed wing. We show that higher harmonic control substantially reduces required power, and that both rotor and propeller efficiencies play an important role in determining the optimal shaft angle, which in turn affects the optimal design of each component. Second, we present a variational approach for determining the optimal (minimum power) torque-balanced coaxial hovering rotor using Blade Element Momentum Theory including swirl. We show that the optimal hovering coaxial rotor generates only a small percentage of its total thrust on the portion of the lower rotor operating in the upper rotor's contracted wake, resulting in an optimal design with very different upper and lower rotor twist and chord distributions. We also show that the swirl component of induced velocity has a relatively small effect on rotor performance at the disk loadings typical of helicopter rotors. Third, we describe a more refined model of the wake of a hovering conventional or coaxial rotor. We approximate the rotor or coaxial rotors as actuator disks (though not necessarily uniformly loaded

  17. Actuator Fault Estimation and Reconfiguration Control for the Quad-Rotor Helicopter

    Directory of Open Access Journals (Sweden)

    Fuyang Chen

    2016-02-01

    Full Text Available In this paper, an improved reconfiguration control scheme via an H∞ fault observer and adaptive control is studied for the quad-rotor helicopter with actuator faults. The bilinear problem is eliminated by constructing fault compensation and control law reconfiguration in the adaptive controller. Fault estimation is achieved by designing the fault observer with an H∞ performance index, which is applied to evaluate the ‘locking in place’ fault of the actuator in a quad-rotor helicopter. By drawing the H∞ performance index into the adaptive fault observer, an asymptotically convergent estimated error can be attained and the burden of the adaptive controller is alleviated. Some simulation and experimental results confirm the availability of the reconfiguration control scheme.

  18. Periodic control of the individual-blade-control helicopter rotor. Ph.D. Thesis

    Science.gov (United States)

    Mckillip, R. M., Jr.

    1984-01-01

    Results of an investigation into methods of controller design for an individual helicopter rotor blade in the high forward-flight speed regime are described. This operating condition poses a unique control problem in that the perturbation equations of motion are linear with coefficients that vary periodically with time. The design of a control law was based on extensions to modern multivariate synthesis techniques and incorporated a novel approach to the reconstruction of the missing system state variables. The controller was tested on both an electronic analog computer simulation of the out-of-plane flapping dynamics, and on a four foot diameter single-bladed model helicopter rotor in the M.I.T. 5x7 subsonic wind tunnel at high levels of advance ratio. It is shown that modal control using the IBC concept is possible over a large range of advance ratios with only a modest amount of computational power required.

  19. DIAGNOSTIC MATHEMATICAL MODEL OF A HYDRAULIC DAMPER OF HELICOPTER ROTOR SLEEVE

    Directory of Open Access Journals (Sweden)

    U. A. Borisov

    2014-01-01

    Full Text Available The article presents an example of the implementation of mathematical modeling in practice of overhaul of units of the helicopter hydraulic system. In particular, it sets out the methodology for constructing diagnostic mathematical model of a hydraulic damper rotor head. A procedure for the analysis of the hydraulic characteristics of the damper valve to determine the flow channel valve defects is suggested.

  20. Magnetostrictively actuated control flaps for vibration reduction in helicopter rotors

    Energy Technology Data Exchange (ETDEWEB)

    Millott, T.; Friedmann, P.P. [Univ. of California, Los Angeles, CA (United States). Mechanical, Aerospace and Nuclear Engineering Dept.

    1994-12-31

    High vibration levels can impose constraints on helicopter operations and hinder passenger acceptance. Vibration reduction using blade root pitch control introduces a significant power penalty and may adversely affect the airworthiness of the flight control system. Comparable levels of vibration reduction can be achieved using considerably less power through an actively controlled trailing edge flap mounted on the blade. Such a device would have no effect on helicopter airworthiness since it is controlled by a loop separate from the primary flight control system which utilizes the swashplate. Control flap actuation using the magnetostrictive material Terfenol-D is studied in this paper by designing a minimum weight actuator, subject to a set of actuation and stress constraints. The resulting device is capable of producing vibration reduction in excess of 90% at cruise conditions.

  1. General model and control of an n rotor helicopter

    DEFF Research Database (Denmark)

    Sidea, Adriana-Gabriela; Brogaard, Rune Yding; Andersen, Nils Axel

    2015-01-01

    The purpose of this study was to create a dynamic, nonlinear mathematical model ofa multirotor that would be valid for different numbers of rotors. Furthermore, a set of SingleInput Single Output (SISO) controllers were implemented for attitude control. Both model andcontrollers were tested exper...

  2. Identification method for helicopter flight dynamics modeling with rotor degrees of freedom

    Directory of Open Access Journals (Sweden)

    Wu Wei

    2014-12-01

    Full Text Available A comprehensive method based on system identification theory for helicopter flight dynamics modeling with rotor degrees of freedom is developed. A fully parameterized rotor flapping equation for identification purpose is derived without using any theoretical model, so the confidence of the identified model is increased, and then the 6 degrees of freedom rigid body model is extended to 9 degrees of freedom high-order model. Bode sensitivity function is derived to increase the accuracy of frequency spectra calculation which influences the accuracy of model parameter identification. Then a frequency domain identification algorithm is established. Acceleration technique is developed furthermore to increase calculation efficiency, and the total identification time is reduced by more than 50% using this technique. A comprehensive two-step method is established for helicopter high-order flight dynamics model identification which increases the numerical stability of model identification compared with single step algorithm. Application of the developed method to identify the flight dynamics model of BO 105 helicopter based on flight test data is implemented. A comparative study between the high-order model and rigid body model is performed at last. The results show that the developed method can be used for helicopter high-order flight dynamics model identification with high accuracy as well as efficiency, and the advantage of identified high-order model is very obvious compared with low-order model.

  3. A Comparative Study of Soviet versus Western Helicopters. Part 1. General Comparison of Designs

    Science.gov (United States)

    1983-03-01

    rotor shaft; ft Srelative tail-rotor distance from main-rotor shaft: x" x/R y tail-rotor elevation over main-rotor hub ; ft "relative tail-rotor...rotor hub and attachment drag is accounted for in the estimates of the whole helicopter flat plate area (M) and there is no "help" in the main-rotor...coefficients computed for two porn -weight values, using data from Fig. .. 17. ,:.:. assumed a being correct, and is shown in Table 5.5 with the corresponding

  4. Heavy Lift Helicopter - Advanced Technology Component Program - Rotor Blade

    Science.gov (United States)

    1977-09-01

    weights have been added to improve forming of the leading edge’radius. A cap made of refrasil, a refractory silicone blanket material, is being used...MODELa ROTOR S’AJVD TO FULL S IM- -400 -4000 ANALYTICAL FULL ")CAU’ (C-GO) -6000 L 0 200 200 3uO 360 B~ LADlE AZMUT - DEGREE Figure 83. Comparison of

  5. The Metallurgical Examination and Inspection of Apache Tail Rotor Strap Pack Laminates and Assemblies

    National Research Council Canada - National Science Library

    Grendahl, Scott

    1999-01-01

    The U.S. Army Research Laboratory-Weapons and Materials Research Directorate (ARL-WMRD) performed a dimensional inspection and metallurgical investigation of AH-64 Apache tail rotor strap pack assemblies and individual laminate sets...

  6. Preliminary Airworthiness Evaluation AH-1S Helicopter with OGEE Tip Shape Rotor Blades

    Science.gov (United States)

    1980-05-01

    cyclic collective pitch, and directional controls, and the elevator were within presecribed limits. The swashplate angles measured with respect to...aircraft axes and tail rotor blade pitch angles are as follows: SWASHPLATE ANGLES Control Position Lateral Angle Longitudinal Angle Neutral 1.5 deg L

  7. Air and ground resonance of helicopters with elastically tailored composite rotor blades

    Science.gov (United States)

    Smith, Edward C.; Chopra, Inderjit

    1993-01-01

    The aeromechanical stability, including air resonance in hover, air resonance in forward flight, and ground resonance, of a helicopter with elastically tailored composite rotor blades is investigated. Five soft-inplane hingeless rotor configurations, featuring elastic pitch-lag, pitch-flap and extension-torsion couplings, are analyzed. Elastic couplings introduced through tailored composite blade spars can have a powerful effect on both air and ground resonance behavior. Elastic pitch-flap couplings (positive and negative) strongly affect body, rotor and dynamic inflow modes. Air resonance stability is diminished by elastic pitch-flap couplings in hover and forwrad flight. Negative pitch-lag elastic coupling has a stabilizing effect on the regressive lag mode in hover and forward flight. The negative pitch-lag coupling has a detrimental effect on ground resonance stability. Extension-torsion elastic coupling (blade pitch decreases due to tension) decreases regressive lag mode stability in both airborne and ground contact conditions. Increasing thrust levels has a beneficial influence on ground resonance stability for rotors with pitch-flap and extension-torsion coupling and is only marginally effective in improving stability of rotors with pitch-lag coupling.

  8. Aeromechanical stability of helicopters with composite rotor blades in forward flight

    Science.gov (United States)

    Smith, Edward C.; Chopra, Inderjit

    1992-01-01

    The aeromechanical stability, including air resonance in hover, air resonance in forward flight, and ground resonance, of a helicopter with elastically tailored composite rotor blades is investigated. Five soft-inplane hingeless rotor configurations, featuring elastic pitch-lag, pitch-flap and extension-torsion couplings, are analyzed. Elastic couplings introduced through tailored composite blade spars can have a powerful effect on both air and ground resonance behavior. Elastic pitch-flap couplings (positive and negative) strongly affect body, rotor and dynamic inflow modes. Air resonance stability is diminished by elastic pitch-flap couplings in hover and forward flight. Negative pitch-lag elastic coupling has a stabilizing effect on the regressive lag mode in hover and forward flight. The negative pitch-lag coupling has a detrimental effect on ground resonance stability. Extension-torsion elastic coupling (blade pitch decreases due to tension) decreases regressive lag mode stability in both airborne and ground contact conditions. Increasing thrust levels has a beneficial influence on ground resonance stability for rotors with pitch-flap and extension-torsion coupling and is only marginally effective in improving stability of rotors with pitch-lag coupling.

  9. Modelling and robust control of an unmanned coaxial rotor helicopter with unstructured uncertainties

    Directory of Open Access Journals (Sweden)

    Zhi-Yan Dong

    2017-01-01

    Full Text Available A complete methodology for an unmanned coaxial rotor helicopter with unstructured uncertainties was proposed to achieve high-accuracy tracking performance from modelling to robust control. An integrative approach was introduced to systematically construct a whole dynamic model. The key parameters were selected carefully after iteratively being checked by empirical coefficients to decrease the budget and risk of programme. Moreover, a new control scheme is proposed to simultaneously incorporate six inputs to control six states based on the investment of singularity value responses and the general rule of relative gain array. Coprime factor uncertainty model is considered to represent a class of unstructured uncertainties, such as unmolded actuator dynamics and unpredicted interferences between two rotors. Furthermore, the H ∞ loop-shaping control was proposed to apply the control design of the coaxial rotor helicopter to manage complicated uncertainties and multivariable coupling. Finally, simulation results show the effectiveness of the proposed controller design in the step response of the closed loop. The stable closed-loop plant is achieved and the tolerant size of unstructured uncertainty is up to 36.09%. Good step responses and satisfied decoupling were also investigated in detail.

  10. Aerodynamic shape optimization for alleviating dynamic stall characteristics of helicopter rotor airfoil

    Directory of Open Access Journals (Sweden)

    Wang Qing

    2015-04-01

    Full Text Available In order to alleviate the dynamic stall effects in helicopter rotor, the sequential quadratic programming (SQP method is employed to optimize the characteristics of airfoil under dynamic stall conditions based on the SC1095 airfoil. The geometry of airfoil is parameterized by the class-shape-transformation (CST method, and the C-topology body-fitted mesh is then automatically generated around the airfoil by solving the Poisson equations. Based on the grid generation technology, the unsteady Reynolds-averaged Navier-Stokes (RANS equations are chosen as the governing equations for predicting airfoil flow field and the highly-efficient implicit scheme of lower–upper symmetric Gauss–Seidel (LU-SGS is adopted for temporal discretization. To capture the dynamic stall phenomenon of the rotor more accurately, the Spalart–Allmaras turbulence model is employed to close the RANS equations. The optimized airfoil with a larger leading edge radius and camber is obtained. The leading edge vortex and trailing edge separation of the optimized airfoil under unsteady conditions are obviously weakened, and the dynamic stall characteristics of optimized airfoil at different Mach numbers, reduced frequencies and angles of attack are also obviously improved compared with the baseline SC1095 airfoil. It is demonstrated that the optimized method is effective and the optimized airfoil is suitable as the helicopter rotor airfoil.

  11. 78 FR 23686 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-04-22

    ... estimate that this proposed AD would affect six helicopters of U.S. registry. Based on an average estimated... January 2, 2008. (g) Subject Joint Aircraft Service Component (JASC) Code: 6520, Tail Rotor Gearbox...

  12. 78 FR 51048 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-08-20

    ... continued airworthiness of these helicopters. Costs of Compliance We estimate that this AD affects six....regulations.gov . (h) Subject Joint Aircraft Service Component (JASC) Code: 6520, Tail Rotor Gearbox. (i...

  13. 77 FR 58925 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2012-09-25

    ... tail rotor hub (TRH) for a crack and removing the TRH if a crack exists. This AD is prompted by reports of cracks on two TRHs. These actions are intended to prevent the tail rotor from jamming, which could...-365N1, AS-365N2 and AS 365 N3 helicopters. Eurocopter reported that a technician found cracks on the TRH...

  14. Impact of structural optimization with aeroelastic/multidisciplinary constraints on helicopter rotor design

    Science.gov (United States)

    Friedmann, Peretz P.

    1992-01-01

    This paper presents a review of the state-of-the-art in the field of structural optimization when applied to vibration reduction of helicopters in forward flight with aeroelastic and multidisciplinary constraints. It emphasizes the application of the modern approach where the optimization is formulated as a mathematical programming problem and the objective function consists of the vibration levels at the hub and behavior constraints are imposed on the blade frequencies, aeroelastic stability margins as well as on a number of additional ingredients which can have a significant effect on the overall performance and flight mechanics of the helicopter. It is shown that the integrated multidisciplinary optimization of rotorcraft offers the potential for substantial improvements which can be achieved by careful preliminary design and analysis without requiring additional hardware such as rotor vibration absorbers or isolation systems.

  15. Some practical issues in the computational design of airfoils for the helicopter main rotor blades

    Directory of Open Access Journals (Sweden)

    Kostić Ivan

    2004-01-01

    Full Text Available Very important requirement for the helicopter rotor airfoils is zero, or nearly zero moment coefficient about the aerodynamic center. Unlike the old technologies used for metal blades, modern production involving application of plastic composites has imposed the necessity of adding a flat tab extension to the blade trailing edge, thus changing the original airfoil shape. Using computer program TRANPRO, the author has developed and verified an algorithm for numerical analysis in this design stage, applied it on asymmetrical reflex camber airfoils, determined the influence of angular tab positioning on the moment coefficient value and redesigned some existing airfoils to include properly positioned tabs that satisfy very low moment coefficient requirement. .

  16. Neutron radiography and other NDE tests of main rotor helicopter blades

    CSIR Research Space (South Africa)

    De Beer, FC

    2004-10-01

    Full Text Available and Isotopes 61 (2004) 609?616 Neutron radiography and other NDE tests of main rotor helicopter blades F.C. de Beera,*, M. Coetzerb, D. Fendeisc, A. Da Costa E Silvad a Radiation Utilization, Nuclear Technology Division, NECSA, P.O. Box 582, Pretoria 0001... and experimental procedure The thermal NRad facility is situated on the beam port floor of the SAFARI-1 nuclear research reactor, whichis located at Pelindaba, 30kmwest of Pretoria. A maximum thermal neutron flux of 1.2 C2107 ncmC02 sC01 is delivered at the object...

  17. Novel controller design demonstration for vibration alleviation of helicopter rotor blades

    Science.gov (United States)

    Ulker, Fatma Demet; Nitzsche, Fred

    2012-04-01

    This paper presents an advanced controller design methodology for vibration alleviation of helicopter rotor sys- tems. Particularly, vibration alleviation in a forward ight regime where the rotor blades experience periodically varying aerodynamic loading was investigated. Controller synthesis was carried out under the time-periodic H2 and H∞ framework and the synthesis problem was solved based on both periodic Riccati and Linear Matrix Inequality (LMI) formulations. The closed-loop stability was analyzed using Floquet-Lyapunov theory, and the controller's performance was validated by closed-loop high-delity aeroelastic simulations. To validate the con- troller's performance an actively controlled trailing edge ap strategy was implemented. Computational cost was compared for both formulations.

  18. Generic icing effects on forward flight performance of a model helicopter rotor

    Science.gov (United States)

    Tinetti, Ana F.; Korkan, Kenneth D.

    1989-01-01

    An experimental program using a commercially available model helicopter has been conducted in the TAMU 7 ft x 10 ft Subsonic Wind Tunnel to investigate main rotor performance degradation due to generic ice adhesion. Base and iced performance data were gathered as functions of fuselage incidence, blade collective pitch, main rotor rotational velocity, and freestream velocity. The experimental values have shown that, in general, the presence of generic ice introduces decrements in performance caused by leading edge separation regions and increased surface roughness. In addition to the expected changes in aerodynamic forces caused by variations in test Reynolds number, forward flight data seemed to be influenced by changes in freestream and rotational velocity. The dependence of the data upon such velocity variations was apparently enhanced by increases in blade chord.

  19. Aeroelastic optimization of a helicopter rotor using an efficient sensitivity analysis

    Science.gov (United States)

    Lim, Joon W.; Chopra, Inderjit

    1990-01-01

    To reduce oscillatory hub loads in forward flight, a structural optimization analysis of a hingeless helicopter rotor has been developed and applied. The aeroelastic analysis of the rotor is based on a finite element method in space and time, and linked with automated optimization algorithms. For the optimization analysis two types of structural representation are used: a generic stiffness-distribution and a single-cell thin-walled beam. For the first type, the design variables are nonstructural mass and its placement, chordwise center of gravity offset from the elastic axis, and stiffness. For the second type, width, height and thickness of spar are used as design variables. For the behavior constraints, frequency placement, autorotational inertia and aeroelastic stability of the blade are included. The required sensitivity derivatives are obtained using a direct analytical approach. An optimum oscillatory hub load shows a 25-77 percent reduction for the generic blade, and 30-50 percent reduction for the box-beam.

  20. Correlate Life Predictions and Condition Indicators in Helicopter Tail Gearbox Bearings

    Science.gov (United States)

    Dempsey, Paula J.; Bolander, Nathan; Haynes, Chris; Branning, Jeremy; Wade, Daniel R.

    2010-01-01

    Research to correlate bearing remaining useful life (RUL) predictions with Helicopter Health Usage Monitoring Systems (HUMS) condition indicators (CI) to indicate the damage state of a transmission component has been developed. Condition indicators were monitored and recorded on UH-60M (Black Hawk) tail gearbox output shaft thrust bearings, which had been removed from helicopters and installed in a bearing spall propagation test rig. Condition indicators monitoring the tail gearbox output shaft thrust bearings in UH-60M helicopters were also recorded from an on-board HUMS. The spal-lpropagation data collected in the test rig was used to generate condition indicators for bearing fault detection. A damage progression model was also developed from this data. Determining the RUL of this component in a helicopter requires the CI response to be mapped to the damage state. The data from helicopters and a test rig were analyzed to determine if bearing remaining useful life predictions could be correlated with HUMS condition indicators (CI). Results indicate data fusion analysis techniques can be used to map the CI response to the damage levels.

  1. Neutron radiography and other NDE tests of main rotor helicopter blades

    Energy Technology Data Exchange (ETDEWEB)

    Beer, F.C. de E-mail: fdebeer@necsa.co.za; Coetzer, M.; Fendeis, D.; Silva, A. da Costa E

    2004-10-01

    A few nondestructive examination (NDE) techniques are extensively being used worldwide to investigate aircraft structures for all types of defects. The detection of corrosion and delaminations, which are believed to be the major initiators of defects leading to aircraft structural failures, are addressed by various NDE techniques. In a combined investigation by means of visual inspection, X-ray radiography and shearography on helicopter main rotor blades, neutron radiography (NRad) at SAFARI-1 research reactor operated by Necsa, was performed to introduce this form of NDE testing to the South African aviation industry to be evaluated for applicability. The results of the shearography, visual inspection and NRad techniques are compared in this paper. The main features and advantages of neutron radiography, within the framework of these investigations, will be highlighted.

  2. Hummingbird wing efficacy depends on aspect ratio and compares with helicopter rotors.

    Science.gov (United States)

    Kruyt, Jan W; Quicazán-Rubio, Elsa M; van Heijst, GertJan F; Altshuler, Douglas L; Lentink, David

    2014-10-06

    Hummingbirds are the only birds that can sustain hovering. This unique flight behaviour comes, however, at high energetic cost. Based on helicopter and aeroplane design theory, we expect that hummingbird wing aspect ratio (AR), which ranges from about 3.0 to 4.5, determines aerodynamic efficacy. Previous quasi-steady experiments with a wing spinner set-up provide no support for this prediction. To test this more carefully, we compare the quasi-steady hover performance of 26 wings, from 12 hummingbird taxa. We spun the wings at angular velocities and angles of attack that are representative for every species and measured lift and torque more precisely. The power (aerodynamic torque × angular velocity) required to lift weight depends on aerodynamic efficacy, which is measured by the power factor. Our comparative analysis shows that AR has a modest influence on lift and drag forces, as reported earlier, but interspecific differences in power factor are large. During the downstroke, the power required to hover decreases for larger AR wings at the angles of attack at which hummingbirds flap their wings (p < 0.05). Quantitative flow visualization demonstrates that variation in hover power among hummingbird wings is driven by similar stable leading edge vortices that delay stall during the down- and upstroke. A side-by-side aerodynamic performance comparison of hummingbird wings and an advanced micro helicopter rotor shows that they are remarkably similar. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  3. Adaptive Dynamic Surface Control is designed for Twin Rotor unmanned helicopter in three-dimensional space

    Directory of Open Access Journals (Sweden)

    Amir Reza Moadeli

    2016-01-01

    Full Text Available In this paper, the system control design problem twin rotors helicopters Unmanned Aerial Vehicles (UAV in three dimensional space Without uncertainty based on the dynamic adaptive control is studied. the adaptive Dynamic surface control approach complexity explosion problem in non-linear control step back or backstepping method [45] using the First-order filters removed. The first helicopter dynamic equations and functions are examined. Then, the Dynamic surface control techniques by compare non-linear control technique back stepping [45] is checked and the system is simulation by both techniques adaptive Dynamic surface control and nonlinear control back stepping method. The proposed adaptive dynamics surface nonlinear control method approach is able to guarantees that all the signals in the closed-loop system are asymptotically stable for all initial conditions and you can also choose appropriate design parameters of the system output converges to a small neighborhood of origin ensured . Finally, simulation results are presented, showing the effectiveness of control methods are given.

  4. 78 FR 27867 - Airworthiness Directives; MD Helicopters Inc. Helicopters

    Science.gov (United States)

    2013-05-13

    ... Helicopter Technology Company (HTC) tail rotor blades installed. The existing AD currently requires reducing... been detected under the paint. This proposed AD would retain some of the requirements in the existing AD but would require paint removal for all pitch horn inspections, inspecting for pitting and the...

  5. Helicopter model rotor-blade vortex interaction impulsive noise: Scalability and parametric variations

    Science.gov (United States)

    Splettstoesser, W. R.; Schultz, K. J.; Boxwell, D. A.; Schmitz, F. H.

    1984-01-01

    Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale remarkable well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224 to 0.270), the scaling deteriorates, suggesting that the model scale rotor is not adequately simulating the full scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters - tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient - are highly sensitive to BVI noise radiation.

  6. Computation of Aerodynamic Noise Radiated from Ducted Tail Rotor Using Boundary Element Method

    Directory of Open Access Journals (Sweden)

    Yunpeng Ma

    2017-01-01

    Full Text Available A detailed aerodynamic performance of a ducted tail rotor in hover has been numerically studied using CFD technique. The general governing equations of turbulent flow around ducted tail rotor are given and directly solved by using finite volume discretization and Runge-Kutta time integration. The calculations of the lift characteristics of the ducted tail rotor can be obtained. In order to predict the aerodynamic noise, a hybrid method combining computational aeroacoustic with boundary element method (BEM has been proposed. The computational steps include the following: firstly, the unsteady flow around rotor is calculated using the CFD method to get the noise source information; secondly, the radiate sound pressure is calculated using the acoustic analogy Curle equation in the frequency domain; lastly, the scattering effect of the duct wall on the propagation of the sound wave is presented using an acoustic thin-body BEM. The aerodynamic results and the calculated sound pressure levels are compared with the known technique for validation. The sound pressure directivity and scattering effect are shown to demonstrate the validity and applicability of the method.

  7. Hovering Characteristics of a Rotor having an Airfoil Section Designed for Flying-Crane Type of Helicopter

    Science.gov (United States)

    Shivers, James P.

    1961-01-01

    Results of an investigation, conducted on the Langley helicopter test tower, of a rotor having an NACA 632A015 airfoil thickness distribution in combination with an NACA 230 mean line are presented. Comparison with a previously reported test of a symmetrical rotor blade efficiency was substantially improved over a wide range of tip Mach numbers. The maximum mean lift coefficient was essentially unchanged from that obtained with uncambered blades. Some data showing the effect of a distributed type of leading-edge roughness are also included.

  8. Analysis of a Swashplate Mechanism of the Hingeless Rotor Hub with the Flybar in a Model Helicopter, Part II: Dynamics

    Science.gov (United States)

    Sabaapour, Mohammad Reza; Zohoor, Hassan

    Swashplate mechanism is the steering control mechanism, used in most helicopters. It is a complex multi-loop closed kinematic chain which controls the angles of attack of the main rotor blades. In most new model helicopters, this mechanism is also equipped with the bell-hiller stabilizer bar (flybar), to improve the stability. The main purpose of this paper is the dynamic analysis of a swashplate mechanism, one of the latest architectures, used for hingeless rotor with the flybar. The underlying kinematics has been discussed in Part I. Thus, the detailed dynamic analysis of the whole mechanism and each part are presented here. The analyses are based on the parallel manipulators concept and the virtual work principle. Also an ADAMS rigid body dynamic model was developed to verify the results of the analytical model. In many simulated cases, the results matched.

  9. Analysis of a Swashplate Mechanism of the Hingeless Rotor Hub with the Flybar in a Model Helicopter, Part I: Kinematics

    Science.gov (United States)

    Sabaapour, Mohammad Reza; Zohoor, Hassan

    Swashplate mechanism is the steering control mechanism used in most helicopters. It is a complex multi-loop closed kinematic chain which controls the angles of attack of the main rotor blades. In most new model helicopters, this mechanism is also equipped with the bell-hiller stabilizer bar (flybar), to improve the stability. This paper aimed at the kinematic analysis of one of the latest architectures of the swashplate mechanism, used for hingeless rotor with the flybar. Hence, the position analysis of each module and whole mechanism, based on parallel manipulators concept with more details involved than other works, was presented here. The kinematic model was further developed to obtain Jacobian matrices, velocity and acceleration analysis in detail. Finally, a particular example was conducted and compared with an ADAMS rigid body dynamic model, to verify the analytical model. In many simulated cases, the results matched.

  10. Improved Helicopter Rotor Performance Prediction through Loose and Tight CFD/CSD Coupling

    Science.gov (United States)

    Ickes, Jacob C.

    Helicopters and other Vertical Take-Off or Landing (VTOL) vehicles exhibit an interesting combination of structural dynamic and aerodynamic phenomena which together drive the rotor performance. The combination of factors involved make simulating the rotor a challenging and multidisciplinary effort, and one which is still an active area of interest in the industry because of the money and time it could save during design. Modern tools allow the prediction of rotorcraft physics from first principles. Analysis of the rotor system with this level of accuracy provides the understanding necessary to improve its performance. There has historically been a divide between the comprehensive codes which perform aeroelastic rotor simulations using simplified aerodynamic models, and the very computationally intensive Navier-Stokes Computational Fluid Dynamics (CFD) solvers. As computer resources become more available, efforts have been made to replace the simplified aerodynamics of the comprehensive codes with the more accurate results from a CFD code. The objective of this work is to perform aeroelastic rotorcraft analysis using first-principles simulations for both fluids and structural predictions using tools available at the University of Toledo. Two separate codes are coupled together in both loose coupling (data exchange on a periodic interval) and tight coupling (data exchange each time step) schemes. To allow the coupling to be carried out in a reliable and efficient way, a Fluid-Structure Interaction code was developed which automatically performs primary functions of loose and tight coupling procedures. Flow phenomena such as transonics, dynamic stall, locally reversed flow on a blade, and Blade-Vortex Interaction (BVI) were simulated in this work. Results of the analysis show aerodynamic load improvement due to the inclusion of the CFD-based airloads in the structural dynamics analysis of the Computational Structural Dynamics (CSD) code. Improvements came in the form

  11. Vision based control of unmanned aerial vehicles with applications to an autonomous four-rotor helicopter, quadrotor

    Science.gov (United States)

    Altug, Erdinc

    Our work proposes a vision-based stabilization and output tracking control method for a model helicopter. This is a part of our effort to produce a rotorcraft based autonomous Unmanned Aerial Vehicle (UAV). Due to the desired maneuvering ability, a four-rotor helicopter has been chosen as the testbed. On previous research on flying vehicles, vision is usually used as a secondary sensor. Unlike previous research, our goal is to use visual feedback as the main sensor, which is not only responsible for detecting where the ground objects are but also for helicopter localization. A novel two-camera method has been introduced for estimating the full six degrees of freedom (DOF) pose of the helicopter. This two-camera system consists of a pan-tilt ground camera and an onboard camera. The pose estimation algorithm is compared through simulation to other methods, such as four-point, and stereo method and is shown to be less sensitive to feature detection errors. Helicopters are highly unstable flying vehicles; although this is good for agility, it makes the control harder. To build an autonomous helicopter, two methods of control are studied---one using a series of mode-based, feedback linearizing controllers and the other using a back-stepping control law. Various simulations with 2D and 3D models demonstrate the implementation of these controllers. We also show global convergence of the 3D quadrotor controller even with large calibration errors or presence of large errors on the image plane. Finally, we present initial flight experiments where the proposed pose estimation algorithm and non-linear control techniques have been implemented on a remote-controlled helicopter. The helicopter was restricted with a tether to vertical, yaw motions and limited x and y translations.

  12. Least square based sliding mode control for a quad-rotor helicopter and energy saving by chattering reduction

    Science.gov (United States)

    Sumantri, Bambang; Uchiyama, Naoki; Sano, Shigenori

    2016-01-01

    In this paper, a new control structure for a quad-rotor helicopter that employs the least squares method is introduced. This proposed algorithm solves the overdetermined problem of the control input for the translational motion of a quad-rotor helicopter. The algorithm allows all six degrees of freedom to be considered to calculate the control input. The sliding mode controller is applied to achieve robust tracking and stabilization. A saturation function is designed around a boundary layer to reduce the chattering phenomenon that is a common problem in sliding mode control. In order to improve the tracking performance, an integral sliding surface is designed. An energy saving effect because of chattering reduction is also evaluated. First, the dynamics of the quad-rotor helicopter is derived by the Newton-Euler formulation for a rigid body. Second, a constant plus proportional reaching law is introduced to increase the reaching rate of the sliding mode controller. Global stability of the proposed control strategy is guaranteed based on the Lyapunov's stability theory. Finally, the robustness and effectiveness of the proposed control system are demonstrated experimentally under wind gusts, and are compared with a regular sliding mode controller, a proportional-differential controller, and a proportional-integral-differential controller.

  13. Vibration reduction in helicopter rotors using an active control surface located on the blade

    Science.gov (United States)

    Millott, T. A.; Friedmann, P. P.

    1992-01-01

    A feasibility study of vibration reduction in a four-bladed helicopter rotor using individual blade control (IBC), which is implemented by an individually controlled aerodynamic surface located on each blade, is presented. For this exploratory study, a simple offset-hinged spring restrained model of the blade is used with fully coupled flap-lag-torsional dynamics for each blade. Deterministic controllers based on local and global system models are implemented to reduce 4/rev hub loads using both an actively controlled aerodynamic surface on each blade as well as conventional IBC, where the complete blade undergoes cyclic pitch change. The effectiveness of the two approaches for simultaneous reduction of the 4/rev hub shears and hub moments is compared. Conventional IBC requires considerably more power to achieve approximately the same level of vibration reduction as that obtained by implementing IBC using an active control surface located on the outboard segment of the blade. The effect of blade torsional flexibility on the vibration reduction effectiveness of the actively controlled surface was also considered and it was found that this parameter has a very substantial influence.

  14. Effects of repetition rate and impulsiveness of simulated helicopter rotor noise on annoyance

    Science.gov (United States)

    Powell, C. A.; Mccurdy, D. A.

    1982-01-01

    Annoyance judgements were obtained for computer generated stimuli simulative of helicopter impulsive rotor noise to investigate effects of repetition rate and impulsiveness. Each of the 82 different stimuli was judged at 3 sound pressure levels by 48 subjects. Impulse repetition rates covered a range from 10 Hz to 115 Hz; crest factors covered a range from 3.2 dB to 19.3 dB. Increases in annoyance with increases in repetition rate were found which were not predicted by common loudness or annoyance metrics and which were independent of noise level. The ability to predict effects of impulsiveness varied between the noise metrics and was found to be dependent on noise level. The ability to predict the effects of impulsiveness was not generally improved by any of several proposed impulsiveness corrections. Instead, the effects of impulsiveness were found to be systematically related to the frequency content of the stimuli. A modified frequency weighting was developed which offers improved annoyance prediction.

  15. Comprehensive aeroelastic analysis of helicopter rotor with trailing-edge flap for primary control and vibration control

    Science.gov (United States)

    Shen, Jinwei

    A comprehensive aeroelastic analytical model of helicopter rotors with trailing-edge flaps for primary and vibration controls has been developed. The derivation of system equations is based on Hamilton principles, and implemented with finite element method in space and time. The blade element consists of fifteen degrees of freedom representing blade flap, lag, torsional, and axial deformations. Three aerodynamic models of flapped airfoils were implemented in the present analysis, the unsteady Hariharan-Leishman model for trailing-edge flaps without aerodynamic balance, a quasi-steady Theodorsen theory for an aerodynamic balanced trailing-edge flap, and table lookup based on wind tunnel test data. The trailing-edge flap deflections may be modeled as a degree of freedom so that the actuator dynamics can be captured properly. The coupled trim procedures for swashplateless rotor are solved in either wind tunnel trim or free flight condition. A multicyclic controller is also implemented to calculate the flap control inputs for minimization of vibratory rotor hub loads. The coupled blade equations of motion are linearized by using small perturbations about a steady trimmed solution. The aeroelastic stability characteristics of trailing-edge flap rotors is then determined from an eigenanalysis of the homogeneous equations using Floquet method. The correlation studies of a typical bearingless rotor and an ultralight teetering rotor are respectively based on wind tunnel test data and simulations of another comprehensive analysis (CAMRAD II). Overall, good correlations are obtained. Parametric study identifies that the effect of actuator dynamics cannot be neglected, especially for a torsionally soft smart actuator system. Aeroelastic stability characteristics of a trailing-edge flap rotor system are shown to be sensitive to flap aerodynamic and mass balances. Key parameters of trailing-edge flap system for primary rotor control are identified as blade pitch index angle

  16. High order accurate and low dissipation method for unsteady compressible viscous flow computation on helicopter rotor in forward flight

    Science.gov (United States)

    Xu, Li; Weng, Peifen

    2014-02-01

    An improved fifth-order weighted essentially non-oscillatory (WENO-Z) scheme combined with the moving overset grid technique has been developed to compute unsteady compressible viscous flows on the helicopter rotor in forward flight. In order to enforce periodic rotation and pitching of the rotor and relative motion between rotor blades, the moving overset grid technique is extended, where a special judgement standard is presented near the odd surface of the blade grid during search donor cells by using the Inverse Map method. The WENO-Z scheme is adopted for reconstructing left and right state values with the Roe Riemann solver updating the inviscid fluxes and compared with the monotone upwind scheme for scalar conservation laws (MUSCL) and the classical WENO scheme. Since the WENO schemes require a six point stencil to build the fifth-order flux, the method of three layers of fringes for hole boundaries and artificial external boundaries is proposed to carry out flow information exchange between chimera grids. The time advance on the unsteady solution is performed by the full implicit dual time stepping method with Newton type LU-SGS subiteration, where the solutions of pseudo steady computation are as the initial fields of the unsteady flow computation. Numerical results on non-variable pitch rotor and periodic variable pitch rotor in forward flight reveal that the approach can effectively capture vortex wake with low dissipation and reach periodic solutions very soon.

  17. RESEARCH OF THE HIGH HARMONICS INDIVIDUAL BLADE CONTROL EFFECT ON VIBRATIONS CAUSED BY THE HELICOPTER MAIN ROTOR THRUST

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available The paper presents numerical results analysis of main rotor vibration due to helicopter main rotor thrust pulsation.The calculation method, the object of research and numerical research results with the aim to reduce the amplitude of the vibrations transmitted to the hub from the helicopters main rotor by the individual blade control in azimuth by the installation angle of blades cyclic changes are set out in the article. The individual blades control law for a five-blade main rotor based on the blade frequencies is made. It allows reducing the vibration from thrust. Research takes into account the main rotor including and excluding the blade flapping motion. The minimal vibrations regime is identified.Numerical study of variable loads caused by unsteady flow around the main rotor blades at high relative speeds of flight, which transmitted to the rotor hub, is made. The scheme of a thin lifting surface and the rotor vortex theory are used for simulation of the aerodynamic loads on blades. Non - uniform loads caused by the thrust, decomposed on the blade harmonic and its overtones. The largest values of deviation from the mean amplitude thrust are received. The analysis of variable loads with a traditional control system is made. Algorithms of higher harmonics individual blade control capable of reducing the thrust pulsation under the average value of thrust are developed.Numerical research shows that individual blade control of high harmonics reduces variable loads. The necessary change in the blade installation is about ± 0,2 degree that corresponds to the maximum displacement of the additional con- trol stick is about 1 mm.To receive the overall picture is necessary to consider all six components of forces and moments. Control law with own constants will obtained for each of them. It is supposed, that each of six individual blade control laws have an impact on other components. Thus, the problem reduces to the optimization issue. The

  18. Crack of a helicopter main rotor actuator attachment: failure analysis and lessons learned

    Directory of Open Access Journals (Sweden)

    L. Allegrucci

    2013-10-01

    Full Text Available A Light Utility Helicopter (LUH, in the course of a training flight, leaving the ground during the taxi to take off, went into an uncontrolled rolling to the right; consequently the helicopter gradually laid down on the right side. The impact with the runway destroyed the rotating blades up to the hubs rotor. The accident investigation focused on main rotor oscillatory plate servo actuators . These components, directly linked to the cloche movements, regulate main rotor blades plane tilt and pitch. Following the preliminary examination, only front servo actuator attachment was found to be broken in two parts. In detail, the present paper deals with the fracture analysis results. The servo actuator attachment material is a 2014 Aluminum alloy extrudate, undergone to T651 heat treatment. Fracture surfaces were examined by optical and electronic microscopy in order to determine the main morphological features and consequently to trace the origin of failure mechanism and causes. The accordance with the specification requirements about alloy composition was verified by quantitative elementary analysis through inductive coupled plasma spectroscopy (ICP; furthermore, semi-quantitative elementary analysis was locally verified by Energy dispersion spectroscopy X ray (EDS_RX. Finally, the hydrogen content of the material was evaluated by the total hydrogen analysis. Microstructural and technological alloy characteristics were verified as well by using metallographic microscopy and hardness testing of the material.Macroscopic fracture surfaces evidences were characterized by the lack of any significant plastic deformations and by the presence of symmetry compared to the servo actuator axis. Microscopic fracture features of both the investigated surfaces were not coherent to the hypothesis of an impact of the main rotor to the soil. Further achieved evidences, such as grain boundary fracture propagation, the presence of corrosion products, were all in

  19. NDT detection and quantification of induced defects on composite helicopter rotor blade and UAV wing sections

    Science.gov (United States)

    Findeis, Dirk; Gryzagoridis, Jasson; Musonda, Vincent

    2008-09-01

    Digital Shearography and Infrared Thermography (IRT) techniques were employed to test non-destructively samples from aircraft structures of composite material nature. Background information on the techniques is presented and it is noted that much of the inspection work reviewed in the literature has focused on qualitative evaluation of the defects rather than quantitative. There is however, need to quantify the defects if the threshold rejection criterion of whether the component inspected is fit for service has to be established. In this paper an attempt to quantify induced defects on a helicopter main rotor blade and Unmanned Aerospace Vehicle (UAV) composite material is presented. The fringe patterns exhibited by Digital Shearography were used to quantify the defects by relating the number of fringes created to the depth of the defect or flaw. Qualitative evaluation of defects with IRT was achieved through a hot spot temperature indication above the flaw on the surface of the material. The results of the work indicate that the Shearographic technique proved to be more sensitive than the IRT technique. It should be mentioned that there is "no set standard procedure" tailored for testing of composites. Each composite material tested is more likely to respond differently to defect detection and this depends generally on the component geometry and a suitable selection of the loading system to suit a particular test. The experimental procedure that is reported in this paper can be used as a basis for designing a testing or calibration procedure for defects detection on any particular composite material component or structure.

  20. A formulation of rotor-airframe coupling for design analysis of vibrations of helicopter airframes

    Science.gov (United States)

    Kvaternik, R. G.; Walton, W. C., Jr.

    1982-01-01

    A linear formulation of rotor airframe coupling intended for vibration analysis in airframe structural design is presented. The airframe is represented by a finite element analysis model; the rotor is represented by a general set of linear differential equations with periodic coefficients; and the connections between the rotor and airframe are specified through general linear equations of constraint. Coupling equations are applied to the rotor and airframe equations to produce one set of linear differential equations governing vibrations of the combined rotor airframe system. These equations are solved by the harmonic balance method for the system steady state vibrations. A feature of the solution process is the representation of the airframe in terms of forced responses calculated at the rotor harmonics of interest. A method based on matrix partitioning is worked out for quick recalculations of vibrations in design studies when only relatively few airframe members are varied. All relations are presented in forms suitable for direct computer implementation.

  1. Helicopter Rotor Load Prediction Using a Geometrically Exact Beam with Multicomponent Model

    DEFF Research Database (Denmark)

    Lee, Hyun-Ku; Viswamurthy, S.R.; Park, Sang Chul

    2010-01-01

    -blade/control-system aeroelastic analysis. The rotor blade analysis was in good agreement and validated by comparing with DYMORE. Numerical results were obtained for a four-bladed, small-scale, articulated rotor rotating in vacuum and in a wind tunnel to simulate forward-flight conditions and its aerodynamic effects. The complete...... rotor-blade/control-system model was loosely coupled with various inflow and wake models in order to simulate both hover and forward-flight conditions. The resulting rotor blade response and pitch link loads are in good agreement with those predicted byCAMRADII. The present analysis features both model...

  2. A New Optimal Control Algorithm for Quad-rotor Helicopter with State Constraints via Sliding-mode Control

    Directory of Open Access Journals (Sweden)

    Zhao Jing

    2015-01-01

    Full Text Available This paper proposes a strategy of a new optimal sliding-mode control for flight control system with state constraints so that the system guarantees the optimal performance index. Besides, the strategy ensures strong robustness to the internal parametric uncertainty and the external disturbances. In order to have fast transient response speed as well as good tracking accuracy, the integral of the time multiplied by the absolute displacement tracking error is introduced as the performance index. By analyzing the state constraints which are specifically the velocity tracking error constraint and the acceleration tracking error constraint, and the performance index, the parameters of sliding-mode surface and control law are obtained. Finally, the authors conduct the semi physical simulation on Qball-X4 quad-rotor helicopter, showing the effectiveness of the proposed strategy.

  3. A 3D imaging system for the non-intrusive in-flight measurement of the deformation of an aircraft propeller and a helicopter rotor

    Science.gov (United States)

    Stasicki, Bolesław; Boden, Fritz; Ludwikowski, Krzysztof

    2017-02-01

    The non-intrusive in-flight deformation measurement and the resulting local pitch of an aircraft propeller or helicopter rotor blade is a demanding task. The idea of an imaging system integrated and rotating with the air-craft propeller has already been presented at the 30th International Congress on High-Speed Imaging and Photonics (ICHSIP30) in 2012. Since then this system has been designed, constructed and tested in the laboratory as well as in-flight on the Cobra VUT100 of Evektor Aerotechnik, Kunovice (CZ). The major aim of the EU FP7 project AIM2 ("Advanced In-flight Measurement techniques 2" - contract No. 266107) was to ascertain the feasibility of this technique under extreme conditions - vibration and large centrifugal forces - to real flight testing. Based on the gained experience a new rotating system for the application on helicopter rotors has recently been constructed and tested on the whirl tower of Airbus Helicopters, Donauwoerth (D). In this paper the principle of the applied Image Pattern Correlation Technique (IPCT), a specialized type of Digital Image Correlation (DIC), is outlined and the construction of both rotating 3D image acquisition systems dedicated to the in-flight deformation measurement of the aircraft propeller and helicopter rotor are described. Furthermore, the results of the ground and in-flight tests of these systems will be shown and discussed. The obtained results will be helpful for manufacturers in the design of their future aircrafts.

  4. Vibration reduction in helicopter rotors using an actively controlled partial span trailing edge flap located on the blade

    Science.gov (United States)

    Millott, T. A.; Friedmann, P. P.

    1994-06-01

    This report describes an analytical study of vibration reduction in a four-bladed helicopter rotor using an actively controlled, partial span, trailing edge flap located on the blade. The vibration reduction produced by the actively controlled flap (ACF) is compared with that obtained using individual blade control (IBC), in which the entire blade is oscillated in pitch. For both cases a deterministic feedback controller is implemented to reduce the 4/rev hub loads. For all cases considered, the ACF produced vibration reduction comparable with that obtained using IBC, but consumed only 10-30% of the power required to implement IBC. A careful parametric study is conducted to determine the influence of blade torsional stiffness, spanwise location of the control flap, and hinge moment correction on the vibration reduction characteristics of the ACF. The results clearly demonstrate the feasibility of this new approach to vibration reduction. It should be emphasized than the ACF, used together with a conventional swashplate, is completely decoupled from the primary flight control system and thus it has no influence on the airworthiness of the helicopter. This attribute is potentially a significant advantage when compared to IBC.

  5. Design of a Symmetrical Quad-rotor Biplane Tail-Sitter Aircraft without Control Surfaces and Experimental Verification

    Directory of Open Access Journals (Sweden)

    Wang Hongyu

    2018-01-01

    Full Text Available This paper presents the design of a symmetrical quad-rotor biplane tail-sitter VTOL UAV (Vertical Take-off and Landing Unmanned Aerial Vehicle which is composed of four rotors and two symmetrically mounted fixed wings. This aircraft achieves high accuracy in the attitude control and smooth flight mode transition with four rotors rather than the conventional VTOL UAVs using control surfaces. The proposal of angled rotor mounting is adopted to address the issue of insufficient yaw control authority. The layout of symmetrically mounted fixed wings makes the aircraft have capability of rapid bidirectional flight mode transition to improve maneuverability. To validate the performance of the aircraft, simulation and flight experiments are both implemented. These results show that the aircraft has a rapid yaw response under condition of the stable attitude control. In comparative experiment, it is shown that the aircraft is more flexible than other similar configuration of aircrafts. This symmetrical quad-rotor biplane tail-sitter VTOL UAV will have a wide range of potential applications in the military and civilian areas due to its superior performance..

  6. Higher harmonic control analysis for vibration reduction of helicopter rotor systems

    Science.gov (United States)

    Nguyen, Khanh Q.

    1994-01-01

    An advanced higher harmonic control (HHC) analysis has been developed and applied to investigate its effect on vibration reduction levels, blade and control system fatigue loads, rotor performance, and power requirements of servo-actuators. The analysis is based on a finite element method in space and time. A nonlinear time domain unsteady aerodynamic model, based on the indicial response formulation, is used to calculate the airloads. The rotor induced inflow is computed using a free wake model. The vehicle trim controls and blade steady responses are solved as one coupled solution using a modified Newton method. A linear frequency-domain quasi-steady transfer matrix is used to relate the harmonics of the vibratory hub loads to the harmonics of the HHC inputs. Optimal HHC is calculated from the minimization of the vibratory hub loads expressed in term of a quadratic performance index. Predicted vibratory hub shears are correlated with wind tunnel data. The fixed-gain HHC controller suppresses completely the vibratory hub shears for most of steady or quasi-steady flight conditions. HHC actuator amplitudes and power increase significantly at high forward speeds (above 100 knots). Due to the applied HHC, the blade torsional stresses and control loads are increased substantially. For flight conditions where the blades are stalled considerably, the HHC input-output model is quite nonlinear. For such cases, the adaptive-gain controller is effective in suppressing vibratory hub loads, even though HHC may actually increase stall areas on the rotor disk. The fixed-gain controller performs poorly for such flight conditions. Comparison study of different rotor systems indicates that a soft-inplane hingeless rotor requires less actuator power at high speeds (above 130 knots) than an articulated rotor, and a stiff-inplane hingeless rotor generally requires more actuator power than an articulated or a soft-inplane hingeless rotor. Parametric studies for a hingeless rotor

  7. Hummingbird wing efficacy depends on aspect ratio and compares with helicopter rotors

    NARCIS (Netherlands)

    Kruyt, J.W.; Quicazan Rubio, E.M.; Heijst, van G.J.F.; Altshuler, D.L.; Lentink, D.

    2014-01-01

    Hummingbirds are the only birds that can sustain hovering. This unique flight behaviour comes, however, at high energetic cost. Based on helicopter and aeroplane design theory, we expect that hummingbird wing aspect ratio (AR), which ranges from about 3.0 to 4.5, determines aerodynamic efficacy.

  8. Development of helicopter attitude axes controlled hover flight without pilot assistance and vehicle crashes

    Science.gov (United States)

    Simon, Miguel

    In this work, we show how to computerize a helicopter to fly attitude axes controlled hover flight without the assistance of a pilot and without ever crashing. We start by developing a helicopter research test bed system including all hardware, software, and means for testing and training the helicopter to fly by computer. We select a Remote Controlled helicopter with a 5 ft. diameter rotor and 2.2 hp engine. We equip the helicopter with a payload of sensors, computers, navigation and telemetry equipment, and batteries. We develop a differential GPS system with cm accuracy and a ground computerized navigation system for six degrees of freedom (6-DoF) free flight while tracking navigation commands. We design feedback control loops with yet-to-be-determined gains for the five control "knobs" available to a flying radio-controlled (RC) miniature helicopter: engine throttle, main rotor collective pitch, longitudinal cyclic pitch, lateral cyclic pitch, and tail rotor collective pitch. We develop helicopter flight equations using fundamental dynamics, helicopter momentum theory and blade element theory. The helicopter flight equations include helicopter rotor equations of motions, helicopter rotor forces and moments, helicopter trim equations, helicopter stability derivatives, and a coupled fuselage-rotor helicopter 6-DoF model. The helicopter simulation also includes helicopter engine control equations, a helicopter aerodynamic model, and finally helicopter stability and control equations. The derivation of a set of non-linear equations of motion for the main rotor is a contribution of this thesis work. We design and build two special test stands for training and testing the helicopter to fly attitude axes controlled hover flight, starting with one axis at a time and progressing to multiple axes. The first test stand is built for teaching and testing controlled flight of elevation and yaw (i.e., directional control). The second test stand is built for teaching and

  9. High-speed helicopter rotor noise - Shock waves as a potent source of sound

    Science.gov (United States)

    Farassat, F.; Lee, Yung-Jang; Tadghighi, H.; Holz, R.

    1991-01-01

    In this paper we discuss the problem of high speed rotor noise prediction. In particular, we propose that from the point of view of the acoustic analogy, shocks around rotating blades are sources of sound. We show that, although for a wing at uniform steady rectilinear motion with shocks the volume quadrupole and shock sources cancel in the far field to the order of 1/r, this cannot happen for rotating blades. In this case, some cancellation between volume quadrupoles and shock sources occurs, yet the remaining shock noise contribution is still potent. A formula for shock noise prediction is presented based on mapping the deformable shock surface to a time independent region. The resulting equation is similar to Formulation 1A of Langley. Shock noise prediction for a hovering model rotor for which experimental noise data exist is presented. The comparison of measured and predicted acoustic data shows good agreement.

  10. Stabilization and control of quad-rotor helicopter using a smartphone device

    Science.gov (United States)

    Desai, Alok; Lee, Dah-Jye; Moore, Jason; Chang, Yung-Ping

    2013-01-01

    In recent years, autonomous, micro-unmanned aerial vehicles (micro-UAVs), or more specifically hovering micro- UAVs, have proven suitable for many promising applications such as unknown environment exploration and search and rescue operations. The early versions of UAVs had no on-board control capabilities, and were difficult for manual control from a ground station. Many UAVs now are equipped with on-board control systems that reduce the amount of control required from the ground-station operator. However, the limitations on payload, power consumption and control without human interference remain the biggest challenges. This paper proposes to use a smartphone as the sole computational device to stabilize and control a quad-rotor. The goal is to use the readily available sensors in a smartphone such as the GPS, the accelerometer, the rate-gyros, and the camera to support vision-related tasks such as flight stabilization, estimation of the height above ground, target tracking, obstacle detection, and surveillance. We use a quad-rotor platform that has been built in the Robotic Vision Lab at Brigham Young University for our development and experiments. An Android smartphone is connected through the USB port to an external hardware that has a microprocessor and circuitries to generate pulse-width modulation signals to control the brushless servomotors on the quad-rotor. The high-resolution camera on the smartphone is used to detect and track features to maintain a desired altitude level. The vision algorithms implemented include template matching, Harris feature detector, RANSAC similarity-constrained homography, and color segmentation. Other sensors are used to control yaw, pitch, and roll of the quad-rotor. This smartphone-based system is able to stabilize and control micro-UAVs and is ideal for micro-UAVs that have size, weight, and power limitations.

  11. Reduced In-Plane, Low Frequency Helicopter Noise of an Active Flap Rotor

    Science.gov (United States)

    Sim, Ben W.; Janakiram, Ram D.; Barbely, Natasha L.; Solis, Eduardo

    2009-01-01

    Results from a recent joint DARPA/Boeing/NASA/Army wind tunnel test demonstrated the ability to reduce in-plane, low frequency noise of the full-scale Boeing-SMART rotor using active flaps. Test data reported in this paper illustrated that acoustic energy in the first six blade-passing harmonics could be reduced by up to 6 decibels at a moderate airspeed, level flight condition corresponding to advance ratio of 0.30. Reduced noise levels were attributed to selective active flap schedules that modified in-plane blade airloads on the advancing side of the rotor, in a manner, which generated counteracting acoustic pulses that partially offset the negative pressure peaks associated with in-plane, steady thickness noise. These favorable reduced-noise operating states are a strong function of the active flap actuation amplitude, frequency and phase. The associated noise reductions resulted in reduced aural detection distance by up to 18%, but incurred significant vibratory load penalties due to increased hub shear forces. Small reductions in rotor lift-to-drag ratios, of no more than 3%, were also measured

  12. Synchronous Averaging of Helicopter Tail Rotor Gearbox Vibration: Phase Reference Considerations.

    Science.gov (United States)

    1998-10-01

    sl and s2 computed via fft % sl = signal 1 % s2 = signal 2 (must be the same length as sl) fl = fft(sl); f2 = fft(s2); xspec = fl .* conj(f2); z...ifft( xspec ); PSYNC1.M function xcmax = psyncl(phi,sl,s2) % xcmax = psyncl(phi) % xcmax = max cross correlation of signals sl and s2 % phi = number of

  13. Analytical design of a high performance stability and control augmentation system for a hingeless rotor helicopter

    Science.gov (United States)

    Miyajima, K.

    1978-01-01

    A stability and control augmentation system (SCAS) was designed based on a set of comprehensive performance criteria. Linear optimal control theory was applied to determine appropriate feedback gains for the stability augmentation system (SAS). The helicopter was represented by six-degree-of-freedom rigid body equations of motion and constant factors were used as weightings for state and control variables. The ratio of these factors was employed as a parameter for SAS analysis and values of the feedback gains were selected on this basis to satisfy three of the performance criteria for full and partial state feedback systems. A least squares design method was then applied to determine control augmentation system (CAS) cross feed gains to satisfy the remaining seven performance criteria. The SCAS gains were then evaluated by nine degree-of-freedom equations which include flapping motion and conclusions drawn concerning the necessity of including the pitch/regressing and roll/regressing modes in SCAS analyses.

  14. A state-space free-vortex hybrid wake model for helicopter rotors

    Science.gov (United States)

    Wasileski, Bryan J.

    This paper presents the development of a new hybrid wake model merging two distinctly different modeling approaches into a single, more comprehensive solution. The objective of the work was to leverage the strengths of each individual wake model creating a more flexible and extensible solution that could be used across the entire flight envelope of a helicopter. The results of the work indicate that the two wakes models can be successfully merged. The results also show that hybrid wake provides a mechanism by which finite-state wake imparts a level of stability on the free wake solution allowing the free wake to provide consistent, repeatable results from hover through high speed forward flight. While the new hybrid wake includes the geometric distortion needed for predicting the off-axis control response, the new model, as configured in this work, shows no sign of improvement in this area.

  15. State Estimation of Main Rotor Flap and Lead-Lag Using Accelerometers and Laser Transducers on the RASCAL UH-60 Helicopter

    Science.gov (United States)

    Fletcher, Jay W.; Chen, Robert T. N.; Strasilla, Eric; Aiken, Edwin W. (Technical Monitor)

    1995-01-01

    Modern rotorcraft flight control system designs which promise to yield high vehicle response bandwidth and good gust rejection can benefit from the use of rotor-state feedbacks. The measurement of main rotor blade motions is also desirable to validate and improve rotorcraft simulation models, to identify high-order linear flight dynamics models, to provide rotor system health monitoring; during flight test, and to provide for correlation with acoustic measurements from wind tunnel and flight tests. However, few attempts have been made to instrument a flight vehicle in this manner, and no previous system has had the robustness and accuracy required for these diverse applications. A rotor blade motion measurement and estimation system has been developed by NASA and the U.S. Army for use on the Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) helicopter. RASCAL is a UH-60 Blackhawk which is being modified at Ames Research Center in a phased development program for use in flight dynamics and controls, navigation, airspace management, and rotorcraft human factors research. The aircraft will feature a full-authority, digital, fly-by-wire research flight control system; a coupled ring laser gyro, differential GPS based navigation system; a stereoscopic color wide field of view helmet, mounted display; programmable panel mounted displays; and advanced navigation sensors. The rotor blade motion system is currently installed for data acquisition only, but will be integrated with the research flight control system when it is installed later this year.

  16. Determination of the structural damping coefficients of six full-scale helicopter rotor blades of different materials and methods of construction

    Science.gov (United States)

    Gibson, Frederick W

    1956-01-01

    Results of an experimental investigation of the structural damping of six full-scale helicopter rotor blades, made to determine the variation of structural damping with materials and methods of construction, are presented. The damping of the blades was determined for the first three flapwise bending modes, first chordwise bending mode, and first torsion mode. The contribution of structural damping to the total damping of the blades is discussed for several aerodynamic conditions in order to point out situations where structural damping is significant.

  17. Helicopter Aeromechanics

    Science.gov (United States)

    1985-04-01

    34, NASA TN D-1548, October 1982. 1975. 96. SHEEHY T.W., "A General Review of Helicopter 113. GALLOT J., "Am6lioration du bilan propulsif Rotor Hub Drag...bearingless rotor (CBR). The rotor used a flat flexbeam of carbon -epoxy, and a torque rod behind the flexbeam. A cantilever torque rod configuration...and low stress) with a midchord torque rod. A damper, consisting of an elastomeric layer bonded to the flex- beam and covered by a stiff carbon fiber

  18. Flexible performance design for the H∞ loop-shaping control based on the linear matrix inequality approach: Application to the coaxial rotor helicopter

    Directory of Open Access Journals (Sweden)

    Zhiyan Dong

    2016-07-01

    Full Text Available This article introduces a new H ∞ loop-shaping control to decrease the complexity of the appropriate selection of the required performance for a coaxial rotor helicopter with unpredicted or unknown unstructured uncertainties. Uncertainty models are normally assumed that some knowledge of type is known. And to model a particular uncertainty as a separate model is necessary in the high-performance design of specified applications. But to model each particular uncertainty will increase the complexity of performance design for the extremely complex plant. H ∞ loop-shaping control provides a competitive and flexible choice to simultaneously represent a family of unpredicted and unconsidered unstructured uncertainty bounded by H ∞ norm. Many researches have been conducted to consider some aspects of this method, for example, the nominal stability, robustness to uncertainty, and implementation issues. However, to decrease the complexity of the appropriate selection of the required performance was not considered seriously. Therefore, a sufficient set of stable condition is derived using linear matrix inequality approach to provide the flexible performance design considering unpredicted and unknown unstructured uncertainties. Furthermore, the proposed method is applied to stabilize the attitude subsystem of a reconstructed coaxial rotor helicopter. Simulations indicate the effectiveness of the proposed method in the step response.

  19. Variable Speed Rotor System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Variable speed rotors will give helicopters several advantages: higher top speed, greater fuel efficiency, momentary emergency over-power, resonance detuning...

  20. Small Business Innovations (Helicopters)

    Science.gov (United States)

    1992-01-01

    The amount of engine power required for a helicopter to hover is an important, but difficult, consideration in helicopter design. The EHPIC program model produces converged, freely distorted wake geometries that generate accurate analysis of wake-induced downwash, allowing good predictions of rotor thrust and power requirements. Continuum Dynamics, Inc., the Small Business Innovation Research (SBIR) company that developed EHPIC, also produces RotorCRAFT, a program for analysis of aerodynamic loading of helicopter blades in forward flight. Both helicopter codes have been licensed to commercial manufacturers.

  1. System and Method for Finite Element Simulation of Helicopter Turbulence

    Science.gov (United States)

    McFarland, R. E. (Inventor); Dulsenberg, Ken (Inventor)

    1999-01-01

    The present invention provides a turbulence model that has been developed for blade-element helicopter simulation. This model uses an innovative temporal and geometrical distribution algorithm that preserves the statistical characteristics of the turbulence spectra over the rotor disc, while providing velocity components in real time to each of five blade-element stations along each of four blades. for a total of twenty blade-element stations. The simulator system includes a software implementation of flight dynamics that adheres to the guidelines for turbulence set forth in military specifications. One of the features of the present simulator system is that it applies simulated turbulence to the rotor blades of the helicopter, rather than to its center of gravity. The simulator system accurately models the rotor penetration into a gust field. It includes time correlation between the front and rear of the main rotor, as well as between the side forces felt at the center of gravity and at the tail rotor. It also includes features for added realism, such as patchy turbulence and vertical gusts in to which the rotor disc penetrates. These features are realized by a unique real time implementation of the turbulence filters. The new simulator system uses two arrays one on either side of the main rotor to record the turbulence field and to produce time-correlation from the front to the rear of the rotor disc. The use of Gaussian Interpolation between the two arrays maintains the statistical properties of the turbulence across the rotor disc. The present simulator system and method may be used in future and existing real-time helicopter simulations with minimal increase in computational workload.

  2. A comparison with theory of peak to peak sound level for a model helicopter rotor generating blade slap at low tip speeds

    Science.gov (United States)

    Fontana, R. R.; Hubbard, J. E., Jr.

    1983-01-01

    Mini-tuft and smoke flow visualization techniques have been developed for the investigation of model helicopter rotor blade vortex interaction noise at low tip speeds. These techniques allow the parameters required for calculation of the blade vortex interaction noise using the Widnall/Wolf model to be determined. The measured acoustics are compared with the predicted acoustics for each test condition. Under the conditions tested it is determined that the dominating acoustic pulse results from the interaction of the blade with a vortex 1-1/4 revolutions old at an interaction angle of less than 8 deg. The Widnall/Wolf model predicts the peak sound pressure level within 3 dB for blade vortex separation distances greater than 1 semichord, but it generally over predicts the peak S.P.L. by over 10 dB for blade vortex separation distances of less than 1/4 semichord.

  3. Acoustic Source and Data Acquisition System for a Helicopter Rotor Blade-Vortex Interaction (BVI) Noise Reduction Experiment

    National Research Council Canada - National Science Library

    Roth, Brian

    1996-01-01

    .... Potentially much can be learned regarding the prospect for success of a candidate rotor blade design at greatly reduced time and money by performing acoustic scattering measurements in an anechoic chamber...

  4. Prediction of Rotor Wake Induced Flow Along the Rocket Trajectories of an Army AH-1G Helicopter

    Science.gov (United States)

    1975-03-01

    the corresponding induced velocity cam- ponents. However, the problem arises that the rotor positions arn not known due to the fact that the firing time...R02-1 02-7 . POITO ALON 400 006 20 Czz0. I2.0 0 -A -1 20 - 2 2 3 4 6 60 1 9 1 1 12 fl 4? ROTOR POSITION1 4I $ ADN 0-- 15 30 45 60) 75 so 106 120 135 󈧢

  5. Aeroelastic analysis for helicopter rotors with blade appended pendulum vibration absorbers. Mathematical derivations and program user's manual

    Science.gov (United States)

    Bielawa, R. L.

    1982-01-01

    Mathematical development is presented for the expanded capabilities of the United Technologies Research Center (UTRC) G400 Rotor Aeroelastic Analysis. This expanded analysis, G400PA, simulates the dynamics of teetered rotors, blade pendulum vibration absorbers and the higher harmonic excitations resulting from prescribed vibratory hub motions and higher harmonic blade pitch control. Formulations are also presented for calculating the rotor impedance matrix appropriate to these higher harmonic blade excitations. This impedance matrix and the associated vibratory hub loads are intended as the rotor blade characteristics elements for use in the Simplified Coupled Rotor/Fuselage Vibration Analysis (SIMVIB). Sections are included presenting updates to the development of the original G400 theory, and material appropriate to the user of the G400PA computer program. This material includes: (1) a general descriptionof the tructuring of the G400PA FORTRAN coding, (2) a detaild description of the required input data and other useful information for successfully running the program, and (3) a detailed description of the output results.

  6. Selected Problems Of Transmission Wear Of The Mi-24 Helicopter

    Directory of Open Access Journals (Sweden)

    Gębura Andrzej

    2015-12-01

    Full Text Available The hypothesis of mutual, destructive impact of the worn upper bearing of the WR-24 transmission on the Mi-24 helicopter's gearbox was stated. The Mi-24 is the only helicopter operated in Poland, in which the gearbox is mounted outside the main transmission – in the centre of the transmission shaft, between the main gearbox and the tail rotor. Damage to the gears in the gearbox of power generators is equivalent to termination of the tail rotor's drive. Such a termination immediately causes rotation of the body in the direction opposite to the direction of rotation of the main rotor. It is associated with the loss of lift and steering. It may lead to a disaster. Such an incident occurred in January 2011 in Afghanistan – both authors participated in its investigation. The authors, taking into account very good, almost legendary combat properties of the Mi-24, and their research of the specifics of wear and tear of the transmission elements, they think that, first, funds for development and implementation of the drive unit monitoring system should be made available specially for this helicopter. For this purpose, the authors propose to use the FAM-C method. It is characterised with significant ergonomics. Thank to this, multiple kinematic pairs can be observed simultaneously, and, therefore, the relationships between them as well.

  7. Wind Tunnel Testing of a 120th Scale Large Civil Tilt-Rotor Model in Airplane and Helicopter Modes

    Science.gov (United States)

    Theodore, Colin R.; Willink, Gina C.; Russell, Carl R.; Amy, Alexander R.; Pete, Ashley E.

    2014-01-01

    In April 2012 and October 2013, NASA and the U.S. Army jointly conducted a wind tunnel test program examining two notional large tilt rotor designs: NASA's Large Civil Tilt Rotor and the Army's High Efficiency Tilt Rotor. The approximately 6%-scale airframe models (unpowered) were tested without rotors in the U.S. Army 7- by 10-foot wind tunnel at NASA Ames Research Center. Measurements of all six forces and moments acting on the airframe were taken using the wind tunnel scale system. In addition to force and moment measurements, flow visualization using tufts, infrared thermography and oil flow were used to identify flow trajectories, boundary layer transition and areas of flow separation. The purpose of this test was to collect data for the validation of computational fluid dynamics tools, for the development of flight dynamics simulation models, and to validate performance predictions made during conceptual design. This paper focuses on the results for the Large Civil Tilt Rotor model in an airplane mode configuration up to 200 knots of wind tunnel speed. Results are presented with the full airframe model with various wing tip and nacelle configurations, and for a wing-only case also with various wing tip and nacelle configurations. Key results show that the addition of a wing extension outboard of the nacelles produces a significant increase in the lift-to-drag ratio, and interestingly decreases the drag compared to the case where the wing extension is not present. The drag decrease is likely due to complex aerodynamic interactions between the nacelle and wing extension that results in a significant drag benefit.

  8. Operational Helicopter Aviation Medicine

    Science.gov (United States)

    1978-12-01

    and tail fuselages are a danger and not neces- sary. They contribute to parasitic power so he puts coax rotors and eliminates tail rotor losses. He has...6vacuations airiennes pour les trois derniers mois de 1965 (500 000 honues estant engages au Vietnam). L’avantage de ce systbwe, sans parlor du...of two occupants. One occurred when an OH-58 pilot was severely lacerated in the thigh by the main rotor blade. The leg became infected from

  9. Hover and Wind-Tunnel Testing of Shrouded Rotors for Improved Micro Air Vehicle Design

    Science.gov (United States)

    2008-01-01

    in-wing application: the shrouded tail-rotor or ‘fan- in-fin’ on helicopters (Figs. 1.6k–l, p. 14). Originally developed by Aérospatiale in France ...MBB) of Germany to form Eurocopter , continued to develop the fenestron [29, 30, 33, 93], and incorporated it in several of its helicopter models...spectrum,” which reduces the per- ceived annoyance, and had been previously used with success in radiator fan designs and by Eurocopter in the design of

  10. Nonlinear State Estimation and Modeling of a Helicopter UAV

    Science.gov (United States)

    Barczyk, Martin

    Experimentally-validated nonlinear flight control of a helicopter UAV has two necessary conditions: an estimate of the vehicle’s states from noisy multirate output measurements, and a nonlinear dynamics model with minimum complexity, physically controllable inputs and experimentally identified parameter values. This thesis addresses both these objectives for the Applied Nonlinear Controls Lab (ANCL)'s helicopter UAV project. A magnetometer-plus-GPS aided Inertial Navigation System (INS) for outdoor flight as well as an Attitude and Heading Reference System (AHRS) for indoor testing are designed, implemented and experimentally validated employing an Extended Kalman Filter (EKF), using a novel calibration technique for the magnetometer aiding sensor added to remove the limitations of an earlier GPS-only aiding design. Next the recently-developed nonlinear observer design methodology of invariant observers is adapted to the aided INS and AHRS examples, employing a rotation matrix representation for the state manifold to obtain designs amenable to global stability analysis, obtaining a direct nonlinear design for gains of the AHRS observer, modifying the previously-proposed Invariant EKF systematic method for computing gains, and culminating in simulation and experimental validation of the observers. Lastly a nonlinear control-oriented model of the helicopter UAV is derived from first principles, using a rigid-body dynamics formulation augmented with models of the on-board subsystems: main rotor forces and blade flapping dynamics, the Bell-Hiller system and flybar flapping dynamics, tail rotor forces, tail gyro unit, engine and rotor speed, servo operation, fuselage drag, and tail stabilizer forces. The parameter values in the resulting models are identified experimentally. Using these the model is further simplified to be tractable for model-based control design.

  11. Control Law Design for Twin Rotor MIMO System with Nonlinear Control Strategy

    Directory of Open Access Journals (Sweden)

    M. Ilyas

    2016-01-01

    Full Text Available Modeling of complex air vehicles is a challenging task due to high nonlinear behavior and significant coupling effect between rotors. Twin rotor multi-input multioutput system (TRMS is a laboratory setup designed for control experiments, which resembles a helicopter with unstable, nonlinear, and coupled dynamics. This paper focuses on the design and analysis of sliding mode control (SMC and backstepping controller for pitch and yaw angle control of main and tail rotor of the TRMS under parametric uncertainty. The proposed control strategy with SMC and backstepping achieves all mentioned limitations of TRMS. Result analysis of SMC and backstepping control schemes elucidates that backstepping provides efficient behavior with the parametric uncertainty for twin rotor system. Chattering and oscillating behaviors of SMC are removed with the backstepping control scheme considering the pitch and yaw angle for TRMS.

  12. Modeling helicopter blade dynamics using a modified Myklestad-Prohl transfer matrix method

    OpenAIRE

    Cuesta, Juan D.

    1994-01-01

    Approved for public release, distribution unlimited Rotor blade vibratory stresses are of utmost importance in helicopter design. A modified Myklestad-Prohl method for rotating beams has been coded to assist in preliminary helicopter rotor blade design. The rotor blade dynamics program is part of the Joint Army/Navy Rotorcraft Analysis and Design (JANRAD) program which was developed to aid in the preliminary design and analysis of helicopter rotor performance, stability and control, and ro...

  13. Some Effects of Varying the Damping in Pitch and Roll on the Flying Qualities of a Small Single-Rotor Helicopter

    National Research Council Canada - National Science Library

    Reeder, John

    1952-01-01

    ... to nearly three times that amount. Longitudinal stability and control characteristics which were unsatisfactory with the device inoperative were improved by increasing the damping of the helicopter and were judged as satisfactory...

  14. Speed benefits of tilt-rotor designs for LHX

    Science.gov (United States)

    Mcdaniel, R. L.; Adams, J. V.; Balberde, A.; Dereska, S. P.; Gearin, C. J.; Shaw, D. E.

    1983-01-01

    The merits of an advanced helicopter and a tilt rotor aircraft for light utility, scout, and attack roles in combat missions envisioned for the year 2000 and beyond were compared. It is demonstrated that speed has increasing value for 11 different mission classes broadly encompassing the intended LHX roles. Helicopter speeds beyond 250 knots are judged to have lower military worth. Since the tilt rotor concept offers a different cost speed relationship than that of helicopters, assessment of a tilt rotor LHX variant was warranted. The technical parameters of an advanced tilt rotor are stablished. Parameters of representative missions are identified, computed relative value of the tilt rotor LHX are compared to the baseline helicopter, a first-order life cycle estimate for the tilt rotor LHX is established, military worth of the alternative design is computed and the results are evaluated. It is suggested that the tilt rotor is the solution with the greatest capability for meeting the uncertainties of future needs.

  15. Helicopter location and tracking using seismometer recordings

    Science.gov (United States)

    Eibl, Eva P. S.; Lokmer, Ivan; Bean, Christopher J.; Akerlie, Eggert

    2017-05-01

    We use frequency domain methods usually applied to volcanic tremor to analyse ground based seismic recordings of a helicopter. We preclude misinterpretations of tremor sources and show alternative applications of our seismological methods. On a volcano, the seismic source can consist of repeating, closely spaced, small earthquakes. Interestingly, similar signals are generated by helicopters due to repeating pressure pulses from the rotor blades. In both cases the seismic signals are continuous and referred to as tremor. As frequency gliding is in this case merely caused by the Doppler effect, not a change in the source, we can use its shape to deduce properties of the helicopter and its flight path. We show in this analysis that the number of rotor blades, rotor revolutions per minute, helicopter speed, flight direction, altitude and location can be deduced from seismometer recordings. Access to GPS determined flight path data from the helicopter offers us a robust way to test our location method.

  16. Helicopter controllability

    OpenAIRE

    Carico, Dean

    1989-01-01

    Approved for public release; distribution is unlimited The concept of helicopter controllability is explained. A background study reviews helicopter development in the U.S. General helicopter configurations, linearized equations of motion, stability, and piloting requirements are discussed. Helicopter flight controls, handling qualities, and associated specification are reviewed. Analytical, simulation and flight test methods for evaluating helicopter automatic flight control systems ar...

  17. Performance and Vibratory Loads Data From a Wind-Tunnel Test of a Model Helicopter Main-Rotor Blade With a Paddle-Type Tip

    Science.gov (United States)

    Yeager, William T., Jr.; Noonan, Kevin W.; Singleton, Jeffrey D.; Wilbur, Matthew L.; Mirick, Paul H.

    1997-01-01

    An investigation was conducted in the Langley Transonic Dynamics Tunnel to obtain data to permit evaluation of paddle-type tip technology for possible use in future U.S. advanced rotor designs. Data was obtained for both a baseline main-rotor blade and a main-rotor blade with a paddle-type tip. The baseline and paddle-type tip blades were compared with regard to rotor performance, oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Data was obtained in hover and forward flight over a nominal range of advance ratios from 0.15 to 0.425. Results indicate that the paddle-type tip offers no performance improvements in either hover or forward flight. Pitch-link oscillatory loads for the paddle-type tip are higher than for the baseline blade, whereas 4-per-rev vertical fixed-system loads are generally lower.

  18. Rotor/body aerodynamic interactions

    Science.gov (United States)

    Betzina, M. D.; Smith, C. A.; Shinoda, P.

    1985-01-01

    A wind tunnel investigation was conducted in which independent, steady state aerodynamic forces and moments were measured on a 2.24 m diam. two bladed helicopter rotor and on several different bodies. The mutual interaction effects for variations in velocity, thrust, tip-path-plane angle of attack, body angle of attack, rotor/body position, and body geometry were determined. The results show that the body longitudinal aerodynamic characteristics are significantly affected by the presence of a rotor and hub, and that the hub interference may be a major part of such interaction. The effects of the body on the rotor performance are presented.

  19. Development and validation of a piloted simulation of a helicopter and external sling load

    Science.gov (United States)

    Shaughnessy, J. D.; Deaux, T. N.; Yenni, K. R.

    1979-01-01

    A generalized, real time, piloted, visual simulation of a single rotor helicopter, suspension system, and external load is described and validated for the full flight envelope of the U.S. Army CH-54 helicopter and cargo container as an example. The mathematical model described uses modified nonlinear classical rotor theory for both the main rotor and tail rotor, nonlinear fuselage aerodynamics, an elastic suspension system, nonlinear load aerodynamics, and a loadground contact model. The implementation of the mathematical model on a large digital computing system is described, and validation of the simulation is discussed. The mathematical model is validated by comparing measured flight data with simulated data, by comparing linearized system matrices, eigenvalues, and eigenvectors with manufacturers' data, and by the subjective comparison of handling characteristics by experienced pilots. A visual landing display system for use in simulation which generates the pilot's forward looking real world display was examined and a special head up, down looking load/landing zone display is described.

  20. Control of a hybrid helicopter with wings

    NARCIS (Netherlands)

    de Wagter, C.; Smeur, E.J.J.

    2017-01-01

    This work investigates the design parameters and their consequences in the control of a helicopter rotor combined with a pair of fixed wings. This hybrid vehicle has a light and aerodynamically efficient rotor with a large range of pitch angles to enable both hover and forward flight. Because of the

  1. Aeroelastic analysis for helicopter rotor blades with time-variable, non-linear structural twist and multiple structural redundancy: Mathematical derivation and program user's manual

    Science.gov (United States)

    Bielawa, R. L.

    1976-01-01

    The differential equations of motion for the lateral and torsional deformations of a nonlinearly twisted rotor blade in steady flight conditions together with those additional aeroelastic features germane to composite bearingless rotors are derived. The differential equations are formulated in terms of uncoupled (zero pitch and twist) vibratory modes with exact coupling effects due to finite, time variable blade pitch and, to second order, twist. Also presented are derivations of the fully coupled inertia and aerodynamic load distributions, automatic pitch change coupling effects, structural redundancy characteristics of the composite bearingless rotor flexbeam - torque tube system in bending and torsion, and a description of the linearized equations appropriate for eigensolution analyses. Three appendixes are included presenting material appropriate to the digital computer program implementation of the analysis, program G400.

  2. The Use of Commercial Remote Sensing Predicting Helicopter Brownout Conditions

    Science.gov (United States)

    2007-09-01

    landing. 4 Figure 2. Soil caught in rotor downwash, start of brownout (from Brownout California soil resource lab) . A second issue ...Sensing in Predicting Helicopter Brownout Conditions. September 2006 (Top Secret). Tan, Kim H., First Edition, Enviromental Soil Science Marcel

  3. Dynamic Gust Load Analysis for Rotors

    Directory of Open Access Journals (Sweden)

    Yuting Dai

    2016-01-01

    Full Text Available Dynamic load of helicopter rotors due to gust directly affects the structural stress and flight performance for helicopters. Based on a large deflection beam theory, an aeroelastic model for isolated helicopter rotors in the time domain is constructed. The dynamic response and structural load for a rotor under the impulse gust and slope-shape gust are calculated, respectively. First, a nonlinear Euler beam model with 36 degrees-of-freedoms per element is applied to depict the structural dynamics for an isolated rotor. The generalized dynamic wake model and Leishman-Beddoes dynamic stall model are applied to calculate the nonlinear unsteady aerodynamic forces on rotors. Then, we transformed the differential aeroelastic governing equation to an algebraic one. Hence, the widely used Newton-Raphson iteration algorithm is employed to simulate the dynamic gust load. An isolated helicopter rotor with four blades is studied to validate the structural model and the aeroelastic model. The modal frequencies based on the Euler beam model agree well with published ones by CAMRAD. The flap deflection due to impulse gust with the speed of 2m/s increases twice to the one without gust. In this numerical example, results indicate that the bending moment at the blade root is alleviated due to elastic effect.

  4. Research on the Propagation of AE Signals in Helicopter Structural Components

    Directory of Open Access Journals (Sweden)

    Urbahs Aleksandrs

    2016-12-01

    Full Text Available The paper contains results of experimental research carried out helicopter bench. In order to create an attenuation chart for AE signal amplitude in helicopter fuselage, a number of experiments were performed on the frame and stringers, inside the fuselage. Later helicopter test bench was used to develop defect localization methodology of helicopter structure fatigue damage technical diagnostics. Analysing helicopter structural defects for different helicopters types it is concluded that the joint elements of helicopter tail boom are still exposed to fatigue crack formation. AE method shows highly effective results predicting fracture of helicopter joint elements.

  5. 78 FR 17593 - Airworthiness Directives; Bell Helicopter Textron, Inc.

    Science.gov (United States)

    2013-03-22

    ... helicopters. This AD requires establishing a lower life limit on certain swashplate outer ring assemblies... helicopters, with a swashplate outer ring assembly (outer ring), part number (P/N) 412- 010-407-105... Component (JASC) Code: 6230, Main Rotor Mast/Swashplate. Issued in Fort Worth, Texas, on March 6, 2013...

  6. Helicopter attitude stabilization using individual-blade-control

    Science.gov (United States)

    Ham, N. D.

    1984-01-01

    A theoretical study is presented on the application of the Individual-Blade-Control concept to helicopter attitude stabilization. The design of a system controlling blade flapping dynamics, and related testing of the system on a model rotor in the wind tunnel, is described. The control inputs considered are blade pitch changes proportional to blade flapping acceleration, velocity, and displacement. The effect of such a system on helicopter rotor damping-in-pitch, and angle-of-attack stability is then evaluated. It is shown that helicopter attitude stabilization is achieved, with a corresponding improvement in flying qualities.

  7. Procedural guide for modelling and analyzing the flight characteristics of a helicopter design using Flightlab

    OpenAIRE

    McVaney, Gary P.

    1993-01-01

    Approved for public release; distribution is unlimited. This thesis presents one method for modelling and analyzing a helicopter design using Flightlab. Flightlab is a computer program that provides for engineering design, analysis and simulation of aircraft using non-linear dynamic modeling techniques. The procedure to model a single main rotor helicopter is outlined using the sample helicopter design in the book 'Helicopter Performance, Stability, and Control' by Ray Prouty. The analysis...

  8. Stability and control modelling. [helicopters in near hovering flight

    Science.gov (United States)

    Curtiss, H. C., Jr.

    1986-01-01

    This paper discusses the influence of rotor dynamics and dynamic inflow on the stability and control characteristics of single rotor helicopters in near hovering flight. Body attitude and rate feedback gain limitations which arise due to rotor dynamics and dynamic inflow are discussed. It is shown that attitude feedback gain is limited primarily by body-flap coupling and rate gain is limited by the lag degrees of freedom. Dynamic inflow is shown to produce significant changes in the modes of motion.

  9. HARP model rotor test at the DNW. [Hughes Advanced Rotor Program

    Science.gov (United States)

    Dawson, Seth; Jordan, David; Smith, Charles; Ekins, James; Silverthorn, Lou

    1989-01-01

    Data from a test of a dynamically scaled model of the Hughes Advanced Rotor Program (HARP) bearingless model main rotor and 369K tail rotor are reported. The history of the HARP program and its goals are reviewed, and the main and tail rotor models are described. The test facilities and instrumentation are described, and wind tunnel test data are presented on hover, forward flight performance, and blade-vortex interaction. Performance data, acoustic data, and dynamic data from near field/far field and shear layer studies are presented.

  10. Performance and Vibration Analyses of Lift-Offset Helicopters

    Directory of Open Access Journals (Sweden)

    Jeong-In Go

    2017-01-01

    Full Text Available A validation study on the performance and vibration analyses of the XH-59A compound helicopter is conducted to establish techniques for the comprehensive analysis of lift-offset compound helicopters. This study considers the XH-59A lift-offset compound helicopter using a rigid coaxial rotor system as a verification model. CAMRAD II (Comprehensive Analytical Method of Rotorcraft Aerodynamics and Dynamics II, a comprehensive analysis code, is used as a tool for the performance, vibration, and loads analyses. A general free wake model, which is a more sophisticated wake model than other wake models, is used to obtain good results for the comprehensive analysis. Performance analyses of the XH-59A helicopter with and without auxiliary propulsion are conducted in various flight conditions. In addition, vibration analyses of the XH-59A compound helicopter configuration are conducted in the forward flight condition. The present comprehensive analysis results are in good agreement with the flight test and previous analyses. Therefore, techniques for the comprehensive analysis of lift-offset compound helicopters are appropriately established. Furthermore, the rotor lifts are calculated for the XH-59A lift-offset compound helicopter in the forward flight condition to investigate the airloads characteristics of the ABC™ (Advancing Blade Concept rotor.

  11. Rotor Flapping Response to Active Control

    Science.gov (United States)

    Nguyen, Khanh; Johnson, Wayne

    2004-01-01

    Rotor active control using higher harmonic blade pitch has been proposed as a means to reduce both rotor radiated noise and airframe vibration and to enhance rotor performance. The higher harmonic input, however, can affect rotor thrust and cyclic flapping - the basic trim characteristics of the rotor. Some of the trim changes can negate the active control benefits. For example, wind tunnel test results of a full scale BO-105 rotor with individual-blade control indicate some rotor performance improvements, accompanied with changes in rotor trim, using two-per-rev blade pitch input. The observed performance benefits could therefore be a simple manifestation of the trim change rather than an efficient redistribution of the rotor airloads. More recently, the flight test of the BO-105 helicopter equip,ped with individual-blade-control actuators also reported trim changes whenever the two-per-rev blade pitch for noise reduction was activated. The pilot had to adjust the trim control to maintain the aircraft under a constant flight path. These two cases highlight the, importance of trim considerations in the application of active control to rotorcraft.

  12. Aeromechanics Analysis of a Compound Helicopter

    Science.gov (United States)

    Yeo, Hyeonsoo; Johnson, Wayne

    2006-01-01

    A design and aeromechanics investigation was conducted for a 100,000-lb compound helicopter with a single main rotor, which is to cruise at 250 knots at 4000 ft/95 deg F condition. Performance, stability, and control analyses were conducted with the comprehensive rotorcraft analysis CAMRAD II. Wind tunnel test measurements of the performance of the H-34 and UH-1D rotors at high advance ratio were compared with calculations to assess the accuracy of the analysis for the design of a high speed helicopter. In general, good correlation was obtained with the increase of drag coefficients in the reverse flow region. An assessment of various design parameters (disk loading, blade loading, wing loading) on the performance of the compound helicopter was made. Performance optimization was conducted to find the optimum twist, collective, tip speed, and taper using the comprehensive analysis. Blade twist was an important parameter on the aircraft performance and most of the benefit of slowing the rotor occurred at the initial 20 to 30% reduction of rotor tip speed. No stability issues were observed with the current design and the control derivatives did not change much with speed, but did exhibit significant coupling.

  13. Optimum Design of a Compound Helicopter

    Science.gov (United States)

    Yeo, Hyeonsoo; Johnson, Wayne

    2006-01-01

    A design and aeromechanics investigation was conducted for a 100,000-lb compound helicopter with a single main rotor, which is to cruise at 250 knots at 4000 ft/95 deg F condition. Performance, stability, and control analyses were conducted with the comprehensive rotorcraft analysis CAMRAD II. Wind tunnel test measurements of the performance of the H-34 and UH-1D rotors at high advance ratio were compared with calculations to assess the accuracy of the analysis for the design of a high speed helicopter. In general, good correlation was obtained when an increase of drag coefficients in the reverse flow region was implemented. An assessment of various design parameters (disk loading, blade loading, wing loading) on the performance of the compound helicopter was conducted. Lower wing loading (larger wing area) and higher blade loading (smaller blade chord) increased aircraft lift-to-drag ratio. However, disk loading has a small influence on aircraft lift-to-drag ratio. A rotor parametric study showed that most of the benefit of slowing the rotor occurred at the initial 20 to 30% reduction of the advancing blade tip Mach number. No stability issues were observed with the current design. Control derivatives did not change significantly with speed, but the did exhibit significant coupling.

  14. Development and evaluation of a generic active helicopter vibration controller

    Science.gov (United States)

    Davis, M. W.

    1984-01-01

    A computerized generic active controller is developed, which alleviates helicopter vibration by closed-loop implementation of higher harmonic control (HHC). In the system, the higher harmonic blade pitch is input through a standard helicopter swashplate; for a four-blade helicopter rotor the 4/rev vibration in the rotorcraft is minimized by inducing cyclic pitch motions at 3, 4, and 5/rev in the rotating system. The controller employs the deterministic, cautious, and dual control approaches and two linear system models (local and global), as well as several methods of limiting control. Based on model testing, performed at moderate to high values of forward velocity and rotor thrust, reductions in the rotor test apparatus vibration from 75 to 95 percent are predicted, with HHC pitch amplitudes of less than one degree. Good performance is also noted for short-duration maneuvers.

  15. Helicopter stability and control modeling improvements and verification on two helicopters

    Science.gov (United States)

    Schrage, D. P.; Peters, D. A.; Prasad, J. V. R.; Stumpf, W. F.; He, Chengjian

    1988-01-01

    A linearized model of helicopter flight dynamics is developed which includes the flapping, lead-lag, and dynamic inflow degrees of freedom (DOF). The model is a combination of analytical terms and numerically determined stability derivatives, and is used to investigate the importance of the rotor DOF to stability and control modeling. The results show that the rotor DOF can have a significant impact on some of the natural modes in a linear model. The flap and dynamic inflow DOF show the greatest influence. Flapping exhibits strong coupling to the body, dynamic inflow, and to lead-lag to a lesser extent. Dynamic inflow tends to damp the high-frequency flapping modes, and reduces the damping on coupled body-flap motion. Dynamic inflow also couples to the flapping motion to produce complex roots. With body-flap and lag regressing modes as exceptions, the results show essentially similar behavior for most modes of articulated and hingeless rotor helicopters.

  16. IMPACT OF AN UNDERSLUNG LOAD ON A HELICOPTER CONTROLLABILITY

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available This article is aimed at finding the causes of controllability variations of a helicopter while transporting sling load.The maximum angular acceleration taken by the helicopter at similar controller displacement at different flight speeds was taken as a quantity characteristic of controllability efficiency to study the load impact on the helicopter cont- rollability.This article offers research results obtained with the use of the НеliСargо software. This software has proven to be a great tool for integrated research of the impact of an underslung load on the parameters of a helicopter controllability, and allows carrying out an analysis of the impact of an underslung load on the parameters of controllability under its dyna- mic behavior.The performed computational experiments have shown that the helicopter maximum angular acceleration with an underslung load significantly rises, as compared to a helicopter without cargo or a helicopter carrying the same load inside the cargo compartment. The data obtained during computational experiments corresponds to the results of analytical computations, and is in line with the literature based on the experience of helicopter flight operations.The cause of the variation in the helicopter controllability parameters during transportation of an underslung load has been found, that is - the underslung load considerably increases the main rotor thrust, due to sling load, as compared to a helicopter without cargo. When compared to a helicopter carrying a load inside the cargo compartment, this increased efficiency is mainly attributed to the fact that a helicopter with an underslung load has lower rotational inertia, since the load is not inside the cargo compartment, but outside.The obtained results can be used to improve flight manuals and flight personnel training publications, which could play a significant part in ensuring flight safety and security, and increasing the operational efficiency of

  17. A NASA helicopter arrives at KSC for painting

    Science.gov (United States)

    2000-01-01

    A NASA helicopter lands on S.R. 3 for transfer to Patrick Air Force Base. It is one of four UH-1H helicopters that will have its blades painted, changing the black to a pattern of white and yellow stripes. The pattern provides better visibility in smoke and fire conditions. When the rotors are turning, the stripes create a yellow and white circle that is more easily seen by a second helicopter from above. The helicopters, primarily used for security and medical evacuation for NASA, will be used to deliver water via buckets during brush fires. The change was made to comply with U.S. Fish and Wildlife and Department of Forestry regulations for helicopter-assisted fire control.

  18. 77 FR 18967 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2012-03-29

    ... to experience a heavy jerk in the yaw control during in-flight autorotation training. This condition, if not corrected, could lead to a temporary loss of tail rotor drive and subsequent loss of control... 18968

  19. Nonlinear Feedforward Control for Wind Disturbance Rejection on Autonomous Helicopter

    DEFF Research Database (Denmark)

    Bisgaard, Morten; la Cour-Harbo, Anders; A. Danapalasingam, Kumeresan

    2010-01-01

    for the purpose. The model is inverted for the calculation of rotor collective and cyclic pitch angles given the wind disturbance. The control strategy is then applied on a small helicopter in a controlled wind environment and flight tests demonstrates the effectiveness and advantage of the feedforward controller....

  20. 77 FR 58794 - Airworthiness Directives; Bell Helicopter Textron, Inc.

    Science.gov (United States)

    2012-09-24

    ... swashplate outer ring assemblies (outer ring). This AD would establish a lower life limit on certain outer... Bell Model 412 and 412EP helicopters, with a swashplate outer ring assembly (outer ring), part number... Component (JASC) Code: 6230, Main Rotor Mast/Swashplate. Issued in Fort Worth, Texas, on September 14, 2012...

  1. Helicopter noise in hover: Computational modelling and experimental validation

    Science.gov (United States)

    Kopiev, V. F.; Zaytsev, M. Yu.; Vorontsov, V. I.; Karabasov, S. A.; Anikin, V. A.

    2017-11-01

    The aeroacoustic characteristics of a helicopter rotor are calculated by a new method, to assess its applicability in assessing rotor performance in hovering. Direct solution of the Euler equations in a noninertial coordinate system is used to calculate the near-field flow around the spinning rotor. The far-field noise field is calculated by the Ffowcs Williams-Hawkings (FW-H) method using permeable control surfaces that include the blade. For a multiblade rotor, the signal obtained is duplicated and shifted in phase for each successive blade. By that means, the spectral characteristics of the far-field noise may be obtained. To determine the integral aerodynamic characteristics of the rotor, software is written to calculate the thrust and torque characteristics from the near-field flow solution. The results of numerical simulation are compared with experimental acoustic and aerodynamic data for a large-scale model of a helicopter main rotor in an open test facility. Two- and four-blade configurations of the rotor are considered, in different hover conditions. The proposed method satisfactorily predicts the aerodynamic characteristics of the blades in such conditions and gives good estimates for the first harmonics of the noise. That permits the practical use of the proposed method, not only for hovering but also for forward flight.

  2. Proceedings of CEAS Forum on Aeroacoustics of Rotors and Propellers, 9-11 June 1999, Rome Italy

    Science.gov (United States)

    1999-06-11

    societies, the Forum will not be limited to aeronautical applications (e.g., helicopter rotors, airplane propellers, tiltrotors). Hence, papers on related fields (e.g., windturbines , fans, ship propellers) are also encouraged.

  3. The potential of genetic algorithms for conceptual design of rotor systems

    Science.gov (United States)

    Crossley, William A.; Wells, Valana L.; Laananen, David H.

    1993-01-01

    The capabilities of genetic algorithms as a non-calculus based, global search method make them potentially useful in the conceptual design of rotor systems. Coupling reasonably simple analysis tools to the genetic algorithm was accomplished, and the resulting program was used to generate designs for rotor systems to match requirements similar to those of both an existing helicopter and a proposed helicopter design. This provides a comparison with the existing design and also provides insight into the potential of genetic algorithms in design of new rotors.

  4. Active control rotor model testing at Princeton's Rotorcraft Dynamics Laboratory

    Science.gov (United States)

    Mckillip, Robert M., Jr.

    1988-01-01

    A description of the model helicopter rotor tests currently in progress at Princeton's Rotorcraft Dynamics Laboratory is presented. The tests are designed to provide data for rotor dynamic modeling for use with active control system design. The model rotor to be used incoporates the capability for Individual Blade Control (IBC) or Higher Harmonic Control through the use of a standard swashplate on a three bladed hub. Sample results from the first series of tests are presented, along with the methodology used for state and parameter identification. Finally, pending experiments and possible research directions using this model and test facility are outlined.

  5. 75 FR 33159 - Airworthiness Directives; Bell Helicopter Textron Canada Model 222, 222B, 222U, 230, and 430...

    Science.gov (United States)

    2010-06-11

    ... based on hours TIS. Additionally, this AD does not require operators to send their blades to Rotor... does not have an excepted S/N or code, certificated in any category. Helicopter model Helicopter S/N... area. Let the area dry for 30 minutes to 1 hour. Then, apply one sealer coat of polyurethane, MILC85285...

  6. Coupled rotor/airframe vibration analysis

    Science.gov (United States)

    Sopher, R.; Studwell, R. E.; Cassarino, S.; Kottapalli, S. B. R.

    1982-01-01

    A coupled rotor/airframe vibration analysis developed as a design tool for predicting helicopter vibrations and a research tool to quantify the effects of structural properties, aerodynamic interactions, and vibration reduction devices on vehicle vibration levels is described. The analysis consists of a base program utilizing an impedance matching technique to represent the coupled rotor/airframe dynamics of the system supported by inputs from several external programs supplying sophisticated rotor and airframe aerodynamic and structural dynamic representation. The theoretical background, computer program capabilities and limited correlation results are presented in this report. Correlation results using scale model wind tunnel results show that the analysis can adequately predict trends of vibration variations with airspeed and higher harmonic control effects. Predictions of absolute values of vibration levels were found to be very sensitive to modal characteristics and results were not representative of measured values.

  7. Active control for performance enhancement of electrically controlled rotor

    Directory of Open Access Journals (Sweden)

    Lu Yang

    2015-10-01

    Full Text Available Electrically controlled rotor (ECR system has the potential to enhance the rotor performance by applying higher harmonic flap inputs. In order to explore the feasibility and effectiveness for ECR performance enhancement using closed-loop control method, firstly, an ECR rotor performance analysis model based on helicopter flight dynamic model is established, which can reflect the performance characteristics of ECR helicopter at high advance ratio. Based on the simulation platform, an active control method named adaptive T-matrix algorithm is adopted to explore the feasibility and effectiveness for ECR performance enhancement. The simulation results verify the effectiveness of this closed-loop control method. For the sample ECR helicopter, about 3% rotor power reduction is obtained with the optimum 2/rev flap inputs at the advance ratio of 0.34. And through analyzing the distributions of attack of angle and drag in rotor disk, the underlying physical essence of ECR power reduction is cleared. Furthermore, the influence of the key control parameters, including convergence factor and weighting matrix, on the effectiveness of closed-loop control for ECR performance enhancement is explored. Some useful results are summarized, which can be used to direct the future active control law design of ECR performance enhancement.

  8. A rotor optimization using regression analysis

    Science.gov (United States)

    Giansante, N.

    1984-01-01

    The design and development of helicopter rotors is subject to the many design variables and their interactions that effect rotor operation. Until recently, selection of rotor design variables to achieve specified rotor operational qualities has been a costly, time consuming, repetitive task. For the past several years, Kaman Aerospace Corporation has successfully applied multiple linear regression analysis, coupled with optimization and sensitivity procedures, in the analytical design of rotor systems. It is concluded that approximating equations can be developed rapidly for a multiplicity of objective and constraint functions and optimizations can be performed in a rapid and cost effective manner; the number and/or range of design variables can be increased by expanding the data base and developing approximating functions to reflect the expanded design space; the order of the approximating equations can be expanded easily to improve correlation between analyzer results and the approximating equations; gradients of the approximating equations can be calculated easily and these gradients are smooth functions reducing the risk of numerical problems in the optimization; the use of approximating functions allows the problem to be started easily and rapidly from various initial designs to enhance the probability of finding a global optimum; and the approximating equations are independent of the analysis or optimization codes used.

  9. Study on Helicopter Antitorque Device Based on Cross-Flow Fan Technology

    Directory of Open Access Journals (Sweden)

    Du Siliang

    2016-01-01

    Full Text Available In order to improve low-altitude flight security of single-rotor helicopter, an experimental model of a helicopter antitorque device is developed for wind tunnel test. The model is based on the flow control technology of the cross-flow fan (CFF. Wind tunnel tests show that the model can produce side force. It is concluded that the influence of the CFF rotating speed, the rotor collective pitch, and the forward flight speed on the side force of the model is great. At the same time, the numerical simulation calculation method of the model has been established. Good agreement between experimental and numerical side force and power shows that results of numerical solution are reliable. Therefore, the results in actual helicopter obtained from Computational Fluid Dynamics (CFD solution are acceptable. This proves that this antitorque device can be used for a helicopter.

  10. Final assessment of vibro-acoustic source strength descriptors of helicopter gearboxes

    DEFF Research Database (Denmark)

    Ohlrich, Mogens; Rasmussen, Ulrik Møller

    1996-01-01

    Two novel measurement techniques have been developed for quantifying the vibro-aqcoustic source strength of lightweight helicopter gearboxes. The accuracy, robustness and implementation of these methods have been examined by a comprehensive investigation, including theoretical studies of simple...... multi-modal beam systems and extensive experiments with more realistic small scale models and with large, detailed 3/4-scale test structures of a medium-size helicopter. In addition, partial verification tests have been conducted with the Eurocopter BK 117 helicopter and its main rotor gearbox....... The results of this work are essential as input for any prediction code of the internal noise in a helicopter cabin, because the prediction requires knowledge of the major sources, that is, the rotors, engines and gearboxes....

  11. Helicopter air resonance modeling and suppression using active control

    Science.gov (United States)

    Takahashi, M. D.; Friedmann, P. P.

    1991-01-01

    A coupled rotor/fuselage helicopter analysis with the important effects of blade torsional flexibility, unsteady aerodynamics, and forward flight is presented. Using this mathematical model, a nominal configuration is selected with an air resonance instability throughout most of its flight envelope. A multivariable compensator is then designed using two swashplate inputs and a single-body roll rate measurement. The controller design is based on the linear quadratic Gaussian technique and the loop transfer recovery method. The controller is shown to suppress the air resonance instability throughout a wide range of helicopter loading conditions and forward flight speeds.

  12. Analysis of potential helicopter vibration reduction concepts

    Science.gov (United States)

    Landgrebe, A. J.; Davis, M. W.

    1985-01-01

    Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location.

  13. Applications of numerical optimization methods to helicopter design problems: A survey

    Science.gov (United States)

    Miura, H.

    1984-01-01

    A survey of applications of mathematical programming methods is used to improve the design of helicopters and their components. Applications of multivariable search techniques in the finite dimensional space are considered. Five categories of helicopter design problems are considered: (1) conceptual and preliminary design, (2) rotor-system design, (3) airframe structures design, (4) control system design, and (5) flight trajectory planning. Key technical progress in numerical optimization methods relevant to rotorcraft applications are summarized.

  14. Applications of numerical optimization methods to helicopter design problems - A survey

    Science.gov (United States)

    Miura, H.

    1985-01-01

    A survey of applications of mathematical programming methods is used to improve the design of helicopters and their components. Applications of multivariable search techniques in the finite dimensional space are considered. Five categories of helicopter design problems are considered: (1) conceptual and preliminary design, (2) rotor-system design, (3) airframe structures design, (4) control system design, and (5) flight trajectory planning. Key technical progress in numerical optimization methods relevant to rotorcraft applications are summarized.

  15. Boeing Smart Rotor Full-scale Wind Tunnel Test Data Report

    Science.gov (United States)

    Kottapalli, Sesi; Hagerty, Brandon; Salazar, Denise

    2016-01-01

    A full-scale helicopter smart material actuated rotor technology (SMART) rotor test was conducted in the USAF National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel at NASA Ames. The SMART rotor system is a five-bladed MD 902 bearingless rotor with active trailing-edge flaps. The flaps are actuated using piezoelectric actuators. Rotor performance, structural loads, and acoustic data were obtained over a wide range of rotor shaft angles of attack, thrust, and airspeeds. The primary test objective was to acquire unique validation data for the high-performance computing analyses developed under the Defense Advanced Research Project Agency (DARPA) Helicopter Quieting Program (HQP). Other research objectives included quantifying the ability of the on-blade flaps to achieve vibration reduction, rotor smoothing, and performance improvements. This data set of rotor performance and structural loads can be used for analytical and experimental comparison studies with other full-scale rotor systems and for analytical validation of computer simulation models. The purpose of this final data report is to document a comprehensive, highquality data set that includes only data points where the flap was actively controlled and each of the five flaps behaved in a similar manner.

  16. Application of higher harmonic control to hingeless rotor systems

    Science.gov (United States)

    Nguyen, Khanh; Chopra, Inderjit

    1990-01-01

    A comprehensive analytical formulation has been dveloped to predict the vibratory hub loads of a helicopter rotor system in forward flight. The analysis is used to calculate the optimal higher harmonic control inputs and associated actuator power required to minimize these hub loads. The present formulation is based on a finite element method in space and time. A nonlinear time domain, unsteady aerodynamic model is used to obtain the airloads, and the rotor induced inflow is calculated using a nonuniform inflow model. Predicted vibratory hub loads are correlated with experimental data obtained from a scaled model rotor. Results of a parametric study on a hingeless rotor show that blade flap, lag and torsion vibration characteristics, offset of blade center of mass from elastic axis, offset of elastic axis from quarter-chord axis, and blade thrust greatly affect the higher harmonic control actuator power requirement.

  17. Simulation of Rotor Blade Element Turbulence

    Science.gov (United States)

    McFarland, R. E.; Duisenberg, Ken

    1996-01-01

    A turbulence model has been developed for blade-element helicopter simulation. This model, called Simulation of Rotor Blade Element Turbulence (SORBET), uses an innovative temporal and geometrical distribution algorithm that preserves the statistical characteristics of the turbulence spectra over the rotor disc, while providing velocity components in real time to each of five blade-element stations along each of four blades. An initial investigation of SORBET has been performed using a piloted, motion-based simulation of the Sikorsky UH60A Black Hawk. Although only the vertical component of stochastic turbulence was used in this investigation, vertical turbulence components induce vehicle responses in all translational and rotational degrees of freedom of the helicopter. The single-degree-of-freedom configuration of SORBET was compared to a conventional full 6-degrees-of-freedom baseline configuration, where translational velocity inputs are superimposed at the vehicle center of gravity, and rotational velocity inputs are created from filters that approximate the immersion rate into the turbulent field. For high-speed flight the vehicle responses were satisfactory for both models. Test pilots could not distinguish differences between the baseline configuration and SORBET. In low-speed flight the baseline configuration received criticism for its high frequency content, whereas the SORBET model elicited favorable pilot opinion. For this helicopter, which has fully articulated blades, results from SORBET show that vehicle responses to turbulent blade-station disturbances are severely attenuated. This is corroborated by in-flight observation of the rotor tip path plane as compared to vehicle responses.

  18. Osvrt na projektovanje glavnog rotora helikoptera / Review of the design of the helicopter rotor / Oбзор проектирования главного ротора вертолета

    Directory of Open Access Journals (Sweden)

    Dalibor P. Petrović

    2015-04-01

    Full Text Available U radu je prikazano projektovanje glavnog rotora helikoptera uz pomoć patentne dokumentacije, kao veoma korisnog alata za dolaženje do konkretnih ideja i konstrukcija, kako bi se na najekonomičniji način pronašlo kvalitetno rešenje za određeni tehnički problem koji je prisutan u postupku konstruisanja. Veliki broj tehničkih informacija prvo se pojavljuje u patentnim dokumentima, a oko dve trećine ovih informacija ne može se naći ni na kojem drugom mestu. Prikazana je struktura patentnih dokumenata sa težištem na delovima koji se odnose na tehničke informacije sa detaljnim objašnjenjem mogućnosti primene patentne dokumentacije u toku projektovanja glavnog rotora helikoptera. Na konkretnom primeru projektovanja rotora helikoptera prikazan je postupak i načini pretraživanja patentne dokumentacije. Korišćena je Espacenet baza patentne dokumentacije, kao najobuhvatnija i najčešće korišćena baza koja sadrži preko osamdeset miliona različitih patentnih dokumenata o pronalascima i tehničkim unapređenjima iz celog sveta. Težišni deo rada odnosi se na prikaz postupka pretraživanja patentne dokumentacije radi dolaženja do rešenja tehničkog problema konstrukcije glavnog rotora helikoptera, koji se odnosi na obezbeđivanje potrebnog zabacivanja i bržeg odziva promene smeštajnog ugla (koraka lopatice krutog rotora helikoptera. / This article - paper presents the design of the main rotor of the helicopter supported by the patent documents, as a very useful tool (instrument to reach the specific ideas and design in order to find the most economical way for the quality solution for a certain technical problem present in the process of design (construction. A large amount of technical information first appears in patent documents and about two thirds of this information cannot be found on any other site. The structure of patent documents is presented with an emphasis on the elements that relate to technical information with

  19. Some thoughts on the implementation of pilot night vision devices for helicopters

    Science.gov (United States)

    Tucker, G. E.

    1984-01-01

    Night vision enhancement devices greatly expand the range and quality of services by extending night operational capabilities. Evolving military tactical concepts for helicopters survivability and battlefield effectiveness necessitate nap-of-the-earth (NOE) flying under both day and night conditions. From a pilot workload standpoint, flying a helicopter NOE in day VFR conditions with minimum clearance between rotors and obstacles is quite demanding. Doing the same job at night is several times more difficult. There are two general categories of night vision devices in operation in helicopter aviation: the Night Vision Goggles (NVG) and forward looking infrared (FLIR) system. The capabilities and limitations of those two devices are discussed.

  20. 77 FR 55166 - Airworthiness Directives; Sikorsky Aircraft Corporation (Sikorsky) Model Helicopters

    Science.gov (United States)

    2012-09-07

    ... for determining the life limit for certain GE engine gas generator turbine (GGT) rotor parts and the....A.(1) and 3.A.(2) of each ESB) for each gas generator turbine (GGT) rotor part. A combination of... Sikorsky Model S-70, S-70A, S-70C, S-70C (M), and S-70C (M1) helicopters with General Electric (GE) T700-GE...

  1. Comparison of acoustic performance of five muffler configurations on a small helicopter. [acoustic properties of modified helicopter exhaust system

    Science.gov (United States)

    Pegg, R. J.; Hilton, D. A.

    1974-01-01

    A field noise measurement program has been conducted on a standard Bell 47 series helicopter and on one that had been modified with specially designed, airframe-mounted mufflers to reduce the engine exhaust noise. The purpose of the study was to evaluate the acoustic performance of five experimental exhaust muffler configurations for a helicopter reciprocating engine in an operational environment. All muffler configurations produced beneficial engine exhaust noise reductions but some configurations were markedly better than others. Flyover noise results indicated that maximum overall noise reductions of approximately 8 db were obtained with the various mufflers. The rotor noise was judged to be the dominant noise component for the muffler-equipped helicopters whereas the engine noise was the dominant component for the basic configuration.

  2. SMART Rotor Development and Wind-Tunnel Test

    Science.gov (United States)

    Lau, Benton H.; Straub, Friedrich; Anand, V. R.; Birchette, Terry

    2009-01-01

    Boeing and a team from Air Force, NASA, Army, Massachusetts Institute of Technology, University of California at Los Angeles, and University of Maryland have successfully completed a wind-tunnel test of the smart material actuated rotor technology (SMART) rotor in the 40- by 80-foot wind-tunnel of the National Full-Scale Aerodynamic Complex at NASA Ames Research Center, figure 1. The SMART rotor is a full-scale, five-bladed bearingless MD 900 helicopter rotor modified with a piezoelectric-actuated trailing-edge flap on each blade. The development effort included design, fabrication, and component testing of the rotor blades, the trailing-edge flaps, the piezoelectric actuators, the switching power amplifiers, the actuator control system, and the data/power system. Development of the smart rotor culminated in a whirl-tower hover test which demonstrated the functionality, robustness, and required authority of the active flap system. The eleven-week wind tunnel test program evaluated the forward flight characteristics of the active-flap rotor, gathered data to validate state-of-the-art codes for rotor noise analysis, and quantified the effects of open- and closed-loop active-flap control on rotor loads, noise, and performance. The test demonstrated on-blade smart material control of flaps on a full-scale rotor for the first time in a wind tunnel. The effectiveness and the reliability of the flap actuation system were successfully demonstrated in more than 60 hours of wind-tunnel testing. The data acquired and lessons learned will be instrumental in maturing this technology and transitioning it into production. The development effort, test hardware, wind-tunnel test program, and test results will be presented in the full paper.

  3. The Effects of Ambient Conditions on Helicopter Harmonic Noise Radiation: Theory and Experiment

    Science.gov (United States)

    Greenwood, Eric; Sim, Ben W.; Boyd, D. Douglas, Jr.

    2016-01-01

    The effects of ambient atmospheric conditions, air temperature and density, on rotor harmonic noise radiation are characterized using theoretical models and experimental measurements of helicopter noise collected at three different test sites at elevations ranging from sea level to 7000 ft above sea level. Significant changes in the thickness, loading, and blade-vortex interaction noise levels and radiation directions are observed across the different test sites for an AS350 helicopter flying at the same indicated airspeed and gross weight. However, the radiated noise is shown to scale with ambient pressure when the flight condition of the helicopter is defined in nondimensional terms. Although the effective tip Mach number is identified as the primary governing parameter for thickness noise, the nondimensional weight coefficient also impacts lower harmonic loading noise levels, which contribute strongly to low frequency harmonic noise radiation both in and out of the plane of the horizon. Strategies for maintaining the same nondimensional rotor operating condition under different ambient conditions are developed using an analytical model of single main rotor helicopter trim and confirmed using a CAMRAD II model of the AS350 helicopter. The ability of the Fundamental Rotorcraft Acoustics Modeling from Experiments (FRAME) technique to generalize noise measurements made under one set of ambient conditions to make accurate noise predictions under other ambient conditions is also validated.

  4. Wind tunnel testing of a full scale helicopter blade section with an upstream active Gurney flap

    NARCIS (Netherlands)

    Loendersloot, Richard; Freire Gomez, J.; Booker, J.D.

    2014-01-01

    Wind tunnel tests were performed on an aerofoil section comparable to that of a full scale helicopter blade section with an upstream active Gurney flap in the framework of the European project CleanSky ITD Green RotorCraft. A modified NACA0012 profile was used, with 23 Kulite pressure transducers

  5. Terfenol-D driven flaps for helicopter vibration reduction

    Science.gov (United States)

    Fenn, Ralph C.; Downer, James R.; Bushko, Dariusz A.; Gondhalekar, Vijay; Ham, Norman D.

    1996-02-01

    The utility of helicopter aviation is limited by the high vibration levels caused by the interaction of each rotor blade with the wake of preceding blades. Existing full-blade actuation using a swashplate has various problems such as insufficient bandwidth, limitations in the number of harmonics controlled, high maintenance, and lack of spanwise lift variation. These problems are avoided by the proposed flap operated, individual blade control system, which uses magnetostrictive actuation technology. Terfenol-D actuation has many advantages over competing technologies such as hydraulic systems, electric motors, and piezoelectric elements. These benefits include all-electric operation, simplicity and reliability, low mass, low voltage, and insensitivity to centripetal acceleration. A blade mounted Terfenol-D actuator was developed for the high-weight-penalty helicopter application. The optimum coil to Terfenol-D volume ratio was derived that gives the highest mechanical power output for a small actuator envelope and mass. A fixed ability to dissipate coil resistive losses is assumed. The magnetostrictive actuation system will weigh less than 1% of gross vehicle weight, and use only 0.7% of cruise power. Other required subsystems of the vibration reduction system are available from commercial sources or are described in the literature. Helicopter vibration reduction greater than 90% is predicted because of superior actuator performance and individual blade control. This magnetostrictive actuator technology will also produce future helicopter systems having lower noise and higher performance. Such advances will significantly improve the utility and competitiveness of helicopters for civilian and military transportation.

  6. Design of an active helicopter control experiment at the Princeton Rotorcraft Dynamics Laboratory

    Science.gov (United States)

    Marraffa, Andrew M.; Mckillip, R. M., Jr.

    1989-01-01

    In an effort to develop an active control technique for reducing helicopter vibrations stemming from the main rotor system, a helicopter model was designed and tested at the Princeton Rotorcraft Dynamics Laboratory (PRDL). A description of this facility, including its latest data acquisition upgrade, are given. The design procedures for the test model and its Froude scaled rotor system are also discussed. The approach for performing active control is based on the idea that rotor states can be identified by instrumenting the rotor blades. Using this knowledge, Individual Blade Control (IBC) or Higher Harmonic Control (HHC) pitch input commands may be used to impact on rotor dynamics in such a way as to reduce rotor vibrations. Discussed here is an instrumentation configuration utilizing miniature accelerometers to measure and estimate first and second out-of-plane bending mode positions and velocities. To verify this technique, the model was tested, and resulting data were used to estimate rotor states as well as flap and bending coefficients, procedures for which are discussed. Overall results show that a cost- and time-effective method for building a useful test model for future active control experiments was developed. With some fine-tuning or slight adjustments in sensor configuration, prospects for obtaining good state estimates look promising.

  7. Aeromechanical stability analysis of a multirotor vehicle with application to hybrid heavy lift helicopter dynamics

    Science.gov (United States)

    Venkatesan, C.; Friedmann, P. P.

    1984-01-01

    The Hybrid Heavy Lift Helicopter (HHLH) is a potential candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure. Four rotor systems are also attached to the supporting structure. Nonlinear equations of motion capable of modeling the dynamics of this multi-rotor/support frame/vehicle system have been developed and used to study the fundamental aeromechanical stability characteristics of this class of vehicles. The mechanism of coupling between the blades, supporting structure and rigid body modes is identified and the effect of buoyancy ratio (buoyant lift/total weight) on the vehicle dynamics is studied. It is shown that dynamics effects have a major role in the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.

  8. Wind Tunnel Test of the SMART Active Flap Rotor

    Science.gov (United States)

    Straub, Friedrich K.; Anand, Vaidyanthan R.; Birchette, Terrence S.; Lau, Benton H.

    2009-01-01

    Boeing and a team from Air Force, NASA, Army, DARPA, MIT, UCLA, and U. of Maryland have successfully completed a wind-tunnel test of the smart material actuated rotor technology (SMART) rotor in the 40- by 80-foot wind-tunnel of the National Full-Scale Aerodynamic Complex at NASA Ames Research Center. The Boeing SMART rotor is a full-scale, five-bladed bearingless MD 900 helicopter rotor modified with a piezoelectric-actuated trailing edge flap on each blade. The eleven-week test program evaluated the forward flight characteristics of the active-flap rotor at speeds up to 155 knots, gathered data to validate state-of-the-art codes for rotor aero-acoustic analysis, and quantified the effects of open and closed loop active flap control on rotor loads, noise, and performance. The test demonstrated on-blade smart material control of flaps on a full-scale rotor for the first time in a wind tunnel. The effectiveness of the active flap control on noise and vibration was conclusively demonstrated. Results showed significant reductions up to 6dB in blade-vortex-interaction and in-plane noise, as well as reductions in vibratory hub loads up to 80%. Trailing-edge flap deflections were controlled within 0.1 degrees of the commanded value. The impact of the active flap on control power, rotor smoothing, and performance was also demonstrated. Finally, the reliability of the flap actuation system was successfully proven in more than 60 hours of wind-tunnel testing.

  9. Dynamic stability of a rotor blade using finite element analysis

    Science.gov (United States)

    Sivaneri, N. T.; Chopra, I.

    1981-01-01

    The aeroelastic stability of flap bending, lead-lag bending, and torsion of a helicopter rotor blade in hover is examined using a finite element formulation based on the principle of virtual work. Quasi-steady two-dimensional airfoil theory is used to obtain the aerodynamic loads. The rotor blade is discretized into beam elements, each with ten modal degrees of freedom. The resulting nonlinear equations of motion are solved for steady-state blade deflections through an iterative procedure. The flutter solution is calculated assuming blade motion to be a small perturbation about the steady solution. The normal mode method based on the coupled rotating natural modes about the steady deflections is used to reduce the number of equations in the flutter eigenanalysis. Results are presented for hingeless and articulated rotor blade configurations.

  10. 78 FR 9777 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-02-12

    ... inspecting certain tail rotor hubs (TRH) for a crack and removing any cracked TRH. This AD requires the same actions but adds more part numbers to the list of affected TRHs. This AD is prompted by further analysis that indicates that additional part-numbered TRHs must be inspected for cracks. The actions specified...

  11. Comprehensive analysis of bearingless rotors - Model development and experimental correlation of modes, response, trim and stability

    Science.gov (United States)

    Jambunathan, V.; Murthy, V. R.

    1993-01-01

    A generic mathematical model that is capable of accurately modeling the multiple load path bearingless rotor blade is developed. A comprehensive, finite element based solution for the natural vibration of the rotor blade is developed. An iterative scheme based on harmonic balance is used to evaluate the nonlinear response of the rotor to control inputs and a Newton-Raphson procedure is employed to evaluate the trim of rotorcraft. Linearized perturbation model of the nonlinear system are presented. The model is validated by comparing with existing whirl tower, wind tunnel and flight test results of BMR/BO-105 helicopter. Frequencies of two bearingless rotor blades compare well with results from experiments. Nonlinear response and trim results are presented for the bearingless BMR/BO-105 rotor. Aeroelastic stability in forward flight, evaluated using floquet theory agrees with test data in general.

  12. Simultaneous Boundary-Layer Transition, Tip Vortex, and Blade Deformation Measurements of a Rotor in Hover

    Science.gov (United States)

    Heineck, James; Schairer, Edward; Ramasamy, Manikandan; Roozeboom, Nettie

    2016-01-01

    This paper describes simultaneous optical measurements of a sub-scale helicopter rotor in the U.S. Army Hover Chamber at NASA Ames Research Center. The measurements included thermal imaging of the rotor blades to detect boundary layer transition; retro-reflective background-oriented schlieren (RBOS) to visualize vortices; and stereo photogrammetry to measure displacements of the rotor blades, to compute spatial coordinates of the vortices from the RBOS data, and to map the thermal imaging data to a three-dimensional surface grid. The test also included an exploratory effort to measure flow near the rotor tip by tomographic particle image velocimetry (tomo PIV)an effort that yielded valuable experience but little data. The thermal imaging was accomplished using an image-derotation method that allowed long integration times without image blur. By mapping the thermal image data to a surface grid it was possible to accurately locate transition in spatial coordinates along the length of the rotor blade.

  13. Effects of higher harmonic control on rotor performance and control loads

    Science.gov (United States)

    Nguyen, Khanh; Chopra, Inderjit

    1990-01-01

    An analytical study, based on an advanced Higher Harmonic Control (HHC) analysis for helicopter rotor systems, is carried out to investigate HHC application for rotor performance enhancement. The effects of HHC on stall characteristics of rotor and blade pitch-link loads when the system is configured to suppress vibration are also examined. For vibration control, simulated results indicate that HHC may promote early blade stall. Effects of blade torsion frequencies on HHC performance are moderate, and torsionally stiff blades require less actuator power than torsionally soft blades. For rotor performance improvement, a 3 to 5 percent reduction in rotor shaft power can be achieved with 2 deg of two-per-rev blade pitch control.

  14. A Hybrid Flight Control for a Simulated Raptor-30 V2 Helicopter

    Directory of Open Access Journals (Sweden)

    Arbab Nighat Khizer

    2015-04-01

    Full Text Available This paper presents a hybrid flight control system for a single rotor simulated Raptor-30 V2 helicopter. Hybrid intelligent control system, combination of the conventional and intelligent control methodologies, is applied to small model helicopter. The proposed hybrid control used PID as a traditional control and fuzzy as an intelligent control so as to take the maximum advantage of advanced control theory. The helicopter?s model used; comes from X-Plane flight simulator and their hybrid flight control system was simulated using MATLAB/SIMULINK in a simulation platform. X-Plane is also used to visualize the performance of this proposed autopilot design. Through a series of numerous experiments, the operation of hybrid control system was investigated. Results verified that the proposed hybrid control has an excellent performance at hovering flight mode.

  15. 78 FR 65180 - Airworthiness Directives; MD Helicopters, Inc., Helicopters

    Science.gov (United States)

    2013-10-31

    ..., 369H, 369HE, 369HM, 369HS, 369F and 369FF helicopters with certain MDHI or Helicopter Technology... the paint. This new AD retains some of the requirements of AD 2003-08-51 and also requires paint... ; Web site http://www.mdhelicopters.com or contact Helicopter Technology Company, 12923 South Spring...

  16. Implementation of a Helicopter Flight Simulator with Individual Blade Control

    Science.gov (United States)

    Zinchiak, Andrew G.

    2011-12-01

    Nearly all modern helicopters are designed with a swashplate-based system for control of the main rotor blades. However, the swashplate-based approach does not provide the level of redundancy necessary to cope with abnormal actuator conditions. For example, if an actuator fails (becomes locked) on the main rotor, the cyclic inputs are consequently fixed and the helicopter may become stuck in a flight maneuver. This can obviously be seen as a catastrophic failure, and would likely lead to a crash. These types of failures can be overcome with the application of individual blade control (IBC). IBC is achieved using the blade pitch control method, which provides complete authority of the aerodynamic characteristics of each rotor blade at any given time by replacing the normally rigid pitch links between the swashplate and the pitch horn of the blade with hydraulic or electronic actuators. Thus, IBC can provide the redundancy necessary for subsystem failure accommodation. In this research effort, a simulation environment is developed to investigate the potential of the IBC main rotor configuration for fault-tolerant control. To examine the applications of IBC to failure scenarios and fault-tolerant controls, a conventional, swashplate-based linear model is first developed for hover and forward flight scenarios based on the UH-60 Black Hawk helicopter. The linear modeling techniques for the swashplate-based helicopter are then adapted and expanded to include IBC. Using these modified techniques, an IBC based mathematical model of the UH-60 helicopter is developed for the purposes of simulation and analysis. The methodology can be used to model and implement a different aircraft if geometric, gravimetric, and general aerodynamic data are available. Without the kinetic restrictions of the swashplate, the IBC model effectively decouples the cyclic control inputs between different blades. Simulations of the IBC model prove that the primary control functions can be manually

  17. Simulation Analysis of Helicopter Ground Resonance Nonlinear Dynamics

    Science.gov (United States)

    Zhu, Yan; Lu, Yu-hui; Ling, Ai-min

    2017-07-01

    In order to accurately predict the dynamic instability of helicopter ground resonance, a modeling and simulation method of helicopter ground resonance considering nonlinear dynamic characteristics of components (rotor lead-lag damper, landing gear wheel and absorber) is presented. The numerical integral method is used to calculate the transient responses of the body and rotor, simulating some disturbance. To obtain quantitative instabilities, Fast Fourier Transform (FFT) is conducted to estimate the modal frequencies, and the mobile rectangular window method is employed in the predictions of the modal damping in terms of the response time history. Simulation results show that ground resonance simulation test can exactly lead up the blade lead-lag regressing mode frequency, and the modal damping obtained according to attenuation curves are close to the test results. The simulation test results are in accordance with the actual accident situation, and prove the correctness of the simulation method. This analysis method used for ground resonance simulation test can give out the results according with real helicopter engineering tests.

  18. CAS, interdiction, and attack helicopters

    OpenAIRE

    Groenke, Andrew S.

    2005-01-01

    Within days of a major failed strike by attack helicopters during Operation Iraqi Freedom (OIF) analysts were questioning the value of such platforms on the modern battlefield. As OIF moved from combat to stability operations, helicopter losses from enemy action actually increased seemingly strengthening the argument of those who see the helicopter as unsuitable to some combat operations. Attack helicopter operations have diverged into two distinct categories, interdiction and close air sup...

  19. A comparison of the acoustic and aerodynamic measurements of a model rotor tested in two anechoic wind tunnels

    Science.gov (United States)

    Boxwell, D. A.; Schmitz, F. H.; Splettstoesser, W. R.; Schultz, K. J.; Lewy, S.; Caplot, M.

    1986-01-01

    Two aeroacoustic facilities--the CEPRA 19 in France and the DNW in the Netherlands--are compared. The two facilities have unique acoustic characteristics that make them appropriate for acoustic testing of model-scale helicopter rotors. An identical pressure-instrumented model-scale rotor was tested in each facility and acoustic test results are compared with full-scale-rotor test results. Blade surface pressures measured in both tunnels were used to correlated nominal rotor operating conditions in each tunnel, and also used to assess the steadiness of the rotor in each tunnel's flow. In-the-flow rotor acoustic signatures at moderate forward speeds (35-50 m/sec) are presented for each facility and discussed in relation to the differences in tunnel geometries and aeroacoustic characteristics. Both reports are presented in appendices to this paper. ;.);

  20. The use of active controls to augment rotor/fuselage stability

    Science.gov (United States)

    Straub, F. K.; Warmbrodt, W.

    1985-01-01

    The use of active blade pitch control to increase helicopter rotor/body damping is studied. Control is introduced through a conventional nonrotating swashplate. State variable feedback of rotor and body states is used. Feedback parameters include cyclic rotor flap and lead-lag states, and body pitch and roll rotations. The use of position, rate, and acceleration feedback is studied for the various state variables. In particular, the influence of the closed loop feedback gain and phase on system stability is investigated. For the rotor/body configuration analyzed, rotor cyclic inplane motion and body roll-rate and roll-acceleration feedback can considerably augment system damping levels and eliminate ground resonance instabilities. Scheduling of the feedback state, phase, and gain with rotor rotation speed can be used to maximize the damping augmentation. This increase in lead-lag damping can be accomplished without altering any of the system modal frequencies. Investigating various rotor design parameters (effective hinge offset, blade precone, blade flap stiffness) indicates that active control for augmenting rotor/body damping will be particularly powerful for hingeless and bearingless rotor hubs.

  1. An Empirical Study of Overlapping Rotor Interference for a Small Unmanned Aircraft Propulsion System

    Directory of Open Access Journals (Sweden)

    Mantas Brazinskas

    2016-10-01

    Full Text Available The majority of research into full-sized helicopter overlapping propulsion systems involves co-axial setups (fully overlapped. Partially overlapping rotor setups (tandem, multirotor have received less attention, and empirical data produced over the years is limited. The increase in demand for compact small unmanned aircraft has exposed the need for empirical investigations of overlapping propulsion systems at a small scale (Reynolds Number < 250,000. Rotor-to-rotor interference at the static state in various overlapping propulsion system configurations was empirically measured using off the shelf T-Motor 16 inch × 5.4 inch rotors. A purpose-built test rig was manufactured allowing various overlapping rotor configurations to be tested. First, single rotor data was gathered, then performance measurements were taken at different thrust and tip speeds on a range of overlap configurations. The studies were conducted in a system torque balance mode. Overlapping rotor performance was compared to an isolated dual rotor propulsion system revealing interference factors which were compared to the momentum theory. Tests revealed that in the co-axial torque-balanced propulsion system the upper rotor outperforms the lower rotor at axial separation ratios between 0.05 and 0.85. Additionally, in the same region, thrust sharing between the two rotors changed by 21%; the upper rotor produced more thrust than the lower rotor at all times. Peak performance was recorded as a 22% efficiency loss when the axial separation ratio was greater than 0.25. The performance of a co-axial torque-balanced system reached a 27% efficiency loss when the axial separation ratio was equal to 0.05. The co-axial system swirl recovery effect was recorded to have a 4% efficiency gain in the axial separation ratio region between 0.05 and 0.85. The smallest efficiency loss (3% was recorded when the rotor separation ratio was between 0.95 and 1 (axial separation ratio was kept at 0

  2. Helicopter Nighttime Parking Test Results - UH-1H

    Science.gov (United States)

    1992-05-01

    done with a large, heavy UH-lH helicopter, the results do not represent the most demanding case. The results of FAA/CT-TN88/30 also indicated that...I MY .. mX.IOW ANFO ,. 0 J 00o0 oWIND TYPE & TOTAL: UJOI -HEAD- 7 CL -TAIL- 8 0 O -CROSS- 7 I-) <o_ r; 01 LLu,- 0-~- H C 0 H C - < 0 >0-5 >5-10 >10-15

  3. Fluid mechanics mechanisms in the stall process of helicopters

    Science.gov (United States)

    Young, W. H., Jr.

    1981-01-01

    Recent experimental results from airfoils in the Mach number, Reynolds number, or reduced frequency ranges typical of helicopter rotor blades have identified the most influential flow mechanisms in the dynamic stall process. The importance of secondary shed vortices, downstream wake action, and the flow in the separated region is generally acknowledged but poorly understood. By means of surface pressure cross-correlations and flow field measurements in static stall, several new hypotheses have been generated. It is proposed that vortex shedding may be caused by acoustic disturbances propagating forward in the lower (pressure) surface boundary layer, that wake closure is a misnomer, and that the shed vortex leaves a trail of vorticity that forms a turbulent free shear layer. The known dynamic stall flow mechanisms are reviewed and the potential importance of recently proposed and hypothetical flow phenomena with respect to helicopter blade aeroelastic response are assessed.

  4. High power for rotors; Rotor unter Starkstrom

    Energy Technology Data Exchange (ETDEWEB)

    Marter, H.J.

    2003-08-01

    Tidal energy is going strong: A new tidal power plant is projected off the coast of southern England. Of the envisaged underwater rotors, one has been installed for test purposes. (orig.) [German] Wellenenergie ist en vogue: Vor der Kueste Suedenglands wird ein neuartiges Tidenkraftwerk getestet. Die starke Stroemung soll maechtige Unterwasser-Rotoren antreiben. Zum Test dreht sich erst einmal nur einer. (orig.)

  5. Maneuver Acoustic Flight Test of the Bell 430 Helicopter Data Report

    Science.gov (United States)

    Watts, Michael E.; Greenwood, Eric; Smith, Charles D.; Snider, Royce; Conner, David A.

    2014-01-01

    A cooperative ight test by NASA, Bell Helicopter and the U.S. Army to characterize the steady state acoustics and measure the maneuver noise of a Bell Helicopter 430 aircraft was accomplished. The test occurred during June/July 2011 at Eglin Air Force Base, Florida. This test gathered a total of 410 test points over 10 test days and compiled an extensive database of dynamic maneuver measurements. Three microphone arrays with up to 31 microphon. es in each were used to acquire acoustic data. Aircraft data included Differential Global Positioning System, aircraft state and rotor state information. This paper provides an overview of the test and documents the data acquired.

  6. Design of a simple active controller to suppress helicopter air resonance

    Science.gov (United States)

    Takahashi, M. D.; Friedmann, P. P.

    1988-01-01

    A coupled rotor/fuselage helicopter analysis with the important effects of blade torsional flexibility, unsteady aerodynamics, and forward flight is presented. Using this mathematical model, a nominal configuration is selected that experiences an air resonance instability throughout most of its flight envelope. A simple multivariable compensator using conventional swashplate inputs and a single body roll rate measurement is then designed. The controller design is based on a linear estimator in conjunction with optimal feedback gains, and the design is done in the frequency domain using the Loop Transfer Recovery method. The controller is shown to suppress the air resonance instability throughout wide range helicopter loading conditions and forward flight speeds.

  7. Terfenol-D-driven flaps for helicopter vibration reduction

    Science.gov (United States)

    Fenn, Ralph C.; Downer, James R.; Bushko, Dariusz A.; Gondhalekar, Vijay; Ham, Norman D.

    1993-09-01

    The utility of helicopter aviation is limited by the high vibration levels caused by interaction of each rotor blade with the wake of preceding blades. Existing full blade actuation using a swashplate has various problems such as insufficient bandwidth, limitations in the number of harmonics controlled, high maintenance, and lack of spanwise lift variation. These problems are avoided by the proposed flap operated, individual blade control system, which uses magnetostrictive actuation technology. Terfenol-D actuation has many advantages over competing technologies such as hydraulic systems, electric motors, and piezoelectric elements. These benefits include all-electric operation, simplicity and reliability, low mass, low voltage, and insensitivity to centripetal acceleration.

  8. Model Predictive Control for a Small Scale Unmanned Helicopter

    Directory of Open Access Journals (Sweden)

    Jianfu Du

    2008-11-01

    Full Text Available Kinematical and dynamical equations of a small scale unmanned helicoper are presented in the paper. Based on these equations a model predictive control (MPC method is proposed for controlling the helicopter. This novel method allows the direct accounting for the existing time delays which are used to model the dynamics of actuators and aerodynamics of the main rotor. Also the limits of the actuators are taken into the considerations during the controller design. The proposed control algorithm was verified in real flight experiments where good perfomance was shown in postion control mode.

  9. Linear Time Invariant Models for Integrated Flight and Rotor Control

    Science.gov (United States)

    Olcer, Fahri Ersel

    2011-12-01

    Recent developments on individual blade control (IBC) and physics based reduced order models of various on-blade control (OBC) actuation concepts are opening up opportunities to explore innovative rotor control strategies for improved rotor aerodynamic performance, reduced vibration and BVI noise, and improved rotor stability, etc. Further, recent developments in computationally efficient algorithms for the extraction of Linear Time Invariant (LTI) models are providing a convenient framework for exploring integrated flight and rotor control, while accounting for the important couplings that exist between body and low frequency rotor response and high frequency rotor response. Formulation of linear time invariant (LTI) models of a nonlinear system about a periodic equilibrium using the harmonic domain representation of LTI model states has been studied in the literature. This thesis presents an alternative method and a computationally efficient scheme for implementation of the developed method for extraction of linear time invariant (LTI) models from a helicopter nonlinear model in forward flight. The fidelity of the extracted LTI models is evaluated using response comparisons between the extracted LTI models and the nonlinear model in both time and frequency domains. Moreover, the fidelity of stability properties is studied through the eigenvalue and eigenvector comparisons between LTI and LTP models by making use of the Floquet Transition Matrix. For time domain evaluations, individual blade control (IBC) and On-Blade Control (OBC) inputs that have been tried in the literature for vibration and noise control studies are used. For frequency domain evaluations, frequency sweep inputs are used to obtain frequency responses of fixed system hub loads to a single blade IBC input. The evaluation results demonstrate the fidelity of the extracted LTI models, and thus, establish the validity of the LTI model extraction process for use in integrated flight and rotor control

  10. Performance results from a test of an S-76 rotor in the NASA Ames 80- by 120-foot wind tunnel

    Science.gov (United States)

    Shinoda, Patrick M.; Johnson, Wayne

    1993-01-01

    A full-scale helicopter rotor wind tunnel test has been conducted which covers a wide range of rotor-shaft angles-of-attack and 0-100 kt thrust conditions. The hover performance data thus obtained were compared with the results of momentum theory calculations; forward flight rotor-performance data were compared with calculations from a comprehensive rotorcraft analysis. These comparisons suggest that hover testing at an outdoor facility in the absence of ground effect is required to make a final determination of the absolute accuracy of the wind tunnel hover data.

  11. The Effects of Crosswind Flight on Rotor Harmonic Noise Radiation

    Science.gov (United States)

    Greenwood, Eric; Sim, Ben W.

    2013-01-01

    In order to develop recommendations for procedures for helicopter source noise characterization, the effects of crosswinds on main rotor harmonic noise radiation are assessed using a model of the Bell 430 helicopter. Crosswinds are found to have a significant effect on Blade-Vortex Interaction (BVI) noise radiation when the helicopter is trimmed with the fuselage oriented along the inertial flight path. However, the magnitude of BVI noise remains unchanged when the pilot orients the fuselage along the aerodynamic velocity vector, crabbing for zero aerodynamic sideslip. The effects of wind gradients on BVI noise are also investigated and found to be smaller in the crosswind direction than in the headwind direction. The effects of crosswinds on lower harmonic noise sources at higher flight speeds are also assessed. In all cases, the directivity of radiated noise is somewhat changed by the crosswind. The model predictions agree well with flight test data for the Bell 430 helicopter captured under various wind conditions. The results of this investigation would suggest that flight paths for future acoustic flight testing are best aligned across the prevailing wind direction to minimize the effects of winds on noise measurements when wind cannot otherwise be avoided.

  12. A moving hum filter to suppress rotor noise in high-resolution airborne magnetic data

    Science.gov (United States)

    Xia, J.; Doll, W.E.; Miller, R.D.; Gamey, T.J.; Emond, A.M.

    2005-01-01

    A unique filtering approach is developed to eliminate helicopter rotor noise. It is designed to suppress harmonic noise from a rotor that varies slightly in amplitude, phase, and frequency and that contaminates aero-magnetic data. The filter provides a powerful harmonic noise-suppression tool for data acquired with modern large-dynamic-range recording systems. This three-step approach - polynomial fitting, bandpass filtering, and rotor-noise synthesis - significantly reduces rotor noise without altering the spectra of signals of interest. Two steps before hum filtering - polynomial fitting and bandpass filtering - are critical to accurately model the weak rotor noise. During rotor-noise synthesis, amplitude, phase, and frequency are determined. Data are processed segment by segment so that there is no limit on the length of data. The segment length changes dynamically along a line based on modeling results. Modeling the rotor noise is stable and efficient. Real-world data examples demonstrate that this method can suppress rotor noise by more than 95% when implemented in an aeromagnetic data-processing flow. ?? 2005 Society of Exploration Geophysicists. All rights reserved.

  13. Assessing inspection sensitivity as it relates to damage tolerance in composite rotor hubs

    Science.gov (United States)

    Roach, Dennis P.; Rackow, Kirk

    2001-08-01

    Increasing niche applications, growing international markets, and the emergence of advanced rotorcraft technology are expected to greatly increase the population of helicopters over the next decade. In terms of fuselage fatigue, helicopters show similar trends as fixed-wing aircraft. The highly unsteady loads experienced by rotating wings not only directly affect components in the dynamic systems but are also transferred to the fixed airframe structure. Expanded use of rotorcraft has focused attention on the use of new materials and the optimization of maintenance practices. The FAA's Airworthiness Assurance Center (AANC) at Sandia National Labs has joined with Bell Helicopter andother agencies in the rotorcraft industry to evaluate nondestructive inspection (NDI) capabilities in light of the damage tolerance of assorted rotorcraft structure components. Currently, the program's emphasis is on composite rotor hubs. The rotorcraft industry is constantly evaluating new types of lightweight composite materials that not only enhance the safety and reliability of rotor components but also improve performance and extended operating life as well. Composite rotor hubs have led to the use of bearingless rotor systems that are less complex and require less maintenance than their predecessors. The test facility described in this paper allows the structural stability and damage tolerance of composite hubs to be evaluated using realistic flight load spectrums of centrifugal force and bending loads. NDI was integrated into the life-cycle fatigue tests in order to evaluate flaw detection sensitivity simultaneously wiht residual strength and general rotor hub peformance. This paper will describe the evolving use of damage tolerance analysis (DTA) to direct and improve rotorcraft maintenance along with the related use of nondestructive inspections to manage helicopter safety. OVeralll, the data from this project will provide information to improve the producibility, inspectability

  14. Genetic algorithms in conceptual design of a light-weight, low-noise, tilt-rotor aircraft

    Science.gov (United States)

    Wells, Valana L.

    1996-01-01

    This report outlines research accomplishments in the area of using genetic algorithms (GA) for the design and optimization of rotorcraft. It discusses the genetic algorithm as a search and optimization tool, outlines a procedure for using the GA in the conceptual design of helicopters, and applies the GA method to the acoustic design of rotors.

  15. Main rotor six degree-of-freedom isolation system analysis

    Science.gov (United States)

    Eastman, L. B.

    1981-01-01

    The design requirements of the system have been defined and an isolator concept satisfies these requirements identified. Primary design objectives for the isolation system are 90% attenuation of all NP main rotor shaft loads at a weight penalty less than or equal to 1% of design gross weight. The configuration is sized for a UH-60A BLACK HAWK helicopter and its performance, risk, and system integration were evaluated through a series of parametric studies. Preliminary design was carried forward to insure that the design is practical and that the details of the integration of the isolator into the helicopter system are considered. Alternate ground and flight test demonstration programs necessary to verify the proposed isolator design are defined.

  16. Reducing rotor weight

    Energy Technology Data Exchange (ETDEWEB)

    Cheney, M.C. [PS Enterprises, Inc., Glastonbury, CT (United States)

    1997-12-31

    The cost of energy for renewables has gained greater significance in recent years due to the drop in price in some competing energy sources, particularly natural gas. In pursuit of lower manufacturing costs for wind turbine systems, work was conducted to explore an innovative rotor designed to reduce weight and cost over conventional rotor systems. Trade-off studies were conducted to measure the influence of number of blades, stiffness, and manufacturing method on COE. The study showed that increasing number of blades at constant solidity significantly reduced rotor weight and that manufacturing the blades using pultrusion technology produced the lowest cost per pound. Under contracts with the National Renewable Energy Laboratory and the California Energy Commission, a 400 kW (33m diameter) turbine was designed employing this technology. The project included tests of an 80 kW (15.5m diameter) dynamically scaled rotor which demonstrated the viability of the design.

  17. Large Rotor Test Apparatus

    Data.gov (United States)

    Federal Laboratory Consortium — This test apparatus, when combined with the National Full-Scale Aerodynamics Complex, produces a thorough, full-scale test capability. The Large Rotor Test Apparatus...

  18. Reduction of Helicopter BVI Noise, Vibration, and Power Consumption Through Individual Blade Control

    Science.gov (United States)

    Jacklin, Stephen A.; Blaas, Achim; Teves, Dietrich; Kube, Roland; Warmbrodt, William (Technical Monitor)

    1994-01-01

    A wind tunnel test was conducted with a full-scale BO 105 helicopter rotor to evaluate the potential of open-loop individual blade control (IBC) to improve rotor performance, to reduce blade vortex interaction (BVI) noise, and to alleviate helicopter vibrations. The wind tunnel test was an international collaborative effort between NASA/U.S. Army AFDD, ZF Luftfahrttechnik, Eurocopter Deutschland, and the German Aerospace Laboratory (DLR) and was conducted under the auspices of the U.S./German MOU on Rotorcraft Aeromechanics. In this test the normal blade pitch links of the rotor were replaced by servo-actuators so that the pitch of each blade could be controlled independently of the other blades. The specially designed servoactuators and IBC control system were designed and manufactured by ZF Luftfahrttechnik, GmbH. The wind tunnel test was conducted in the 40- by 80-Foot Wind Tunnel at the NASA Ames Research Center. An extensive amount of measurement information was acquired for each IBC data point. These data include rotor performance, static and dynamic hub forces and moments, rotor loads, control loads, inboard and outboard blade pitch motion, and BVI noise data. The data indicated very significant (80 percent) simultaneous reductions in both BVI noise and hub vibrations could be obtained using multi-harmonic input at the critical descent (terminal approach) condition. The data also showed that performance improvements of up to 7 percent could be obtained using 2P input at high-speed forward flight conditions.

  19. A directional array approach for the measurement of rotor noise source distributions with controlled spatial resolution

    Science.gov (United States)

    Brooks, T. F.; Marcolini, M. A.; Pope, D. S.

    1987-01-01

    A special array system has been designed to examine noise source distributions over a helicopter rotor model. The particular measurement environment is for a rotor operating in the open jet of an anechoic wind tunnel. An out-of-flow directional microphone element array is used with a directivity pattern whose major directional lobe projects on the rotor disk. If significant contributions from extraneous tunnel noise sources in the direction of the side lobes are excluded, the dominant output from the array would be that noise emitted from the projected area on the rotor disk. The design incorporates an array element signal blending features which serves to control the spatial resolution of the size of the directional lobes. (Without blending, the resolution and side lobe size are very strong functions of frequency, which severely limits the array's usefulness).

  20. Fundamental understanding, prediction and validation of rotor vibratory loads in steady-level flight

    Science.gov (United States)

    Datta, Anubhav

    This work isolates the physics of aerodynamics and structural dynamics from the helicopter rotor aeromechanics problem, investigates them separately, identifies the prediction deficiencies in each, improves upon them, and couples them back together. The objective is to develop a comprehensive analysis capability for accurate and consistent prediction of rotor vibratory loads in steady level flight. The rotor vibratory loads are the dominant source of helicopter vibration. There are two critical vibration regimes for helicopters in steady level flight: (1) low speed transition and (2) high speed forward flight. The mechanism of rotor vibration at low speed transition is well understood---inter-twinning of blade tip vortices below the rotor disk. The mechanism of rotor vibration at high speed is not clear. The focus in this research is on high speed flight. The goal is to understand the key mechanisms involved and accurately model them. Measured lift, chord force, pitching moment and damper force from the UH-60A Flight Test Program are used to predict, validate and refine the rotor structural dynamics. The prediction errors originate entirely from structural modeling. Once validated, the resultant blade deformations are used to predict and validate aerodynamics. Air loads are calculated using a table look up based unsteady lifting-line model and compared with predictions from a 3-dimensional unsteady CFD model. Both Navier-Stokes and Euler predictions are studied. (Abstract shortened by UMI.) The 3D Navier-Stokes CFD analysis is then consistently coupled with a rotor comprehensive analysis to improve prediction of rotor vibratory loads at high speed. The CFD-comprehensive code coupling is achieved using a loose coupling methodology. The CFD analysis significantly improves section pitching moment prediction near the blade tip, because it captures the steady and unsteady 3D transonic effects. Accurate pitching moments drive elastic twist deformations which together

  1. Helicopter visual aid system

    Science.gov (United States)

    Baisley, R. L.

    1973-01-01

    The helicopter visual aid system has been built and flight tested in situations representative of actual flight missions. The mechanisms discussed contributed greatly to the successful performance of the system throughout the 160 hours of flight testing. It has demonstrated that the visual aid concept can provide improved daytime visual capability, greatly improved nighttime capability, surveillance from greater distances and/or altitudes, covert operation at night through the use of the IR searchlight, and a photographic recording at the scene being viewed.

  2. Sliding Mode Control Technique: Application to a Four Rotors Mini-Flying Robot

    Science.gov (United States)

    Zemalache, K. M.; Tahar, M.; Omari, A.; Maaref, H.

    2009-03-01

    This paper presents the study of stabilization with motion planning of the four rotors mini-flying robot (helicopter with four rotors). The dynamic model involves four control inputs which are computed to stabilize the engine with predefined trajectories path. The tracking feedback controller is based on receding horizon point to point steering. It is clear that our device belongs to families of under-actuated systems. Our aim is to obtain control algorithms using the cascade sliding mode approach in order to stabilize the engine and to generate its trajectory.

  3. A study of helicopter stability and control including blade dynamics

    Science.gov (United States)

    Zhao, Xin; Curtiss, H. C., Jr.

    1988-01-01

    A linearized model of rotorcraft dynamics has been developed through the use of symbolic automatic equation generating techniques. The dynamic model has been formulated in a unique way such that it can be used to analyze a variety of rotor/body coupling problems including a rotor mounted on a flexible shaft with a number of modes as well as free-flight stability and control characteristics. Direct comparison of the time response to longitudinal, lateral and directional control inputs at various trim conditions shows that the linear model yields good to very good correlation with flight test. In particular it is shown that a dynamic inflow model is essential to obtain good time response correlation, especially for the hover trim condition. It also is shown that the main rotor wake interaction with the tail rotor and fixed tail surfaces is a significant contributor to the response at translational flight trim conditions. A relatively simple model for the downwash and sidewash at the tail surfaces based on flat vortex wake theory is shown to produce good agreement. Then, the influence of rotor flap and lag dynamics on automatic control systems feedback gain limitations is investigated with the model. It is shown that the blade dynamics, especially lagging dynamics, can severly limit the useable values of the feedback gain for simple feedback control and that multivariable optimal control theory is a powerful tool to design high gain augmentation control system. The frequency-shaped optimal control design can offer much better flight dynamic characteristics and a stable margin for the feedback system without need to model the lagging dynamics.

  4. Stability and control issues associated with lightly loaded rotors autorotating in high advance ratio flight

    Science.gov (United States)

    Rigsby, James Michael

    Interest in high speed rotorcraft has directed attention toward the slowed-rotor, high advance ratio compound autogyro concept as evidenced by the current DARPA Heliplane project. The behavior of partially unloaded rotors, autorotating at high advance ratio is not well understood and numerous technical issues must be resolved before the vehicle can be realized. Autorotation in helicopters usually indicates an emergency loss of power. For the concept vehicle autorotation is the normal working state of the rotor. The necessity for a reduction in rotor speed with increasing flight speed results in high advance ratio operation where the retreating side of the rotor is dominated by the reverse flow region. Further, rotor speed changes also affect the rotor dynamics and the associated hub moments generated by cyclic flapping. The result is rotor characteristics that vary widely depending on advance ratio. In the present work, rotor behavior is characterized in terms of issues relevant to the control system conceptual design and the rotor impact on the intrinsic vehicle flight dynamics characteristics. A series of trim, stability, and control analyses, based on features inherent in the concept vehicle, are performed. Trends are identified through parametric variation of rotor operating conditions, augmented by inclusion of the sensitivities to blade mass and blade stiffness properties. In this research, non-linear models, including the rotor speed degree of freedom, were created and analyzed with FLIGHTLAB(TM) rotorcraft modeling software. Performance analysis for rotors trimmed to autorotate with zero average hub pitching and rolling moments indicates reduced rotor thrust is achieved primarily through rotor speed reduction at lower shaft incidence angle, and imposing hub moment trim constraints results in a thrust increment sign reversal with collective pitch angle above advance ratio mu ˜ 1.0. Swashplate control perturbations from trim indicate an increase in control

  5. Correlation of AH-1G airframe flight vibration data with a coupled rotor-fuselage analysis

    Science.gov (United States)

    Sangha, K.; Shamie, J.

    1990-01-01

    The formulation and features of the Rotor-Airframe Comprehensive Analysis Program (RACAP) is described. The analysis employs a frequency domain, transfer matrix approach for the blade structural model, a time domain wake or momentum theory aerodynamic model, and impedance matching for rotor-fuselage coupling. The analysis is applied to the AH-1G helicopter, and a correlation study is conducted on fuselage vibration predictions. The purpose of the study is to evaluate the state-of-the-art in helicopter fuselage vibration prediction technology. The fuselage vibration predicted using RACAP are fairly good in the vertical direction and somewhat deficient in the lateral/longitudinal directions. Some of these deficiencies are traced to the fuselage finite element model.

  6. Conceptual Design of a Helicopter Composite Truss Tail Boom.

    Science.gov (United States)

    1980-04-01

    sequence. First, the deep web grooves for the frame and diagonal members were wound. These members were wound alter- nately to achieve an interweaving of...fibers. Once the deep web grooves were filled level to the lower surface of the sand mandrel, the longeron, frame, and diagonal flange winding was...begun. As with the deep webs , the winding of the longeron, frame, and diagonal flanges was done on an alternate basis in order to achieve interwoven

  7. 76 FR 10489 - Special Conditions: Bell Helicopter Textron Canada Limited Model 407 Helicopter, Installation of...

    Science.gov (United States)

    2011-02-25

    ... control functions, since this model helicopter has been certificated to meet the applicable requirements... Federal Aviation Administration 14 CFR Part 27 Special Conditions: Bell Helicopter Textron Canada Limited Model 407 Helicopter, Installation of a Hoh Aeronautics, Inc. Autopilot/ Stabilization Augmentation...

  8. NACA Conference on Helicopters

    Science.gov (United States)

    1954-05-01

    19. 0 4. Parrack, Horace 0.: Physiological and Psycological Effects of Noise. Proc. Second Annual National Noise Abatement Symposium, vol. 2...flutter on the model blades. These motion pictures gave a visual record of the character and violence of the classical-type rotor- blade flutter...reemphasize the violence of the flutter oscillations. In addition to the experimental results discussed so far, some lim- ited analytical studies have been

  9. The Autonomous Helicopter System

    Science.gov (United States)

    Gilmore, John F.

    1984-06-01

    This paper describes an autonomous airborne vehicle being developed at the Georgia Tech Engineering Experiment Station. The Autonomous Helicopter System (AHS) is a multi-mission system consisting of three distinct sections: vision, planning and control. Vision provides the local and global scene analysis which is symbolically represented and passed to planning as the initial route planning constraints. Planning generates a task dependent path for the vehicle to traverse which assures maximum mission system success as well as safety. Control validates the path and either executes the given route or feeds back to previous sections in order to resolve conflicts.

  10. Fabricated Helicopter Transmission Housing Analysis

    Science.gov (United States)

    1975-01-01

    rotor head, rotor blades, swashplate assembly, main rotor controls, and internal gearing. Flight loads on the fabricated housing were determined for...The servo support brackets react induced loads from the swashplate on the servos. A swashplate guide is mounted to the top of the upper housing and...serves to locate the swashplate and react any induced side loads. The scissor bracket connects the upper main housing and the stationary swashplate

  11. Design of the Active Elevon Rotor for Low Vibration

    Science.gov (United States)

    Fulton, Mark V.; Rutkowski, Michael (Technical Monitor)

    2000-01-01

    Helicopter fuselages vibrate more than desired, and traditional solutions have limited effectiveness and can impose an appreciable weight penalty. Alternative methods of combating high vibration, including Higher Harmonic Control (HHC) via harmonic swashplate motion and Individual Blade Control (IBC) via active pitch links, have been studied for several decades. HHC via an on-blade control surface was tested in 1977 on a full scale rotor using a secondary active swashplate and a mechanical control system. Recent smart material advances have prompted new research into the use of on-blade control concepts. Recent analytical studies have indicated that the use of on-blade control surfaces produces vibration reduction comparable to swashplate-based HHC but for less power. Furthermore, smart materials (such as piezoceramics) have been shown to provide sufficient control authority for preliminary rotor experiments. These experiments were initially performed at small scale for reduced tip speeds. More recent experiments have been conducted at or near full tip speeds, and a full-scale active rotor is under development by Boeing with Eurocopter et al. pursuing a similarly advanced full-scale implementation. The US Army Aeroflightdynamics Directorate has undertaken a new research program called the Active Elevon Rotor (AER) Focus Demo. This program includes the design, fabrication, and wind. tunnel testing of a four-bladed, 12.96 ft diameter rotor with one or two on-blade elevons per blade. The rotor, which will be Mach scaled, will use 2-5/rev elevon motion for closed-loop control and :will be tested in late 2001. The primary goal of the AER Focus Demo is the reduction of vibratory hub loads by 80% and the reduction of vibratory blade structural loads. A secondary goal is the reduction of rotor power. The third priority is the measurement and possible reduction of Blade Vortex Interaction (BVI) noise. The present study is focused on elevon effectiveness, that is, the elevon

  12. Process Improvements for the AH-64 Tail Rotor Vibration Analysis

    Science.gov (United States)

    2007-06-01

    blades with pitch bearings and pitch links which transfer the inputs to the blades via the swashplate . When both pedals are centered (50% pedal input...blades, each with a length of 4.58ft. The blades are collectively controlled similar to a swashplate where all blades will move simultaneously in...s CONTROLCONNECT ! DEFINE CONTROL CONNECTION TO ELEMENTS ! Control Swashplate Swashplate Element Type Element

  13. Parametric Investigation of the Effect of Hub Pitching Moment on Blade Vortex Interaction (BVI) Noise of an Isolated Rotor

    Science.gov (United States)

    Malpica, Carlos; Greenwood, Eric; Sim, Ben

    2016-01-01

    At the most fundamental level, main rotor loading noise is caused by the harmonically-varying aerodynamic loads (acoustic pressures) exerted by the rotating blades on the air. Rotorcraft main rotor noise is therefore, in principle, a function of rotor control inputs, and thus the forces and moments required to achieve steady, or "trim", flight equilibrium. In certain flight conditions, the ensuing aerodynamic loading on the rotor(s) can result in highly obtrusive harmonic noise. The effect of the propulsive force, or X-force, on Blade-Vortex Interaction (BVI) noise is well documented. This paper presents an acoustics parametric sensitivity analysis of the effect of varying rotor aerodynamic pitch hub trim moments on BVI noise radiated by an S-70 helicopter main rotor. Results show that changing the hub pitching moment for an isolated rotor, trimmed in nominal 80 knot, 6 and 12 deg descent, flight conditions, alters the miss distance between the blades and the vortex in ways that have varied and noticeable effects on the BVI radiated-noise directionality. Peak BVI noise level is however not significantly altered. The application of hub pitching moment allows the attitude of the fuselage to be controlled; for example, to compensate for the uncomfortable change in fuselage pitch attitude introduced by a fuselage-mounted X-force controller.

  14. Modeling, Control and Coordination of Helicopter Systems

    CERN Document Server

    Ren, Beibei; Chen, Chang; Fua, Cheng-Heng; Lee, Tong Heng

    2012-01-01

    Modeling, Control and Coordination of Helicopter Systems provides a comprehensive treatment of helicopter systems, ranging from related nonlinear flight dynamic modeling and stability analysis to advanced control design for single helicopter systems, and also covers issues related to the coordination and formation control of multiple helicopter systems to achieve high performance tasks. Ensuring stability in helicopter flight is a challenging problem for nonlinear control design and development. This book is a valuable reference on modeling, control and coordination of helicopter systems,providing readers with practical solutions for the problems that still plague helicopter system design and implementation. Readers will gain a complete picture of helicopters at the systems level, as well as a better understanding of the technical intricacies involved. This book also: Presents a complete picture of modeling, control and coordination for helicopter systems Provides a modeling platform for a general class of ro...

  15. Identification, control and visually-guided behavior for a model helicopter

    Science.gov (United States)

    Saripalli, Srikanth

    Research on unmanned aerial vehicles is motivated by applications where human intervention is impossible, risky or expensive e.g. hazardous material recovery, traffic monitoring, disaster relief support, military operations etc. Due to its vertical take-off, landing and hover capabilities, a helicopter is an attractive platform for such applications. There are significant challenges to building an autonomous robotic helicopter - these span the areas of system identification, low-level control, state estimation, and planning. Towards the goal of fully-autonomous helicopters this thesis makes the following contributions. A continuous-discrete extended Kalman filter has been developed that combines inertial data with GPS and compass data to provide estimates of the 6DOF state of the helicopter. Using this filter a model for the helicopter has been identified based on frequency response techniques. The model has been validated in flight tests on a small helicopter testbed (1.6 m rotor diameter) at speeds upto 5 m/s. Based on evidence from this model a decoupled low-level controller has been developed which is embedded in a control architecture suitable for visually-guided navigation. As a novel application, we show how such a controller can be used to perform trajectory following on the helicopter where the desired trajectories are typical spacecraft landing trajectories, and the only controls available are thrusters. This in effect, produces a low-cost testbed for testing spacecraft landing and hazard avoidance on a planetary surface. Finally, we develop and extensively experimentally characterize algorithms for vision-based autonomous landing, object tracking, and sensor deployment.

  16. Flight validated high-order models of UAV helicopter dynamics in hover and forward flight using analytical and parameter identification techniques

    Science.gov (United States)

    Bhandari, Subodh

    There has been a significant growth in the use of UAV helicopters for a multitude of military and civilian applications over the last few years. Due to these numerous applications, from crop dusting to remote sensing, UAV helicopters are now a major topic of interest within the aerospace community. The main research focus is on the development of automatic flight control systems (AFCS). The design of AFCS for these vehicles requires a mathematical model representing the dynamics of the vehicle. The mathematical model is developed either from first-principles, using the equations of motion of the vehicle, or from the flight data, using parameter identification techniques. The traditional six-degrees-of-freedom (6-DoF) dynamics model is not suitable for high-bandwidth control system design. Such models are valid only within the low- to mid-frequency range. The agility and high maneuverability of small-scale helicopters require a high-bandwidth control system for full authority autonomous performance. The design of a high-bandwidth control system in turn requires a high-fidelity simulation model that is able to capture the key dynamics of the helicopter. These dynamics include the rotor dynamics. This dissertation presents the development of a 14-degrees-of-freedom (14-DoF) state-space linear model for the KU Thunder Tiger Raptor 50 UAV helicopter from first-principles and from flight test data using a parameter identification technique for the hovering and forward flight conditions. The model includes rigid body, rotor regressive, rotor inflow, stabilizer bar, and rotor coning dynamics. The model is implemented within The MathWork's MATLAB/Simulink environment. The simulation results show that the high-order model is able to predict the helicopter's dynamics up to the frequency of 30 rad/sec. The main contributions of this dissertation are the development of a high-order simulation model for a small UAV helicopter from first-principles and the identification of a

  17. Vertebral pain in helicopter pilots

    Science.gov (United States)

    Auffret, R.; Delahaye, R. P.; Metges, P. J.; VICENS

    1980-01-01

    Pathological forms of spinal pain engendered by piloting helicopters were clinically studied. Lumbalgia and pathology of the dorsal and cervical spine are discussed along with their clinical and radiological signs and origins.

  18. Rotor Vibration Reduction Using Multi-Element Multi-Path Design

    Science.gov (United States)

    Su, Keye

    Multi-Element Multi-Path (MEMP) structural design is a new concept for rotor vibration reduction. This thesis explores the possibility of applying MEMP design to helicopter rotor blades. A conceptual design is developed to investigate the MEMP blade's vibration reduction performance. In the design, the rotor blade is characterized by two centrifugally loaded beams which are connected to each other through linear and torsional springs. A computer program is built to simulate the behavior of such structures. Detailed parametric studies are conducted. The main challenges in this thesis involve the blade hub load vibration analysis, the blade thickness constraint and the blade parameter selection. The results show substantial vibration reduction for the MEMP design but the large relative deflection between the two beams, conceptualized as an internal spar and airfoil shell, remains a problem for further study.

  19. Control of a Quadrotor Equipped with a Fixed-wing by Tilting Some of Four Rotors

    Directory of Open Access Journals (Sweden)

    Yoshikazu Nakamura

    2017-03-01

    Full Text Available Abstract—Unmanned aerial vehicles (UAVs are beingexpected to be used for the vegetational observation and theinformation collection of disaster sites. Especially, rotorcraftstypified by helicopters are attractive, because they are able tohover and achieve vertical take-off and landing (VTOL.However, rotorcrafts have a disadvantage that it cannot have along-distance flight, because they fly by the thrust of upwarddirection. Aircrafts with tilt rotors are developed in order toovercome such disadvantages. Such aircrafts can be hovering andtake a VTOL and also a long-distance flight by changing theangle of the rotor. In this research, it is aimed at proposing aVTOL-type UAV with a fixed-wing and four tiltable rotors andcontrolling it.

  20. Helicopter Fatigue Life Assessment

    Science.gov (United States)

    1981-03-01

    confrontation avec l’expdrience en service, sur le ddveloppement de technologies nouvelles et sur l’apparition de concepts nouveaux. Tel est l’objet de !a...sur les fausses pales du rotor et le corps est libre (montage sismique) ce qui perrnet d’introduire des efforts relativemont importants avec des...en place sur la nouvelle corni~re mais los contraintes rnesur6es W’ont pins fait d6celer un chargement’ anormalement 6lev6. La nouvelle corni~re

  1. Investigation of Rotor Performance and Loads of a UH-60A Individual Blade Control System

    Science.gov (United States)

    Yeo, Hyeonsoo; Romander, Ethan A.; Norman, Thomas R.

    2011-01-01

    Wind tunnel measurements of performance, loads, and vibration of a full-scale UH-60A Black Hawk main rotor with an individual blade control (IBC) system are compared with calculations obtained using the comprehensive helicopter analysis CAMRAD II and a coupled CAMRAD II/OVERFLOW 2 analysis. Measured data show a 5.1% rotor power reduction (8.6% rotor lift to effective-drag ratio increase) using 2/rev IBC actuation with 2.0 amplitude at = 0.4. At the optimum IBC phase for rotor performance, IBC actuator force (pitch link force) decreased, and neither flap nor chord bending moments changed significantly. CAMRAD II predicts the rotor power variations with the IBC phase reasonably well at = 0.35. However, the correlation degrades at = 0.4. Coupled CAMRAD II/OVERFLOW 2 shows excellent correlation with the measured rotor power variations with the IBC phase at both = 0.35 and = 0.4. Maximum reduction of IBC actuator force is better predicted with CAMRAD II, but general trends are better captured with the coupled analysis. The correlation of vibratory hub loads is generally poor by both methods, although the coupled analysis somewhat captures general trends.

  2. Testing of rotor blades

    Energy Technology Data Exchange (ETDEWEB)

    Busmann, H.G.; Kensche, C.; Berg-Pollack, A.; Buerkner, F.; Sayer, F.; Wiemann, K. [Fraunhofer-Center fuer Windenergie- und Meerestechnik, Bremerhaven (Germany)

    2007-02-15

    Current approval of rotor blades comprises characterization of materials, full-blade tests with static up- and down-bending, and a modal analysis. In addition to these tests, cyclic testing of full-size rotor blades is increasingly discussed to become subject of official certification procedures. Open questions regarding their operational relevance, large investment costs and long duration of up to 4 months for forthcoming large blades now deepen the demand for a new testing methodology. Component testing and scaling methods, highly developed calculation methods, and the definition of blade families of closely related structures are proposed to increase the relevance as well as to decrease costs and duration of the approval procedure. (orig.)

  3. Rotor for a pyrolysis centrifuge reactor

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a rotor for a pyrolysis centrifuge reactor, said rotor comprising a rotor body having a longitudinal centre axis, and at least one pivotally mounted blade being adapted to pivot around a pivot axis under rotation of the rotor body around the longitudinal centre axis....... Moreover, the present invention relates to a pyrolysis centrifuge reactor applying such a rotor....

  4. Application of magnetostrictive smart materials in rotor servoflap control

    Science.gov (United States)

    Ghorayeb, Solomon R.; Hansen, Toby T.; Straub, Friedrich K.

    1995-05-01

    The main theme of this research project has been to analytically develop a proof-of-concept design to demonstrate the effectiveness of a smart material actuator employing ETREMA TERFENOL-DTM for helicopter rotor servoflap control. This design enables the control of the rotor blade flap with an actuator embedded in the blade itself. By moving the control to the rotor blades, the swashplate system could be eliminated. Requirements such as applied load and motions were the key issues that needed to be accounted for in order to achieve a successful design employing the `giant' magnetostrictive material. A series of loading conditions characterized by an additive process of Steady-State. Cyclic, and Active control functions were considered for Sustained flight. Optimization of the overall system gave rise to a system gain of 3.7 for Sustained motion. At this same optimal gain value, and using an ETREMA TERFENOL-DTM rod length of at least 22.7 inches, a net peak-to-peak displacement of as high as 42 mils (1.07 mm) was obtained.

  5. Development of a Nonlinear 6-Degree of Freedom Miniature Rotary-Wing Unmanned Aerial Vehicle Software Model and PID Flight Path Controller Using MathWorks Simulink Simulation Environment

    Science.gov (United States)

    2009-09-01

    rad] trh Tail rotor moment arm. Vertical length from tail rotor hub to .08[m] helicopter c.g. line of sight trl Tail rotor moment arm. Length...tail rotor yaw ( trl r ), and angular velocity of the tail due to roll ( trh p ). If the vehicle travels in the positive y direction, a positive yaw...91 trl m Tail rotor hub location behind cg .08 trh m Tail rotor height above cg 166 Nm/radbL  Longitudinal flapping spring derivative at hover

  6. Helicopter gust alleviation, attitude stabilization, and vibration alleviation using individual-blade-control through a conventional swash plate

    Science.gov (United States)

    Ham, N. D.

    1985-01-01

    The novel active control system presented for helicopter rotor aerodynamic and aeroelastic problems involves the individual control of each blade in the rotating frame over a wide range of frequencies (up to the sixth harmonic of rotor speed). This Individual Blade Control (IBC) system controls blade pitch by means of broadband electrohydraulic actuators attached to the swash plate (in the case of three blades) or individually to each blade, using acceleratometer signals to furnish control commands to the actuators. Attention is given to IBC's application to blade lag, flapping, and bending dynamics. It is shown that gust alleviation, attitude stabilization, vibration alleviation, and air/ground resonance suppression, are all achievable with a conventional helicopter swash plate.

  7. The NASA/industry Design Analysis Methods for Vibrations (DAMVIBS) program : Bell Helicopter Textron accomplishments

    Science.gov (United States)

    Cronkhite, James D.

    1993-01-01

    Accurate vibration prediction for helicopter airframes is needed to 'fly from the drawing board' without costly development testing to solve vibration problems. The principal analytical tool for vibration prediction within the U.S. helicopter industry is the NASTRAN finite element analysis. Under the NASA DAMVIBS research program, Bell conducted NASTRAN modeling, ground vibration testing, and correlations of both metallic (AH-1G) and composite (ACAP) airframes. The objectives of the program were to assess NASTRAN airframe vibration correlations, to investigate contributors to poor agreement, and to improve modeling techniques. In the past, there has been low confidence in higher frequency vibration prediction for helicopters that have multibladed rotors (three or more blades) with predominant excitation frequencies typically above 15 Hz. Bell's findings under the DAMVIBS program, discussed in this paper, included the following: (1) accuracy of finite element models (FEM) for composite and metallic airframes generally were found to be comparable; (2) more detail is needed in the FEM to improve higher frequency prediction; (3) secondary structure not normally included in the FEM can provide significant stiffening; (4) damping can significantly affect phase response at higher frequencies; and (5) future work is needed in the areas of determination of rotor-induced vibratory loads and optimization.

  8. Development and whirl tower test of the SMART active flap rotor

    Science.gov (United States)

    Straub, Friedrich K.; Kennedy, Dennis K.; Stemple, Alan D.; Anand, V. R.; Birchette, Terry S.

    2004-07-01

    A full scale Smart Material Actuated Rotor Technology (SMART) system with piezoelectric actuated blade flaps was developed and whirl tower tested. The development effort included design, fabrication, and component testing of rotor blades, trailing edge flaps, piezoelectric actuators, switching power amplifiers, and the data/power system. Simulations and model scale wind tunnel tests have shown that this system can provide 80% vibration reduction, 10dB noise reduction for a helicopter passing overhead, and substantial aerodynamic performance gains. Whirl tower testing of the 34-foot diameter rotor demonstrated the functionality, robustness, and required authority of the active flap system. The program involved extensive development work and risk reduction tests which resulted in a robust, high performance actuator and a tightly integrated actuator, flap, and blade system. The actuator demonstrated excellent performance during bench testing and has accumulated over 60 million cycles under a spectrum of loading conditions. The flight worthy active flap rotor blades were based on a modified design of the FAA certified MD900 Explorer production rotor blade. Whirl tower testing was conducted with full rotor instrumentation and a 5-component balance. The rotor was tested for 13 hours under a range of conditions, including 7 hours of flap operation. Flap inputs included open loop static and dynamic commands. The flaps showed excellent authority with oscillatory thrust greater than 10% of the steady baseline thrust. Various flap actuation frequency sweeps were run to investigate the dynamics of the rotor and the flap system. Limited closed loop tests used hub accelerations and hub loads for feedback. Proving the integration, robust operation, and authority of the flap system were the key objectives met by the whirl tower test. This success depended on tailoring the piezoelectric materials and actuator to the application and meeting actuator/blade integration requirements

  9. Fundamental Understanding of Rotor Aeromechanics at High Advance Ratio Through Wind Tunnel Testing

    Science.gov (United States)

    Berry, Benjamin

    The purpose of this research is to further the understanding of rotor aeromechanics at advance ratios (mu) beyond the maximum of 0.5 (ratio of forward airspeed to rotor tip speed) for conventional helicopters. High advance ratio rotors have applications in high speed compound helicopters. In addition to one or more conventional main rotors, these aircraft employ either thrust compounding (propellers), lift compounding (fixed-wings), or both. An articulated 4-bladed model rotor was constructed, instrumented, and tested up to a maximum advance ratio of mu=1.6 in the Glenn L. Martin Wind Tunnel at the University of Maryland. The data set includes steady and unsteady rotor hub forces and moments, blade structural loads, blade flapping angles, swashplate control angles, and unsteady blade pressures. A collective-thrust control reversal--where increasing collective pitch results in lower rotor thrust--was observed and is a unique phenomenon to the high advance ratio flight regime. The thrust reversal is explained in a physical manner as well as through an analytical formulation. The requirements for the occurrence of the thrust reversal are enumerated. The effects of rotor geometry design on the thrust reversal onset are explored through the formulation and compared to the measured data. Reverse-flow dynamic stall was observed to extend the the lifting capability of the edgewise rotor well beyond the expected static stall behavior of the airfoil sections. Through embedded unsteady blade surface pressure transducers, the normal force, pitching moment, and shed dynamic stall vortex time histories at a blade section in strong reverse flow were analyzed. Favorable comparisons with published 2-D pitching airfoil reverse flow dynamic stall data indicate that the 3-D stall environment can likely be predicted using models developed from such 2-D experiments. Vibratory hub loads were observed to increase with advance ratio. Maximum amplitude was observed near mu=1, with a

  10. Investigating Flight with a Toy Helicopter

    Science.gov (United States)

    Liebl, Michael

    2010-01-01

    Flight fascinates people of all ages. Recent advances in battery technology have extended the capabilities of model airplanes and toy helicopters. For those who have never outgrown a childhood enthusiasm for the wonders of flight, it is possible to buy inexpensive, remotely controlled planes and helicopters. A toy helicopter offers an opportunity…

  11. Model-based sensor location selection for helicopter gearbox monitoring

    Science.gov (United States)

    Jammu, Vinay B.; Wang, Keming; Danai, Kourosh; Lewicki, David G.

    1996-01-01

    A new methodology is introduced to quantify the significance of accelerometer locations for fault diagnosis of helicopter gearboxes. The basis for this methodology is an influence model which represents the effect of various component faults on accelerometer readings. Based on this model, a set of selection indices are defined to characterize the diagnosability of each component, the coverage of each accelerometer, and the relative redundancy between the accelerometers. The effectiveness of these indices is evaluated experimentally by measurement-fault data obtained from an OH-58A main rotor gearbox. These data are used to obtain a ranking of individual accelerometers according to their significance in diagnosis. Comparison between the experimentally obtained rankings and those obtained from the selection indices indicates that the proposed methodology offers a systematic means for accelerometer location selection.

  12. Rotor and wind turbine formalism

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre

    2017-01-01

    The main conventions used in this book for the study of rotors are introduced in this chapter. The main assumptions and notations are provided. The formalism specific to wind turbines is presented. The forces, moments, velocities and dimensionless coefficients used in the study of rotors...

  13. A New Framework For Helicopter Vibration Suppression; Time-Periodic System Identification and Controller Design

    Science.gov (United States)

    Ulker, Fatma Demet

    In forward flight, helicopter rotor blades function within a highly complex aerodynamic environment that includes both near-blade and far-blade aerodynamic phenomena. These aerodynamic phenomena cause fluctuating aerodynamic loads on the rotor blades. These loads when coupled with the dynamic characteristics and elastic motion of the blade create excessive amount of vibration. These vibrations degrade helicopter performance, passenger comfort and contributes to high cost maintenance problems. In an effort to suppress helicopter vibration, recent studies have developed active control strategies using active pitch links, flaps, twist actuation and higher harmonic control of the swash plate. In active helicopter vibration control, designing a controller in a computationally efficient way requires accurate reduced-order models of complex helicopter aeroelasticity. In previous studies, controllers were designed using aeroelastic models that were obtained by coupling independently reduced aerodynamic and structural dynamic models. Unfortunately, these controllers could not satisfy stability and performance criteria when implemented in high-fidelity computer simulations or real-time experiments. In this thesis, we present a novel approach that provides accurate time-periodic reduced-order models and time-periodic H2 and H infinity controllers that satisfy the stability and performance criteria. Computational efficiency and the necessity of using the approach were validated by implementing an actively controlled flap strategy. In this proposed approach, the reduced-order models were directly identified from high-fidelity coupled aeroelastic analysis by using the time-periodic subspace identification method. Time-periodic H2 and Hinfinity controllers that update the control actuation at every time step were designed. The control synthesis problem was solved using Linear Matrix Inequality and periodic Riccati Equation based formulations, for which an in-house periodic

  14. Dynamics Control Approaches to Improve Vibratory Environment of the Helicopter Aircrew

    Science.gov (United States)

    Wickramasinghe, Viresh Kanchana

    Although helicopter has become a versatile mode of aerial transportation, high vibration levels leads to poor ride quality for its passengers and aircrew. Undesired vibration transmitted through the helicopter seats have been known to cause fatigue and discomfort to the aircrew in the short-term as well as neck strain and back pain injuries due to long-term exposure. This research study investigated the use of novel active as well as passive methodologies integrated in helicopter seats to mitigate the aircrew exposure to high vibration levels. Due to significantly less certification effort required to modify the helicopter seat structure, application of novel technologies to the seat is more practical compared to flight critical components such as the main rotor to reduce aircrew vibration. In particular, this research effort developed a novel adaptive seat mount approach based on active vibration control technology. This novel design that incorporated two stacked piezoelectric actuators as active struts increases the bending stiffness to avoid the low frequency resonance while generating forces to counteract higher harmonic vibration peaks. A real-time controller implemented using a feed-forward algorithm based on adaptive notches counteracted the forced vibration peaks while a robust feedback control algorithm suppressed the resonance modes. The effectiveness of the adaptive seat mount system was demonstrated through extensive closed-loop control tests on a full-scale helicopter seat using representative helicopter floor vibration profiles. Test results concluded that the proposed adaptive seat mount approach based on active control technology is a viable solution for the helicopter seat vibration control application. In addition, a unique flight test using a Bell-412 helicopter demonstrated that the aircrew is exposed to high levels of vibration during flight and that the whole body vibration spectrum varied substantially depending on operating conditions as

  15. Helicopter Icing Review.

    Science.gov (United States)

    1980-09-01

    WILLIAMS LIQUID WATER CONTENT INDICATOR 142 iv LIST OF ILLUSTRATIONS (Continued) FIGCURE TI TLE PAGE 2-45 LASER SPECTROMETERS 1 43 LIST OF TABLES IABLE...tail surfaces. 44 -22 0.04 45 -40 0.01 Il-N 46 32 0.3 Continuous 47 14 0.2 Is Normal 48 .4 0.1 49 -22 ɘ.1 IV -M is Freen" so to 0.15 1000. 01oS,000...liquid water content. Applicable to: Components of the sirplane for which no protection would be supplied after considering clases I. It, end Ill

  16. Unified continuum damage model for matrix cracking in composite rotor blades

    Energy Technology Data Exchange (ETDEWEB)

    Pollayi, Hemaraju; Harursampath, Dineshkumar [Nonlinear Multifunctional Composites - Analysis and Design Lab (NMCAD Lab) Department of Aerospace Engineering Indian Institute of Science Bangalore - 560012, Karnataka (India)

    2015-03-10

    This paper deals with modeling of the first damage mode, matrix micro-cracking, in helicopter rotor/wind turbine blades and how this effects the overall cross-sectional stiffness. The helicopter/wind turbine rotor system operates in a highly dynamic and unsteady environment leading to severe vibratory loads present in the system. Repeated exposure to this loading condition can induce damage in the composite rotor blades. These rotor/turbine blades are generally made of fiber-reinforced laminated composites and exhibit various competing modes of damage such as matrix micro-cracking, delamination, and fiber breakage. There is a need to study the behavior of the composite rotor system under various key damage modes in composite materials for developing Structural Health Monitoring (SHM) system. Each blade is modeled as a beam based on geometrically non-linear 3-D elasticity theory. Each blade thus splits into 2-D analyzes of cross-sections and non-linear 1-D analyzes along the beam reference curves. Two different tools are used here for complete 3-D analysis: VABS for 2-D cross-sectional analysis and GEBT for 1-D beam analysis. The physically-based failure models for matrix in compression and tension loading are used in the present work. Matrix cracking is detected using two failure criterion: Matrix Failure in Compression and Matrix Failure in Tension which are based on the recovered field. A strain variable is set which drives the damage variable for matrix cracking and this damage variable is used to estimate the reduced cross-sectional stiffness. The matrix micro-cracking is performed in two different approaches: (i) Element-wise, and (ii) Node-wise. The procedure presented in this paper is implemented in VABS as matrix micro-cracking modeling module. Three examples are presented to investigate the matrix failure model which illustrate the effect of matrix cracking on cross-sectional stiffness by varying the applied cyclic load.

  17. A simple active controller to suppress helicopter air resonance in hover and forward flight

    Science.gov (United States)

    Friedmann, P. P.; Takahashi, M. D.

    1989-01-01

    A coupled rotor/fuselage helicopter analysis with the important effects of blade torsional flexibility, unsteady aerodynamics, and forward flight is presented. This model is used to illustrate the effect of unsteady aerodynamics, forward flight, and torsional flexibility on air resonance. Next, a nominal configuration, which experiences air resonance in forward flight, is selected. A simple multivariable compensator using conventional swashplate inputs and a single body roll rate measurement is then designed. The controller design is based on a linear estimator in conjunction with optimal feedback gains, and the design is done in the frequency domain using the loop-transfer recovery method. The controller is shown to suppress the air resonance instability throughout wide range helicopter loading conditions and forward flight speeds.

  18. 77 FR 12991 - Airworthiness Directives; Robinson Helicopter Company Helicopters

    Science.gov (United States)

    2012-03-05

    ... Airplane Directorate, FAA, 3960 Paramount Blvd., Lakewood, CA 90712; telephone (562) 627-5348; email [email protected] (regarding Model R22 helicopters); or Fred Guerin, Aerospace Engineer, Los Angeles Aircraft Certification Office, Transport Airplane Directorate, FAA, 3960 Paramount Blvd., Lakewood, CA...

  19. 78 FR 45845 - Airworthiness Directives; Bell Helicopter Textron Helicopters

    Science.gov (United States)

    2013-07-30

    ..., corrosion (may be indicated by blistering, peeling, flaking, bubbling, or cracked paint), a nick, scratch... helicopter. (iv) If any blistering, peeling, flaking, bubbling, or cracked paint is detected anywhere on the blade, remove the paint from the affected area by sanding in a spanwise direction with abrasive cloth or...

  20. Low-speed wind tunnel test results of the Canard Rotor/Wing concept

    Science.gov (United States)

    Bass, Steven M.; Thompson, Thomas L.; Rutherford, John W.; Swanson, Stephen

    1993-01-01

    The Canard Rotor/Wing (CRW), a high-speed rotorcraft concept, was tested at the National Aeronautics and Space Administration (NASA) Ames Research Center's 40- by 80-Foot Wind Tunnel in Mountain View, California. The 1/5-scale model was tested to identify certain low-speed, fixed-wing, aerodynamic characteristics of the configuration and investigate the effectiveness of two empennages, an H-Tail and a T-Tail. The paper addresses the principal test objectives and the results achieved in the wind tunnel test. These are summarized as: i) drag build-up and differences between the H-Tail and T-Tail configuration, ii) longitudinal stability of the H-Tail and T-Tail configurations in the conversion and cruise modes, iii) control derivatives for the canard and elevator in the conversion and cruise modes, iv) aerodynamic characteristics of varying the rotor/wing azimuth position, and v) canard and tail lift/trim capability for conversion conditions.

  1. Heavy tails of OLS

    DEFF Research Database (Denmark)

    Mikosch, Thomas Valentin; de Vries, Casper

    2013-01-01

    Suppose the tails of the noise distribution in a regression exhibit power law behavior. Then the distribution of the OLS regression estimator inherits this tail behavior. This is relevant for regressions involving financial data. We derive explicit finite sample expressions for the tail...

  2. The Finite-Bladed Betz Rotor

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær

    2016-01-01

    The finite-bladed optimum Betz rotor is treated. It is first very recently that a complete description of this rotor has been derived. In the chapter, a full analytical solution to the Betz rotor problem will be given, and the results will be compared to other optimum rotor models, both...

  3. Rotor blade assembly having internal loading features

    Science.gov (United States)

    Soloway, Daniel David

    2017-05-16

    Rotor blade assemblies and wind turbines are provided. A rotor blade assembly includes a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge and a trailing edge each extending between a tip and a root, the rotor blade defining a span and a chord, the exterior surfaces defining an interior of the rotor blade. The rotor blade assembly further includes a loading assembly, the loading assembly including a weight disposed within the interior and movable generally along the span of the rotor blade, the weight connected to a rotor blade component such that movement of the weight towards the tip causes application of a force to the rotor blade component by the weight. Centrifugal force due to rotation of the rotor blade biases the weight towards the tip.

  4. Aircraft Rotor Surface Coating Qualification Testing Aircraft Rotor Surface Coating

    National Research Council Canada - National Science Library

    2006-01-01

    .... The Aviation and Missile Research, Development and Engineering Center "AMRDEC" located at Redstone Arsenal, AL selected the NCDMM to coordinate the initial effort to qualify a new aircraft rotor...

  5. Smart actuation for helicopter rotorblades

    NARCIS (Netherlands)

    Paternoster, Alexandre; Loendersloot, Richard; de Boer, Andries; Akkerman, Remko; Berselli, G.; Vertechy, R.; Vassura, G.

    2012-01-01

    Successful rotorcrafts were only achieved when the differences between hovering flight conditions and a stable forward flight were understood. During hovering, the air speed on all helicopter blades is linearly distributed along each blade and is the same for each. However, during forward flight,

  6. Helicopter Toy and Lift Estimation

    Science.gov (United States)

    Shakerin, Said

    2013-01-01

    A $1 plastic helicopter toy (called a Wacky Whirler) can be used to demonstrate lift. Students can make basic measurements of the toy, use reasonable assumptions and, with the lift formula, estimate the lift, and verify that it is sufficient to overcome the toy's weight. (Contains 1 figure.)

  7. Helicopter-Ship Qualification Testing

    NARCIS (Netherlands)

    Hoencamp, A.

    2015-01-01

    The goal of this research project is to develop a novel test methodology which can be used for optimizing cost and time efficiency of helicopter-ship qualification testing without reducing safety. For this purpose, the so-called “SHOL-X” test methodology has been established, which includes the

  8. Helicopter detection and classification demonstrator

    NARCIS (Netherlands)

    Koersel, A.C. van

    2000-01-01

    A technology demonstrator that detects and classifies different helicopter types automatically, was developed at TNO-FEL. The demonstrator is based on a PC, which receives its acoustic input from an all-weather microphone. The demonstrator uses commercial off-the-shelf hardware to digitize the

  9. Anticipatory routing of police helicopters

    NARCIS (Netherlands)

    van Urk, Rick; van Urk, Rick; Mes, Martijn R.K.; Hans, Elias W.

    2013-01-01

    We have developed a decision support application for the Dutch Aviation Police and Air Support unit for routing their helicopters in anticipation of unknown future incidents. These incidents are not known in advance, yet do require a swift response. A response might include the dispatch of a police

  10. Analysis of U.S. Military Helicopter Operations in Support of Humanitarian Assistance and Disaster Relief

    Science.gov (United States)

    2011-12-01

    operate is essential. During OUR, there was only one aircraft power cart and liquid oxygen cart available to support 13 aircraft forward deployed to... mass causality situation resulting from the earthquake quickly overwhelmed the medical capability on the scene. Request for MEDEVAC flights far...Cost BCM Cost AHXC MAIN ROTOR DAMPER $20,899.00 $15,794.00 0.01292 6.20 8.68 11 14 3 $47,382.00 $181,495.58 AHXC TAIL ROTOR PITCH SHAFT SUPPORT

  11. Hybrid magnetorheological fluid elastomeric lag dampers for helicopter stability augmentation

    Science.gov (United States)

    Hu, Wei; Wereley, Norman M.

    2008-08-01

    A laboratory demonstration of a hybrid magnetorheological fluid-elastomeric (MRFE) damper is investigated for adjustable or programmable lag mode damping in helicopters, so that damping requirements can be varied as a function of different flight conditions. The laboratory demonstration of this hybrid MRFE lag damper consists of a double lap shear elastomeric damper in parallel with two magnetorheological (MR) flow mode dampers. This is compared to a damper where only elastomeric materials are implemented, i.e., a double lap shear specimen. The relationship between the output force and the quasi-steady harmonic displacement input to a flow mode MR damper is exploited, where the output force can be adjusted as a function of applied magnetic field. Equivalent viscous damping is used to compare the damping characteristics of the hybrid damper to a conventional elastomeric damper under steady-state sinusoidal displacement excitation. To demonstrate feasibility, a hybrid MRFE damper test setup is designed, and single frequency (lag frequency or rotor in-plane bending frequency) and dual frequency (lag frequency and rotor frequency) tests are conducted under different magnetic fields. The hybrid MRFE damper exhibits amplitude-dependent damping behavior. However, with application of a magnetic field, the damping level is controlled to a specific damping level objective as a function of displacement amplitude. Similarly, under dual frequency conditions, damping degradation at the lag frequency, because of lag motion at the rotor frequency, can also be recovered by increasing magnetic field. A time-domain analysis is developed to study the nonlinear dynamic behavior of the hybrid MRFE damper. Using rate-dependent elasto-slides, the amplitude-dependent behavior of the hybrid MRFE damper is accurately reconstructed using both constant and current-dependent (i.e. controllable) parameters. The analysis is physically motivated and can be applied to the elastomer and MR fluid

  12. A real-time blade element helicopter simulation for handling qualities analysis

    Science.gov (United States)

    Du Val, Ronald W.

    1989-01-01

    A simulation model which utilizes parallel processing platforms is described in terms of its contributions to improved real-time helicopter simulation. The FLIGHTLAB parallel processing environment is explained, and the relative advantages of the blade element and rotor map models for rigid and elastic articulated blades are discussed. A UH-60 simulation is conducted by means of a rigid model with 14 degrees of freedom, as well as an elastic model with 26 degrees of freedom, to compare trim conditions, longitudinal static margins, and longitudinal and lateral frequency responses. The FLIGHTLAB system is shown to facilitate restructuring for parallel processing as well as the systematic comparison of a variety of models. The system can facilitate the comparison of rigid and elastic blade element rotor models at NASA-Ames and other research facilities.

  13. Design sensitivity analysis for an aeroelastic optimization of a helicopter blade

    Science.gov (United States)

    Lim, Joon; Chopra, Inderjit

    1987-01-01

    The sensitivity of vibratory hub loads of a four-bladed hingeless rotor with respect to blade design parameters is investigated using a finite element formulation in space and time. Design parameters include nonstructural mass distribution (spanwise and chordwise), chordwise offset of center of gravity from aerodynamic center, blade bending stiffnesses (flap, lag and torsion). Hub loads selected are 4/rev vertical hub shear and 3/rev hub moment in the rotating reference frame. The sensitivity derivatives of vertical hub loads with respect to blade design parameters are compared using two approaches, finite difference scheme and analytical approach using chain rule differentiation. The analytical derivative approach developed as an integral part of response solution (finite element in time) is a powerful method for an aeroelastic optimization of a helicopter rotor.

  14. Genetics Home Reference: Rotor syndrome

    Science.gov (United States)

    ... TYPE Sources for This Page Strassburg CP. Hyperbilirubinemia syndromes (Gilbert-Meulengracht, Crigler-Najjar, Dubin-Johnson, and Rotor syndrome). Best Pract Res Clin Gastroenterol. 2010 Oct;24( ...

  15. Rotor Wake Vortex Definition: Initial Evaluation of 3-C PIV Results of the Hart-II Study

    Science.gov (United States)

    Burley, Casey L.; Brooks, Thomas F.; vanderWall, Berend; Richard, Hughes; Raffel, Markus; Beaumier, Philippe; Delrieux, Yves; Lim, Joon W.; Yu, Yung H.; Tung, Chee

    2002-01-01

    An initial evaluation is made of extensive three-component (3C) particle image velocimetry (PIV) measurements within the wake across a rotor disk plane. The model is a 40 percent scale BO-105 helicopter main rotor in forward flight simulation. This study is part of the HART II test program conducted in the German-Dutch Wind Tunnel (DNW). Included are wake vortex field measurements over the advancing and retreating sides of the rotor operating at a typical descent landing condition important for impulsive blade-vortex interaction (BVI) noise. Also included are advancing side results for rotor angle variations from climb to steep descent. Using detailed PIV vector maps of the vortex fields, methods of extracting key vortex parameters are examined and a new method was developed and evaluated. An objective processing method, involving a center-of-vorticity criterion and a vorticity 'disk' integration, was used to determine vortex core size, strength, core velocity distribution characteristics, and unsteadiness. These parameters are mapped over the rotor disk and offer unique physical insight for these parameters of importance for rotor noise and vibration prediction.

  16. Vibration response of misaligned rotors

    Science.gov (United States)

    Patel, Tejas H.; Darpe, Ashish K.

    2009-08-01

    Misalignment is one of the common faults observed in rotors. Effect of misalignment on vibration response of coupled rotors is investigated in the present study. The coupled rotor system is modelled using Timoshenko beam elements with all six dof. An experimental approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation. Misalignment effect at coupling location of rotor FE model is simulated using nodal force vector. The force vector is found using misalignment coupling stiffness matrix, derived from experimental data and applied misalignment between the two rotors. Steady-state vibration response is studied for sub-critical speeds. Effect of the types of misalignment (parallel and angular) on the vibration behaviour of the coupled rotor is examined. Along with lateral vibrations, axial and torsional vibrations are also investigated and nature of the vibration response is also examined. It has been found that the misalignment couples vibrations in bending, longitudinal and torsional modes. Some diagnostic features in the fast Fourier transform (FFT) of torsional and longitudinal response related to parallel and angular misalignment have been revealed. Full spectra and orbit plots are effectively used to reveal the unique nature of misalignment fault leading to reliable misalignment diagnostic information, not clearly brought out by earlier studies.

  17. Robust Decentralized Nonlinear Control for a Twin Rotor MIMO System.

    Science.gov (United States)

    Belmonte, Lidia María; Morales, Rafael; Fernández-Caballero, Antonio; Somolinos, José Andrés

    2016-07-27

    This article presents the design of a novel decentralized nonlinear multivariate control scheme for an underactuated, nonlinear and multivariate laboratory helicopter denominated the twin rotor MIMO system (TRMS). The TRMS is characterized by a coupling effect between rotor dynamics and the body of the model, which is due to the action-reaction principle originated in the acceleration and deceleration of the motor-propeller groups. The proposed controller is composed of two nested loops that are utilized to achieve stabilization and precise trajectory tracking tasks for the controlled position of the generalized coordinates of the TRMS. The nonlinear internal loop is used to control the electrical dynamics of the platform, and the nonlinear external loop allows the platform to be perfectly stabilized and positioned in space. Finally, we illustrate the theoretical control developments with a set of experiments in order to verify the effectiveness of the proposed nonlinear decentralized feedback controller, in which a comparative study with other controllers is performed, illustrating the excellent performance of the proposed robust decentralized control scheme in both stabilization and trajectory tracking tasks.

  18. 76 FR 2607 - Airworthiness Directives; MD Helicopters, Inc. (MDHI) Model MD900 Helicopters

    Science.gov (United States)

    2011-01-14

    ... MDHI Model MD900 helicopters. That AD currently requires turning on both Vertical Stabilizer Control... Stability Augmentation System (YSAS) for the Model 500N and 600N helicopters and to the VSCS for the Model... also requires turning ON both VSCS switches to reduce pilot workload and to help control the helicopter...

  19. AERODYNAMIC CHARACTERISTICS CALCULATION ON SINGLE ROTOR BLADE USING FLOEFD, ANSYS FLUENT AND RC-VTOL

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available The results of computational simulation of helicopter rotor's single blade flow, for which experimental (model test data are published, are represented in this article. The calculations were made in the universal software package of CFD modeling FloEFD, which was based on the solution of averaged equations' system of Navier-Stocks, as well as in the program software RC-VTOL using the vortex method. The obtained results are compared with experimental data and modeling results in the program software ANSYS Fluent (license of TsAGI Nr. 501024. The work shows satisfactory, and in some cases good calculation data reconciliation getting with different techniques including experimental.

  20. Design of fault tolerant control system for individual blade control helicopters

    Science.gov (United States)

    Tamayo, Sergio

    This dissertation presents the development of a fault tolerant control scheme for helicopters fitted with individually controlled blades. This novel approach attempts to improve fault tolerant capabilities of helicopter control system by increasing control redundancy using additional actuators for individual blade input and software re-mixing to obtain nominal or close to nominal conditions under failure. An advanced interactive simulation environment has been developed including modeling of sensor failure, swashplate actuator failure, individual blade actuator failure, and blade delamination to support the design, testing, and evaluation of the control laws. This simulation environment is based on the blade element theory for the calculation of forces and moments generated by the main rotor. This discretized model allows for individual blade analysis, which in turn allows measuring the consequences of a stuck blade, or loss of the surface area of the blade itself, with respect to the dynamics of the whole helicopter. The control laws are based on non-linear dynamic inversion and artificial neural network augmentation, which is a mix of linear and nonlinear methods that compensates for model inaccuracies due to linearization or failure. A stability analysis based on the Lyapunov function approach has shown that bounded tracking error is guaranteed, and under specific circumstances, global stability is guaranteed as well. An analysis over the degrees of freedom of the mechanical system and its impact over the helicopter handling qualities is also performed to measure the degree of redundancy achieved with the addition of individual blade actuators as compared to a classic swashplate helicopter configuration. Mathematical analysis and numerical simulation, using reconfiguration of the individual blade control under failure have shown that this control architecture can potentially improve the survivability of the aircraft and reduce pilot workload under failure

  1. 78 FR 9309 - Airworthiness Directives; MD Helicopters, Inc., Helicopters

    Science.gov (United States)

    2013-02-08

    ... with an airworthy T-T strap. The service bulletins specify the T-T strap to be replaced within six, 12... accomplished prior to that time. (e) Required Actions (1) Within six months, determine the manufacturer's cure... rotor blades. Issued in Fort Worth, Texas, on January 29, 2013. Lance T. Gant, Acting Directorate...

  2. 78 FR 65195 - Airworthiness Directives; MD Helicopters, Inc. (MDHI) Helicopters

    Science.gov (United States)

    2013-10-31

    ... rotor blade (MRB) retention bolts (bolts) installed. This AD requires a daily check of the position of... identified in this AD, contact MDHI, Attn: Customer Support Division, 4555 E. McDowell Rd., Mail Stop M615... (ASB SB900-116). ASB SB900-116 specifies a repetitive check of the blade retention bolts, part number...

  3. A full potential rotor analysis with wake influence using an inner-outer domain technique

    Science.gov (United States)

    Egolf, T. A.; Sparks, S. P.

    1986-01-01

    A three-dimensional, quasi-steady, full potential flow solver was adapted to include realistic rotor wake influence for the aerodynamic analysis of helicopter rotors. The method uses an inner/outer domain technique to accommodate wake effects. Nonlinear flow is computed in the inner domain using a finite difference solution method. The wake is modeled using prescribed wake techniques to allow for the inclusion of realistic wake geometries. Portions of the wake passing inside the inner domain are treated using an embedded vortex technique. The procedure couples the wake influence with the inner domain solution in a consistent and efficient solution process. Correlation with measured lifting transonic data in hover and forward flight is shown which demonstrates the merits of the approach.

  4. Review and analysis of the DNW/Model 360 rotor acoustic data base

    Science.gov (United States)

    Zinner, R. A.; Boxwell, D. A.; Spencer, R. H.

    1989-01-01

    A comprehensive model rotor aeroacoustic data base was collected in a large anechoic wind tunnel in 1986. Twenty-six microphones were positioned around the azimuth to collect acoustic data for approximately 150 different test conditions. A dynamically scaled, blade-pressure-instrumented model of the forward rotor of the BH360 helicopter simultaneously provided blade pressures for correlation with the acoustic data. High-speed impulsive noise, blade-vortex interaction noise, low-frequency noise, and broadband noise were all captured in this extensive data base. Trends are presentes for each noise source, with important parametric variations. The purpose of this paper is to introduce this data base and illustrate its potential for predictive code validation.

  5. Flight service evaluation of composite components on the Bell Helicopter model 206L: Design, fabrication and testing

    Science.gov (United States)

    Zinberg, H.

    1982-01-01

    The design, fabrication, and testing phases of a program to obtain long term flight service experience on representative helicopter airframe structural components operating in typical commercial environments are described. The aircraft chosen is the Bell Helicopter Model 206L. The structural components are the forward fairing, litter door, baggage door, and vertical fin. The advanced composite components were designed to replace the production parts in the field and were certified by the FAA to be operable through the full flight envelope of the 206L. A description of the fabrication process that was used for each of the components is given. Static failing load tests on all components were done. In addition fatigue tests were run on four specimens that simulated the attachment of the vertical fin to the helicopter's tail boom.

  6. Optimal Design and Acoustic Assessment of Low-Vibration Rotor Blades

    Directory of Open Access Journals (Sweden)

    G. Bernardini

    2016-01-01

    Full Text Available An optimal procedure for the design of rotor blade that generates low vibratory hub loads in nonaxial flow conditions is presented and applied to a helicopter rotor in forward flight, a condition where vibrations and noise become severe. Blade shape and structural properties are the design parameters to be identified within a binary genetic optimization algorithm under aeroelastic stability constraint. The process exploits an aeroelastic solver that is based on a nonlinear, beam-like model, suited for the analysis of arbitrary curved-elastic-axis blades, with the introduction of a surrogate wake inflow model for the analysis of sectional aerodynamic loads. Numerical results are presented to demonstrate the capability of the proposed approach to identify low vibratory hub loads rotor blades as well as to assess the robustness of solution at off-design operating conditions. Further, the aeroacoustic assessment of the rotor configurations determined is carried out in order to examine the impact of low-vibration blade design on the emitted noise field.

  7. Analytical methods in rotor dynamics

    CERN Document Server

    Dimarogonas, Andrew D; Chondros, Thomas G

    2013-01-01

    The design and construction of rotating machinery operating at supercritical speeds was, in the 1920s, an event of revolutionary importance for the then new branch of dynamics known as rotor dynamics. In the 1960s, another revolution occurred: In less than a decade, imposed by operational and economic needs, an increase in the power of turbomachinery by one order of magnitude took place. Dynamic analysis of complex rotor forms became a necessity, while the importance of approximate methods for dynamic analysis was stressed. Finally, the emergence of fracture mechanics, as a new branch of applied mechanics, provided analytical tools to investigate crack influence on the dynamic behavior of rotors. The scope of this book is based on all these developments. No topics related to the well-known classical problems are included, rather the book deals exclusively with modern high-power turbomachinery.

  8. On cup anemometer rotor aerodynamics.

    Science.gov (United States)

    Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

    2012-01-01

    The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

  9. Flight test of MMW radar for brown-out helicopter landing

    Science.gov (United States)

    Martin, Christopher A.; Kolinko, Vladimir; Otto, Gregory P.; Lovberg, John A.

    2012-06-01

    Trex Enterprises and US Army RDECOM CERDEC Night Vision Electronic Sensors Directorate developed and tested helicopter radar to aid in brown-out landing situations. A brown-out occurs when sand and dust kicked up by the helicopter rotors impair the pilot's vision. Millimeter-wave (MMW) radiation penetrates sand and dust with little loss or scattering, and radar at this frequency can provide a pilot with an image of the intended landing zone. The Brown-out Situational Awareness System (BSAS) is a frequency-modulated, continuous-wave radar that measures range to the ground across a conical field-of-view and uses that range information to create an image for the pilot. The BSAS collected imagery from a helicopter in a blowing sand environment with obstacles including ditches, hills, posts, poles, wires, buildings and vehicles. The BSAS proved the capability to form images of the ground through heavy blowing sand and resolve images of some obstacles. The BSAS also attempted to differentiate flat ground from bumpy ground with limited success at some viewing angles. The BSAS test imagery includes some artifacts formed by high radar cross-section targets in the field-of-view or sidelobes. The paper discusses future improvements that could limit these artifacts.

  10. Differential infrared thermography for boundary layer transition detection on pitching rotor blade models

    Science.gov (United States)

    Raffel, Markus; Merz, Christoph B.; Schwermer, Till; Richter, Kai

    2015-02-01

    Differential infrared thermography (DIT) was investigated and applied for the detection of unsteady boundary layer transition locations on a pitching airfoil and on a rotating blade under cyclic pitch. DIT is based on image intensity differences between two successively recorded infrared images. The images were recorded with a high framing rate infrared camera. A pitching NACA0012 airfoil served as the first test object. The recorded images were used in order to investigate and to further improve evaluation strategies for periodically moving boundary layer transition lines. The measurement results are compared with the results of unsteady CFD simulations based on the DLR-TAU code. DIT was then used for the first time for the optical measurement of unsteady transition locations on helicopter rotor blade models under cyclic pitch and rotation. Image de-rotation for tracking the blade was employed using a rotating mirror to increase exposure time without causing motion blur. The paper describes the challenges that occurred during the recording and evaluation of the data in detail. However, the results were found to be encouraging to further improve the method toward the measurement of unsteady boundary layer transition lines on helicopter rotor models in forward flight.

  11. Validation of a mathematical model for Bell 427 Helicopter using parameter estimation techniques and flight test data

    Science.gov (United States)

    Crisan, Emil Gabriel

    Certification requirements, optimization and minimum project costs, design of flight control laws and the implementation of flight simulators are among the principal applications of system identification in the aeronautical industry. This document examines the practical application of parameter estimation techniques to the problem of estimating helicopter stability and control derivatives from flight test data provided by Bell Helicopter Textron Canada. The purpose of this work is twofold: a time-domain application of the Output Error method using the Gauss-Newton algorithm and a frequency-domain identification method to obtain the aerodynamic and control derivatives of a helicopter. The adopted model for this study is a fully coupled, 6 degree of freedom (DoF) state space model. The technique used for rotorcraft identification in time-domain was the Maximum Likelihood Estimation method, embodied in a modified version of NASA's Maximum Likelihood Estimator program (MMLE3) obtained from the National Research Council (NRC). The frequency-domain system identification procedure is incorporated in a comprehensive package of user-oriented programs referred to as CIFERRTM. The coupled, 6 DoF model does not include the high frequency main rotor modes (flapping, lead-lag, twisting), yet it is capable of modeling rotorcraft dynamics fairly accurately as resulted from the model verification. The identification results demonstrate that MMLE3 is a powerful and effective tool for extracting reliable helicopter models from flight test data. The results obtained in frequency-domain approach demonstrated that CIFERRTM could achieve good results even on limited data.

  12. Trajectory tracking for two-degree of freedom helicopter system using a controller-disturbance observer integrated design.

    Science.gov (United States)

    Zarei, Amin; Poutari, M Sedigh; Barakati, S Masoud

    2018-01-29

    Trajectory tracking control for helicopters, which are widely used in severe situations such as military and rescue missions, is a challenging field of research. In helicopter system, the stability problem and predefined trajectories tracking are main challenges, especially in the presence of external disturbances and dynamic model uncertainties. Hence, a robust control design is needed for tracking the desired references. There has been a lot of motivation for solving these problems with simpler methods and also reducing the couplings in the helicopter system to achieve better performance, as the presented paper attempts to fill these gaps. This paper focuses on designing control laws for two-degree of freedom helicopter system while assuring the closed-loop stability. A nonlinear disturbance observer-based control (NDOBC) is designed for attenuating the effects of exogenous disturbances. Trajectory tracking controller and nonlinear disturbance observer are formulated in the form of two linear matrix inequality (LMI) problems. The closed-loop system stability, including controller and observer, is investigated by Lyapunov theorem. The effectiveness of the proposed design for tracking the trajectories (vertical flight and pitch angle rotor blade) and disturbance estimation is verified by simulation results. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

  13. Development of swashplateless helicopter blade pitch control system using the limited angle direct-drive motor (LADDM

    Directory of Open Access Journals (Sweden)

    Wang Jian

    2015-10-01

    Full Text Available It can be greatly beneficial to remove the swashplate of conventional helicopter, because the swashplate is usually complicated, aerodynamically resistive, and obstacle of more complex pitch control for improving performance. The present technologies for helicopter vibration reduction are usually narrow in effective range or requiring additional actuators and signal transfer links, and more effective technology is desired. Helicopter blade pitch control system, which is removed of swashplate and integrated high-frequency pitch control function for active vibration reduction, is likely the suitable solution at current technical level. Several potential implementation schemes are discussed, such as blades being directly or indirectly driven by actuators mounted in rotating frame and application of different types of actuators, especially implementation schemes of electro-mechanical actuator with or without gear reducer. It is found that swashplateless blade pitch control system based on specially designed limited angle direct-drive motor (LADDM is a more practical implementation scheme. An experimental prototype of the finally selected implementation scheme has been designed, fabricated and tested on rotor tower. The test results show considerable feasibility of the swashplateless helicopter blade pitch control system using the LADDM.

  14. Estimating tail probabilities

    Energy Technology Data Exchange (ETDEWEB)

    Carr, D.B.; Tolley, H.D.

    1982-12-01

    This paper investigates procedures for univariate nonparametric estimation of tail probabilities. Extrapolated values for tail probabilities beyond the data are also obtained based on the shape of the density in the tail. Several estimators which use exponential weighting are described. These are compared in a Monte Carlo study to nonweighted estimators, to the empirical cdf, to an integrated kernel, to a Fourier series estimate, to a penalized likelihood estimate and a maximum likelihood estimate. Selected weighted estimators are shown to compare favorably to many of these standard estimators for the sampling distributions investigated.

  15. Lead-Lag Control for Helicopter Vibration and Noise Reduction

    Science.gov (United States)

    Gandhi, Farhan

    1995-01-01

    As a helicopter transitions from hover to forward flight, the main rotor blades experience an asymmetry in flow field around the azimuth, with the blade section tangential velocities increasing on the advancing side and decreasing on the retreating side. To compensate for the reduced dynamic pressure on the retreating side, the blade pitch angles over this part of the rotor disk are increased. Eventually, a high enough forward speed is attained to produce compressibility effects on the advancing side of the rotor disk and stall on the retreating side. The onset of these two phenomena drastically increases the rotor vibratory loads and power requirements, thereby effectively establishing a limit on the maximum achievable forward speed. The alleviation of compressibility and stall (and the associated decrease in vibratory loads and power) would potentially result in an increased maximum forward speed. In the past, several methods have been examined and implemented to reduce the vibratory hub loads. Some of these methods are aimed specifically at alleviating vibration at very high flight speeds and increasing the maximum flight speed, while others focus on vibration reduction within the conventional flight envelope. Among the later are several types passive as well as active schemes. Passive schemes include a variety of vibration absorbers such as mechanical springs, pendulums, and bifilar absorbers. These mechanism are easy to design and maintain, but incur significant weight and drag penalties. Among the popular active control schemes in consideration are Higher Harmonic Control (HHC) and Individual Blade Control (IBC). HHC uses a conventional swash plate to generate a multi-cyclic pitch input to the blade. This requires actuators capable of sufficiently high power and bandwidth, increasing the cost and weight of the aircraft. IBC places actuators in the rotating reference frame, requiring the use of slip rings capable of transferring enough power to the actuators

  16. Tail posture predicts tail damage among weaned piglets

    NARCIS (Netherlands)

    Zonderland, J.J.; Riel, van J.W.; Bracke, M.B.M.; Kemp, B.; Hartog, den L.A.; Spoolder, H.A.M.

    2009-01-01

    Tail biting in pigs is a widespread behavioural vice with significant animal welfare and economic consequences. All too often, tail biting is not diagnosed nor dealt with until tail damage is present. To effectively reduce the negative effects of tail biting, it must be diagnosed in an early stage.

  17. Reported tailings dam failures

    Energy Technology Data Exchange (ETDEWEB)

    Rico, M. [CSIC - Instituto Pirenaico de Ecologia, Zaragoza (Spain)], E-mail: mayterico@ipe.csic.es; Benito, G. [CSIC - Centro de Ciencias Medioambientales, Madrid (Spain); Salgueiro, A.R. [CERENA - Centro de Recursos Naturais e Ambiente of IST, Lisboa (Portugal); Diez-Herrero, A. [Geological Hazards Unit, Spanish Geological Survey (IGME), Madrid (Spain); Pereira, H.G. [CERENA - Centro de Recursos Naturais e Ambiente of IST, Lisboa (Portugal)

    2008-04-01

    A detailed search and re-evaluation of the known historical cases of tailings dam failure was carried out. A corpus of 147 cases of worldwide tailings dam disasters, from which 26 located in Europe, was compiled in a database. This contains six sections, including dam location, its physical and constructive characteristics, actual and putative failure cause, sludge hydrodynamics, socio-economical consequences and environmental impacts. Europe ranks in second place in reported accidents (18%), more than one third of them in dams 10-20 m high. In Europe, the most common cause of failure is related to unusual rain, whereas there is a lack of occurrences associated with seismic liquefaction, which is the second cause of tailings dam breakage elsewhere in the world. Moreover, over 90% of incidents occurred in active mines, and only 10% refer to abandoned ponds. The results reached by this preliminary analysis show an urgent need for EU regulations regarding technical standards of tailings disposal.

  18. Inequalities between hypergeometric tails

    Directory of Open Access Journals (Sweden)

    Mary C. Phipps

    2003-01-01

    Full Text Available A special inequality between the tail probabilities of certain related hypergeometrics was shown by Seneta and Phipps [19] to suggest useful ‘quasi-exact’ alternatives to Fisher's [5] Exact Test. With this result as motivation, two inequalities of Hájek and Havránek [6] are investigated in this paper and are generalised to produce inequalities in the form required. A parallel inequality in binomial tail probabilities is also established.

  19. Coaxial Compound Helicopter for Confined Urban Operations

    Science.gov (United States)

    2016-01-22

    for the six passengers, but the design mission is flown with only four passengers. Disk Loading and Rotor Diameter Table 17 shows the impact of...weight with rotor diameter for the baseline configuration, and for the aircraft with ITEP engine, two pilots, and six passengers. Lines of constant...Analysis showed that this combination of requirements is best satisfied by a coaxial main- rotor configuration, with lift compounding to off-load

  20. Back muscle EMG of helicopter pilots in flight: effects of fatigue, vibration, and posture.

    Science.gov (United States)

    de Oliveira, Carlos Gomes; Nadal, Jurandir

    2004-04-01

    The high prevalence of low back pain in helicopter pilots has been attributed to back muscle fatigue due to a pilot's required posture and/or aircraft vibration. This study investigated the effect of posture and vibration on the surface electromyogram (EMG) of right and left erector spinae (ES) muscles of pilots and evaluated ES fatigue during flight. There were 12 male pilots who were monitored during helicopter flights lasting an average of 2 h. Prior to the flight, a maximal voluntary contraction (MVC) of ES was performed and the EMG was recorded. Vibration was measured at the pilot's seat through a triaxial accelerometer. The effect of posture on EMG was tested by comparing four characteristics of left and right EMG expressed as % MVC. Effect of Z vibration on EMG was investigated by coherence function and through correlation between coherently averaged EMG and Z for the frequencies of the main rotor of the helicopter (1R) and its first harmonic (2R). Fatigue was investigated through median frequencies (MF) of the EMG power spectra. No effect of posture on EMG was found for any parameter (p > 0.05). Data from one pilot suggested an effect of 1R on EMG, but statistical tests revealed this not to be significant (p > 0.05) for any pilot. No fatigue was evidenced by linear regression of MF. While the scientific literature contains the hypothesis that low back pain in helicopter pilots is mainly due to muscle fatigue caused by posture and/or vibration, the present study did not lend support to this hypothesis.

  1. Dynamic Calibration of the NASA Ames Rotor Test Apparatus Steady/Dynamic Rotor Balance

    Science.gov (United States)

    Peterson, Randall L.; vanAken, Johannes M.

    1996-01-01

    The NASA Ames Rotor Test Apparatus was modified to include a Steady/Dynamic Rotor Balance. The dynamic calibration procedures and configurations are discussed. Random excitation was applied at the rotor hub, and vibratory force and moment responses were measured on the steady/dynamic rotor balance. Transfer functions were computed using the load cell data and the vibratory force and moment responses from the rotor balance. Calibration results showing the influence of frequency bandwidth, hub mass, rotor RPM, thrust preload, and dynamic loads through the stationary push rods are presented and discussed.

  2. Darmstadt Rotor No. 2, II: Design of Leaning Rotor Blades

    Directory of Open Access Journals (Sweden)

    Jörg Bergner

    2003-01-01

    Full Text Available For Darmstadt University of Technology's axial singlestage transonic compressor rig, a new three-dimensional aft-swept rotor was designed and manufactured at MTU Aero Engines in Munich, Germany. The application of carbon fiber–reinforced plastic made it possible to overcome structural constraints and therefore to further increase the amount of lean and sweep of the blade. The aim of the design was to improve the mechanical stability at operation that is close to stall.

  3. STUDY ON SAFETY TECHNOLOGY SCHEME OF THE UNMANNED HELICOPTER

    Directory of Open Access Journals (Sweden)

    Z. Lin

    2013-08-01

    Full Text Available Nowadays the unmanned helicopter is widely used for its' unique strongpoint, however, the high failure rate of unmanned helicopter seriously limits its further application and development. For solving the above problems, in this paper, the reasons for the high failure rate of unmanned helicopter is analyzed and the corresponding solution schemes are proposed. The main problem of the failure cause of the unmanned helicopter is the aircraft engine fault, and the failure cause of the unmanned helicopter is analyzed particularly. In order to improving the safety performance of unmanned helicopter system, the scheme of adding the safety parachute system to the unmanned helicopter system is proposed and introduced. These schemes provide the safety redundancy of the unmanned helicopter system and lay on basis for the unmanned helicopter applying into residential areas.

  4. Development of an aeroelastic methodology for surface morphing rotors

    Science.gov (United States)

    Cook, James R.

    Helicopter performance capabilities are limited by maximum lift characteristics and vibratory loading. In high speed forward flight, dynamic stall and transonic flow greatly increase the amplitude of vibratory loads. Experiments and computational simulations alike have indicated that a variety of active rotor control devices are capable of reducing vibratory loads. For example, periodic blade twist and flap excitation have been optimized to reduce vibratory loads in various rotors. Airfoil geometry can also be modified in order to increase lift coefficient, delay stall, or weaken transonic effects. To explore the potential benefits of active controls, computational methods are being developed for aeroelastic rotor evaluation, including coupling between computational fluid dynamics (CFD) and computational structural dynamics (CSD) solvers. In many contemporary CFD/CSD coupling methods it is assumed that the airfoil is rigid to reduce the interface by single dimension. Some methods retain the conventional one-dimensional beam model while prescribing an airfoil shape to simulate active chord deformation. However, to simulate the actual response of a compliant airfoil it is necessary to include deformations that originate not only from control devices (such as piezoelectric actuators), but also inertial forces, elastic stresses, and aerodynamic pressures. An accurate representation of the physics requires an interaction with a more complete representation of loads and geometry. A CFD/CSD coupling methodology capable of communicating three-dimensional structural deformations and a distribution of aerodynamic forces over the wetted blade surface has not yet been developed. In this research an interface is created within the Fully Unstructured Navier-Stokes (FUN3D) solver that communicates aerodynamic forces on the blade surface to University of Michigan's Nonlinear Active Beam Solver (UM/NLABS -- referred to as NLABS in this thesis). Interface routines are developed for

  5. Noise Measurement Flight Test: Data/Analyses, Hughes 500 D/E Helicopter,

    Science.gov (United States)

    1984-05-01

    source frequency content and different absoprtion characteris- tics on the various test days. Table 9.18 provides a brief examination of propagation...500D 21.15 Average 20.91 Table 9.16 HUGHES 500D LEVEL FLYOVJER PROPAATIO4-AI. AL OPERATION tllC 5 tIC 1 MIC 4 WEIGHTED AVERAGE W, 7 77 500’ (0.9vh) AVG...TENPERATUREHUIIIOITYOR AIRCRAFT DEVIATION FR061 REF FLIGHT TRACK Ir ~ ~V ~ *< *r4~~~ W * .’*: .-- . TAILE NO. A.6-5.2 HES 500 HELICOPTER 81T/TU1/15/83 SUNWY NOISE LEYE

  6. Helicopter Urban Navigation Training Using Virtual Environments

    National Research Council Canada - National Science Library

    Wright, George

    2000-01-01

    .... Navigation is a means to an end. Helicopter operations, being inherently expensive and unforgiving of mistakes, are prime candidates for such innovative training techniques as virtual (3-D) fly-throughs...

  7. Helicopter Flight Procedures for Community Noise Reduction

    Science.gov (United States)

    Greenwood, Eric

    2017-01-01

    A computationally efficient, semiempirical noise model suitable for maneuvering flight noise prediction is used to evaluate the community noise impact of practical variations on several helicopter flight procedures typical of normal operations. Turns, "quick-stops," approaches, climbs, and combinations of these maneuvers are assessed. Relatively small variations in flight procedures are shown to cause significant changes to Sound Exposure Levels over a wide area. Guidelines are developed for helicopter pilots intended to provide effective strategies for reducing the negative effects of helicopter noise on the community. Finally, direct optimization of flight trajectories is conducted to identify low noise optimal flight procedures and quantify the magnitude of community noise reductions that can be obtained through tailored helicopter flight procedures. Physically realizable optimal turns and approaches are identified that achieve global noise reductions of as much as 10 dBA Sound Exposure Level.

  8. Small crack test program for helicopter materials

    Science.gov (United States)

    Annigeri, Bal; Schneider, George

    1994-01-01

    Crack propagation tests were conducted to determine crack growth behavior in five helicopter materials for surface cracks between 0.005 to 0.020 inches in depth. Constant amplitude tests were conducted at stress ratios R equals 0.1 and 0.5, and emphasis was placed on near threshold data (i.e., 10-8 to 10-6 inches/cycle). Spectrum tests were conducted using a helicopter spectrum. The test specimen was an unnotched tension specimen, and cracks were initiated from a small EDM notch. An optical/video system was used to monitor crack growth. The material for the test specimens was obtained from helicopter part forgings. Testing was conducted at stresses below yield to reflect actual stresses in helicopter parts.

  9. Rotor blades for turbine engines

    Science.gov (United States)

    Piersall, Matthew R; Potter, Brian D

    2013-02-12

    A tip shroud that includes a plurality of damping fins, each damping fin including a substantially non-radially-aligned surface that is configured to make contact with a tip shroud of a neighboring rotor blade. At least one damping fin may include a leading edge damping fin and at least one damping fin may include a trailing edge damping fin. The leading edge damping fin may be configured to correspond to the trailing edge damping fin.

  10. Rotor Design Options for Improving XV-15 Whirl-Flutter Stability Margins

    Science.gov (United States)

    Acree, C. W., Jr.; Peyran, R. J.; Johnson, Wayne

    2004-01-01

    Rotor design changes intended to improve tiltrotor whirl-flutter stability margins were analyzed. A baseline analytical model of the XV-15 was established, and then a thinner, composite wing was designed to be representative of a high-speed tiltrotor. The rotor blade design was modified to increase the stability speed margin for the thin-wing design. Small rearward offsets of the aerodynamic-center locus with respect to the blade elastic axis created large increases in the stability boundary. The effect was strongest for offsets at the outboard part of the blade, where an offset of the aerodynamic center by 10% of tip chord improved the stability margin by over 100 knots. Forward offsets of the blade center of gravity had similar but less pronounced effects. Equivalent results were seen for swept-tip blades. Appropriate combinations of sweep and pitch stiffness completely eliminated whirl flutter within the speed range examined; alternatively, they allowed large increases in pitch-flap coupling (delta-three) for a given stability margin. A limited investigation of the rotor loads in helicopter and airplane configuration showed only minor increases in loads.

  11. Case Studies for the Statistical Design of Experiments Applied to Powered Rotor Wind Tunnel Tests

    Science.gov (United States)

    Overmeyer, Austin D.; Tanner, Philip E.; Martin, Preston B.; Commo, Sean A.

    2015-01-01

    The application of statistical Design of Experiments (DOE) to helicopter wind tunnel testing was explored during two powered rotor wind tunnel entries during the summers of 2012 and 2013. These tests were performed jointly by the U.S. Army Aviation Development Directorate Joint Research Program Office and NASA Rotary Wing Project Office, currently the Revolutionary Vertical Lift Project, at NASA Langley Research Center located in Hampton, Virginia. Both entries were conducted in the 14- by 22-Foot Subsonic Tunnel with a small portion of the overall tests devoted to developing case studies of the DOE approach as it applies to powered rotor testing. A 16-47 times reduction in the number of data points required was estimated by comparing the DOE approach to conventional testing methods. The average error for the DOE surface response model for the OH-58F test was 0.95 percent and 4.06 percent for drag and download, respectively. The DOE surface response model of the Active Flow Control test captured the drag within 4.1 percent of measured data. The operational differences between the two testing approaches are identified, but did not prevent the safe operation of the powered rotor model throughout the DOE test matrices.

  12. Development of helicopter engine seals

    Science.gov (United States)

    Lynwander, P.

    1973-01-01

    An experimental evaluation of main shaft seals for helicopter gas turbine engines was conducted with shaft speeds to 213 m/s(700 ft/sec), air pressures to 148 N/sq cm (215 psia), and air temperatures to 645 K (675 F). Gas leakage test results indicate that conventional seals will not be satisfactory for high-pressure sealing because of excessive leakage. The self-acting face seal, however, had significantly lower leakage and operated with insignificant wear during a 150-hour endurance test at sliding speeds to 145 m/s (475 ft/sec), air pressures to 124 N/sq cm (180 psia), and air temperatures to 408 K (275 F). Wear measurements indicate that noncontact operation was achieved at shaft speeds of 43,000 rpm. Evaluation of the self-acting circumferential seal was inconclusive because of seal dimensional variations.

  13. Analysis and control of the transient aeroelastic response of rotors during shipboard engagement and disengagement operations

    Science.gov (United States)

    Keller, Jonathan Allen

    2001-11-01

    An analysis has been developed to predict the transient aeroelastic response of a helicopter rotor system during shipboard engagement and disengagement operations. The coupled flap-lag-torsion equations of motion were developed using Hamilton's Principle and discretized spatially using the finite element method. Aerodynamics were simulated using nonlinear quasi-steady or time domain nonlinear unsteady models. The ship airwake environment was simulated with simple deterministic airwake distributions, results from experimental measurements or numerical predictions. The transient aeroelastic response of the rotor blades was then time-integrated along a specified rotor speed profile. The control of the rotor response for an analytic model of the H-46 Sea Knight rotor system was investigated with three different passive control techniques. Collective pitch scheduling was only successful in reducing the blade flapping response in a few isolated cases. In the majority of cases, the blade transient response was increased. The use of a discrete flap damper in the very low rotor speed region was also investigated. Only by raising the flap stop setting and using a flap damper four times the strength of the lag damper could the downward flap deflections be reduced. However, because the flap stop setting was raised the upward flap deflections were often increased. The use of extendable/retractable, gated leading-edge spoilers in the low rotor speed region was also investigated. Spoilers covering the outer 15% R of the rotor blade were shown to significantly reduce both the upward and downward flap response without increasing rotor torque. Previous aeroelastic analyses developed at the University of Southampton and at Penn State University were completed with flap-torsion degrees of freedom only. The addition of the lag degree of freedom was shown to significantly influence the blade response. A comparison of the two aerodynamic models showed that the nonlinear quasi

  14. Progress in helicopter infrared signature suppression

    Directory of Open Access Journals (Sweden)

    Zhang Jingzhou

    2014-04-01

    Full Text Available Due to their low-attitude and relatively low-speed fight profiles, helicopters are subjected to serious threats from radio, infrared (IR, visual, and aural detection and tracking. Among these threats, infrared detection and tracking are regarded as more crucial for the survivability of helicopters. In order to meet the requirements of infrared stealth, several different types of infrared suppressor (IRS for helicopters have been developed. This paper reviews contemporary developments in this discipline, with particular emphasis on infrared signature suppression, advances in mixer-ejectors and prediction for helicopters. In addition, several remaining challenges, such as advanced IRS, emissivity optimization technique, helicopter infrared characterization, etc., are proposed, as an initial guide and stimulation for future research. In the future, the comprehensive infrared suppression in the 3–5 μm and 8–14 μm bands will doubtfully become the emphasis of helicopter stealth. Multidisciplinary optimization of a complete infrared suppression system deserves further investigation.

  15. Comprehensive Modeling and Analysis of Rotorcraft Variable Speed Propulsion System With Coupled Engine/Transmission/Rotor Dynamics

    Science.gov (United States)

    DeSmidt, Hans A.; Smith, Edward C.; Bill, Robert C.; Wang, Kon-Well

    2013-01-01

    This project develops comprehensive modeling and simulation tools for analysis of variable rotor speed helicopter propulsion system dynamics. The Comprehensive Variable-Speed Rotorcraft Propulsion Modeling (CVSRPM) tool developed in this research is used to investigate coupled rotor/engine/fuel control/gearbox/shaft/clutch/flight control system dynamic interactions for several variable rotor speed mission scenarios. In this investigation, a prototypical two-speed Dual-Clutch Transmission (DCT) is proposed and designed to achieve 50 percent rotor speed variation. The comprehensive modeling tool developed in this study is utilized to analyze the two-speed shift response of both a conventional single rotor helicopter and a tiltrotor drive system. In the tiltrotor system, both a Parallel Shift Control (PSC) strategy and a Sequential Shift Control (SSC) strategy for constant and variable forward speed mission profiles are analyzed. Under the PSC strategy, selecting clutch shift-rate results in a design tradeoff between transient engine surge margins and clutch frictional power dissipation. In the case of SSC, clutch power dissipation is drastically reduced in exchange for the necessity to disengage one engine at a time which requires a multi-DCT drive system topology. In addition to comprehensive simulations, several sections are dedicated to detailed analysis of driveline subsystem components under variable speed operation. In particular an aeroelastic simulation of a stiff in-plane rotor using nonlinear quasi-steady blade element theory was conducted to investigate variable speed rotor dynamics. It was found that 2/rev and 4/rev flap and lag vibrations were significant during resonance crossings with 4/rev lagwise loads being directly transferred into drive-system torque disturbances. To capture the clutch engagement dynamics, a nonlinear stick-slip clutch torque model is developed. Also, a transient gas-turbine engine model based on first principles mean

  16. Flywheel Rotor Safe-Life Technology

    Science.gov (United States)

    Ratner, J. K. H.; Chang, J. B.; Christopher, D. A.; McLallin, Kerry L. (Technical Monitor)

    2002-01-01

    Since the 1960s, research has been conducted into the use of flywheels as energy storage systems. The-proposed applications include energy storage for hybrid and electric automobiles, attitude control and energy storage for satellites, and uninterruptible power supplies for hospitals and computer centers. For many years, however, the use of flywheels for space applications was restricted by the total weight of a system employing a metal rotor. With recent technological advances in the manufacturing of composite materials, however, lightweight composite rotors have begun to be proposed for such applications. Flywheels with composite rotors provide much higher power and energy storage capabilities than conventional chemical batteries. However, the failure of a high speed flywheel rotor could be a catastrophic event. For this reason, flywheel rotors are classified by the NASA Fracture Control Requirements Standard as fracture critical parts. Currently, there is no industry standard to certify a composite rotor for safe and reliable operation forth( required lifetime of the flywheel. Technical problems hindering the development of this standard include composite manufacturing inconsistencies, insufficient nondestructive evaluation (NDE) techniques for detecting defects and/or impact damage, lack of standard material test methods for characterizing composite rotor design allowables, and no unified proof (over-spin) test for flight rotors. As part of a flywheel rotor safe-life certification pro-ram funded b the government, a review of the state of the art in composite rotors is in progress. The goal of the review is to provide a clear picture of composite flywheel rotor technologies. The literature review has concentrated on the following topics concerning composites and composite rotors: durability (fatigue) and damage tolerance (safe-life) analysis/test methods, in-service NDE and health monitoring techniques, spin test methods/ procedures, and containment options

  17. Optimization of wind turbine rotors

    Energy Technology Data Exchange (ETDEWEB)

    Nygaard, Tor Anders

    1999-07-01

    The Constrained Steepest Descent method has been applied to the optimization of wind turbine rotors through the development of a numerical model. The model consists of an optimization kernel, an aerodynamic model, a structural dynamic model of a rotating beam, and a cost model for the wind turbine. The cost of energy is minimized directly by varying the blade design, the rotational speed and the resulting design of the drive-train and tower. The aerodynamic model is a combination of a fast engineering model based on strip-theory and two and three-dimensional Euler solvers. The two-dimensional Euler solver is used for generation of pre-stall airfoil data. Comparisons with experimental data verify that the engineering model effectively approximates non-stalled flow, except at the blade tip. The three-dimensional Euler solver is in good agreement with the experimental data at the tip, and is therefore a useful supplement for corrections of the tip-loss model, and evaluation of an optimized design. The structural dynamic model evaluates stresses and deformations for the blade. It is based on constitutive relations for a slender beam that are solved with the equations of motions using a finite-difference method. The cost model evaluates the design change of the wind turbine and the resulting costs that occur when a change in blade design modifies the blade mass and the overall forces. The cost model is based on engineering design rules for the drive-train and tower. The model was applied using a Danish 600 kW wind turbine as a reference. Two rotors were optimized using traditional NACA airfoils and a new low-lift airfoil family developed specifically for wind turbine purposes. The cost of energy decreased four percent for the NACA rotor, and seven percent for the low-lift rotor. Optimizations with a high number of degrees of freedom show that a designer has considerable flexibility in choosing some primary parameters such as rated power and rotor diameter, if the rest

  18. Injurious tail biting in pigs

    DEFF Research Database (Denmark)

    D'Eath, R.B.; Amott, G.; Turner, S. P.

    2014-01-01

    Tail biting is a serious animal welfare and economic problem in pig production. Tail docking, which reduces but does not eliminate tail biting, remains widespread. However, in the EU tail docking may not be used routinely, and some ‘alternative’ forms of pig production and certain countries do...... not allow tail docking at all. Against this background, using a novel approach focusing on research where tail injuries were quantified, we review the measures that can be used to control tail biting in pigs without tail docking. Using this strict criterion, there was good evidence that manipulable...... substrates and feeder space affect damaging tail biting. Only epidemiological evidence was available for effects of temperature and season, and the effect of stocking density was unclear. Studies suggest that group size has little effect, and the effects of nutrition, disease and breed require further...

  19. Telling tails: selective pressures acting on investment in lizard tails.

    Science.gov (United States)

    Fleming, Patricia A; Valentine, Leonie E; Bateman, Philip W

    2013-01-01

    Caudal autotomy is a common defense mechanism in lizards, where the animal may lose part or all of its tail to escape entrapment. Lizards show an immense variety in the degree of investment in a tail (i.e., length) across species, with tails of some species up to three or four times body length (snout-vent length [SVL]). Additionally, body size and form also vary dramatically, including variation in leg development and robustness and length of the body and tail. Autotomy is therefore likely to have fundamentally different effects on the overall body form and function in different species, which may be reflected directly in the incidence of lost/regenerating tails within populations or, over a longer period, in terms of relative tail length for different species. We recorded data (literature, museum specimens, field data) for relative tail length (n=350 species) and the incidence of lost/regenerating tails (n=246 species). We compared these (taking phylogeny into account) with intrinsic factors that have been proposed to influence selective pressures acting on caudal autotomy, including body form (robustness, body length, leg development, and tail specialization) and ecology (foraging behavior, physical and temporal niches), in an attempt to identify patterns that might reflect adaptive responses to these different factors. More gracile species have relatively longer tails (all 350 spp., P tails (P tails for nocturnal lizards (all 246 spp., P tail may be due to locomotor mechanics, although the patterns observed are also largely consistent with predictions based on predation pressure.

  20. Energy from Swastika-Shaped Rotors

    Directory of Open Access Journals (Sweden)

    McCulloch M. E.

    2015-04-01

    Full Text Available It is suggested here that a swastika-shaped rotor exposed to waves will rotate in the di- rection its arms are pointing (towards the arm-tips due to a sheltering effect. A formula is derived to predict the motion obtainable from swastika rotors of different sizes given the ocean wave height and phase speed and it is suggested that the rotor could provide a new, simpler method of wave energy generation. It is also proposed that the swastika rotor could generate energy on a smaller scale from sound waves and Brownian motion, and potentially the zero point field.

  1. "Tails" of Linguistic Survival

    Science.gov (United States)

    Timmis, Ivor

    2010-01-01

    Given the relatively short history of computerized corpora of spoken language, it is not surprising that few diachronic studies have been done on the grammatical features recently highlighted by the analysis of such corpora. This article, however, does take a diachronic perspective on one such feature: the syntactic feature of "tails"…

  2. White-tailed deer

    Science.gov (United States)

    Paul E. Johns; John C. Kilgo

    2005-01-01

    from a public relations standpoint, the white-tailed deer (Odocileus virginiamus) is probably the most important wildlife species occurring on the Savannah River Site (SRS). The SRS deer herd has been the subject of more scientific investigations than any comparable deer population in the world, resulting in more than 125 published papers. Each year...

  3. Estimation of Jump Tails

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Todorov, Victor

    We propose a new and flexible non-parametric framework for estimating the jump tails of Itô semimartingale processes. The approach is based on a relatively simple-to-implement set of estimating equations associated with the compensator for the jump measure, or its "intensity", that only utilizes...

  4. Examining the stability derivatives of a compound helicopter

    OpenAIRE

    Ferguson, Kevin; Thomson, Douglas

    2017-01-01

    Some helicopter manufacturers are exploring the compound helicopter design as it could potentially satisfy the new emerging requirements placed on the next generation of rotorcraft. It is well understood that the main benefit of the compound helicopter is its ability to reach speeds that significantly surpass the conventional helicopter. However, it is possible that the introduction of compounding may lead to a vehicle with significantly different flight characteristics when compared to a con...

  5. Does Helicopter Emergency Care Service Improve Blunt Trauma Mortality

    Science.gov (United States)

    1991-01-01

    NUMBERS Does Helicopter Emergency Care Service Improve Blunt Trauma Mortality 6. AUTHOR(S) Kenneth Duane Oefinger, Major 7. PERFORMING ORGANIZATION NAME...8217 = ’:" ’ _’ -. " 9 DOES HELICOPTER EMERGENCY CARE SE,’RV-E . IMPROVE BLUNT TRAUMA MORTALITY BY Major Kenneth Duane Oefina, USAF NC 4991 38 ,-ages Masters of...helicopter should be dispatched. This would allow for the monitoring of effective utilization of the hospital service. DOES HELICOPTER EMERGENCY CARE SERVICE

  6. Application of hybrid methodology to rotors in steady and maneuvering flight

    Science.gov (United States)

    Rajmohan, Nischint

    Helicopters are versatile flying machines that have capabilities that are unparalleled by fixed wing aircraft, such as operating in hover, performing vertical takeoff and landing on unprepared sites. This makes their use especially desirable in military and search-and-rescue operations. However, modern helicopters still suffer from high levels of noise and vibration caused by the physical phenomena occurring in the vicinity of the rotor blades. Therefore, improvement in rotorcraft design to reduce the noise and vibration levels requires understanding of the underlying physical phenomena, and accurate prediction capabilities of the resulting rotorcraft aeromechanics. The goal of this research is to study the aeromechanics of rotors in steady and maneuvering flight using hybrid Computational Fluid Dynamics (CFD) methodology. The hybrid CFD methodology uses the Navier-Stokes equations to solve the flow near the blade surface but the effect of the far wake is computed through the wake model. The hybrid CFD methodology is computationally efficient and its wake modeling approach is nondissipative making it an attractive tool to study rotorcraft aeromechanics. Several enhancements were made to the CFD methodology and it was coupled to a Computational Structural Dynamics (CSD) methodology to perform a trimmed aeroelastic analysis of a rotor in forward flight. The coupling analyses, both loose and tight were used to identify the key physical phenomena that affect rotors in different steady flight regimes. The modeling enhancements improved the airloads predictions for a variety of flight conditions. It was found that the tightly coupled method did not impact the loads significantly for steady flight conditions compared to the loosely coupled method. The coupling methodology was extended to maneuvering flight analysis by enhancing the computational and structural models to handle non-periodic flight conditions and vehicle motions in time accurate mode. The flight test

  7. A summary and evaluation of semi-empirical methods for the prediction of helicopter rotor noise

    Science.gov (United States)

    Pegg, R. J.

    1979-01-01

    Existing prediction techniques are compiled and described. The descriptions include input and output parameter lists, required equations and graphs, and the range of validity for each part of the prediction procedures. Examples are provided illustrating the analysis procedure and the degree of agreement with experimental results.

  8. Development of Virtual Blade Model for Modelling Helicopter Rotor Downwash in OpenFOAM

    Science.gov (United States)

    2013-12-01

    management and regulation work for the RAAF, which included undertaking of the structural life assessment of the PC-9/A fleet, structural life...in Kelvin. 2. The exhaust gas is visualised using iso -temperature contour plot. 3. The prevailing wind is relative to the aircraft heading...distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY ; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A

  9. Design Framework for Vibration Monitoring Systems for Helicopter Rotor Blade Monitoring Using Wireless Sensor Networks

    NARCIS (Netherlands)

    Sanchez Ramirez, Andrea; Loendersloot, Richard; Jauregui Becker, Juan Manuel; Tinga, Tiedo; Chang, F.K.

    2013-01-01

    The pursue of methods for supporting Structural Health Monitoring (SHM) has been an important driver for the technological innovation in several engineering fields such as wireless communication, sensing and power harvesting. However, despite of the innovative and scientific value of these advances,

  10. A Trade-off Study of Tilt Rotor Aircraft versus Helicopters Using VASCOMP 2 and HESCOMP

    Science.gov (United States)

    1986-03-01

    and rescue 3. Reconnaissance/surveillance 4. Law enforcement 5. Medical evacuation 6. Public transportation 7. Corporate/executive transport 8...objective in conducting this experiment was to aanalyze the differences in aircraft canabi ]it’es for civet! values of mission radius. SP3 D. EXPERIMENT

  11. Failure Analysis of the Main Rotor Retention Nut from AH-64 Helicopter

    Science.gov (United States)

    1992-06-01

    1202 and the MTL indepen- dently supplied material. Fracture toughness and Charpy impact tests demonstrated no significant difference between all the...MECHANICAL PROPERTIES Charpy Impact KIc Hardness Specimen (fi-lb) (ksi vrin.) Rockwell C MDHC. Spec. - 48-53 *0257-Al 9.0 - 51.7 *0223-BI 17.0 - 49.9...Hamburg 1 Mr. A. Wilson Republic Steel Corporation, 410 Oberlin Avenue SW, Massillon, OH 44646 1 ATTN: Mr. R. Sweeney 1 Mr. W. H. Brechtel 1 Mr. T. M

  12. A Review of Sparsity-Based Methods for Analysing Radar Returns from Helicopter Rotor Blades

    Science.gov (United States)

    2016-09-01

    of the sensing matrix Φ, there is still probability of failure of the RIP for a particular realisation of a random matrix. In addition, testing ...implications for compressed sensing’. In: Comptes Rendus Mathematique 346 (910), 589–592. 19. Candes, E. J., Romberg , J. and Tao, T. (Feb. 2006) ‘Robust

  13. Stability and Control Analysis of the Slowed-Rotor Compound Helicopter Configuration

    Science.gov (United States)

    2007-07-01

    deg of collective pitch to maintain positive lift. The model was also more complex, including a swashplate and unmodified (lift and drag) airfoil...with a swashplate , airfoil tables, and 1 deg collective pitch is very similar to Fig. 9 with only a few missing points where a converged solution

  14. Calculation of a Helicopter Rotor in Hover by Viscous-Inviscid Interaction

    DEFF Research Database (Denmark)

    Filippone, Antonino; Sørensen, Jens Nørkær

    1995-01-01

    A viscous inviscid interaction model has been developed for the calculation of steady and unsteady aerodynamic flows. The model is validfor two-dimensional and three-dimensional flows alike. We use a fully three-dimensional boundary element method as inviscid flow model, and a two-dimensional or ...

  15. 3D Warping Actuation Driven Dynamic Camber Control Concept for Helicopter Rotor Blades Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In a rotorcraft, optimized camber change not only reduces vibratory hub loads and noise but also increases available thrust and improved flight control augmentation....

  16. A piloted simulator investigation of static stability and stability/control augmentation effects on helicopter handling qualities for instrument approach

    Science.gov (United States)

    Lebacqz, J. V.; Forrest, R. D.

    1980-01-01

    A ground simulator experiment was conducted on the Flight Simulator for Advanced Aircraft at Ames Research Center to investigate the influence of several static stability and stability/control augmentation design parameters on helicopter flying qualities during terminal area operations in instrument conditions. Effects of light turbulence were included. Two levels of static stability in each rotational axis (pitch, roll, yaw) were examined for a hingeless rotor configuration. The variations in pitch and roll were: (1) stable and (2) neutral static stability; in yaw there were two stable levels. Four types of stability/control augmentation were also examined for the lower level of static stability in each axis. This latter investigation covered three helicopter rotor types: hingeless, articulated, and teetering. Four pilots performed a total of 105 evaluations of these parameters for a representative VOR instrument approach task. Pilot rating results indicate the acceptability of neutral static stability longitudinally and laterally and the need for pitch-roll attitude augmentation to achieve a satisfactory system.

  17. 77 FR 18965 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2012-03-29

    ... Directives; Eurocopter France Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice... Eurocopter France Model SA341G helicopters. This proposed AD is prompted by an analysis and tests performed... 26, 2004, to correct an unsafe condition for Eurocopter France Model SA 341/342 helicopters. The DGAC...

  18. 78 FR 18230 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-03-26

    ... new airworthiness directive (AD) for Eurocopter France (Eurocopter) Model EC130 B4 helicopters with a... proposed to amend 14 CFR part 39 to include an AD that would apply to Eurocopter Model EC130 B4 helicopters...), to correct an unsafe condition for the Eurocopter Model EC130 B4 helicopter. EASA advises of a...

  19. 77 FR 43738 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2012-07-26

    ... EC130 B4 helicopters with a cabin vibration damper installed. This proposed AD is prompted by a crack... condition for Eurocopter Model EC130 B4 helicopters. EASA advises of a cracked cabin vibration damper blade...) Applicability This AD applies to Model EC130 B4 helicopters with a cabin vibration damper installed, except...

  20. Innovative multi rotor wind turbine designs

    Energy Technology Data Exchange (ETDEWEB)

    Kale, S.A.; Sapali, S.N. [College of Engineering. Mechanical Engineering Dept, Pune (India)

    2012-07-01

    Among the renewable energy sources, today wind energy is the most recognized and cost effective. Developers and researchers in this sector are optimistic and continuously working innovatively to improve the technology. The wind power obtained is proportional to the swept area of wind turbine. The swept area is increased by using a single rotor of large diameter or multi rotors in array. The rotor size is growing continuously with mature technology. Multi rotor technology has a long history and the multi rotor concept persists in a variety of modern innovative systems but the concept has fallen out of consideration in mainstream design from the perception that is complex and unnecessary as very large single rotor units are now technically feasible. This work addresses the evaluation of different multi rotor wind turbine systems. These innovative wind turbines are evaluated on the basis of feasibility, technological advantages, security of expected power performance, cost, reliability, impact of innovative system, comparison with existing wind turbine design. The findings of this work will provide guidelines for the practical and economical ways for further research on the multi rotor wind turbines. (Author)

  1. Rotor theories by Professor Joukowsky: Momentum theories

    DEFF Research Database (Denmark)

    van Kuik, G. A. M.; Sørensen, Jens Nørkær; Okulov, V. L.

    2015-01-01

    This paper is the first of two papers on the history of rotor aerodynamics with special emphasis on the role of Joukowsky. The present one focuses on the development of the momentum theory while the second one surveys the development of vortex theory for rotors. Joukowsky has played a major role ...

  2. 14 CFR 33.34 - Turbocharger rotors.

    Science.gov (United States)

    2010-01-01

    ... STANDARDS: AIRCRAFT ENGINES Design and Construction; Reciprocating Aircraft Engines § 33.34 Turbocharger rotors. Each turbocharger case must be designed and constructed to be able to contain fragments of a... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Turbocharger rotors. 33.34 Section 33.34...

  3. Evolution of civil aeromedical helicopter aviation.

    Science.gov (United States)

    Meier, D R; Samper, E R

    1989-07-01

    The rapid increase in the use of helicopters for hospital transport during the 1980s is the culmination of several hundred years of military medical innovation. Mass battefield casualties spurred both technologic and medical changes necessary for today's sophisticated helicopter systems in use worldwide, particularly in the United States. The Napoleonic Era and the American Civil War provided the framework for the evolution of today's state-of-the-art emergency medical techniques. The use of airplanes to evacuate the wounded eventually led to using helicopters for rescue missions in World War II. The combat experiences of the United States in Korea, the British in Malaya, and the French in Indochina proved that rotary-wing aircraft were invaluable in reducing battlefield death rates. Any skepticism about the efficacy of helicopter medical evacuation was erased during the Vietnam conflict. As an integral part of the modern battlefield, these specialized aircraft became a necessity. The observations and experience of American servicemen and medical personnel in Vietnam established the foundation for the acceptance of helicopter transport in modern hospital systems.

  4. Exploration of micro-diamagnetic levitation rotor

    Science.gov (United States)

    Su, Yufeng; Zhang, Kun; Ye, Zhitong; Xiao, Zhiming; Takahata, Kenichi

    2017-12-01

    We investigated a micro-diamagnetic levitation rotor system (MDLRS) in which the rotor freely levitates above the magnets. To explore the characteristics of the rotor, we carried out numerical simulations of and experiments on the MDLRS. Numerical simulation results show that the steady-state levitation height of the rotor is 130 µm, which is basically consistent with the experimental result (132 µm). Under the actuation of a regulated nitrogen flow, experimental results from the rotation speed of the rotor show that the maximum rate is 500 rpm at a flow rate of 28.16 sccm. Furthermore, an empirical model of the relationship between the flow rate and the rotation speed is proposed.

  5. Open Rotor - Analysis of Diagnostic Data

    Science.gov (United States)

    Envia, Edmane

    2011-01-01

    NASA is researching open rotor propulsion as part of its technology research and development plan for addressing the subsonic transport aircraft noise, emission and fuel burn goals. The low-speed wind tunnel test for investigating the aerodynamic and acoustic performance of a benchmark blade set at the approach and takeoff conditions has recently concluded. A high-speed wind tunnel diagnostic test campaign has begun to investigate the performance of this benchmark open rotor blade set at the cruise condition. Databases from both speed regimes will comprise a comprehensive collection of benchmark open rotor data for use in assessing/validating aerodynamic and noise prediction tools (component & system level) as well as providing insights into the physics of open rotors to help guide the development of quieter open rotors.

  6. Substantially parallel flux uncluttered rotor machines

    Science.gov (United States)

    Hsu, John S.

    2012-12-11

    A permanent magnet-less and brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by polyphase alternating currents. An uncluttered rotor is positioned within the magnetic rotating field and is spaced apart from the stator. An excitation core is spaced apart from the stator and the uncluttered rotor and magnetically couples the uncluttered rotor. The brushless excitation source generates a magnet torque by inducing magnetic poles near an outer peripheral surface of the uncluttered rotor, and the stator currents also generate a reluctance torque by a reaction of the difference between the direct and quadrature magnetic paths of the uncluttered rotor. The system can be used either as a motor or a generator

  7. Tail autotomy, tail size, and locomotor performance in lizards.

    Science.gov (United States)

    McElroy, Eric J; Bergmann, Philip J

    2013-01-01

    The effect of tail autotomy on locomotor performance has been studied in a number of lizard species. Most of these studies (65%) show that tail autotomy has a negative effect on sprint speed, some studies (26%) show no effect of autotomy on sprint speed, and a few (9%) show a positive effect of autotomy on sprint speed. A variety of hypotheses have been proposed to explain the variation across these studies, but none has been tested. We synthesize these data using meta-analysis and then test whether any of four variables explain the variation in how tail autotomy impacts sprint speed: (1) differences in methodology in previous studies, (2) phylogeny, (3) relative tail size, and (4) habitat use. We find little evidence that methodology or habitat use influences how sprint speed changes following tail autotomy. Although the sampling is phylogenetically sparse, phylogeny appears to play a role, with skinks and iguanids showing fairly consistent decreases in speeds after autotomy and with lacertids and geckos showing large variation in how autotomy impacts speed. After removing two outlying species with unusually large and long tails (Takydromus sp.), we find a positive relationship between relative tail size and sprint speed change after autotomy. Lizards with larger tails exhibit a greater change in speed after tail loss. This finding suggests that future studies of tail autotomy and locomotor performance might profitably incorporate variation in tail size and that species-specific responses to autotomy need to be considered.

  8. Helicopter industry - early beginnings to now; an outlook on the helicopter market and its major players in the rotorcraft industry

    NARCIS (Netherlands)

    Spranger, L.

    2013-01-01

    The helicopter is probably the most flexible aircraft that we know today. Although its history dates back to around 1500, the first practical helicopter wasn’t manufactured until the 1940s, roughly three decades after the Wright brothers’ first powered human flight. Today, helicopters fulfil a wide

  9. 76 FR 79157 - Takes of Marine Mammals Incidental to Specified Activities; St. George Reef Light Station...

    Science.gov (United States)

    2011-12-21

    ...); 172 Steller sea lions (Eumetopias jubatus); and six northern fur seals (Callorhinus ursinus) by Level... Rotor and Wing, LLC. The Raven R44, which seats three passengers and one pilot, is a compact-sized (1134 kilograms (kg), 2500 pounds (lbs)) helicopter with two-bladed main and tail rotors. Both sets of rotors are...

  10. Rotors stress analysis and design

    CERN Document Server

    Vullo, Vincenzo

    2013-01-01

    Stress and strain analysis of rotors subjected to surface and body loads, as well as to thermal loads deriving from temperature variation along the radius, constitutes a classic subject of machine design. Nevertheless attention is limited to rotor profiles for which governing equations are solvable in closed form. Furthermore very few actual engineering issues may relate to structures for which stress and strain analysis in the linear elastic field and, even more, under non-linear conditions (i.e. plastic or viscoelastic conditions) produces equations to be solved in closed form. Moreover, when a product is still in its design stage, an analytical formulation with closed-form solution is of course simpler and more versatile than numerical methods, and it allows to quickly define a general configuration, which may then be fine-tuned using such numerical methods. In this view, all subjects are based on analytical-methodological approach, and some new solutions in closed form are presented. The analytical formul...

  11. Simulation of Flow around Isolated Helicopter Fuselage

    Directory of Open Access Journals (Sweden)

    Garipov A.O.

    2013-04-01

    Full Text Available Low fuselage drag has always been a key target of helicopter manufacturers. Therefore, this paper focuses on CFD predictions of the drag of several components of a typical helicopter fuselage. In the first section of the paper, validation of the obtained CFD predictions is carried out using wind tunnel measurements. The measurements were carried out at the Kazan National Research Technical University n.a. A. Tupolev. The second section of the paper is devoted to the analysis of drag contributions of several components of the ANSAT helicopter prototype fuselage using the RANS approach. For this purpose, several configurations of fuselages are considered with different levels of complexity including exhausts and skids. Depending on the complexity of the considered configuration and CFD mesh both the multi-block structured HMB solver and the unstructured commercial tool Fluent are used. Finally, the effect of an actuator disk on the predicted drag is addressed.

  12. Simultaneous State and Parameter Estimation Based Actuator Fault Detection and Diagnosis for an Unmanned Helicopter

    Directory of Open Access Journals (Sweden)

    Wu Chong

    2015-03-01

    Full Text Available Simultaneous state and parameter estimation based actuator fault detection and diagnosis (FDD for single-rotor unmanned helicopters (UHs is investigated in this paper. A literature review of actuator FDD for UHs is given firstly. Based on actuator healthy coefficients (AHCs, which are introduced to represent actuator faults, a combined dynamic model is established with the augmented state containing both the flight state and AHCs. Then the actuator fault detection and diagnosis problem is transformed into a general nonlinear estimation one: given control inputs and the measured flight state contaminated by measurement noises, estimate both the flight state and AHCs recursively in each time-step, which is also known as the simultaneous state and parameter estimation problem. The estimated AHCs can further be used for fault tolerant control (FTC. Based on the existing widely used nonlinear estimation methods such as the unscented Kalman filter (UKF and the extended set-membership filter (ESMF, three kinds of adaptive schemes (KF-UKF, MIT-UKF and MIT-ESMF are proposed by our team to improve the actuator FDD performance. A comprehensive comparative study on these different estimation methods is given in detail to illustrate their advantages and disadvantages when applied to unmanned helicopter actuator FDD.

  13. Efficient fault diagnosis of helicopter gearboxes

    Science.gov (United States)

    Chin, H.; Danai, K.; Lewicki, D. G.

    1993-01-01

    Application of a diagnostic system to a helicopter gearbox is presented. The diagnostic system is a nonparametric pattern classifier that uses a multi-valued influence matrix (MVIM) as its diagnostic model and benefits from a fast learning algorithm that enables it to estimate its diagnostic model from a small number of measurement-fault data. To test this diagnostic system, vibration measurements were collected from a helicopter gearbox test stand during accelerated fatigue tests and at various fault instances. The diagnostic results indicate that the MVIM system can accurately detect and diagnose various gearbox faults so long as they are included in training.

  14. Sliding mode disturbance observer-based control of a twin rotor MIMO system.

    Science.gov (United States)

    Rashad, Ramy; El-Badawy, Ayman; Aboudonia, Ahmed

    2017-07-01

    This work proposes a robust tracking controller for a helicopter laboratory setup known as the twin rotor MIMO system (TRMS) using an integral sliding mode controller. To eliminate the discontinuity in the control signal, the controller is augmented by a sliding mode disturbance observer. The actuator dynamics is handled using a backstepping approach which is applicable due to the continuous chattering-free nature of the command signals generated using the disturbance observer based controller. To avoid the complexity of analytically differentiating the command signals, a first order sliding mode differentiator is used. Stability analysis of the closed loop system and the ultimate boundedness of the tracking error is proved using Lyapunov stability arguments. The proposed controller is validated by several simulation studies and is compared to other schemes in the literature. Experimental results using a hardware-in-the-loop system validate the robustness and effectiveness of the proposed controller. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  15. 75 FR 62639 - Air Ambulance and Commercial Helicopter Operations, Part 91 Helicopter Operations, and Part 135...

    Science.gov (United States)

    2010-10-12

    .... Helicopter air medical transportation was first used prominently during the Korean War to move injured... Drug and Alcohol Testing Program, and would therefore not be required to undergo drug testing...

  16. 14 CFR 27.547 - Main rotor structure.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main rotor structure. 27.547 Section 27.547... structure. (a) Each main rotor assembly (including rotor hubs and blades) must be designed as prescribed in this section. (b) (c) The main rotor structure must be designed to withstand the following loads...

  17. Wind rotor with vertical axis. Vindrotor med vertikal axel

    Energy Technology Data Exchange (ETDEWEB)

    Colling, J.; Sjoenell, B.

    1987-06-15

    This rotor is of dual type i.e. a paddle wheel shaped rotor close to the vertical axis and a second rotor consisting of vertical blades with wing profile and attached to radial spokes which are fixed to the axis together with the paddle wheel rotor. (L.F.).

  18. Reference Model 2: "Rev 0" Rotor Design

    Energy Technology Data Exchange (ETDEWEB)

    Barone, Matthew F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Berg, Jonathan Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Griffith, Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2011-12-01

    The preliminary design for a three-bladed cross-flow rotor for a reference marine hydrokinetic turbine is presented. A rotor performance design code is described, along with modifications to the code to allow prediction of blade support strut drag as well as interference between two counter-rotating rotors. The rotor is designed to operate in a reference site corresponding to a riverine environment. Basic rotor performance and rigid-body loads calculations are performed to size the rotor elements and select the operating speed range. The preliminary design is verified with a simple finite element model that provides estimates of bending stresses during operation. A concept for joining the blades and support struts is developed and analyzed with a separate finite element analysis. Rotor mass, production costs, and annual energy capture are estimated in order to allow calculations of system cost-of-energy. Evaluation Only. Created with Aspose.Pdf.Kit. Copyright 2002-2011 Aspose Pty Ltd Evaluation Only. Created with Aspose.Pdf.Kit. Copyright 2002-2011 Aspose Pty Ltd

  19. Equipment for pre-hospital airway management on Helicopter Emergency Medical System helicopters in central Europe.

    Science.gov (United States)

    Schmid, M; Schüttler, J; Ey, K; Reichenbach, M; Trimmel, H; Mang, H

    2011-05-01

    For advanced out-of-hospital airway management, skilled personnel and adequate equipment are key prerequisites. There are little data on the current availability of airway management equipment and standards of medical staff on Helicopter Emergency Medical System (HEMS) helicopters in central Europe. An internet search identified all HEMS helicopters in Austria, Switzerland and Luxembourg. We identified 15 HEMS helicopter bases in Switzerland, 28 in Austria and three in Luxembourg. A questionnaire was sent to all bases, asking both for the details of the clinical background and experience of participating staff, and details of airway management equipment carried routinely on board. Replies were received from 14 helicopter bases in Switzerland (93%), 25 bases in Austria (89%) and all three bases in Luxembourg. Anaesthesiologists were by far the most frequent attending physicians (68-85%). All except one bases reported to have at least one alternative supraglottic airway device. All bases had capnometry and succinylcholine. All bases in the study except two in Austria had commercial pre-packed sets for a surgical airway. All helicopters were equipped with automatic ventilators, although not all were suitable for non-invasive ventilation (NIV; Switzerland: 43%, Austria: 12%, Luxembourg: 100%). Masks for NIV were rarely available in Switzerland (two bases; 14%) and in Austria (three bases; 12%), whereas all three bases in Luxembourg carried those masks. Most HEMS helicopters carry appropriate equipment to meet the demands of modern advanced airway management in the pre-hospital setting. Further work is needed to ensure that appropriate airway equipment is carried on all HEMS helicopters.

  20. Does Modern Helicopter Construction Reduce Noise Exposure in Helicopter Rescue Operations?

    OpenAIRE

    Küpper, Thomas; Jansing, Paul; Schöffl, Volker; van Der Giet, Simone

    2017-01-01

    Background: During helicopter rescue operations the medical personnel are at high risk for hearing damage by noise exposure. There are two important factors to be taken into account: first, the extreme variability, with some days involving no exposure but other days with extreme exposure; second, the extreme noise levels during work outside the helicopter, e.g. during winch operations. The benefit of modern, less noisier constructions and the consequences for noise protection are still unknow...

  1. Apparatus and method for magnetically unloading a rotor bearing

    Energy Technology Data Exchange (ETDEWEB)

    Sanders, Seth Robert

    2018-02-13

    An apparatus and method for unloading a rotor bearing is described. The apparatus includes an electromagnet for levitating the rotor. In one embodiment, a sensor of the magnetic field near the electromagnet is used to control the current to levitate the rotor. In another embodiment, a method is provided that includes rotating the rotor, increasing the current to levitate the rotor and decrease the gap between electromagnet and rotor, and then reducing the current to levitate the rotor with a minimal amount of electric power to the electromagnet.

  2. Measurement and Modelling of Multicopter UAS Rotor Blades in Hover

    Science.gov (United States)

    Nowicki, Nathalie

    2016-01-01

    Multicopters are becoming one of the more common and popular type of unmanned aircraft systems (UAS) which have both civilian and military applications. One example being the concept of drone deliveries proposed by the distribution company Amazon [1]. The electrical propulsion is considered to have both faster and easier deliveries and also environmental benefits compared to other vehicles that still use fossil fuel. Other examples include surveillance and just simple entertainment. The reason behind their success is often said to be due to their small size, relatively low cost, simple structure and finally simple usage. With an increase in the UAS market comes challenges in terms of security, as both people and other aircrafts could be harmed if not used correctly. Therefore further studies and regulations are needed to ensure that future use of drones, especially in the civilian and public sectors, are safe and efficient. Thorough research has been done on full scale, man or cargo transporting, helicopters so that most parts of flight and performance are fairly well understood. Yet not much of it have been verified for small multicopters. Until today many studies and research projects have been done on the control systems, navigation and aerodynamics of multicopters. Many of the methods used today for building multicopters involve a process of trial an error of what will work well together, and once that is accomplished some structural analysis of the multicopter bodies might be done to verify that the product will be strong enough and have a decent aerodynamic performance. However, not much has been done on the research of the rotor blades, especially in terms of structural stress analyses and ways to ensure that the commonly used parts are indeed safe and follow safety measures. Some producers claim that their propellers indeed have been tested, but again that usually tends towards simple fluid dynamic analyses and even simpler stress analyses. There is no real

  3. Multiple piece turbine rotor blade

    Energy Technology Data Exchange (ETDEWEB)

    Kimmel, Keith D.; Plank, William L.

    2016-07-19

    A spar and shell turbine rotor blade with a spar and a tip cap formed as a single piece, the spar includes a bottom end with dovetail or fir tree slots that engage with slots on a top end of a root section, and a platform includes an opening on a top surface for insertion of the spar in which a shell made from an exotic high temperature resistant material is secured between the tip cap and the platform. The spar is tapered to form thinner walls at the tip end to further reduce the weight and therefore a pulling force due to blade rotation. The spar and tip cap piece is made from a NiAL material to further reduce the weight and the pulling force.

  4. Cyclic Control Optimization for a Smart Rotor

    DEFF Research Database (Denmark)

    Bergami, Leonardo; Henriksen, Lars Christian

    2012-01-01

    bending moment within a rotor revolution. The method is applied to a rotor equipped with trailing edge flaps, and capable of individual blade pitching. Results show that the optimized cyclic control significantly alleviates the load variations from periodic disturbances; the combination of both cyclic......The paper presents a method to determine cyclic control trajectories for a smart rotor undergoing periodic-deterministic load variations. The control trajectories result from a constrained optimization problem, where the cost function to minimize is given by the variation of the blade root flapwise...... flap and pitch allows to reduce the action (and hence the wear) on the pitch actuators, and still to achieve considerable load alleviation....

  5. Rotor inflow variability with advance ratio

    Science.gov (United States)

    Hoad, Danny R.; Althoff, Susan L.; Elliott, Joe W.

    1988-01-01

    A comparative study is conducted for the results of inflow calculations based on several analytical wake methods and laser-velocimeter rotor inflow measurements near a rectangular four-bladed rotor system operating in forward flight. The induced-flow characteristics at all advance ratios were found to be unsymmetrical about the longitudinal centerline, with maximum downwash in the rear portion of the disk, and skewed toward the advancing blade-side. Comparisons among analytical methods show that the region of induced upflow over the rotor disk was effectively modeled only at an advance ratio value of 0.15.

  6. TO THE DEVELOPMENT OF AERODYNAMIC SHAPE OF MEDIUM SIZED PERSPECTIVE HELICOPTER FUSELAGE

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available This paper presents the initial stage of work out of the helicopter body aerodynamic configuration. The main pur- pose of this work is to design the model of the fuselage and to minimize its drag.The analysis of experimental data obtained in TsAGI and other research centers was made at the first stage of the work. All features of flow around parts of the fuselage obtained from experimental data were taken into account. The de- pendencies of the fuselage component drag, such as the bow, fairings exhaust pipes of helicopter, sponsons, and tail sectionof the fuselage, on their form are described in this article.At the second stage the fuselage geometry was created in program SolidWorks. All the features of the flow around various fuselage components derived from the experimental data were considered in designing.The third stage is calculating of fuselage model aerodynamic characteristics. The calculations were made in the program ANSYS CFX (TsAGI License №501024. Boundary conditions were chosen so as to correspond to normal at- mospheric conditions at 1,000 meters with velocity of flight is V = 85 m/s. The output of the hot jet from engines is takinginto account in computation. The purpose of this calculation is to find the optimal angle of the engine exhaust pipe whenthe hot spray does not intersect with the tail and stabilizer and creates the maximum of propulsive force. The volume of the grid in computational domain is approximately 13 million cells.Data analysis has shown that the fuselage has a 20% less drag at cruising flight (аf = -4 ° compared to the original model. The hot jets do not intersect with the tail and stabilizers at cruising flight so the fuselage is protected from overheating.

  7. A Study of Coaxial Rotor Performance and Flow Field Characteristics

    Science.gov (United States)

    2016-01-22

    Inc. Ames, Iowa, USA ABSTRACT As a precursor to studying the acoustics of a coaxial rotor system, the aerodynamics and flow field of a coaxial rotor... aerodynamics model, was used to predict coaxial rotor performance in hover and forward flight. RotUNS steady hover calculations showed improved performance...small unmanned aerial vehicles ( UAVs ) market. As with all rotorcraft, the rotor noise generated by a coaxial rotor system must be mitigated to minimize

  8. Helicopter Maritime Environment Trainer: Software Test Document

    Science.gov (United States)

    2011-06-01

    flying pilot ( NFP ) takes control while the flying pilot (FP) continues to watch the instruments. This case does not apply because a single helicopter... NFP Non-Flying Pilot OOW Officer of The Watch OSD Operational Sequence Diagrams PC Personal Computer PDV Post Delivery Validation PROM

  9. HH-60D night hawk helicopter

    Science.gov (United States)

    Richardson, C. S.

    1984-01-01

    Fundamental development issues, system requirements and improvements are reported for the HH-60D night hawk helicopter. The HH-60D mission requirements are for combat search and rescue (aerospace rescue and recovery service user based at Scott AFB) and special operations (special operations forces based at Hurlburt AFB). Cockpit design, computer architecture and software are described in detail.

  10. Multicenter observational prehospital resuscitation on helicopter study.

    Science.gov (United States)

    Holcomb, John B; Swartz, Michael D; DeSantis, Stacia M; Greene, Thomas J; Fox, Erin E; Stein, Deborah M; Bulger, Eileen M; Kerby, Jeffrey D; Goodman, Michael; Schreiber, Martin A; Zielinski, Martin D; O'Keeffe, Terence; Inaba, Kenji; Tomasek, Jeffrey S; Podbielski, Jeanette M; Appana, Savitri N; Yi, Misung; Wade, Charles E

    2017-07-01

    Earlier use of in-hospital plasma, platelets, and red blood cells (RBCs) has improved survival in trauma patients with severe hemorrhage. Retrospective studies have associated improved early survival with prehospital blood product transfusion (PHT). We hypothesized that PHT of plasma and/or RBCs would result in improved survival after injury in patients transported by helicopter. Adult trauma patients transported by helicopter from the scene to nine Level 1 trauma centers were prospectively observed from January to November 2015. Five helicopter systems had plasma and/or RBCs, whereas the other four helicopter systems used only crystalloid resuscitation. All patients meeting predetermined high-risk criteria were analyzed. Patients receiving PHT were compared with patients not receiving PHT. Our primary analysis compared mortality at 3 hours, 24 hours, and 30 days, using logistic regression to adjust for confounders and site heterogeneity to model patients who were matched on propensity scores. Twenty-five thousand one hundred eighteen trauma patients were admitted, 2,341 (9%) were transported by helicopter, of which 1,058 (45%) met the highest-risk criteria. Five hundred eighty-five of 1,058 patients were flown on helicopters carrying blood products. In the systems with blood available, prehospital median systolic blood pressure (125 vs 128) and Glasgow Coma Scale (7 vs 14) was significantly lower, whereas median Injury Severity Score was significantly higher (21 vs 14). Unadjusted mortality was significantly higher in the systems with blood products available, at 3 hours (8.4% vs 3.6%), 24 hours (12.6% vs 8.9%), and 30 days (19.3% vs 13.3%). Twenty-four percent of eligible patients received a PHT. A median of 1 unit of RBCs and plasma were transfused prehospital. Of patients receiving PHT, 24% received only plasma, 7% received only RBCs, and 69% received both. In the propensity score matching analysis (n = 109), PHT was not significantly associated with mortality

  11. Development of a snubber type magnetorheological fluid elastomeric lag damper for helicopter stability augmentation

    Science.gov (United States)

    Ngatu, Grum T.

    Most advanced helicopter rotors are typically fitted with lag dampers, such as elastomeric or hybrid fluid-elastomeric (FE) lag dampers, which have lower parts counts, are lighter in weight, easier to maintain, and more reliable than conventional hydraulic dampers. However, the damping and stiffness properties of elastomeric and fluid elastomeric lag dampers are non-linear functions of lag/rev frequency, dynamic lag amplitude, and operating temperature. It has been shown that elastomeric damping and stiffness levels diminish markedly as amplitude of damper motion increases. Further, passive dampers tend to present severe damping losses as damper operating temperature increases either due to in-service self-heating or hot atmospheric conditions. Magnetorheological (MR) dampers have also been considered for application to helicopter rotor lag dampers to mitigate amplitude and frequency dependent damping behaviors. MR dampers present a controllable damping with little or no stiffness. Conventional MR dampers are similar in configuration to linear stroke hydraulic type dampers, which are heavier, occupy a larger space envelope, and are unidirectional. Hydraulic type dampers require dynamic seal to prevent leakage, and consequently, frequent inspections and maintenance are necessary to ensure the reliability of these dampers. Thus, to evaluate the potential of combining the simplicity and reliability of FE and smart MR technologies in augmenting helicopter lag mode stability, an adaptive magnetorheological fluid-elastomeric (MRFE) lag damper is developed in this thesis as a retrofit to an actual fluid-elastomeric (FE) lag damper. Consistent with the loading condition of a helicopter rotor system, single frequency (lag/rev) and dual frequency (lag/rev at 1/rev) sinusoidal loading were applied to the MRFE damper at varying temperature conditions. The complex modulus method was employed to linearly characterize and compare the performance of the MRFE damper with the

  12. A novel potential/viscous flow coupling technique for computing helicopter flow fields

    Science.gov (United States)

    Summa, J. Michael; Strash, Daniel J.; Yoo, Sungyul

    1993-01-01

    The primary objective of this work was to demonstrate the feasibility of a new potential/viscous flow coupling procedure for reducing computational effort while maintaining solution accuracy. This closed-loop, overlapped velocity-coupling concept has been developed in a new two-dimensional code, ZAP2D (Zonal Aerodynamics Program - 2D), a three-dimensional code for wing analysis, ZAP3D (Zonal Aerodynamics Program - 3D), and a three-dimensional code for isolated helicopter rotors in hover, ZAPR3D (Zonal Aerodynamics Program for Rotors - 3D). Comparisons with large domain ARC3D solutions and with experimental data for a NACA 0012 airfoil have shown that the required domain size can be reduced to a few tenths of a percent chord for the low Mach and low angle of attack cases and to less than 2-5 chords for the high Mach and high angle of attack cases while maintaining solution accuracies to within a few percent. This represents CPU time reductions by a factor of 2-4 compared with ARC2D. The current ZAP3D calculation for a rectangular plan-form wing of aspect ratio 5 with an outer domain radius of about 1.2 chords represents a speed-up in CPU time over the ARC3D large domain calculation by about a factor of 2.5 while maintaining solution accuracies to within a few percent. A ZAPR3D simulation for a two-bladed rotor in hover with a reduced grid domain of about two chord lengths was able to capture the wake effects and compared accurately with the experimental pressure data. Further development is required in order to substantiate the promise of computational improvements due to the ZAPR3D coupling concept.

  13. Rotor dynamic analysis of main coolant pump

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chong Won; Seo, Jeong Hwan; Kim, Choong Hwan; Shin, Jae Chul; Wang, Lei Tian [Korea Advanced Institute of Science and Technology, Taejon (Korea)

    1999-03-01

    A rotor dynamic analysis program DARBS/MCP, for the main coolant pump of the integral reactor, has been developed. The dynamic analysis model of the main coolant pump includes a vertical shaft, three grooved radial journal bearings and gaps that represent the structure-fluid interaction effects between the rotor and the lubricant fluid. The electromagnetic force from the motor and the hydro-dynamic force induced by impeller are the major sources of vibration that may affect the rotor system stability. DARBS/MCP is a software that is developed to effectively analyze the dynamics of MCP rotor systems effectively by applying powerful numerical algorithms such as FEM with modal truncation and {lambda}-matrix method for harmonic analysis. Main design control parameters, that have much influence to the dynamic stability, have been found by Taguchi's sensitivity analysis method. Design suggestions to improve the stability of MCP rotor system have been documented. The dynamic bearing parameters of the journal bearings used for main coolant pump have been determined by directly solving the Reynolds equation using FDM method. Fluid-structure interaction effect that occurs at the small gaps between the rotor and the stator were modeled as equivalent seals, the electromagnetic force effect was regarded as a linear negative radial spring and the impeller was modeled as a rigid disk with hydrodynamic and static radial force. Although there exist critical speeds in the range of operational speeds for type I and II rotor systems, the amplitude of vibration appears to be less than the vibration limit set by the API standards. Further more, it has been verified that the main design parameters such as the clearance and length of journal bearings, and the static radial force of impeller should be properly adjusted, in order to the improve dynamic stability of the rotor system. (author). 39 refs., 81 figs., 17 tabs.

  14. Aeroelastic Considerations for Torsionally Soft Rotors,

    Science.gov (United States)

    1986-08-01

    the rotor controls and R rotor radius, ft. drive system. It is powered by a variable frequency synchronous motor rated at 47 hp V free-stream velocity...Anhedral Tipo I I* 9.2 ACR2 0 ACM1F LHNGIIUDINNL NOSE-OOWN ELASTICCYCLIC TWIS 0fC. ~J~M PITCH SLa ELASTIC .4 ICIIIDAt AT At# qV. AT , C I 0. 4 a, PIC

  15. Transonic Axial Splittered Rotor Tandem Stator Stage

    Science.gov (United States)

    2016-12-01

    and Frost [3], and Figure 1 is a cascade view of the rotor incorporating splitter vanes. Figure 2 is a projected view of Wennerstrom’s rotor...Numbered from the upstream direction where the flow of air is coming from as seen in Figure 6. These three rings are holed where sensor instrumentation can...be placed. AS1 contains the inlet temperature and pressure sensors , AS2 contains the casing transient pressure sensors , and AS3 contains the outlet

  16. Thermal Bending of the Rotor Due to Rotor-to-Stator Rub

    Directory of Open Access Journals (Sweden)

    Paul Goldman

    2000-01-01

    Full Text Available The rotor thermal bending due to the rotor-to-stator rubbing can lead to one of three types of observed rotor lateral motion: (1 spiral with increasing amplitude, (2 oscillating between rub]no-rub conditions, and (3 asymptotical approach to the rotor limit cycle. Based on the machinery observations, it is assumed in the analytical part of the paper that the speed scale of transient thermal effects is considerably lower than that of rotor vibrations, and that the thermal effect reflects only on the rotor steady-state vibrational response. This response would change due to thermally induced bow of the rotor, which can be considered to slowly vary in timefor the purpose of rotor vibration calculations. Thus uncoupled from the thermal problem, the rotor vibration is analyzed. The major consideration is given to the rotor which experiences intermittent contact with the stator, due to predetermined thermal bow, unbalance force, and radial constant load force. In the case of inelastic impact, it causes an on/off, step-change in the stiffness of the system. Using a specially developed variable transformation for the system with discontinuities, and averaging technique the resonance regimes of motion are obtained. These regimes are used to calculate the heat generated during contact stage, as a function of thermal bow modal parameters, which is used as a boundary condition for the rotor heat transfer problem. The latter is treated as quasi-static, which reduces the problem to an ordinary differential equation for the thermal bow vector. It is investigated from the stability standpoint.

  17. Testing and Life Prediction for Composite Rotor Hub Flexbeams

    Science.gov (United States)

    Murri, Gretchen B.

    2004-01-01

    A summary of several studies of delamination in tapered composite laminates with internal ply-drops is presented. Initial studies used 2D FE models to calculate interlaminar stresses at the ply-ending locations in linear tapered laminates under tension loading. Strain energy release rates for delamination in these laminates indicated that delamination would likely start at the juncture of the tapered and thin regions and grow unstably in both directions. Tests of glass/epoxy and graphite/epoxy linear tapered laminates under axial tension delaminated as predicted. Nonlinear tapered specimens were cut from a full-size helicopter rotor hub and were tested under combined constant axial tension and cyclic transverse bending loading to simulate the loading experienced by a rotorhub flexbeam in flight. For all the tested specimens, delamination began at the tip of the outermost dropped ply group and grew first toward the tapered region. A 2D FE model was created that duplicated the test flexbeam layup, geometry, and loading. Surface strains calculated by the model agreed very closely with the measured surface strains in the specimens. The delamination patterns observed in the tests were simulated in the model by releasing pairs of MPCs along those interfaces. Strain energy release rates associated with the delamination growth were calculated for several configurations and using two different FE analysis codes. Calculations from the codes agreed very closely. The strain energy release rate results were used with material characterization data to predict fatigue delamination onset lives for nonlinear tapered flexbeams with two different ply-dropping schemes. The predicted curves agreed well with the test data for each case studied.

  18. A methodology for exploiting the tolerance for imprecision in genetic fuzzy systems and its application to characterization of rotor blade leading edge materials

    Science.gov (United States)

    Sánchez, Luciano; Couso, Inés; Palacios, Ana M.; Palacios, José L.

    2013-05-01

    A methodology for obtaining fuzzy rule-based models from uncertain data is proposed. The granularity of the linguistic discretization is decided with the help of a new estimation of the mutual information between ill-known random variables, and a combination of boosting and genetic algorithms is used for discovering new rules. This methodology has been applied to predict whether the coating of an helicopter rotor blade is adequate, considering the shear adhesion strength of ice to different materials. The discovered knowledge is intended to increase the level of post-processing interpretation accuracy of experimental data obtained during the evaluation of ice-phobic materials for rotorcraft applications.

  19. Dynamics of High-Speed Rotors Supported in Sliding Bearings

    Science.gov (United States)

    Šimek, J.; Svoboda, R.

    The higher the operating speed, the more serious are problems with rotor stability. Three basic groups of rotors are analyzed and some methods of suppressing instability are shown. In the first group are classical elastic rotors supported in hydrodynamic bearings. Practically all high-speed rotors now run in tilting pad bearings, which are inherently stable, but in specific conditions even tiling pad bearings may not ensure rotor stability. The second group is composed of combustion engines turbocharger rotors, which are characteristic by heavy impellers at both overhung ends of elastic shaft. These rotors are in most cases supported in floating ring bearings, which bring special features to rotor behaviour. The third group of rotors with gas bearings exhibits special features.

  20. Mythical 'Tails of Lockwood'.

    Science.gov (United States)

    Nightingale, Sophie S; Al Shareef, Yasir R; Hutson, John M

    2008-11-01

    The cause of testicular ectopia has long been a mystery, and over the years, many hypotheses have been suggested to explain the condition. The most famous of these hypotheses is that of the 'Tails of Lockwood'. This developed from a paper written in 1888 by Charles Barrett Lockwood. Although little evidence has ever been found to corroborate this hypothesis, it remains in many textbooks and journal articles to the present day. In the 21st century, this theory should no longer be given as the cause for ectopic testes. Current biological evidence supports a complex process of growth, by elongation and migration of the gubernaculum, rather than a simple mechanical process of testicular descent, as proposed in the 18th century.

  1. LQR Based PID Controller Design for 3-DOF Helicopter System

    OpenAIRE

    Santosh Kr. Choudhary

    2014-01-01

    In this article, LQR based PID controller design for 3DOF helicopter system is investigated. The 3-DOF helicopter system is a benchmark laboratory model having strongly nonlinear characteristics and unstable dynamics which make the control of such system a challenging task. This article first presents the mathematical model of the 3DOF helicopter system and then illustrates the basic idea and technical formulation for controller design. The paper explains the simple appro...

  2. 78 FR 52407 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-08-23

    ... issued AD 2011-0185 to correct an unsafe condition for Eurocopter Model EC120 and EC130 helicopters. EASA... 0, dated July 11, 2011 (ASB EC120-25A026), for Model EC120B helicopters and ASB No. EC130-25A042, Revision 0, dated July 11, 2011 (ASB EC130-25A042), for Model EC130B4 helicopters. Both ASBs specify...

  3. 78 FR 22213 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-04-15

    ... correct an unsafe condition for the Eurocopter Model EC120 and EC130 helicopters. EASA advises that during..., 2011 (ASB EC120-25A026), for Model EC120B helicopters and ASB No. EC130-25A042, Revision 0, dated July 11, 2011 (ASB EC130-25A042), for Model EC130B4 helicopters. Both ASBs specify modifying certain part...

  4. Planning German Army helicopter maitenance and mission assignment

    OpenAIRE

    Sgaslik, Achim

    1994-01-01

    Approved for public release; distribution unlimited. German Army light helicopter transportation regiments operate 45 Bell UH-1D helicopters to support demanding missions throughout Europe. Maintenance period scheduling, major exercise and regular mission assignment decisions directly influence the readiness of the helicopter fleet. Currently, all planning is done manually, which is unstructured and time consuming. This thesis describes a decision support system designed to assist with mai...

  5. 78 FR 44045 - Airworthiness Directives; Sikorsky Aircraft Corporation (Sikorsky) Helicopters

    Science.gov (United States)

    2013-07-23

    ... effect on the States, on ] the relationship between the national Government and the States, or on the..., P/N 70102-08105-102; (4) Main Rotor Control Horn, P/N 70102-08111-047; (5) Main Rotor Hub, P/N 70103... Main Rotor Spindle Nut.. 8,000 6,400 10,000 70102-08111-047 Main Rotor Control Horn. 20,000/1,300 10...

  6. Electric Drive Control with Rotor Resistance and Rotor Speed Observers Based on Fuzzy Logic

    Directory of Open Access Journals (Sweden)

    C. Ben Regaya

    2014-01-01

    Full Text Available Many scientific researchers have proposed the control of the induction motor without speed sensor. These methods have the disadvantage that the variation of the rotor resistance causes an error of estimating the motor speed. Thus, simultaneous estimation of the rotor resistance and the motor speed is required. In this paper, a scheme for estimating simultaneously the rotor resistance and the rotor speed of an induction motor using fuzzy logic has been developed. We present a method which is based on two adaptive observers using fuzzy logic without affecting each other and a simple algorithm in order to facilitate the determination of the optimal values of the controller gains. The control algorithm is proved by the simulation tests. The results analysis shows the characteristic robustness of the two observers of the proposed method even in the case of variation of the rotor resistance.

  7. THE DESIGN OF AXIAL PUMP ROTORS USING THE NUMERICAL METHODS

    Directory of Open Access Journals (Sweden)

    Ali BEAZIT

    2010-06-01

    Full Text Available The researches in rotor theory, the increasing use of computers and the connection between design and manufacturing of rotors, have determined the revaluation and completion of classical rotor geometry. This paper presents practical applications of mathematical description of rotor geometry. A program has been created to describe the rotor geometry for arbitrary shape of the blade. The results can be imported by GAMBIT - a processor for geometry with modeling and mesh generations, to create a mesh needed in hydrodynamics analysis of rotor CFD. The results obtained are applicable in numerical methods and are functionally convenient for CAD/CAM systems.

  8. Stability of Rotor Systems: A Complex Modelling Approach

    DEFF Research Database (Denmark)

    Kliem, Wolfhard; Pommer, Christian; Stoustrup, Jakob

    1996-01-01

    with the results of the classical approach using Rayleighquotients. Several rotor systems are tested: a simple Laval rotor, a Laval rotor with additional elasticity and damping in thr bearings, and a number of rotor systems with complex symmetric 4x4 randomly generated matrices.......A large class of rotor systems can be modelled by a complex matrix differential equation of secondorder. The angular velocity of the rotor plays the role of a parameter. We apply the Lyapunov matrix equation in a complex setting and prove two new stability results which are compared...

  9. H II control for model helicopter in hover

    Science.gov (United States)

    Kim, Moo Seok; Kim, Joon Ki; Han, Jeong Yup; Park, Hong Bae; Kang, Soon Ju

    2005-12-01

    This paper presents mathematical model of six degree-of-freedom (6-DOF) helicopter (ERGO50) in hover, and H II feedback controller which is a powerful technique for the MIMO system as a helicopter. Mathematical model of the helicopter is multi-input multi-output (MIMO) and linearized system which accommodates aerodynamics. H II controller based on optimal control theory is used in a myriad application and plays an important role as a valuable precursor to other advanced methods for future work, when we need to improve stability of the helicopter. We design linear-quadratic-gaussian controller as H II controller. Simulation results show good performance.

  10. Helicopter mission optimization study. [portable computer technology for flight optimization

    Science.gov (United States)

    Olson, J. R.

    1978-01-01

    The feasibility of using low-cost, portable computer technology to help a helicopter pilot optimize flight parameters to minimize fuel consumption and takeoff and landing noise was demonstrated. Eight separate computer programs were developed for use in the helicopter cockpit using a hand-held computer. The programs provide the helicopter pilot with the ability to calculate power required, minimum fuel consumption for both range and endurance, maximum speed and a minimum noise profile for both takeoff and landing. Each program is defined by a maximum of two magnetic cards. The helicopter pilot is required to key in the proper input parameter such as gross weight, outside air temperature or pressure altitude.

  11. Automatic guidance and control laws for helicopter obstacle avoidance

    Science.gov (United States)

    Cheng, Victor H. L.; Lam, T.

    1992-01-01

    The authors describe the implementation of a full-function guidance and control system for automatic obstacle avoidance in helicopter nap-of-the-earth (NOE) flight. The guidance function assumes that the helicopter is sufficiently responsive so that the flight path can be readily adjusted at NOE speeds. The controller, basically an autopilot for following the derived flight path, was implemented with parameter values to control a generic helicopter model used in the simulation. Evaluation of the guidance and control system with a 3-dimensional graphical helicopter simulation suggests that the guidance has the potential for providing good and meaningful flight trajectories.

  12. 78 FR 40956 - Airworthiness Directives; Eurocopter Deutschland (Eurocopter) Helicopters

    Science.gov (United States)

    2013-07-09

    ... Deutschland (Eurocopter) Helicopters AGENCY: Federal Aviation Administration (FAA), Department of... Eurocopter Deutschland (Eurocopter): Amendment 39-17484; Docket No. FAA-2013-0520; Directorate Identifier...

  13. 78 FR 54792 - Airworthiness Directives; Eurocopter France (Eurocopter) Helicopters

    Science.gov (United States)

    2013-09-06

    ... create oscillations in the main rotor which can transfer dynamic loads to the structure, the main gearbox... rotor, which, in return, transfer dynamic loads to the structure. These return dynamic loads give... condition as oscillations in the main rotor which can transfer dynamic loads to the structure, the main...

  14. Structural Dynamics, Stability, and Control of Helicopters

    Science.gov (United States)

    Meirovitch, L.; Hale, A. L.

    1978-01-01

    The dynamic synthesis of gyroscopic structures consisting of point-connected substructures is investigated. The objective is to develop a mathematical model capable of an adequate simulation of the modal characteristics of a helicopter using a minimum number of degrees of freedom. The basic approach is to regard the helicopter structure as an assemblage of flexible substructures. The variational equations for the perturbed motion about certain equilibrium solutions are derived. The discretized variational equations can be conveniently exhibited in matrix form, and a great deal of information about the system modal characteristics can be extracted from the coefficient matrices. The derivation of the variational equations requires a monumental amount of algebraic operations. To automate this task a symbolic manipulation program on a digital computer is developed.

  15. Cost Modelling of Composite Componentsfor Helicopter Applications

    OpenAIRE

    Idstam, Patrik

    2015-01-01

    Composite materials are becoming more popular than ever. The increasing envi-ronmental concerns results in new challenges, where one of the biggest is to reduce the emission of greenhouse gases. Both the aerospace industry and the automotive industry work hard to become more environmental friendly. To reduce the emissions of vehicles such as cars, planes and helicopters reduction of weight is important as lower weight reduces fuel consumptions. To save weight more of the structural and load-b...

  16. Smart rotor modeling aero-servo-elastic modeling of a smart rotor with adaptive trailing edge flaps

    CERN Document Server

    Bergami, Leonardo

    2014-01-01

    A smart rotor is a wind turbine rotor that, through a combination of sensors, control units and actuators actively reduces the variation of the aerodynamic loads it has to withstand. Smart rotors feature?promising load alleviation potential and might provide the technological breakthrough required by the next generation of large wind turbine rotors.The book presents the aero-servo-elastic model of a smart rotor with Adaptive Trailing Edge Flaps for active load alleviation and provides an insight on the rotor aerodynamic, structural and control modeling. A novel model for the unsteady aerodynam

  17. Power harvesting in a helicopter lag damper

    NARCIS (Netherlands)

    de Jong, Pieter; Loendersloot, Richard; de Boer, Andries; van der Hoogt, Peter

    2011-01-01

    Currently the lifespan of rotor blades is determined based on a conservative lifetime calculation. This leads to blades being discarded while they still possess a significant residual amount of flight-hours. Blade health monitoring systems are desired to actively track the strains in the blade

  18. Mercury's Dynamic Magnetic Tail

    Science.gov (United States)

    Slavin, James A.

    2010-01-01

    The Mariner 10 and MESSENGER flybys of Mercury have revealed a magnetosphere that is likely the most responsive to upstream interplanetary conditions of any in the solar system. The source of the great dynamic variability observed during these brief passages is due to Mercury's proximity to the Sun and the inverse proportionality between reconnection rate and solar wind Alfven Mach number. However, this planet's lack of an ionosphere and its small physical dimensions also contribute to Mercury's very brief Dungey cycle, approx. 2 min, which governs the time scale for internal plasma circulation. Current observations and understanding of the structure and dynamics of Mercury's magnetotail are summarized and discussed. Special emphasis will be placed upon such questions as: 1) How much access does the solar wind have to this small magnetosphere as a function of upstream conditions? 2) What roles do heavy planetary ions play? 3) Do Earth-like substorms take place at Mercury? 4) How does Mercury's tail respond to extreme solar wind events such coronal mass ejections? Prospects for progress due to advances in the global magnetohydrodynamic and hybrid simulation modeling and the measurements to be taken by MESSENGER after it enters Mercury orbit on March 18, 2011 will be discussed.

  19. Tip Vortex and Wake Characteristics of a Counterrotating Open Rotor

    Science.gov (United States)

    VanZante, Dale E.; Wernet, Mark P.

    2012-01-01

    One of the primary noise sources for Open Rotor systems is the interaction of the forward rotor tip vortex and blade wake with the aft rotor. NASA has collaborated with General Electric on the testing of a new generation of low noise, counterrotating Open Rotor systems. Three-dimensional particle image velocimetry measurements were acquired in the intra-rotor gap of the Historical Baseline blade set. The velocity measurements are of sufficient resolution to characterize the tip vortex size and trajectory as well as the rotor wake decay and turbulence character. The tip clearance vortex trajectory is compared to results from previously developed models. Forward rotor wake velocity profiles are shown. Results are presented in a form as to assist numerical modeling of Open Rotor system aerodynamics and acoustics.

  20. Estimation of dynamic rotor loads for the rotor systems research aircraft: Methodology development and validation

    Science.gov (United States)

    Duval, R. W.; Bahrami, M.

    1985-01-01

    The Rotor Systems Research Aircraft uses load cells to isolate the rotor/transmission systm from the fuselage. A mathematical model relating applied rotor loads and inertial loads of the rotor/transmission system to the load cell response is required to allow the load cells to be used to estimate rotor loads from flight data. Such a model is derived analytically by applying a force and moment balance to the isolated rotor/transmission system. The model is tested by comparing its estimated values of applied rotor loads with measured values obtained from a ground based shake test. Discrepancies in the comparison are used to isolate sources of unmodeled external loads. Once the structure of the mathematical model has been validated by comparison with experimental data, the parameters must be identified. Since the parameters may vary with flight condition it is desirable to identify the parameters directly from the flight data. A Maximum Likelihood identification algorithm is derived for this purpose and tested using a computer simulation of load cell data. The identification is found to converge within 10 samples. The rapid convergence facilitates tracking of time varying parameters of the load cell model in flight.

  1. On the capability of helicopter gravimetry.

    Science.gov (United States)

    Bielenberg, Olaf; Meyer, Uwe; Götze, Hans-Jürgen; Choi, Sungchan

    2010-05-01

    Affordable, high performance inertial navigation systems, their integration with GPS, and modern high performance airborne vertical sensors make helicopter gravimetry an attractive alternative to other methods for obtaining gravity data. As part of the Dead Sea Integrated Research Project (DESIRE) in late spring 2007 a helicopter borne gravimetry survey was conducted over the Dead Sea Basin along and across the rift between Aquaba and the Dead Sea. A German Sikorsky S-76B helicopter system was used to carry a GT-1A gravity meter system supplied by Canadian Micro Gravity. The GT-1A is an airborne, single vertical sensor, GPS-INS scalar gravity meter with a Schuler-tuned three-axis gyro-stabilized inertial platform, that uses intelligent platform control to maintain platform verticality during turbulent motion. Low speed and terrain following helicopter gravity flights were performed to acquire the best possible data quality and high resolution, considering extreme elevation differences associated with the Dead Sea Basin. The Dead Sea Valley lies more than 400 m below sea level, while the shoulders are more than 1500 m high. The resulting initial airborne gravity data were merged with existent ground based data for enhanced mapping and modelling providing a seamless gravity map of the area. During terrain following flights the vertical accelerations effecting the helicopter and also the vertical sensor of the gravity meter are logically much higher compared to straight level flights. To investigate the effects of this two different flight performances on the gravity measurements, a test flight over flat terrain at a constant altitude with very small vertical accelerations was performed. The acceleration data occurred during this simulated airborne survey flight were recorded using an inertial measurement unit iVRU-FC constructed by iMAR-Navigation, which was also part of the equipment used during the gravimetry survey flights of DESIRE. This means that the

  2. TAIL ASYMPTOTICS OF LIGHT-TAILED WEIBULL-LIKE SUMS

    DEFF Research Database (Denmark)

    Asmussen, Soren; Hashorva, Enkelejd; Laub, Patrick J.

    2017-01-01

    We consider sums of n i.i.d. random variables with tails close to exp{-x(beta)} for some beta > 1. Asymptotics developed by Rootzen (1987) and Balkema, Kluppelberg, and Resnick (1993) are discussed from the point of view of tails rather than of densities, using a somewhat different angle......, and supplemented with bounds, results on a random number N of terms, and simulation algorithms....

  3. Wireless Light-Emitting Electrochemical Rotors.

    Science.gov (United States)

    Eßmann, Vera; Voci, Silvia; Loget, Gabriel; Sojic, Neso; Schuhmann, Wolfgang; Kuhn, Alexander

    2017-10-05

    Bipolar electrochemistry has been shown to enable and control various kinds of propulsion of nonwired conducting objects: translation, rotation, and levitation. There is a very rapid development in the field of controlled motion combined with other functionalities. Here we integrate two different concepts in one system to generate wireless electrochemical motion of a specifically designed rotor and track its polarization simultaneously by electrochemical light emission. Locally produced hydrogen bubbles at the cathodic pole of the bipolar rotor are the driving force of the motion, whereas [Ru(bpy)3]Cl2 and tripropylamine react at the anodic extremity, thus generating an electrochemiluminescence signal with an intensity directly correlated with the orientation of the rotor arms. This allows in a straightforward way the qualitative visualization of the changing interfacial potential differences during rotation and shows for the first time that light emission can be coupled to autonomously rotating bipolar electrodes.

  4. Wind Turbine Rotors with Active Vibration Control

    DEFF Research Database (Denmark)

    Svendsen, Martin Nymann

    This thesis presents a framework for structural modeling, analysis and active vibration damping of rotating wind turbine blades and rotors. A structural rotor model is developed in terms of finite beam elements in a rotating frame of reference. The element comprises a representation of general...... formulation. The element provides an accurate representation of the eigenfrequencies and whirling modes of the gyroscopic system, and identifies lightly damped edge-wise modes. By adoption of a method for active, collocated resonant vibration of multi-degree-of-freedom systems it is demonstrated...... that these are geometrically well separated. For active vibration control in three-bladed wind turbine rotors the present work presents a resonance-based method for groups of one collective and two whirling modes. The controller is based on the existing resonant format and introduces a dual system targeting the collective...

  5. Evolution of Rotor Wake in Swirling Flow

    Science.gov (United States)

    El-Haldidi, Basman; Atassi, Hafiz; Envia, Edmane; Podboy, Gary

    2000-01-01

    A theory is presented for modeling the evolution of rotor wakes as a function of axial distance in swirling mean flows. The theory, which extends an earlier work to include arbitrary radial distributions of mean swirl, indicates that swirl can significantly alter the wake structure of the rotor especially at large downstream distances (i.e., for moderate to large rotor-stator spacings). Using measured wakes of a representative scale model fan stage to define the mean swirl and initial wake perturbations, the theory is used to predict the subsequent evolution of the wakes. The results indicate the sensitivity of the wake evolution to the initial profile and the need to have complete and consistent initial definition of both velocity and pressure perturbations.

  6. Diagnosis of wind turbine rotor system

    DEFF Research Database (Denmark)

    Niemann, Hans Henrik; Mirzaei, Mahmood; Henriksen, Lars Christian

    2016-01-01

    is based on available standard sensors on wind turbines. The method can be used both on-line as well as off-line. Faults or changes in the rotor system will result in asymmetries, which can be monitored and diagnosed. This can be done by using the multi-blade coordinate transformation. Changes in the rotor......This paper describes a model free method for monitoring and fault diagnosis of the elements in a rotor system for a wind turbine. The diagnosis as well as the monitoring is done without using any model of the wind turbine and the applied controller or a description of the wind profile. The method...... system that can be diagnosed and monitored are: actuator faults, sensor faults and internal blade changes as e.g. change in mass of a blade....

  7. Modal dynamics of structures with bladed isotropic rotors and its complexity for 2-bladed rotors

    DEFF Research Database (Denmark)

    Hansen, Morten Hartvig

    2016-01-01

    The modal dynamics of structures with bladed isotropic rotors is analyzed using Hill’s method. First, analytical derivation of the periodic system matrix shows that isotropic rotors with more than two blades can be represented by an exact Fourier series with 3/rev as the highest order. For 2-bladed...... rotors, the inverse mass matrix has an infinite Fourier series with harmonic components of decreasing norm, thus the system matrix can be approximated by a truncated Fourier series of predictable accuracy. Second, a novel method for automatically identifying the principal solutions of Hill’s eigenvalue...

  8. ASPECTS REGARDING THE ROTOR BLADE GEOMETRY

    Directory of Open Access Journals (Sweden)

    MARZA Carmen

    2017-05-01

    Full Text Available The consumers’ energy needs and the variable wind potential have led the wind turbine producers to construct turbines that could efficiently operate in an as wide as possible range of wind speed power and domain. The rotor blade geometry is one of the factors that directly affect the turbine efficiency. The performance of the wind turbine depends upon blade and shape size but also upon their number. One of the main objectives in the design of the rotor blades lies in having an aerodynamic shape with high lift capacity and small drag force.

  9. Variable diameter wind turbine rotor blades

    Science.gov (United States)

    Jamieson, Peter McKeich; Hornzee-Jones, Chris; Moroz, Emilian M.; Blakemore, Ralph W.

    2005-12-06

    A system and method for changing wind turbine rotor diameters to meet changing wind speeds and control system loads is disclosed. The rotor blades on the wind turbine are able to adjust length by extensions nested within or containing the base blade. The blades can have more than one extension in a variety of configurations. A cable winching system, a hydraulic system, a pneumatic system, inflatable or elastic extensions, and a spring-loaded jack knife deployment are some of the methods of adjustment. The extension is also protected from lightning by a grounding system.

  10. Sleep and Alertness in North Sea Helicopter Operations

    NARCIS (Netherlands)

    Simons, M.; Wilschut, E.S.; Valk, P.J.L.

    2011-01-01

    Introduction : Dutch North Sea helicopter operations are characterized by multiple sector flights to offshore platforms under difficult environmental conditions. In the context of a Ministry of Transport program to improve safety levels of helicopter operations, we assessed effects of pre-duty

  11. Basic Helicopter Handbook, Revised. AC 61-13A.

    Science.gov (United States)

    Federal Aviation Administration (DOT), Washington, DC. Flight Standards Service.

    This technical manual was designed to assist applicants preparing for the private, commercial, and flight instructor pilot certificates with a helicopter rating. The chapters outline general aerodynamics, aerodynamics of flight, loads and load factors, function of controls, other helicopter components and their functions, introduction to the…

  12. 29 CFR 1926.958 - External load helicopters.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false External load helicopters. 1926.958 Section 1926.958 Labor... External load helicopters. In all operations performed using a rotorcraft for moving or placing external loads, the provisions of § 1926.551 of subpart N of this part shall be complied with. ...

  13. 78 FR 21233 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-04-10

    ...-010-AD; Amendment 39-17409; AD 2013-07-05] RIN 2120-AA64 Airworthiness Directives; Eurocopter France... new airworthiness directive (AD) for Eurocopter France EC130B4 helicopters. This AD requires visually... 39 to include an AD that would apply to Eurocopter France EC130B4 helicopters with a center...

  14. 77 FR 56755 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2012-09-14

    ...-51-AD; Amendment 39-17172; AD 2012-17-09] RIN 2120-AA64 Airworthiness Directives; Eurocopter France... new airworthiness directive (AD) for Eurocopter France Model SA341G helicopters. This AD requires... apply to Eurocopter France Model SA341G helicopters, with rotating star, part number (P/N) 341A31.4116...

  15. 78 FR 36129 - Airworthiness Directives; Eurocopter France (Eurocopter) Model Helicopters

    Science.gov (United States)

    2013-06-17

    ... Directives; Eurocopter France (Eurocopter) Model Helicopters AGENCY: Federal Aviation Administration, DOT... directive (AD) for Eurocopter Model AS350B, BA, B1, B2, C, D, and D1 helicopters and Model AS355E, F, F1, F2... identified in this proposed AD, contact American Eurocopter Corporation, 2701 N. Forum Drive, Grand Prairie...

  16. 77 FR 36213 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2012-06-18

    ... Federal Aviation Administration 14 CFR Part 39 RIN 2120-AA64 Airworthiness Directives; Eurocopter France...). SUMMARY: We propose to adopt a new airworthiness directive (AD) for Eurocopter France EC130B4 helicopters... unsafe condition for the Eurocopter France EC130B4 helicopters. EASA states that it received reports that...

  17. 78 FR 857 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-01-07

    ...-17302; AD 2012-26-07] RIN 2120-AA64 Airworthiness Directives; Eurocopter France Helicopters AGENCY... airworthiness directive (AD) for Eurocopter France (Eurocopter) Model AS350BA helicopters with certain AERAZUR... amends Sec. 39.13 by adding the following new airworthiness directive (AD): 2012-26-07 Eurocopter France...

  18. 78 FR 57047 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2013-09-17

    ...-034-AD; Amendment 39-17541; AD 2013-16-03] RIN 2120-AA64 Airworthiness Directives; Eurocopter France... new airworthiness directive (AD) for Eurocopter France (Eurocopter) Model AS350 and AS355 helicopters...): 2013-16-03 EUROCOPTER FRANCE HELICOPTERS (EUROCOPTER): Amendment 39- 17541; Docket No. FAA-2013-0119...

  19. 77 FR 54796 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2012-09-06

    ...-007-AD; Amendment 39-17166; AD 2012-17-03] RIN 2120-AA64 Airworthiness Directives; Eurocopter France... new airworthiness directive (AD) for certain Eurocopter France Model AS350 helicopters. This AD...): 2012-17-03 Eurocopter France Helicopters: Amendment 39-17166; Docket No. FAA-2012-0222; Directorate...

  20. 77 FR 5991 - Airworthiness Directives; Eurocopter France Helicopters

    Science.gov (United States)

    2012-02-07

    ... the Eurocopter France (ECF) Model AS332L2 helicopter and superseding an AD for the Model EC225LP... 2010-SW-091-AD; Amendment 39-16914; AD 2012-01-03] RIN 2120-AA64 Airworthiness Directives; Eurocopter France Helicopters AGENCY: Federal Aviation Administration (FAA), Department of Transportation (DOT...

  1. Hover flight control of helicopter using optimal control theory

    Directory of Open Access Journals (Sweden)

    Ahmed ABOULFTOUH

    2015-09-01

    Full Text Available This paper represents the optimal control theory and its application to the full scale helicopters. Generally the control of a helicopter is a hard task, because its system is very nonlinear, coupled and sensitive to the control inputs and external disturbances which might destabilize the system. As a result of these instabilities, it is essential to use a control process that helps to improve the systems performance, confirming stability and robustness. The main objective of this part is to develop a control system design technique using Linear Quadratic Regulator (LQR to stabilize the helicopter near hover flight. In order to achieve this objective, firstly, the nonlinear model of the helicopter is linearized using small disturbance theory. The linear optimal control theory is applied to the linearized state space model of the helicopter to design the LQR controller. To clarify robustness of the controller, the effects of external wind gusts and mass change are taken into concern. Wind gusts are taken as disturbances in all directions which are simulated as a sine wave. Many simulations were made to validate and verify the response of the linear controller of the helicopter. The results show that the use of an optimal control process as LQR is a good solution for MIMO helicopter system, achieving a good stabilization and refining the final behavior of the helicopter and handling the external wind gusts disturbances as shown in the different simulations.

  2. 78 FR 12648 - Airworthiness Directives; Robinson Helicopter Company

    Science.gov (United States)

    2013-02-25

    ... Company AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed rulemaking (NPRM). SUMMARY: We propose to supersede an existing airworthiness directive (AD) for Robinson Helicopter Company... identified in this proposed AD, contact Robinson Helicopter Company, 2901 Airport Drive, Torrance, CA 90505...

  3. Input Shaping for Helicopter Slung Load Swing Reduction

    DEFF Research Database (Denmark)

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    2008-01-01

    This chapter presents a feedforward swing reducing control system for augmenting already existing helicopter controllers and enables slung load flight with autonomous helicopters general cargo transport. The feedforward controller is designed to avoid excitation of the lightly damped modes of the...

  4. The Helicopter Parent (Part 2): International Arrivals and Departures

    Science.gov (United States)

    Somers, Patricia; Settle, Jim

    2010-01-01

    The phenomenon of helicopter parenting has been widely reported, yet the research literature is anemic on the topic. Based on interviews and focus groups involving 190 academic and student services professionals, this article continues by discussing the social, psychological, economic, and cultural factors that influence helicoptering; exploring…

  5. The Helicopter Parent: Research toward a Typology (Part I)

    Science.gov (United States)

    Somers, Patricia; Settle, Jim

    2010-01-01

    With 117,000 hits on a recent Google[TM] search, the phenomenon of helicopter parenting has been widely reported in the popular press. Yet the scholarly literature is anemic on the topic. This article, part one of a two-part series, presents the small body of research on helicopter parenting and describes a qualitative study of 190 participants…

  6. Heat stress reduction of helicopter crew wearing a ventilated vest

    NARCIS (Netherlands)

    Reffeltrath, P.A.

    2006-01-01

    Background: Helicopter pilots are often exposed to periods of high heat strain, especially when wearing survival suits. Therefore, a prototype of a ventilated vest was evaluated on its capability to reduce the heat strain of helicopter pilots during a 2-h simulated flight. Hypothesis: It was

  7. Small-Scale Helicopter Automatic Autorotation : Modeling, Guidance, and Control

    NARCIS (Netherlands)

    Taamallah, S.

    2015-01-01

    Our research objective consists in developing a, model-based, automatic safety recovery system, for a small-scale helicopter Unmanned Aerial Vehicle (UAV) in autorotation, i.e. an engine OFF flight condition, that safely flies and lands the helicopter to a pre-specified ground location. In pursuit

  8. 77 FR 30230 - Airworthiness Directives; Eurocopter Deutschland Helicopters

    Science.gov (United States)

    2012-05-22

    ... Deutschland Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed... Deutschland GmbH Model MBB-BK117 C-2 helicopters with certain Generator Control Units (GCU) installed. This... September 30, 2011 (AD ] 2011-0149R1), to correct an unsafe condition for the Eurocopter Deutschland GmbH...

  9. 77 FR 7005 - Airworthiness Directives; Eurocopter Deutschland GMBH Helicopters

    Science.gov (United States)

    2012-02-10

    ... Directives; Eurocopter Deutschland GMBH Helicopters AGENCY: Federal Aviation Administration (FAA), DOT... (AD) for Eurocopter Deutschland GMBH (ECD) Model MBB-BK 117 C-1 and C-2 helicopters. This proposed AD... Directive (AD): Eurocopter Deutschland GMBH: Docket No. FAA-2012-0101; Directorate Identifier 2010-SW-042-AD...

  10. Low Back Pain: Considerations for Rotary-Wing Aircrew (Reprint)

    Science.gov (United States)

    2012-12-01

    effectively ‘ tilting ’ the rotor disk). This controls the direction and magni- tude of the thrust vector. Antitorque pedals vary pitch (resultant... thrust ) of the tail rotor, counteracting main rotor torque and controlling heading and yaw. Some helicopters are designed with two tandem main rotors...base of feet; unable to place “ fl at on the fl oor ” with LE support 3 Hips and knees fl exed (psoas and iliacus fatigue) with feet dorsifl

  11. Power Properties of Two Interacting Wind Turbine Rotors

    DEFF Research Database (Denmark)

    Okulov, Valery; Mikkelsen, Robert Flemming; Sørensen, Jens Nørkær

    2016-01-01

    rotors are threebladed and designed using blade element/lifting line (BE/LL) optimum theory at a tip speed ratio, λ, of 5 with a constant design lift coefficient along the span, CL= 0.8. Measurements of the rotor characteristics were conducted by strain sensors installed in the rotor mounting...

  12. Power Properties of Two Interacting Wind Turbine Rotors

    DEFF Research Database (Denmark)

    Okulov, Valery; Mikkelsen, Robert Flemming; Sørensen, Jens Nørkær

    2017-01-01

    rotors are three-bladed and designed using blade element/lifting line (BE/LL) optimum theory at a tip-speed ratio, λ, of 5 with a constant design lift coefficient along the span, CL = 0.8. Measurements of the rotor characteristics were conducted by strain sensors installed in the rotor mounting...

  13. Calculation in the Field of Segmental Rotor Machines Taking into ...

    African Journals Online (AJOL)

    The stator mmf over a segment of the segmental rotor reluctance machine is treated as an infinite array of generators feeding a common busbar, and the magnetic potential of the rotor segment is obtained as the potential of the equivalent busbar. The rotor potential for any airgap profile is readily obtained and it is shown ...

  14. Fine tuning of molecular rotor function in photochemical molecular switches

    NARCIS (Netherlands)

    ter Wiel, Matthijs K. J.; Feringa, Ben L.

    2009-01-01

    Molecular switches are used as scaffolds for the construction of controlled molecular rotors. The internal position of the switching entity in the molecule controls the dynamic behaviour of the rotor moiety in the molecule. Six new molecular motors with o-xylyl rotor moieties were prepared on the

  15. Light Rotor: The 10-MW reference wind turbine

    DEFF Research Database (Denmark)

    Bak, Christian; Bitsche, Robert; Yde, Anders

    2012-01-01

    This paper describes the design of a rotor and a wind turbine for an artificial 10-MW wind turbine carried out in the Light Rotor project. The turbine called the Light Rotor 10-MW Reference Wind Turbine (LR10-MW RWT), is designed with existing methods and techniques and serves as a reference...

  16. Dovetail Rotor Construction For Permanent-Magnet Motors

    Science.gov (United States)

    Kintz, Lawrence J., Jr.; Puskas, William J.

    1988-01-01

    New way of mounting magnets in permanent-magnet, electronically commutated, brushless dc motors. Magnets wedge shaped, tapering toward center of rotor. Oppositely tapered pole pieces, electron-beam welded to rotor hub, retain magnets against centrifugal force generated by spinning rotor. To avoid excessively long electron-beam welds, pole pieces assembled in segments rather than single long bars.

  17. More tail lesions among undocked than tail docked pigs in a conventional herd

    DEFF Research Database (Denmark)

    Lahrmann, H. P.; Busch, M. E.; D'Eath, R. B.

    2017-01-01

    The vast majority of piglets reared in the European Union (EU) and worldwide is tail docked to reduce the risk of being tail bitten, even though EU animal welfare legislation bans routine tail docking. Many conventional herds experience low levels of tail biting among tail docked pigs, however...... it is not known, what the prevalence would have been had the pigs not been tail docked. The aim of this study was to compare the prevalence of tail lesions between docked and undocked pigs in a conventional piggery in Denmark with very low prevalence of tail biting among tail docked pigs. The study included 1922...... that housing pigs with intact tails in conventional herds with very low prevalence of tail biting among tail docked pigs, will increase the prevalence of pigs with tail lesions considerably, and pig producers will need more hospital pens. Abattoir data indicate that tail biting remarks from meat inspection...

  18. Swashplateless Helicopter Experimental Investigation: Primary Control with Trailing Edge Flaps Actuated with Piezobenders

    Science.gov (United States)

    Copp, Peter

    Helicopter rotor primary control is conventionally carried out using a swashplate with pitch links. Eliminating the swashplate promises to reduce the helicopter's parasitic power in high speed forward flight, as well as may lead to a hydraulic-less vehicle. A Mach-scale swashplateless rotor is designed with integrated piezobender-actuated trailing edge flaps and systematically tested on the benchtop, in the vacuum chamber and on the hoverstand. The blade is nominally based on the UH-60 rotor with a hover tip Mach number of 0.64. The blade diameter is 66 inches requiring 2400 RPM for Mach scale simulation. The rotor hub is modified to reduce the blade fundamental torsional frequency to less than 2.0/rev by replacing the rigid pitch links with linear springs, which results in an increase of the blade pitching response to the trailing edge flaps. Piezoelectric multilayer benders provide the necessary bandwidth, stroke and stiffness to drive the flaps for primary control while fitting inside the blade profile and withstanding the high centrifugal forces. This work focuses on several key issues. A piezobender designed from a soft piezoelectric material, PZT-5K4, is constructed. The new material is used to construct multi-layer benders with increased stroke for the same stiffness relative to hard materials such as PZT-5H2. Each layer has a thickness of 10 mils. The soft material with gold electrodes requires a different bonding method than hard material with nickel electrodes. With this new bonding method, the measured stiffness matches precisely the predicted stiffness for a 12 layer bender with 1.26 inch length and 1.0 inch width with a stiffness of 1.04 lb/mil. The final in-blade bender has a length of 1.38 inches and 1.0 inch width with a stiffness of 0.325 lb/mil and stroke of 20.2 mils for an energy output of 66.3 lb-mil. The behavior of piezobenders under very high electric fields is investigated. High field means +18.9 kV/cm (limited by arcing in air) and -3.54k

  19. Tails, Fears and Risk Premia

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Todorov, Victor

    We show that the compensation for rare events accounts for a large fraction of the equity and variance risk premia in the S&P 500 market index. The probability of rare events vary significantly over time, increasing in periods of high market volatility, but the risk premium for tail events cannot...... solely be explained by the level of the volatil- ity. Our empirical investigations are essentially model-free. We estimate the expected values of the tails under the statistical probability measure from "medium" size jumps in high-frequency intraday prices and an extreme value theory approximation...... for the corresponding jump tail density. Our estimates for the risk-neutral expectations are based on short maturity out-of-the money options and new model-free option implied variation measures explicitly designed to separate the tail probabilities. At a general level, our results suggest that any satisfactory...

  20. Autonomous Navigation, Guidance and Control of Small Electric Helicopter

    Directory of Open Access Journals (Sweden)

    Satoshi Suzuki

    2013-01-01

    Full Text Available In this study, we design an autonomous navigation, guidance and control system for a small electric helicopter. Only small, light-weight, and inaccurate sensors can be used for the control of small helicopters because of the payload limitation. To overcome the problem of inaccurate sensors, a composite navigation system is designed. The designed navigation system enables us to precisely obtain the position and velocity of the helicopter. A guidance and control system is designed for stabilizing the helicopter at an arbitrary point in three-dimensional space. In particular, a novel and simple guidance system is designed using the combination of optimal control theory and quaternion kinematics. The designs of the study are validated experimentally, and the experimental results verify the efficiency of our navigation, guidance and control system for a small electric helicopter.

  1. A Simplified Mobile Ad Hoc Network Structure for Helicopter Communication

    Directory of Open Access Journals (Sweden)

    Abdeldime Mohamed Salih Abdelgader

    2016-01-01

    Full Text Available There are a number of volunteer and statutory organizations who are capable of conducting an emergency response using helicopters. Rescue operations require a rapidly deployable high bandwidth network to coordinate necessary relief efforts between rescue teams on the ground and helicopters. Due to massive destruction and loss of services, ordinary communication infrastructures may collapse in these situations. Consequently, information exchange becomes one of the major challenges in these circumstances. Helicopters can be also employed for providing many services in rugged environments, military applications, and aerial photography. Ad hoc network can be used to provide alternative communication link between a set of helicopters, particularly in case of significant amount of data required to be shared. This paper addresses the ability of using ad hoc networks to support the communication between a set of helicopters. A simplified network structure model is presented and extensively discussed. Furthermore, a streamlined routing algorithm is proposed. Comprehensive simulations are conducted to evaluate the proposed routing algorithm.

  2. EPA Region VIII's Opinion on Otter Tail Power Company's Coyote Station Low Pressure Rotor Upgrade Proposal

    Science.gov (United States)

    This document may be of assistance in applying the New Source Review (NSR) air permitting regulations including the Prevention of Significant Deterioration (PSD) requirements. This document is part of the NSR Policy and Guidance Database.

  3. 78 FR 4759 - Airworthiness Directives; Bell Helicopter Textron, Inc. (Bell) Helicopters

    Science.gov (United States)

    2013-01-23

    ... Helicopter model Types of operation lifts and takeoffs hours TIS factor hours TIS x hours TIS factor) Yokes...-power or higher magnifying glass, visually inspect each pillow block bushing hole, spindle radius, and... glass, visually inspect each pillow block bushing hole, spindle radius, and center section web for any...

  4. 78 FR 24368 - Airworthiness Directives; Bell Helicopter Textron, Inc. (Bell) Model Helicopters

    Science.gov (United States)

    2013-04-25

    ... should include procedures to slowly operate the cockpit anti-torque control pedals during the inspection... the Model 204B helicopter, which specifies to visually inspect the chain using a 10-power magnifying...-hour TIS intervals using a 10-power or higher magnifying glass and a light; revising the inspection...

  5. 78 FR 34286 - Airworthiness Directives; Bell Helicopter Textron Canada Limited (Bell) Helicopters

    Science.gov (United States)

    2013-06-07

    ...) Install placard P/N 230-075-213-111, or equivalent, directly below the NR/NP dual tachometer. (f... certain Bell Model 407 helicopters. This proposed AD would require installing a placard beneath the NR/NP... to the ``Mail'' address between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays...

  6. Effect of Rotor Diameter on the Thermal Stresses of a Turbine Rotor Model

    Science.gov (United States)

    Dávalos, J. O.; García, J. C.; Urquiza, G.; Castro-Gómez, L. L.; Rodríguez, J. A.; De Santiago, O.

    2016-04-01

    Thermal stresses in a simplified steam turbine rotor model during a cold startup are analyzed using finite element analysis (FEA). In order to validate the numerical model, an experimental array is developed in which a hollow cylinder is heated with hot air in the external surface. At the thick wall of the cylinder, temperature distribution is measured in real time, while at the same time an algorithm computes thermal stresses. Additional computational fluid dynamics (CFD) calculations are made to obtain magnitudes of velocity and pressure in order to compute convective heat transfer coefficient. The experimental results show good agreement with the FEA computations. To evaluate the effect of rotor diameter size, FEA computations with variation in external and internal diameters are performed. Results show that thermal stresses are proportional to rotor diameter size. Also, zones of higher stress concentration are found in the external and internal surfaces of the rotor.

  7. Performance prediction and flow-field analysis of rotors in hover using a coupled Euler/boundary layer method; Previsions des performances et de l`ecoulement pour des rotors en vol stationnaire par une methode couplee Euler/couche limite

    Energy Technology Data Exchange (ETDEWEB)

    Beaumier, P. [ONERA, 92 - Chatillon (France); Castellin, C.; Arnaud, G. [Eurocopter France, 13 - Marignane (France)

    1998-12-31

    The performance prediction of helicopter in hover is of key importance for manufacturers because hover is a design configuration for the definition of a rotor-craft. A lot of efforts have been made for more than 10 years all over the world in order to develop and validate numerical methods based on CFD. An Euler method (WAVES) developed by ONERA and coupled with a boundary layer code (MI3DI) is presented, validated and applied to compute the total performance of rotors with different tip shapes. A new boundary condition for the Euler code has been tested and enables better calculation by eliminating `numerical` recirculation. The code has demonstrated its ability to rank two rotors with different planforms in good agreement with experiment. Under industrial requirements new grid strategies have been studied and should allow to reduce CPU time consumption. It is shown that WAVES/MI3DI can be efficiently used in the aerodynamic design process of a new rotor. (authors) 7 refs.

  8. Does modern helicopter construction reduce noise exposure in helicopter rescue operations?

    Science.gov (United States)

    Küpper, Thomas; Jansing, Paul; Schöffl, Volker; van Der Giet, Simone

    2013-01-01

    During helicopter rescue operations the medical personnel are at high risk for hearing damage by noise exposure. There are two important factors to be taken into account: first, the extreme variability, with some days involving no exposure but other days with extreme exposure; second, the extreme noise levels during work outside the helicopter, e.g. during winch operations. The benefit of modern, less noisier constructions and the consequences for noise protection are still unknown. We estimated the noise exposure of the personnel for different helicopter types used during rescue operations in the Alps and in other regions of the world with special regard to the advanced types like Eurocopter EC 135 to compare the benefit of modern constructions for noise protection with earlier ones. The rescue operations over 1 year of four rescue bases in the Alps (Raron and Zermatt in Switzerland; Landeck and Innsbruck in Austria, n = 2731) were analyzed for duration of rescue operations (noise exposure). Noise levels were measured during rescue operations at defined points inside and outside the different aircraft. The setting is according to the European standard (Richtlinie 2003/10/EG Amtsblatt) and to Class 1 DIN/IEC 651. With both data sets the equivalent noise level L(eq8h) was calculated. For comparison it was assumed that all rescue operations were performed with a specific type of helicopter. Then model calculations for noise exposure by different helicopter types, such as Alouette IIIb, Alouette II 'Lama', Ecureuil AS350, Bell UH1D, Eurocopter EC135, and others were performed. Depending on modern technologies the situation for the personnel has been improved significantly. Nevertheless noise prevention, which includes noise intermissions in spare time, is essential. Medical checks of the crews by occupational medicine (e.g. 'G20' in Germany) are still mandatory.

  9. Priority for empirical methods development

    Science.gov (United States)

    King, R. J.

    1982-01-01

    Several noise sources combine to make up the total helicopter noise spectrum. The sources that are most important to community annoyance are the tail rotor (discrete), main rotor (unsteady), and engine (unsteady). The periodic and broadband noise components of the helicopter rotor were enumerated, and an approach to rotorcraft noise prediction was discussed. Helicopter noise sources were prioritized, and design improvements to reduce noise were reviewed. Main rotor noise is believed to be the key to quieter helicopters since there are proven and relatively inexpensive ways to handle the tail rotor. Blade Vortex Interaction (BVI) noise is a problem to some extent with all helicopters, particularly in the descent mode. Methodology must be developed to allow forecast and control of this type of noise. Additional means of controlling it, such as reduced rotor speeds for terminal operations should also be pursued because they may be the most effective means of control and they apply to all helicopter models. Main rotor broadband noise is the limiting factor in overall helicopter noise generation. Development of semi-empirical methods to predict its behavior is necessary if results are to be achieved in the short time period available.

  10. Ornicopter Multidisciplinary Analyses and Conceptual Design

    NARCIS (Netherlands)

    Wan, J.

    2014-01-01

    The tail rotor of conventional helicopters has always been considered a necessary 'evil'. It is necessary to counteract the reaction torque of the engine and to control the helicopter in yaw but it consumes substantial power, has only marginal control authority under unfavourable wind conditions,

  11. SUBAQUEOUS DISPOSAL OF MILL TAILINGS

    Energy Technology Data Exchange (ETDEWEB)

    Neeraj K. Mendiratta; Roe-Hoan Yoon; Paul Richardson

    1999-09-03

    A study of mill tailings and sulfide minerals was carried out in order to understand their behavior under subaqueous conditions. A series of electrochemical experiments, namely, cyclic voltammetry, electrochemical impedance spectroscopy and galvanic coupling tests were carried out in artificial seawater and in pH 6.8 buffer solutions with chloride and ferric salts. Two mill tailings samples, one from the Kensington Mine, Alaska, and the other from the Holden Mine, Washington, were studied along with pyrite, galena, chalcopyrite and copper-activated sphalerite. SEM analysis of mill tailings revealed absence of sulfide minerals from the Kensington Mine mill tailings, whereas the Holden Mine mill tailings contained approximately 8% pyrite and 1% sphalerite. In order to conduct electrochemical tests, carbon matrix composite (CMC) electrodes of mill tailings, pyrite and galena were prepared and their feasibility was established by conducting a series of cyclic voltammetry tests. The cyclic voltammetry experiments carried out in artificial seawater and pH 6.8 buffer with chloride salts showed that chloride ions play an important role in the redox processes of sulfide minerals. For pyrite and galena, peaks were observed for the formation of chloride complexes, whereas pitting behavior was observed for the CMC electrodes of the Kensington Mine mill tailings. The electrochemical impedance spectroscopy conducted in artificial seawater provided with the Nyquist plots of pyrite and galena. The Nyquist plots of pyrite and galena exhibited an inert range of potential indicating a slower rate of leaching of sulfide minerals in marine environments. The galvanic coupling experiments were carried out to study the oxidation of sulfide minerals in the absence of oxygen. It was shown that in the absence of oxygen, ferric (Fe3+) ions might oxidize the sulfide minerals, thereby releasing undesirable oxidation products in the marine environment. The source of Fe{sup 3{minus}} ions may be

  12. Time Frequency Features of Rotor Systems with Slowly Varying Mass

    Directory of Open Access Journals (Sweden)

    Tao Yu

    2011-01-01

    Full Text Available With the analytic method and numerical method respectively, the asymptotic solutions and finite element model of rotor system with single slowly varying mass is obtained to investigate the time frequency features of such rotor system; furthermore, with given model of slowly varying mass, the rotor system with dual slowly varying mass is studied. For the first order approximate solution is used, there exists difference between the results with analytic method and numerical method. On the base of common characteristics of rotor system with dual slowly varying mass, the general rules and formula describing the frequency distribution of rotor system with multiple slowly varying mass are proposed.

  13. T700 power turbine rotor multiplane/multispeed balancing demonstration

    Science.gov (United States)

    Burgess, G.; Rio, R.

    1979-01-01

    Research was conducted to demonstrate the ability of influence coefficient based multispeed balancing to control rotor vibration through bending criticals. Rotor dynamic analyses were conducted of the General Electric T700 power turbine rotor. The information was used to generate expected rotor behavior for optimal considerations in designing a balance rig and a balance technique. The rotor was successfully balanced 9500 rpm. Uncontrollable coupling behavior prevented observations through the 16,000 rpm service speed. The balance technique is practical and with additional refinement it can meet production standards.

  14. Development of the optimum rotor theories

    DEFF Research Database (Denmark)

    Okulov, Valery; Sørensen, Jens Nørkær; van Kuik, Gijs A.M.

    The purpose of this study is the examination of optimum rotor theories with ideal load distributions along the blades, to analyze some of the underlying ideas and concepts, as well as to illuminate them. The book gives the historical background of the issue and presents the analysis of the proble...

  15. Impedance Calculations of Induction Machine Rotor Conductors ...

    African Journals Online (AJOL)

    The exact calculation of the impedance of induction machine rotor conductors at several operating frequencies are necessary if the dynamic behaviour of the machine is to give a good correlation between the simulated starting torque and current and the experimental results. This paper describes a method of' calculating ...

  16. The Evolution of Rotor and Blade Design

    Energy Technology Data Exchange (ETDEWEB)

    Tangler, J.

    2000-08-01

    The objective of this paper is to provide a historical perspective of the evolution of rotor and blade design during the last 20 years. This evolution is a balanced integration of economic, aerodynamic, structural dynamic, noise, and aesthetic considerations, which are known to be machine type and size dependent.

  17. Rotor Vibration Reduction via Active Hybrid Bearings

    DEFF Research Database (Denmark)

    Nicoletti, Rodrigo; Santos, Ilmar

    2002-01-01

    The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... with experiment, and simulations show the feasibility of controlling shaft vibration through this active device....

  18. Rotor Design for Diffuser Augmented Wind Turbines

    Directory of Open Access Journals (Sweden)

    Søren Hjort

    2015-09-01

    Full Text Available Diffuser augmented wind turbines (DAWTs can increase mass flow through the rotor substantially, but have often failed to fulfill expectations. We address high-performance diffusers, and investigate the design requirements for a DAWT rotor to efficiently convert the available energy to shaft energy. Several factors can induce wake stall scenarios causing significant energy loss. The causality between these stall mechanisms and earlier DAWT failures is discussed. First, a swirled actuator disk CFD code is validated through comparison with results from a far wake swirl corrected blade-element momentum (BEM model, and horizontal-axis wind turbine (HAWT reference results. Then, power efficiency versus thrust is computed with the swirled actuator disk (AD code for low and high values of tip-speed ratios (TSR, for different centerbodies, and for different spanwise rotor thrust loading distributions. Three different configurations are studied: The bare propeller HAWT, the classical DAWT, and the high-performance multi-element DAWT. In total nearly 400 high-resolution AD runs are generated. These results are presented and discussed. It is concluded that dedicated DAWT rotors can successfully convert the available energy to shaft energy, provided the identified design requirements for swirl and axial loading distributions are satisfied.

  19. rotor of the SC rotating condenser

    CERN Multimedia

    1974-01-01

    The rotor of the rotating condenser was installed instead of the tuning fork as the modulating element of the radiofrequency system, when the SC accelerator underwent extensive improvements between 1973 to 1975 (see object AC-025). The SC was the first accelerator built at CERN. It operated from August 1957 until it was closed down at the end of 1990.

  20. Modeling, State Estimation and Control of Unmanned Helicopters

    Science.gov (United States)

    Lau, Tak Kit

    Unmanned helicopters hold both tremendous potential and challenges. Without risking the lives of human pilots, these vehicles exhibit agile movement and the ability to hover and hence open up a wide range of applications in the hazardous situations. Sparing human lives, however, comes at a stiff price for technology. Some of the key difficulties that arise in these challenges are: (i) There are unexplained cross-coupled responses between the control axes on the hingeless helicopters that have puzzled researchers for years. (ii) Most, if not all, navigation on the unmanned helicopters relies on Global Navigation Satellite Systems (GNSSs), which are susceptible to jamming. (iii) It is often necessary to accommodate the re-configurations of the payload or the actuators on the helicopters by repeatedly tuning an autopilot, and that requires intensive human supervision and/or system identification. For the dynamics modeling and analysis, we present a comprehensive review on the helicopter actuation and dynamics, and contributes toward a more complete understanding on the on-axis and off-axis dynamical responses on the helicopter. We focus on a commonly used modeling technique, namely the phase-lag treatment, and employ a first-principles modeling method to justify that (i) why that phase-lag technique is inaccurate, (ii) how we can analyze the helicopter actuation and dynamics more accurately. Moreover, these dynamics modeling and analysis reveal the hard-to-measure but crucial parameters on a helicopter model that require the constant identifications, and hence convey the reasoning of seeking a model-implicit method to solve the state estimation and control problems on the unmanned helicopters. For the state estimation, we present a robust localization method for the unmanned helicopter against the GNSS outage. This method infers position from the acceleration measurement from an inertial measurement unit (IMU). In the core of our method are techniques of the sensor

  1. Utilization of rotor kinetic energy storage for hybrid vehicles

    Science.gov (United States)

    Hsu, John S [Oak Ridge, TN

    2011-05-03

    A power system for a motor vehicle having an internal combustion engine, the power system comprises an electric machine (12) further comprising a first excitation source (47), a permanent magnet rotor (28) and a magnetic coupling rotor (26) spaced from the permanent magnet rotor and at least one second excitation source (43), the magnetic coupling rotor (26) also including a flywheel having an inertial mass to store kinetic energy during an initial acceleration to an operating speed; and wherein the first excitation source is electrically connected to the second excitation source for power cycling such that the flywheel rotor (26) exerts torque on the permanent magnet rotor (28) to assist braking and acceleration of the permanent magnet rotor (28) and consequently, the vehicle. An axial gap machine and a radial gap machine are disclosed and methods of the invention are also disclosed.

  2. Rotor for a line start permanent magnet machine

    Science.gov (United States)

    Melfi, Mike; Schiferl, Rich; Umans, Stephen

    2017-07-11

    A rotor comprises laminations with a plurality of rotor bar slots with an asymmetric arrangement about the rotor. The laminations also have magnet slots equiangularly spaced about the rotor. The magnet slots extend near to the rotor outer diameter and have permanent magnets disposed in the magnet slots creating magnetic poles. The magnet slots may be formed longer than the permanent magnets disposed in the magnets slots and define one or more magnet slot apertures. The permanent magnets define a number of poles and a pole pitch. The rotor bar slots are spaced from adjacent magnet slots by a distance that is at least 4% of the pole pitch. Conductive material is disposed in the rotor bar slots, and in some embodiments, may be disposed in the magnet slot apertures.

  3. Research on Long Tail Recommendation Algorithm

    Science.gov (United States)

    Hu, Xuezhi; Zhang, Chuang; Wu, Ming; Zeng, Yang

    2017-10-01

    Most recommendation systems in the major electronic commerce platforms are influenced by the long tail effect more or less. There are sufficient researches of how to assess recommendation effect while no criteria to evaluate long tail recommendation rate. In this study, we first discussed the existing problems of recommending long tail products through specific experiments. Then we proposed a long tail evaluation criteria and compared the performance in long tail recommendation between different models.

  4. CH-47F Improved Cargo Helicopter (CH-47F)

    Science.gov (United States)

    2015-12-01

    funding lines changed starting in FY 2010 to CH-47 Helicopter (A05101) - a parent (roll-up) of New Build and Service Life Extension Program (SLEP...Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-278 CH-47F Improved Cargo Helicopter (CH-47F) As of FY 2017 President’s Budget Defense...December 2015 SAR March 21, 2016 18:18:21 UNCLASSIFIED 4 LTC Richard Bratt Office of the Project Manager Cargo Helicopters Building 5678 Redstone Arsenal

  5. Adaptive Control System for Autonomous Helicopter Slung Load Operations

    DEFF Research Database (Denmark)

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    2010-01-01

    system on the helicopter that measures the position of the slung load. The controller is a combined feedforward and feedback scheme for simultaneous avoidance of swing excitation and active swing damping. Simulations and laboratory flight tests show the effectiveness of the combined control system......This paper presents design and verification of an estimation and control system for a helicopter slung load system. The estimator provides position and velocity estimates of the slung load and is designed to augment existing navigation in autonomous helicopters. Sensor input is provided by a vision...

  6. Simulating effectiveness of helicopter evasive manoeuvres to RPG attack

    Science.gov (United States)

    Anderson, D.; Thomson, D. G.

    2010-04-01

    The survivability of helicopters under attack by ground troops using rocket propelled grenades has been amply illustrated over the past decade. Given that an RPG is unguided and it is infeasible to cover helicopters in thick armour, existing optical countermeasures are ineffective - the solution is to compute an evasive manoeuvre. In this paper, an RPG/helicopter engagement model is presented. Manoeuvre profiles are defined in the missile approach warning sensor camera image plane using a local maximum acceleration vector. Required control inputs are then computed using inverse simulation techniques. Assessments of platform survivability to several engagement scenarios are presented.

  7. 78 FR 1838 - Takes of Marine Mammals Incidental to Specified Activities; St. George Reef Light Station...

    Science.gov (United States)

    2013-01-09

    ... lions (Eumetopias jubatus) within the eastern U.S. Stock; and six northern fur seals (Callorhinus... Air Shasta Rotor and Wing, LLC. The Raven R44, which seats three passengers and one pilot, is a compact-sized (1134 kilograms (kg), 2500 pounds (lbs)) helicopter with two-bladed main and tail rotors...

  8. Helicopter type and accident severity in Helicopter Emergency Medical Services missions.

    Science.gov (United States)

    Hinkelbein, Jochen; Schwalbe, Mandy; Wetsch, Wolfgang A; Spelten, Oliver; Neuhaus, Christopher

    2011-12-01

    Whereas accident rates and fatal accident rates for Helicopter Emergency Medical Services (HEMS) were investigated sufficiently, resulting consequences for the occupants remain largely unknown. The present study aimed to classify HEMS accidents in Germany to prognosticate accident severity with regard to the helicopter model used. German HEMS accidents (1 Sept. 1970-31 Dec. 2009) were gathered as previously reported. Accidents were categorized in relation to the most severe injury, i.e., (1) no; (2) slight; (3) severe; and (4) fatal injuries. Only helicopter models with at least five accidents were analyzed to retrieve representative data. Prognostication was estimated by the relative percentage of each injury type compared to the total number of accidents. The model BO105 was most often involved in accidents (38 of 99), followed by BK117 and UH-1D. OfN = 99 accidents analyzed, N = 63 were without any injuries (63.6%), N = 8 resulted in minor injuries of the occupants (8.1%), and N = 9 in major injuries (9.1%). Additionally, N = 19 fatal accidents (19.2%) were registered. EC135 and BK1 17 had the highest incidence of uninjured occupants (100% vs. 88.2%) and the lowest percentage of fatal injuries (0% vs. 5.9%; all P > 0.05). Most fatal accidents occurred with the models UH-1D, Bell 212, and Bell 412. Use of the helicopter models EC135 and BK117 resulted in a high percentage of uninjured occupants. In contrast, the fatality rate was highest for the models Bell UH-I D, Bell 222, and Bell 412. Data from the present study allow for estimating accident risk in HEMS missions and prognosticating resulting fatalities, respectively.

  9. Aerodynamic design of the National Rotor Testbed.

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, Christopher Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-10-01

    A new wind turbine blade has been designed for the National Rotor Testbed (NRT) project and for future experiments at the Scaled Wind Farm Technology (SWiFT) facility with a specific focus on scaled wakes. This report shows the aerodynamic design of new blades that can produce a wake that has similitude to utility scale blades despite the difference in size and location in the atmospheric boundary layer. Dimensionless quantities circulation, induction, thrust coefficient, and tip-speed-ratio were kept equal between rotor scales in region 2 of operation. The new NRT design matched the aerodynamic quantities of the most common wind turbine in the United States, the GE 1.5sle turbine with 37c model blades. The NRT blade design is presented along with its performance subject to the winds at SWiFT. The design requirements determined by the SWiFT experimental test campaign are shown to be met.

  10. CFD simulations of the MEXICO rotor

    DEFF Research Database (Denmark)

    Bechmann, Andreas; Sørensen, Niels N.; Zahle, Frederik

    2011-01-01

    The wake behind a wind turbine model is investigated using Computational Fluid Dynamics (CFD), and results are compared with measurements. The turbine investigated is the three‐bladed test rotor (D = 4.5 m) used in the Model Experiments in Controlled Conditions (MEXICO) wind tunnel experiment....... During the MEXICO experiment, particle image velocimetry measurements of the induction upstream and downstream of the rotor were performed for different operating conditions, giving a unique dataset to verify theoretical models and CFD models. The present paper first describes the efforts in reproducing...... the experimental results using the Reynold‐Averaged Navier‐Stokes method. Second, three‐dimensional airfoil characteristics are extracted that allow simulations with simpler wake models. Copyright © 2011 John Wiley & Sons, Ltd....

  11. Disturbance Observer Based Control of Multirotor Helicopters Based on a Universal Model with Unstructured Uncertainties

    Directory of Open Access Journals (Sweden)

    Ye Xie

    2015-01-01

    Full Text Available To handle different perspectives of unstructured uncertainties, two robust control techniques on the basis of a universal model are studied in this paper. Rather than building a model only applicable to a specific small-scale multirotor helicopter (MHeli, the paper proposes a modeling technique to develop a universal model-framework. Particularly, it is straightforward to apply the universal model to a certain MHeli because the contribution and allocation matrix is proposed in the model-framework. Based on the model uncertainties, the load perturbation of the rotor is the primary focus due to its indispensable importance in the tracking performance. In contrast to the common methods, it is proposed to take this unstructured uncertainty in that external disturbance and designs disturbance observer (DOB. In addition, a class of lead-compensator is specifically designed as for compensating phase lag induced by DOB. Compared with H∞ loop-shaping, greater robust tracking performance on rejecting load perturbation could be achieved as a tradeoff between robust stability and tracking performance which is successfully avoided with DOB-based control strategy.

  12. Evaluation of MEMS-Based Wireless Accelerometer Sensors in Detecting Gear Tooth Faults in Helicopter Transmissions

    Science.gov (United States)

    Lewicki, David George; Lambert, Nicholas A.; Wagoner, Robert S.

    2015-01-01

    The diagnostics capability of micro-electro-mechanical systems (MEMS) based rotating accelerometer sensors in detecting gear tooth crack failures in helicopter main-rotor transmissions was evaluated. MEMS sensors were installed on a pre-notched OH-58C spiral-bevel pinion gear. Endurance tests were performed and the gear was run to tooth fracture failure. Results from the MEMS sensor were compared to conventional accelerometers mounted on the transmission housing. Most of the four stationary accelerometers mounted on the gear box housing and most of the CI's used gave indications of failure at the end of the test. The MEMS system performed well and lasted the entire test. All MEMS accelerometers gave an indication of failure at the end of the test. The MEMS systems performed as well, if not better, than the stationary accelerometers mounted on the gear box housing with regards to gear tooth fault detection. For both the MEMS sensors and stationary sensors, the fault detection time was not much sooner than the actual tooth fracture time. The MEMS sensor spectrum data showed large first order shaft frequency sidebands due to the measurement rotating frame of reference. The method of constructing a pseudo tach signal from periodic characteristics of the vibration data was successful in deriving a TSA signal without an actual tach and proved as an effective way to improve fault detection for the MEMS.

  13. Unsupervised Pattern Classifier for Abnormality-Scaling of Vibration Features for Helicopter Gearbox Fault Diagnosis

    Science.gov (United States)

    Jammu, Vinay B.; Danai, Kourosh; Lewicki, David G.

    1996-01-01

    A new unsupervised pattern classifier is introduced for on-line detection of abnormality in features of vibration that are used for fault diagnosis of helicopter gearboxes. This classifier compares vibration features with their respective normal values and assigns them a value in (0, 1) to reflect their degree of abnormality. Therefore, the salient feature of this classifier is that it does not require feature values associated with faulty cases to identify abnormality. In order to cope with noise and changes in the operating conditions, an adaptation algorithm is incorporated that continually updates the normal values of the features. The proposed classifier is tested using experimental vibration features obtained from an OH-58A main rotor gearbox. The overall performance of this classifier is then evaluated by integrating the abnormality-scaled features for detection of faults. The fault detection results indicate that the performance of this classifier is comparable to the leading unsupervised neural networks: Kohonen's Feature Mapping and Adaptive Resonance Theory (AR72). This is significant considering that the independence of this classifier from fault-related features makes it uniquely suited to abnormality-scaling of vibration features for fault diagnosis.

  14. Balancing of Rigid and Flexible Rotors

    Science.gov (United States)

    1986-01-01

    IA14 nf~VO1lS t’ , f,~ riabtiB SVM-12 Balancing of Rigid and Flexible Rotors Neville F. Rieger Stress Technology, Inc. 1986 The Shock end Vibration...a bearing or other Atructural components by fatigue . Unbalance is therefore recognized as an important potential cause of machinery failure. A number...runout on slow rotation, stress relaxation with time often heavy vibration during rota- "tion Section of blade or vane broken Visually observable; bearing

  15. A Magnetorheological Fluid Damper for Rotor Applications

    OpenAIRE

    Forte, P.; Paternò, M.; Rustighi, E.

    2004-01-01

    Even though we are still far from industrial applications, in the last decade there has been increasing attention directed toward the employment of electrorheological (ER) and magnetorheological (MR) fluids in active bearings and active squeeze film dampers in rotordynamics. MR fluids react to magnetic fields undergoing reversible changes in their mechanical characteristics, viscosity, and stiffness in particular. In previous literature, some applications of ER fluids in rotor squeeze film da...

  16. Quantum diffusion in the quasiperiodic kicked rotor

    OpenAIRE

    Lignier, Hans; Garreau, Jean Claude; Szriftgiser, Pascal; Delande, Dominique

    2004-01-01

    We study the mechanisms responsible for quantum diffusion in the quasiperiodic kicked rotor. We report experimental measurements of the diffusion constant on the atomic version of the system and develop a theoretical approach (based on the Floquet theorem) explaining the observations, especially the ``sub-Fourier'' character of the resonances observed in the vicinity of exact periodicity, i.e. the ability of the system to distinguish two neighboring driving frequencies in a time shorter than ...

  17. Commercial Pilot Practical Test Standards for Rotorcraft, Helicopter, Gyroplane

    Science.gov (United States)

    1996-04-01

    The Commercial Pilot Rotorcraft (Helicopter and Gyroplane) Practical Test : Standards (PTS) book has been published by the Federal Aviation : Administration (FAA) to establish the standards for commercial pilot certification : practical tests for the...

  18. Full State Estimation for Helicopter Slung Load System

    DEFF Research Database (Denmark)

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    2007-01-01

    coordinate formulation and can be used to model all body to body slung load suspension systems. Both estimators include bias estimation for the accelerometers and gyros and the model based estimator furthermore includes estimation of external wind disturbances. A vision system is used to measure the motion......This paper presents the design of a state estimator system for a generic helicopter based slung load system. The estimator is designed to deliver full rigid body state information for both helicopter and load and is based on the unscented Kalman filter. Two different approaches are investigated......: One based on a parameter free kinematic model and one based on a full aerodynamic helicopter and slung load model. The kinematic model approach uses acceleration and rate information from two Inertial Measurement Units, one on the helicopter and one on the load, to drive a simple kinematic model...

  19. Full State Estimation for Helicopter Slung Load System

    DEFF Research Database (Denmark)

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    coordinate formulation and can be used to model all body to body slung load suspension systems. Both estimators include bias estimation for the accelerometers and gyros and the model based estimator furthermore includes estimation of external wind disturbances. A vision system is used to measure the motion......This paper presents the design of a state estimator system for a generic helicopter based slung load system. The estimator is designed to deliver full rigid body state information for both helicopter and load and is based on the unscented Kalman filter. Two different approaches are investigated......: One based on a parameter free kinematic model and one based on a full aerodynamic helicopter and slung load model. The kinematic model approach uses acceleration and rate information from two Inertial Measurement Units, one on the helicopter and one on the load, to drive a simple kinematic model...

  20. Modeling, Estimation, and Control of Helicopter Slung Load System

    DEFF Research Database (Denmark)

    Bisgaard, Morten

    This thesis treats the subject of autonomous helicopter slung load flight and presents the reader with a methodology describing the development path from modeling and system analysis over sensor fusion and state estimation to controller synthesis. The focus is directed along two different....... This first major contribution of this thesis is the development of a complete helicopter and slung load system model that is shared between the two branches. The generic slung load model can be used to model all body to body slung load suspension types and gives an intuitive and easy-to-use way of modeling...... and simulating different slung load suspension types. It further includes detection and response to wire slacking and tightening, it models the aerodynamic coupling between the helicopter and the load, and can be used for multilift systems with any combination of multiple helicopters and multiple loads...

  1. Reporting Helicopter Emergency Medical Services in Major Incidents

    DEFF Research Database (Denmark)

    Fattah, Sabina; Johnsen, Anne Siri; Sollid, Stephen J M

    2016-01-01

    OBJECTIVE: Research on helicopter emergency medical services (HEMS) in major incidents is predominately based on case descriptions reported in a heterogeneous fashion. Uniform data reported with a consensus-based template could facilitate the collection, analysis, and exchange of experiences...

  2. Helicopter Fatigue Load and Life Determination Methods

    Science.gov (United States)

    1975-08-01

    c.g. BI = 20% b, nominal c.g. B2 = 60% b3 aft c.g. B3 = 20% 2 rotor RPM class intervals c = 2 cI RPM <. 98 design RPM C1 = 10% cz RPM >. 98 design RPM...particular full- scala test item can then be used in conjunction with the deterministic function, f, to define working S-N curves. Now, E cannot be...to estimate a B2 . If, however, the additional assumption is made that qB 2 is constant for all flight conditions under investigation, then there are

  3. Theoretical Analysis and Experimental Researches regarding the Asymmetrical Fluid Flow Applied in Aeronautics

    Directory of Open Access Journals (Sweden)

    Ionică Cîrciu

    2015-01-01

    Full Text Available The current paper has been written in order to find the best solutions to replace the antitorque rotor of single-rotor helicopters, with removal of its disadvantages through the Coandă Effect. This would significantly increase the flight performance. The research mainly aims at obtaining a controlled lateral force due to Coandă flows through the tail boom, a force which would be useful for the stabilization needed because of the lifting rotor during the flight of single-rotor helicopters.

  4. Theoretical Analysis and Experimental Researches regarding the Asymmetrical Fluid Flow Applied in Aeronautics

    OpenAIRE

    Cîrciu, Ionică; Luculescu, Doru; Prisacariu, Vasile; Mihai, Eduard; Rotaru, Constantin

    2015-01-01

    The current paper has been written in order to find the best solutions to replace the antitorque rotor of single-rotor helicopters, with removal of its disadvantages through the Coandă Effect. This would significantly increase the flight performance. The research mainly aims at obtaining a controlled lateral force due to Coandă flows through the tail boom, a force which would be useful for the stabilization needed because of the lifting rotor during the flight of single-rotor helicopters.

  5. Ruin problems and tail asymptotics

    DEFF Research Database (Denmark)

    Rønn-Nielsen, Anders

    The thesis Ruin Problems and Tail Asymptotics provides results on ruin problems for several classes of Markov processes. For a class of diffusion processes with jumps an explicit expression for the joint Laplace transform of the first passage time and the corresponding undershoot is derived...

  6. Capital regulation and tail risk

    NARCIS (Netherlands)

    Perotti, E.; Ratnovski, L.; Vlahu, R.

    2011-01-01

    The paper studies risk mitigation associated with capital regulation, in a context where banks may choose tail risk assets. We show that this undermines the traditional result that higher capital reduces excess risk taking driven by limited liability. Moreover, higher capital may have an unintended

  7. Capital regulation and tail risk

    NARCIS (Netherlands)

    Perotti, E.; Ratnovski, L.; Vlahu, R.

    2011-01-01

    The paper studies risk mitigation associated with capital regulation, in a context when banks may choose tail risk assets. We show that this undermines the traditional result that higher capital reduces excess risk-taking driven by limited liability. When capital raising is costly, poorly

  8. Detection of Mercury's Potassium Tail

    Science.gov (United States)

    Schmidt, Carl; Leblanc, Francois; Moore, Luke; Bida, Thomas A.

    2017-10-01

    Ground-based observations of Mercury's exosphere bridge the gap between the MESSENGER and BepiColombo missions and provide a broad counterpart to their in situ measurements. Here we report the first detection of Mercury's potassium tail in both emission lines of the D doublet. The sodium to potassium abundance ratio at 5 planetary radii down-tail is approximately 95, near the mid-point of a wide range of values that have been quoted over the planet's disk. This is several times the Na/K present in atmospheres of the Galilean satellites and more than an order of magnitude above Mercury's usual analogue, the Moon. The observations confirm that Mercury's anomalously high Na/K ratios cannot be explained by differences in neutral loss rates. The width and structure of the Na and K tails is comparable and both exhibit a persistent enhancement in their northern lobe. We interpret this as a signature of Mercury's offset magnetosphere; the exosphere's source rates are locally enhanced at the southern surface, and sloshing from radiation pressure and gravity guides this population into the northern region of the tail.

  9. An experimental study on improvement of Savonius rotor performance

    Directory of Open Access Journals (Sweden)

    N.H. Mahmoud

    2012-03-01

    In this work different geometries of Savonius wind turbine are experimentally studied in order to determine the most effective operation parameters. It was found that, the two blades rotor is more efficient than three and four ones. The rotor with end plates gives higher efficiency than those of without end plates. Double stage rotors have higher performance compared to single stage rotors. The rotors without overlap ratio (β are better in operation than those with overlap. The results show also that the power coefficient increases with rising the aspect ratio (α. The conclusions from the measurements of the static torque for each rotor at different wind speeds verify the above summarized results of this work.

  10. Hover flight control of helicopter using optimal control theory

    OpenAIRE

    Ahmed ABOULFTOUH; Gamal EL-BAYOUMI; Mohamed MADBOULI

    2015-01-01

    This paper represents the optimal control theory and its application to the full scale helicopters. Generally the control of a helicopter is a hard task, because its system is very nonlinear, coupled and sensitive to the control inputs and external disturbances which might destabilize the system. As a result of these instabilities, it is essential to use a control process that helps to improve the systems performance, confirming stability and robustness. The main objective of this part is to ...

  11. The Evolution of the U.S. Helicopter Industry.

    Science.gov (United States)

    1984-12-01

    The failure of another ASW program, the Drone AntiSubmarine Helicopter (DASH) program, left Navy destroyers without an ASW capability. This pro...rapidly followed by the Frelon (a three turbine naval helicopter) in 1959, the Super Frelon (a thirty place three turbine upgrade of the Frelon ) in...leading to the Puma (twin engined 8000 lb. tactical transport), and the Super Frelon (three engined 15,000 lb. antisubmarine, passenger and cargo

  12. Evaluation of Dutch Helicopter Emergency Medical Services in transporting children.

    Science.gov (United States)

    Peters, Joost; Beekers, Christian; Eijk, Ruud; Edwards, Michael; Hoogerwerf, Nico

    2014-01-01

    In the Netherlands, helicopter emergency medical services (HEMS) function as an adjunct to paramedic ambulance service delivering hospital-level medical care to a prehospital location. The main goal of Dutch HEMS is to provide on-scene medical expertise and not primarily to serve as transport. The transportation of patients to specialized hospitals is sometimes mandatory, especially in cases of critically ill or wounded children. In the literature, no support can be found to support the safety of transportation by helicopter. We retrospectively evaluated the safety of this type of transportation and if any problems were encountered transporting children by helicopter. We reviewed our local HEMS database for all children (, 16 years) transported by helicopter to a level 1 trauma center between January 2007 and December 2012. A total number of 430 patients were transported by helicopter to a hospital (0-87 years, mean 5 31.6 years). Of these patients, 83 (19%) were younger than 16 years (0-15.7 years, mean 5 6.6 years). Causes for HEMS transport in children varied, but the main groups were road traffic accidents (40%), cardiopulmonary arrests (15%), falls from height (12%), and horse riding accidents (7%). In the children group, 1 accidental extubation of the orotracheal tube was noted while lifting the patient (10 years old) into the helicopter. This was immediately noticed, and the patient was reintubated without complications. No further adverse events were encountered during transportation time. The accidental extubation is not a specific complication of helicopter transportation but is inextricably linked with moving severely injured and intubated patients/children. We conclude that transporting children by helicopter is a safe method of transportation for critically ill children to adequately equipped medical centers. Copyright © 2014 Air Medical Journal Associates. Published by Elsevier Inc. All rights reserved.

  13. Time Periodic Control of a Multi-Blade Helicopter.

    Science.gov (United States)

    1988-05-01

    motion (13-22). Friedmann and Silverthorn (13) examined the flap-lag motion of a cantilevered rotor blade at arbitrary d, advance ratios. They concluded...Advance Ratio,* NASA SP-352: 25-34 (1974). 13. Friedmann, P. and L. J. Silverthorn . "Aeroelastic Stability of Periodic Systems with Applications to Rotor

  14. Idiopathic Syringomyelia in a Military Helicopter Pilot.

    Science.gov (United States)

    Schiemer, Anthony

    2017-10-01

    A syrinx is a fluid-filled cavity within the spinal cord. They can lead to a variety of symptoms, including limb weakness and back pain. Incidental finding of syringomyelia provides a challenge for clinicians due to the wide variety of possible symptoms. In military aviation, neurological findings in pilots can result in extensive investigation that can lead to potentially invasive management. Conversely, the potential for chronic progression of a spinal syrinx and subsequent neurological deterioration makes early identification critical. Ultimately, the discovery of a lesion may have implications for flying status and operational capability. A 25-yr-old man working as a navy Seahawk helicopter pilot presented with episodes of right arm paraesthesia and pain between the scapulae. On at least one occasion, these symptoms woke him at night. Upon magnetic resonance imaging, dilatation of the central canal in a syrinx-like pattern in the lower cervical region was noted. Neurology review suggested the finding was persistent and unlikely to be responsible for his symptoms. No surgical input was recommended. His symptoms were attributed to mild cervical spondylosis, which resolved with ongoing physiotherapy, and he was returned to flying status. This case highlights several issues involved with the incidental finding of a syringomyelia. Surgical intervention has been known to worsen symptoms. Conversely, studies have identified minimal radiological progression in cases of idiopathic syringomyelia, with fewer individuals displaying neurological deterioration. For aircrew, potentially unnecessary neurosurgical intervention poses risks to a flying career and overall operational capability.Schiemer A. Idiopathic syringomyelia in a military helicopter pilot. Aerosp Med Hum Perform. 2017; 88(10):962-965.

  15. Equations of motion for a rotor blade, including gravity, pitch action and rotor speed variations

    DEFF Research Database (Denmark)

    Kallesøe, Bjarne Skovmose

    2007-01-01

    This paper extends Hodges-Dowell's partial differential equations of blade motion, by including the effects from gravity, pitch action and varying rotor speed. New equations describing the pitch action and rotor speeds are also derived. The physical interpretation of the individual terms...... in the equations is discussed. The partial differential equations of motion are approximated by ordinary differential equations of motion using an assumed mode method. The ordinary differential equations are used to simulate a sudden pitch change of a rotating blade. This work is a part of a project on pitch blade...

  16. Rotor Performance Enhancement Using Slats on the Inner Part of a 10MW Rotor

    DEFF Research Database (Denmark)

    Gaunaa, Mac; Zahle, Frederik; Sørensen, Niels N.

    2013-01-01

    The present work continues the investigations of using slats on the inner parts of wind turbine rotors by using an updated version of the 2D CFD based airfoil/slat design tool earlier used by the authors in combination with the rotor design methods from [8] to design slats for 0:1 > r=R > 0:3 for...... to predictions of a lifting line based computational tool based on 2D airfoil polars to highlight the 3D rotational effects on airfoil coefficients of the slatted inner airfoil sections....

  17. Rotor Performance Enhancement Using Slats on the Inner Part of a 10MW Rotor

    DEFF Research Database (Denmark)

    The present work continues the investigations of using slats on the inner parts of wind turbine rotors by using an updated version of the 2D CFD based airfoil/slat design tool earlier used by the authors in combination with the rotor design methods from [8] to design slats for 0:1 > r=R > 0:3 for...... to predictions of a lifting line based computational tool based on 2D airfoil polars to highlight the 3D rotational effects on airfoil coefficients of the slatted inner airfoil sections....

  18. Numerical modeling of a rotor misalignment; Modelado numerico del desalineamiento de un rotor

    Energy Technology Data Exchange (ETDEWEB)

    Leon Pina, Roberto

    2009-12-15

    In the turbo-machinery area after an unbalancing, the misalignment is the fault that most frequently appears, and this one has been little studied compared to the unbalance. The misalignment appears when the geometric centers of two shafts and/or bearings do not coincide, these differences take place by different factors such as: incorrect installation of the bearings or rotors, thermal effects, or rotor weight, to mention some of them. The of the misalignment diagnosis continues being an area little studied, since the effects it generates are complex and include diverse physical processes reason why it presents/displays similar symptoms to those of other faults; thus, one of the methods that are used to diagnose this fault, is based on analyzing the vibration phantoms but this works only under particular conditions. In order to reproduce the dynamic behavior of a misaligned rotor, in the present work non-linear simplified models of the supports are used, whose objective is to contribute to facilitate future studies of the flow-dynamic behavior of the bearing, helping to identify the type and magnitude of the existing non-linearity in the supports and leaning in the analysis of the vibratory behavior of misaligned rotors observed in the field. [Spanish] En el area de turbomaquinaria despues del desbalance, el desalineamiento es la falla que se presenta con mayor frecuencia, y esta se ha estudiado poco comparada con el desbalance. El desalineamiento se presenta cuando los centros geometricos de dos flechas y/o chumaceras no coinciden, estas diferencias se producen por diferentes factores como: instalacion incorrecta de las chumaceras o rotores, efectos termicos, o el peso del rotor, por mencionar algunos. El diagnostico del desalineamiento sigue siendo una area poco estudiada, ya que los efectos que genera son complejos y abarcan diversos procesos fisicos por lo que presenta sintomas similares a los de otras fallas; asi, uno de los metodos que se utilizan para

  19. Tunneling of coupled methyl quantum rotors in 4-methylpyridine: Single rotor potential versus coupling interaction

    Science.gov (United States)

    Khazaei, Somayeh; Sebastiani, Daniel

    2017-11-01

    We study the influence of rotational coupling between a pair of methyl rotators on the tunneling spectrum in condensed phase. Two interacting adjacent methyl groups are simulated within a coupled-pair model composed of static rotational potential created by the chemical environment and the interaction potential between two methyl groups. We solve the two-dimensional time-independent Schrödinger equation analytically by expanding the wave functions on the basis set of two independent free-rotor functions. We investigate three scenarios which differ with respect to the relative strength of single-rotor and coupling potential. For each scenario, we illustrate the dependence of the energy level scheme on the coupling strength. It is found that the main determinant of splitting energy levels tends to be a function of the ratio of strengths of coupling and single-rotor potential. The tunnel splitting caused by coupling is maximized for the coupled rotors in which their total hindering potential is relatively shallow. Such a weakly hindered methyl rotational potential is predicted for 4-methylpyridine at low temperature. The experimental observation of multiple tunneling peaks arising from a single type of methyl group in 4-methylpyridine in the inelastic neutron scattering spectrum is widely attributed to the rotor-rotor coupling. In this regard, using a set of first-principles calculations combined with the nudged elastic band method, we investigate the rotational potential energy surface (PES) of the coaxial pairs of rotors in 4-methylpyridine. A Numerov-type method is used to numerically solve the two-dimensional time-independent Schrödinger equation for the calculated 2D-density functional theory profile. Our computed energy levels reproduce the observed tunneling transitions well. Moreover, the calculated density distribution of the three methyl protons resembles the experimental nuclear densities obtained from the Fourier difference method. By mapping the

  20. Mechanical coupling for a rotor shaft assembly of dissimilar materials

    Science.gov (United States)

    Shi, Jun [Glastonbury, CT; Bombara, David [New Hartford, CT; Green, Kevin E [Broad Brook, CT; Bird, Connic [Rocky Hill, CT; Holowczak, John [South Windsor, CT

    2009-05-05

    A mechanical coupling for coupling a ceramic disc member to a metallic shaft includes a first wedge clamp and a second wedge clamp. A fastener engages a threaded end of a tie-bolt to sandwich the ceramic disc between the wedge clamps. An axial spring is positioned between the fastener and the second wedge clamp to apply an axial preload along the longitudinal axis. Another coupling utilizes a rotor shaft end of a metallic rotor shaft as one wedge clamp. Still another coupling includes a solid ceramic rotor disc with a multiple of tie-bolts radially displaced from the longitudinal axis to exert the preload on the solid ceramic rotor disc.