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1
Frey, Felix, Jakob Thiemeier, Constantin Öhrle, Manuel Keßler, and Ewald Krämer. "Aerodynamic Interactions on Airbus Helicopters' Compound Helicopter RACER in Cruise Flight." Journal of the American Helicopter Society 65, no. 4 (October 1, 2020): 1–14. http://dx.doi.org/10.4050/jahs.65.042001.
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With the pursuit of extending the flight envelopes of helicopters toward higher cruise speed, helicopter manufacturers increasingly have come up with nonconventional configurations in recent years. Among these, Airbus Helicopters' RACER (Rapid And Cost-Efficient Rotorcraft) is a compound helicopter equipped with a boxwing and lateral pusher rotors. In combination with the main rotor, these additional components determine the aerodynamic characteristics of the helicopter. Thereby, depending on the flight conditions, their individual performance is influenced by a variety of interactions. As the understanding of these interactions is vital for the evaluation of the overall system, the respective mutual influence of main rotor, wings, and lateral rotors is analyzed in this paper for cruise flight. For this reason, high-fidelity coupled aerodynamic simulations are conducted not only for the full RACER configuration but also for reduced setups omitting individual components to isolate the effect of these components on the helicopter's aerodynamic performance.
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Stalewski, Wienczyslaw, and Wieslaw Zalewski. "Performance improvement of helicopter rotors through blade redesigning." Aircraft Engineering and Aerospace Technology 91, no. 5 (May 13, 2019): 747–55. http://dx.doi.org/10.1108/aeat-01-2018-0009.
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Purpose The purpose of this paper is to determine dependencies between a rotor-blade shape and a rotor performance as well as to search for optimal shapes of blades dedicated for helicopter main and tail rotors. Design/methodology/approach The research is conducted based on computational methodology, using the parametric-design approach. The developed parametric model takes into account several typical blade-shape parameters. The rotor aerodynamic characteristics are evaluated using the unsteady Reynolds-averaged Navier–Stokes solver. Flow effects caused by rotating blades are modelled based on both simplified approach and truly 3D simulations. Findings The computational studies have shown that the helicopter-rotor performance may be significantly improved even through relatively simple aerodynamic redesigning of its blades. The research results confirm high potential of the developed methodology of rotor-blade optimisation. Developed families of helicopter-rotor-blade airfoils are competitive compared to the best airfoils cited in literature. The finally designed rotors, compared to the baselines, for the same driving power, are characterised by 5 and 32% higher thrust, in case of main and tail rotor, respectively. Practical implications The developed and implemented methodology of parametric design and optimisation of helicopter-rotor blades may be used in future studies on performance improvement of rotorcraft rotors. Some of presented results concern the redesigning of main and tail rotors of existing helicopters. These results may be used directly in modernisation processes of these helicopters. Originality/value The presented study is original in relation to the developed methodology of optimisation of helicopter-rotor blades, families of modern helicopter airfoils and innovative solutions in rotor-blade-design area.
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Fletcher, T. M., and R. E. Brown. "Modelling the interaction of helicopter main rotor and tail rotor wakes." Aeronautical Journal 111, no. 1124 (October 2007): 637–43. http://dx.doi.org/10.1017/s0001924000004814.
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Abstract The mutual interaction between the main rotor and tail rotor wakes is central to some of the most problematic dynamic phenomena experienced by helicopters. Yet achieving the ability to model the growth and propagation of helicopter rotor wakes with sufficient realism to capture the details of this interaction has been a significant challenge to rotorcraft aerodynamicists for many decades. A novel computational fluid dynamics code tailored specifically for rotorcraft applications, the vorticity transport model, has been used to simulate the interaction of the rotors of a helicopter with a single main rotor and tail rotor in both hover and low-speed quartering flight, and with the tail rotor rotating both top-forward and top-aft. The simulations indicate a significant level of unsteadiness in the performance of both main and tail rotors, especially in quartering flight, and a sensitivity to the direction of rotation of the tail rotor. Although the model thus captures behaviour that is similar to that observed in practice, the challenge still remains to integrate the information from high fidelity simulations such as these into routine calculations of the flight dynamics of helicopters.
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Ishiki, Takahiro, Kai Washizaki, and Makoto Kumon. "Evaluation of Microphone Array for Multirotor Helicopters." Journal of Robotics and Mechatronics 29, no. 1 (February 20, 2017): 168–76. http://dx.doi.org/10.20965/jrm.2017.p0168.
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[abstFig src='/00290001/16.jpg' width='300' text='UAV with a microphone array whose performance is evaluated' ] High expectations are placed on the use of unmanned aerial vehicles (UAVs) in such tasks as rescue operations, which require a system that makes use of visual or auditory information to recognize the surrounding environment. As an example of such a system, this study examines the recognition of the environment using a helicopter mounted with a microphone array. Because the rotors of a helicopter generate high noise during operation, it is necessary to reduce the effects of this noise and those from other sources to record the audio signals coming from the ground with onboard microphones. In particular, because of helicopter body control, the rotor speed changes continuously and causes an unsteady rotor noise, which implies that it would be effective to arrange the microphones at a sufficient distance from the rotors. When a large microphone array is employed, however, the array weight may alter the helicopter’s flight characteristics and increase the noise, presenting a dilemma. This paper presents a model of rotor noise that takes into account the effect of the microphone array on the helicopter’s dynamic characteristics and proposes a method of evaluating the optimality of the array configuration, which is necessary for design. The validity of the proposed method is investigated using a multirotor helicopter mounted with a microphone array previously developed by the authors. In addition, an application example for locating sound sources on the ground using this helicopter is presented.
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Stanisławski, Jarosław. "Performance of Quiet Helicopter." Transactions on Aerospace Research 2020, no. 1 (March 1, 2020): 1–17. http://dx.doi.org/10.2478/tar-2020-0001.
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AbstractNoise generated by helicopters is one of the main problems associated with the operation of rotorcrafts. Requirements for reduction of helicopter noise were reflected in the regulations introducing lower limits of acceptable rotorcraft noise. A significant source of noise generated by helicopters are the main rotor and tail rotor blades. Radical noise reduction can be obtained by slowing down the blade tips speed of main and tail rotors. Reducing the rotational speed of the blades may decrease rotor thrust and diminish helicopter performance. The problem can be solved by attaching more blades to main rotor. The paper presents results of calculation regarding improvement of the helicopter performance which can be achieved for reduced rotor speed but with increased number of rotor blades. The calculations were performed for data of hypothetical light helicopter. Results of simulation include rotor loads and blade deformations in chosen flight conditions. Equations of motion of flexible rotor blades were solved using the Galerkin method which takes into account selected eigen modes of the blades. The simulation analyzes can help to determine the performance and loads of a quiet helicopter with reduced rotor speed within the operational envelope of helicopter flight states.
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Dudnik, Vitaly. "DETERMINATION OF LOADS IN THE ULTRALIGHT HELICOPTER BLADES." Aviation 27, no. 4 (November 28, 2023): 242–47. http://dx.doi.org/10.3846/aviation.2023.20236.
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The article describes research that was carried out on coaxial a single-seat ultralight helicopter Rotorschmiede VA-115 which is manufactured by German firm RS Helikopter GmbH. The purpose of the work was to determine the blades’ loads necessary for further blade fatigue analysis and ground bench tests. The methodology for the load determination consisted of deformation measurements using strain gauges in various flight modes from hovering to maximum speed flight, including climb, descent, acceleration, and braking. Ultralight helicopters occupy the smallest cost niche and, as a rule, full-fledged fatigue studies are not performed for such helicopters. The requirements for ultralight helicopters are also quite loyal, allowing them to pass such experiments. Analysis of the data shows that the amplitude of bending moments on the lower rotor is higher by 1.2 to 2 times the value on the upper rotor. The absolute maximum value of the bending moment is significantly greater at the minimum weight, although the oscillation amplitude becomes smaller. The presented data can be useful for designers of ultralight and UAV helicopters with teetering hinge rotors.
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Dai, Yuting, Linpeng Wang, Chao Yang, and Xintan Zhang. "Dynamic Gust Load Analysis for Rotors." Shock and Vibration 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/5727028.
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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.
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Aleksandrov, Dmitri, and Igor Penkov. "Optimization of Lift Force of Mini Quadrotor Helicopter by Changing of Gap Size between Rotors." Solid State Phenomena 198 (March 2013): 226–31. http://dx.doi.org/10.4028/www.scientific.net/ssp.198.226.
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This paper describes comparison between virtual simulation of quadrotor flying platforms (mini UAV - Unmanned Aerial Vehicle) and real experiments. In quadrotor helicopter (quadrocopter) air flows that are going out from rotors and affecting each other were simulated. Analysis of several helicopters that have different distances between rotors on different angular velocities were compared. During virtual simulation (with CFD Computational Fluid Dynamics software) there were conducted similar to real experiments with the use of scanned rotors (with 3D scanner) and same environment conditions. These experiments were compared with real experiments. Optimal gap distance between rotors is determined, when helicopter mass is minimum and rotors are creating maximum lifting force and consuming minimum energy (minimum impact on air flows to each other).
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KACHEL, Stanisław, Robert ROGÓLSKI, and Jakub KOCJAN. "Review of Modern Helicopter Constructions and an Outline of Rotorcraft Design Parameters." Problems of Mechatronics Armament Aviation Safety Engineering 12, no. 3 (September 30, 2021): 27–52. http://dx.doi.org/10.5604/01.3001.0015.2427.
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This work contains the results of a modern helicopter construction analysis. It includes the comparison of almost seventy rotorcraft constructions in terms of size in line with EASA requirements – large and small helicopters. The helicopters are also divided because of a mission purpose. The proposed division for large aircrafts is: transport, multipurpose, attack and for small aircrafts: observation, training, and utility. The aircraft construction features are described. Average dimension values of airframes and rotors are shown. Helicopter rotor arrangements are presented in terms of an operational purpose. Next, the rotorcraft design inputs are described. The mathematical formulas for design inputs are given. The ratios are calculated and gathered for the compared aircrafts. Correlation between the analysed parameters is presented on charts. Design inputs are also presented in the paper as a function of MTOW. The function trends are determined to provide an evaluation tool for helicopter designers. In addition, the parameters are presented as possible optimisation variables.
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Tran, Ngoc Khanh, Van Quang Dao, Phu Khanh Nguyen, Thi Kim Dung Hoang, and Van Khang Nguyen. "Numerical Investigations of Aerodynamics Characteristics of Main Rotors in Helicopter UAV Used for Pesticide Spraying in Agriculture." Applied Mechanics and Materials 889 (March 2019): 425–33. http://dx.doi.org/10.4028/www.scientific.net/amm.889.425.
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In the last several decades past, Helicopters UAVs (Unmanned Aerial Vehicles) have quickly developed and day by day, they play an important role in human life. As it is well-known, helicopters UAV make some outstanding characteristics such as light weight, flexibility and particularly automatically controlled. By applying these characteristics, we research and manufacture Helicopter UAV using for spraying pesticide in agriculture. One of the most important components is main rotor because main rotor generated thrust, drag and momentum. Helicopters UAV efficient changed depending on main rotor. The research works focus on aerodynamics characterization of main rotor in helicopter UAV. This work uses CFD tool in ANSYS CFX software to calculate the aerodynamics parameters generated by main rotor using in UAV. The aim is to characterize the aerodynamics characteristics such as thrust, drag, pressure, aerodynamics quality on the different flight modes (hover, vertical and forward flight). Firstly, the simulations are carried out in hover flight mode with different blade pitch angles. The results are compared to experiment date in another research to validate numerical results. Then, the simulations are carried out in vertical flight mode and forward flight mode. The results showed that thrust and drag coefficient creased with increasing blade pitch angle. When blade pitch angle started from 1800, thrust coefficient decreased but drag coefficient increased sharply. The rotor performance was measured by aerodynamics quality and numerical results showed that the best rotor performance was at 900. In the vertical flight mode, the thrust and drag coefficient decreased with increasing vertical velocity but rotor performance increased slightly. The best vertical velocity for vertical flight is around 2 m/s and 3 m/s. Finally, in forward flight mode, the aerodynamics characterizations of rotors depended on azimuthal angular position of blade or time. Our helicopter operates in environment with light gust. The results showed the change of aerodynamics coefficient to time. Both thrust and drag coefficient changed but the rotor performance did not change much.
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von Frankenberg, Florentin, and Scott B. Nokleby. "Inclined landing testing of an omni-directional unmanned aerial vehicle." Transactions of the Canadian Society for Mechanical Engineering 42, no. 1 (March 1, 2018): 61–70. http://dx.doi.org/10.1139/tcsme-2017-0008.
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Traditional multi-rotors and helicopters control translational movement by changing the orientation of the entire vehicle. This approach limits the effectiveness of these vehicles in applications — such as a mobile manipulator base — in which it is often necessary to fly near large structures where unpredictable aerodynamic conditions exist. Maintaining precise control of position requires counteracting disturbance forces quickly. Having to roll and pitch the entire vehicle induces a delay that limits the ability of traditional multi-rotors and helicopters to maintain position precisely. Additionally, a mobile base must be capable of resisting arbitrary combinations of force and torque resulting from use of a manipulator arm. Traditional multi-rotors and helicopters do not have this ability. This paper presents a novel unmanned aerial vehicle (UAV) concept that features the addition of four rotors orthogonal to the main lift rotors of a traditional quadrotor design. These rotors allow decoupling of orientation from translational movement. Tests done on a physical prototype demonstrated the ability to sustain roll or pitch angles up to 15° independent of translational movement, including the ability to move backwards at an angle and to dock on inclined surfaces in a controlled manner. The tests show that the OmniCopter can successfully land on surfaces with up to 30° inclination. This type of motion is impossible for a traditional multi-rotor vehicle.
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Sałaciński, Michał, Rafał Kowalski, Michał Szmidt, and Sławomir Augustyn. "A New Approach to Modelling and Testing the Fatigue Strength of Helicopter Rotor Blades during Repair Process." Fatigue of Aircraft Structures 2019, no. 11 (December 1, 2019): 56–67. http://dx.doi.org/10.2478/fas-2019-0006.
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AbstractThe fatigue test was carried out on an element of a rotor blade removed from the Mi-2 helicopter. The purpose of the test was to check the fatigue strength of the repaired rotor blade. Metal composite rotor blades have a metal spar in the form of a box and the trailing sections in the form of metallic honeycomb sandwich panels. The trailing sections are bonded to the spar. The repair had been carried out at the point where the trailing section became debonded from the spar at the Air Force Institute of Technology in Warsaw using a methodology developed for carrying out repairs of rotor blades’ damage. All types of the Mi family helicopters are equipped with metal composite rotors blades. Depending on MTOW (Maximum Take-Off Weight) and destination of helicopters, blades differ in dimensions, but their design solutions are practically the same. For this reason, the developed repair methodology can be used for all characteristic rotor blades structures for Mi helicopters. The fatigue test was performed at the Łukasiewicz - Institute of Aviation in Warsaw, using a hydraulically driven fatigue machine. The fatigue test was carried out by performing over 1.1 million load cycles. In repair places, upon completion of fatigue testing, no damage was found.
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Kelley, Bartram. "RIGID ROTORS VS. HINGED ROTORS FOR HELICOPTERS." Annals of the New York Academy of Sciences 107, no. 1 (December 15, 2006): 40–48. http://dx.doi.org/10.1111/j.1749-6632.1963.tb13269.x.
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Han, D., and G. N. Barakos. "Variable-speed tail rotors for helicopters with variable-speed main rotors." Aeronautical Journal 121, no. 1238 (February 23, 2017): 433–48. http://dx.doi.org/10.1017/aer.2017.4.
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ABSTRACTVariable tail rotor speed is investigated as a method for reducing tail rotor power, and improving helicopter performance. A helicopter model able to predict the main rotor and tail rotor powers is presented, and the flight test data of the UH-60A helicopter is used for validation. The predictions of the main and tail rotor powers are generally in good agreement with flight tests, which justifies the use of the present method in analysing main and tail rotors. Reducing the main rotor speed can result in lower main rotor power at certain flight conditions. However, it increases the main rotor torque and the corresponding required tail rotor thrust to trim, which then decreases the yaw control margin of the tail rotor. In hover, the tail rotor may not be able to provide enough thrust to counter the main rotor torque, if it is slowed to follow the main rotor speed. The main rotor speed corresponding to the minimum main rotor power increases, if the change of tail rotor power in hover is considered. As a helicopter translates to cruise, the induced power decreases, and the profile power increases, with the profile power dominating the tail rotor. Reducing the tail rotor speed in cruise reduces the profile power to give a 37% reduction in total tail rotor power and a 1.4% reduction to total helicopter power. In high-speed flight, varying the tail rotor speed is ineffective for power reduction. The power reduction obtained by the variable tail rotor speed is reduced for increased helicopter weight.
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Barra, Federico, Matteo Scanavino, and Giorgio Guglieri. "A methodology for multirotor aircraft power budget analysis." Aircraft Engineering and Aerospace Technology 92, no. 6 (May 6, 2020): 909–16. http://dx.doi.org/10.1108/aeat-09-2019-0183.
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Purpose The primary purpose of this study is to analyse the performance of multirotor unmanned aircraft system platforms for passenger transport and compare them with an ordinary helicopter solution. This study aims to define a standard procedure for power budget analysis of unconventional vehicles recently proposed in the aerospace industry, providing guidelines on rotor sizing in terms of required power and the total number of rotors. The ultimate purpose of the proposed work is to describe a methodology for power estimation with regard to emerging electric vertical takeoff and landing (EVTOL) vehicles. Design/methodology/approach In the context of urban mobility, short-range passenger transport between critical hubs in cities is taken into account and innovative aircraft and traditional helicopters are compared according to a common mission profile. The power budget equations used in the helicopter literature are revisited to consider different multirotor configurations (up to 20 rotors) and evaluate the feasibility of innovative aerospace vehicle design. Findings The paper includes insights into the maximum number of rotors that ensure a significative, relative power reduction compared to helicopter platforms (the power-to-cruise over power-to-hover ratio appears to be improved). Based on this preliminary analysis, the results suggest the benefit of reducing the installed rotors to avoid excessive power loss in forward flight. Practical implications The proposed study provides guidelines for further design considerations and the future development of EVTOL multirotor aircraft. Originality/value This paper fulfils the identified need for a systematic approach on performance analysis for innovative vehicles involved in commercial applications.
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Gennaretti, Massimo, Giovanni Bernardini, Jacopo Serafini, Alessandro Anobile, and Sander Hartjes. "Helicopter noise footprint prediction in unsteady maneuvers." International Journal of Aeroacoustics 16, no. 3 (April 2017): 165–80. http://dx.doi.org/10.1177/1475472x17709927.
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This paper investigates different methodologies for the evaluation of the acoustic disturbance emitted by helicopter’s main rotors during unsteady maneuvers. Nowadays, the simulation of noise emitted by helicopters is of great interest to designers, both for the assessment of the acoustic impact of helicopter flight on communities and for the identification of optimal-noise trajectories. Typically, the numerical predictions consist of the atmospheric propagation of a near-field noise model, extracted from an appropriate database determined through steady-state flight simulations/measurements (quasi-steady approach). In this work, three techniques for maneuvering helicopter noise predictions are compared: one considers a fully unsteady solution process, whereas the others are based on quasi-steady approaches. These methods are based on a three-step solution procedure: first, the main rotor aeroelastic response is evaluated by a nonlinear beam-like rotor blade model coupled with a boundary element method for potential flow aerodynamics; then, the aeroacoustic near field is evaluated through the 1A Farassat formulation; finally, the noise is propagated to the ground by a ray tracing model. Only the main rotor component is examined, although tail rotor contribution might be included as well. The numerical investigation examines the differences among the noise predictions provided by the three techniques, focusing on the assessment of the reliability of the results obtained through the two quasi-steady approaches as compared with those from the fully unsteady aeroacoustic solver.
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Krake, Luther. "Helicopter Airframe Fatigue Spectra Generation." Advanced Materials Research 891-892 (March 2014): 720–25. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.720.
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Helicopter airframe fatigue cracking is a cause of significant and growing cost of ownership and operational readiness concerns for the operators of (primarily) metallic airframe helicopters. Airframe fatigue has often had relatively low priority for helicopters, with research and design concentrated on the fatigue of flight critical rotating structural components such as rotor blades and pitch links. The Australian Defence Science and Technology Organisation (DSTO) and the US Naval Air Systems Command are collaborating to develop improved methods and technologies that can be used to assess the fatigue damage endured by ageing helicopter airframes. The flight load sequencesor fatigue spectraexperienced by a helicopter airframe in its lifetime contain many billions of load cycles due to rotor revolutions. Fatigue spectra developed for helicopter airframe certification tests are heavily simplified for reasons such as computational efficiency, test practicality and cost. Real airframe fatigue spectra are likely to be influenced by the modes of vibration that might be present on the airframe, the attenuation of the vibratory loading that is introduced at the main and tail rotors and the relative magnitudes and influences of both quasi-static (manoeuvre induced) and vibratory loading. To better capture such complexity, more realistic, higher fidelity fatigue spectra are required. Fatigue spectra generation involves creating realistic flight-by-flight sequences of flight conditions and assigning high-fidelity flight loads data to those sequences. This paper details DSTOs development of a novel computer-automated process which pseudo-randomly generates realistic sequences of flight conditions to match a known or assumed usage spectrum.
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Zi, Nie, and Chen Ming. "Stability and Control Analysis on a Small-Scale Coaxial Helicopter with Bell-Hiller Stabilizer Bar." Applied Mechanics and Materials 340 (July 2013): 862–66. http://dx.doi.org/10.4028/www.scientific.net/amm.340.862.
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In the paper, we present a linearized mathematical model of a small scale coaxial helicopter with Bell-Hiller stabilizer bar, which is extracted from numerical linearization of a non-linear mathematical model with small perturbation theory. Stability and control derivatives calculated by numerical method are compared and analyzed for stability and control analysis on coaxial helicopters equipped with different type stabilizer bar. The study indicates that the coaxial helicopter with stabilizer bar fixed on the upper rotors has better capability on stability and control.
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Han, Wei, Jie Liu, Chun Liu, Lei Chen, Xichao Su, and Peng Zhao. "Flap motion of helicopter rotors with novel, dynamic stall model." Open Physics 14, no. 1 (January 1, 2016): 239–46. http://dx.doi.org/10.1515/phys-2016-0019.
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AbstractIn 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.
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Li, Miaomiao, Zhao Zhang, Xi Wang, Shuai Liu, and Rupeng Zhu. "Study on the Tooth Profile Parameters Design Method of Crown Gear Coupling for Helicopter Tail Folding Device." Journal of Engineering 2022 (August 9, 2022): 1–11. http://dx.doi.org/10.1155/2022/1280865.
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Shipboard helicopter folding technology can increase the number of helicopters parked on board aircraft carriers. Crown gear coupling is the trend in helicopter tail rotor folding technology due to its ability to automatically and quickly engage and disengage helicopter tail rotors. This paper presents a method for the design of tooth parameters for crown gear coupling for folding devices. The model of the relationship between tooth shape parameters and angular displacement of the crown gear coupling and the model of the relationship between angular displacement and shaft line angle of the crown gear coupling were established, respectively, and the basic parameters of tooth shape and modified parameters of the crown gear coupling were designed. The correctness of the design method of the tooth parameters of the crown gear coupling for the folding device was also verified through motion simulation. The results of the study provide a theoretical basis for the design and optimization of crown gear couplings for folding devices.
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Tanabe, Yasutada, Hideaki Sugawara, Shigeru Sunada, Koichi Yonezawa, and Hiroshi Tokutake. "Quadrotor Drone Hovering in Ground Effect." Journal of Robotics and Mechatronics 33, no. 2 (April 20, 2021): 339–47. http://dx.doi.org/10.20965/jrm.2021.p0339.
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A variable-pitch-controlled quadrotor drone was simulated in the ground effect using a high-fidelity CFD solver. In contrast to a single rotor in the ground effect, which has been extensively studied for conventional helicopters, the flow fields around multiple rotors are complex. In this study, the rotating speed of the rotors was maintained constant, and the blade pitch angles were adjusted so that the total thrust of the multicopter was the same regardless of the rotor height from the ground. It was observed that the power required for the quadrotors, which generate the same thrust, decreases when the rotors are approaching the ground from the height where they can be considered to be out of the ground effect, but increases locally when the rotor height is approximately the rotor radius, owing to flow recirculation into the rotor, and then decreases abruptly when the rotors further approach the ground. The outwash from the quadrotors depends heavily on the direction relative to the quadrotor layout. Along the plane crossing the diagonal rotor centers, the outwash velocity profiles resemble those of a single rotor; however, the outwash from the rotor gaps is stronger and extends to a much higher altitude.
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Rovere, F., G. N. Barakos, and R. Steijl. "Brownout Simulations of Model-Rotors In Ground Effect." MATEC Web of Conferences 314 (2020): 01006. http://dx.doi.org/10.1051/matecconf/202031401006.
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In this work computational fluid dynamics is used to validate experimental results for a two-bladed small rotor In Ground Effect conditions. The paper focuses on the evaluation and prediction of the rotor outwash generated in ground effect. Time-averaged outflow velocities are compared with experimental results, and the simulated flow field is used for safety studies using the PAXman model and particle tracking methods. The aircraft weights have been studied, evaluating scaling factors to define how helicopter weight can affect the outflow forces and the particle paths. Results show how the wake generated by heavier helicopters can lead to stronger forces on ground personnel and push the particles farther away from the rotor.
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Promkajin, Nicom, and Manukid Parnichkun. "Development of a robust attitude control for nonidentical rotor quadrotors using sliding mode control." International Journal of Advanced Robotic Systems 15, no. 1 (January 1, 2018): 172988141775355. http://dx.doi.org/10.1177/1729881417753554.
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This work proposes a novel development of sliding mode control (SMC) for quadrotor helicopters utilizing offset cancellation technique. Most of the works on sliding mode control for quadrotors assumed that all rotors were identical, but in fact, the rotors even from the same factory are not exactly the same in aerodynamics properties. In addition, rotor deformation due to shock or heavy usage during operation may cause changes in parameters such as lift and drag coefficients, and so on, which, lead to offset error in the responses of attitude control. By applying the proposed offset cancellation technique to the sliding mode control, the attitude error is forced to have a zero average. The proposed controller is used to control attitude and position of a quadrotor helicopter which is composed of four direct current (DC) brushless motors to generate lift forces independently. Performance comparison with the other control algorithms such as the proportional–integral–derivative controller and the conventional sliding mode control is simulated and experimented on two real quadrotor platforms and results are discussed.
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de Voogt, Alexander J., Caio Hummel Hohl, and Hilary Kalagher. "Fatality and Operational Specificity of Helicopter Accidents on the Ground." Aerospace Medicine and Human Performance 92, no. 7 (July 1, 2021): 593–96. http://dx.doi.org/10.3357/amhp.5801.2021.
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INTRODUCTION: Accidents with aircraft standing are more likely with helicopters than fixed-wing aircraft due to the common presence of off-airport landings and the possibility of the rotor system to strike objects in its immediate surroundings.METHODS: A total of 115 accidents involving helicopters characterized as standing as a broad phase of flight were selected from the NTSB online database for the period 1998 until 2018.RESULTS: Accidents reporting fatal (8.7) or serious injuries (7.8) were significantly less likely to occur when the aircraft was substantially damaged (84.3) or destroyed (5.2). The majority of the cases occurred after off-airport landings (57.4), which were reported significantly more often in Alaska (N= 15). A main rotor strike with an individual was at the basis of each of the 10 fatal accidents in the dataset and in 8 of these cases the cause of the accident was attributed to the victim. None of the accidents occurred in instrument meteorological conditions, but, in particular, high winds and gusts proved a main cause of accident (18.3).CONCLUSION: Pilot, passengers, and crew endangered themselves when they were outside the aircraft while the rotors were still turning. Helicopter operating manuals should highlight the limitations and dangers for wind and wind gusts not only during takeoff and flight, but specifically when standing.de Voogt AJ, Hummel C, Kalagher H. Fatality and operational specificity of helicopter accidents on the ground. Aerosp Med Hum Perform. 2021; 92(7):593596.
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Liu, Jianbo, Rongqiang Guan, Yongming Yao, Hui Wang, and Linqiang Hu. "A Novel Comprehensive Kinematic and Inverse Dynamic Model for the Flybar-Less Swashplate Mechanism: Application on a Small-Scale Unmanned Helicopter." Symmetry 12, no. 11 (November 9, 2020): 1849. http://dx.doi.org/10.3390/sym12111849.
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In this paper, we propose a novel kinematic and inverse dynamic model for the flybar-less (FBL) swashplate mechanism of a small-scale unmanned helicopter. The swashplate mechanism is an essential configuration of helicopter flight control systems. It is a complex, multi-loop chain mechanism that controls the main rotor. In recent years, the demand for compact swashplate designs has increased owing to the development of small-scale helicopters. The swashplate mechanism proposed in this paper is the latest architectures used for hingeless rotors without a Bell-Hiller mixer. Firstly, the kinematic analysis is derived from the parallel manipulators concepts. Then, based on the principle of virtual work, a methodology for deriving a closed-form dynamic equation of the FBL swashplate mechanism is developed. Finally, the correctness and efficiency of the presented analytical model are demonstrated by numerical examples and the influence factors of the loads acted on actuators are discussed.
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Gan, Ze Feng (Ted), Vitor Tumelero Valente, Kenneth S. Brentner, and Eric Greenwood. "Multirotor broadband noise modulation." Journal of the Acoustical Society of America 155, no. 3_Supplement (March 1, 2024): A111. http://dx.doi.org/10.1121/10.0026987.
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Rotor broadband noise spectra are typically analyzed over time scales on the order of one or more rotor periods. However, modulation of the broadband noise spectrum with the blade passage frequency (BPF) has been shown to be significant for noise levels and perception of wind turbines and helicopters. In contrast, time-varying broadband noise has not been extensively studied for aircraft with many rotors, such as unmanned aerial vehicles (UAVs) or advanced air mobility aircraft. In this work, significant broadband noise modulation was measured in flight and anechoic chamber tests of hexacopter UAVs at various observer angles. This modulation is aperiodic with the BPF such that the modulation amplitude varies substantially between blade passages, even when the BPFs are controlled to be nearly constant between all rotors at all times. Furthermore, the azimuthal phasing between rotors greatly affects the measured modulation, such that the modulation of multiple rotors may be less than or greater than for a single rotor, depending on the phase offsets. The effects of phase variations on acoustic interactions between rotors is studied by comparing the sum of the modulation of individual rotors to the modulation of those rotors operating simultaneously. This is done not only using measurements, but also noise predictions made using PSU-WOPWOP. These results contribute understanding to how the noise modulation of rotors sum together, including the resulting directivity and aperiodicity.
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Liu, Shi Ming, Wei Dong Yang, Ling Hua Dong, and Jie Wu. "Performance and Loads Investigation of Optimum Speed Rotors." Applied Mechanics and Materials 607 (July 2014): 500–506. http://dx.doi.org/10.4028/www.scientific.net/amm.607.500.
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Performance of helicopters can be significantly influenced by rotor speed variation. A comprehensive model is built to exam the influences of rotating speed on performance and blade loads of a variable speed rotor. The results indicate that for a 2,200kg gross weight helicopter, power reduction is up to 30% at 100km/h by slowing the rotor properly. For lower gross weights, the reductions in rotor rotating speed and power savings are more apparent. The optimum rotating speed may cause a 20.5% increase in endurance and 8.5% in range by thoroughly consuming 400kg of fuel. Rotor RPM variation has an important effect on blade loads. For 100km/h and 2,200kg gross weight, amplitudes for most of the harmonic loads decrease with reduced rotor RPM.
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Piriyanont, Busara, Naoki Uchiyama, and Shigenori Sano. "Model Reference Control for Collision Avoidance of a Human-Operated Quadrotor Helicopter." Journal of Advanced Computational Intelligence and Intelligent Informatics 15, no. 5 (July 20, 2011): 617–23. http://dx.doi.org/10.20965/jaciii.2011.p0617.
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Because quadrotor helicopter has four fixed-pitch rotors, its control system can be much simpler than that of conventional helicopters; thus, it is expected to find wide application in many remote control situations, such as in hazardous environments. This paper proposes a collision avoidance control for a quadrotor helicopter based on the concept of a social force model. The proposed control incorporates commands given from human operators and compensates for operator mistakes in real time to achieve collision avoidance of a quadrotor helicopter. The proposed method uses distance sensors to achieve real-time collision avoidance. Its effectiveness is shown by experimental results, in which the algorithm successfully drives the helicopter along the desired trajectory without a collision.
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L. Lvov, Nikolay, Stanislav S. Khabarov, and Mikhail Yu. Gavrikov. "Creation of an Integrated System for Monitoring the Technical Condition of High-Quality Helicopter Units based on Fiber-Optic Technology." International Journal of Engineering & Technology 7, no. 4.38 (December 3, 2018): 1162. http://dx.doi.org/10.14419/ijet.v7i4.38.27755.
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This article discusses the problems of creating an integrated system for monitoring the technical condition of highly responsible helicopter units, and analyzed options for its creation. Fiber-optical technology is considered as a technology, on the basis of which it is possible to build an integrated system, since this technology makes it possible to measure various physical parameters such as vibration, deformation, temperature, acoustic emission and other parameters, and due to the miniature dimensions of the fiber-optic light guide. It can be built into the PCM design, which is a relevant factor due to the growth use of PCM in the design and manufacture of helicopters. The results of bench and flight tests of helicopter pilot and rotor blades with fasteners using fiber optic deformation sensors based on a Bragg fiber grille demonstrate the fundamental possibility of creating a system for monitoring the technical condition of helicopter rotors using fiber optic sensors .Also, there are examples of creating other elements of an integrated monitoring system based on the use of fiber-optic technology, such as a system for signaling the breakdown of air flow and flutter on the helicopter rotor blades, a system for measuring the weight and alignment of helicopter cargo and a system for monitoring the technical condition of the airframe.
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Murakami, Y., and S. S. Houston. "Dynamic inflow modelling for autorotating rotors." Aeronautical Journal 112, no. 1127 (January 2008): 47–53. http://dx.doi.org/10.1017/s0001924000001986.
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Abstract The dynamic inflow model is a powerful tool for predicting the induced velocity distribution over a rotor disc. On account of its closed form and simplicity, the model is especially practical for studying flight mechanics or for designing control systems for helicopters. Scant attention has, however, been paid so far in utilising the dynamic inflow model to analyse an autorotating rotor, which is different from a powered rotor in the geometric relation between the direction of the inflow and the rotor disc. Autorotation is an abnormal condition for helicopters, but for gyroplanes it is the normal mode of operation. Therefore the theoretical discussion on an autorotating rotor is of importance not only to improve the understanding of present gyroplanes, but also in the development of new gyroplanes and to analyse the windmill-brake state of helicopters. Dynamic inflow modelling is reviewed from first principles, and this identifies a modification to the mass flow parameter. A qualitative assessment of this change indicates that it is likely to have a negligible impact on the trim state of rotorcraft in autorotation, but a significant effect on the dynamic inflow modes in certain flight conditions. This is confirmed by numerical simulation, although considerable differences only become apparent for steep descents with low forward speed. It is concluded that while modification of the mass flow parameter is perhaps mathematically accurate, for practical purposes it is required only in a limited area of the flight envelope of autorotating rotorcraft.
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Yuan, Y., D. Thomson, and R. Chen. "Variable rotor speed strategy for coaxial compound helicopters with lift–offset rotors." Aeronautical Journal 124, no. 1271 (September 27, 2019): 96–120. http://dx.doi.org/10.1017/aer.2019.113.
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ABSTRACTThe coaxial compound helicopter with lift-offset rotors has been proposed as a concept for future high-performance rotorcraft. This helicopter usually utilizes a variable-speed rotor system to improve the high-speed performance and the cruise efficiency. A flight dynamics model of this helicopter associated with rotor speed governor/engine model is used in this article to investigate the effect of the rotor speed change and to study the variable rotor speed strategy. Firstly, the power-required results at various rotor rotational speeds are calculated. This comparison indicates that choice of rotor speed can reduce the power consumption, and the rotor speed has to be reduced in high-speed flight due to the compressibility effects at the blade tip region. Furthermore, the rotor speed strategy in trim is obtained by optimizing the power required. It is demonstrated that the variable rotor speed successfully improves the performance across the flight range, but especially in the mid-speed range, where the rotor speed strategy can reduce the overall power consumption by around 15%. To investigate the impact of the rotor speed strategy on the flight dynamics properties, the trim characteristics, the bandwidth and phase delay, and eigenvalues are investigated. It is shown that the reduction of the rotor speed alters the flight dynamics characteristics as it affects the stability, damping, and control power provided by the coaxial rotor. However, the handling qualities requirements are still satisfied with different rotor speed strategies. Finally, a rotor speed strategy associated with the collective pitch is designed for maneuvering flight considering the normal load factor. Inverse simulation is used to investigate this strategy on maneuverability in the Push-up & Pull-over Mission-Task-Element (MTE). It is shown that the helicopter can achieve Level 1 ratings with this rotor speed strategy. In addition, the rotor speed strategy could further reduce the power consumption and pilot workload during the maneuver.
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Neville, T. "Dynamic and Aerodynamic Clearance of the Apache AH Mk1 Attack Helicopter for Embarked Operations." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 219, no. 5 (May 1, 2005): 459–69. http://dx.doi.org/10.1243/095441005x30342.
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The introduction into service of the Westland manufactured Apache AH Mk1 has coincided with a thrust within the UK armed services for a greater emphasis on amphibious operations within the littoral environment. From this background has emerged a requirement for an embarked, attack helicopter capability, for which the Apache AH Mk1 has been earmarked. However, this helicopter being, by design, optimized for the battlefield environment, cannot be presumed to adapt to the naval environment without presenting certain challenges. This article describes how Westland Helicopters Ltd has sought to determine the feasibility of conducting embarked operations with Apache AH Mk1 by deriving limits to be respected during Ship Helicopter Operating Limits (SHOL) trials using a variety of analytical methods. Aspects of operation considered include aircraft lashing, landing, stability on deck with rotors running or stationary and when being towed, rotor engagement and disengagement, ground resonance, and main rotor spreading and folding. The article considers further aspects of importance to embarked operations and summarizes the trials process that results in an operational envelope for service use. It concludes that a practical operating envelope can be achieved, anticipates a successful outcome for the SHOL trials, and includes a projection for future activities to enhance the aircraft's maritime operational capabilities.
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van der Wall, Berend G. "Influence of Rotor Inflow, Tip Loss, and Aerodynamics Modeling on the Maximum Thrust Computation in Hover." Aerospace 11, no. 5 (April 29, 2024): 357. http://dx.doi.org/10.3390/aerospace11050357.
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Comprehensive rotorcraft simulation codes are the workhorses for designing and simulating helicopters and their rotors under steady and unsteady operating conditions. These codes are also used to predict helicopters’ limits as they approach rotor stall conditions. This paper focuses on the prediction of maximum rotor thrust when hovering (due to stall limits) and the thrust and power characteristics when the collective control angle is further increased. The aerodynamic factors that may significantly affect the results are as follows: steady vs. unsteady aerodynamics, steady vs. dynamic stall, blade tip losses, curvature flow, yaw angle, inflow model, and blade-vortex interaction. The inflow model and tip losses are found to be the most important factors. For real-world applications vortex-based inflow models are considered the best choice, as they reflect the blade circulation distribution within the inflow distribution. Because the focus is on the impact of aerodynamic modeling on rotor stall, the blade design and its flexibility are intentionally not considered.
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Sanchez-Cuevas, Pedro, Guillermo Heredia, and Anibal Ollero. "Characterization of the Aerodynamic Ground Effect and Its Influence in Multirotor Control." International Journal of Aerospace Engineering 2017 (2017): 1–17. http://dx.doi.org/10.1155/2017/1823056.
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This paper analyzes the ground effect in multirotors, that is, the change in the thrust generated by the rotors when flying close to the ground due to the interaction of the rotor airflow with the ground surface. This effect is well known in single-rotor helicopters but has been assumed erroneously to be similar for multirotors in many cases in the literature. In this paper, the ground effect for multirotors is characterized with experimental tests in several cases and the partial ground effect, a situation in which one or some of the rotors of the multirotor (but not all) are under the ground effect, is also characterized. The influence of the different cases of ground effect in multirotor control is then studied with several control approaches in simulation and validated with experiments in a test bench and with outdoor flights.
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Soltani, M. R., and F. Rasi Marzabadi. "Effect of plunging amplitude on the performance of a wind turbine blade section." Aeronautical Journal 111, no. 1123 (September 2007): 571–87. http://dx.doi.org/10.1017/s0001924000001846.
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In many engineering applications (e.g. helicopters, turbines, compressors), lifting surfaces experience unsteady motion or are perturbed by unsteady incoming flows. Horizontal axis wind turbine rotors experience large time dependent variations in angle-of-attack as a result of control input angles, blade flapping, structural response and wake inflow. In addition, the blade sections encounter substantial periodic variations in local velocity and sweep angle. Thus, the unsteady aerodynamic behaviour of the blade sections must be properly understood to enable accurate predictions of the air loads and aero elastic response of the rotor system.
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Гребеников, А. Г., И. А. Воронько, Ю. В. Дьяченко, В. В. Коллеров, И. В. Малков, В. А. Урбанович, and Н. И. Москаленко. "КОНСТРУКТИВНО-ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ МЕТАЛЕВИХ ЛОПАТЕЙ НЕСУЧОГО І РУЛЬОВОГО ГВИНТІВ ВЕРТОЛЬОТА." Open Information and Computer Integrated Technologies, no. 87 (June 30, 2020): 5–51. http://dx.doi.org/10.32620/oikit.2020.87.01.
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Analysis of the foreign and domestic work experience, manufacturing and operation of the helicopters with metal blades of the main (MR) and tail (TR) rotors is performed. General requirements for the helicopter MR and TR blades design are formulated. Structural arrangement of the helicopter MR metal blade is reviewed, features of the construction materials for the metal blades are noted. Features of the MR and TR metal blades design with the pressed spar and aluminum honeycomb core are given. Parametric modeling technique of the helicopter MR metal blade is presented. The manufacturing rout technology and the method of the surface strengthening of the metal blade tip are presented. The scheme and the manufacturing rout technology of the pressed aluminum spar are given; the geometrical twist features, the surface strengthening and the assembling of the spar with the blade tip are re- viewed. The features of the electric-heating patch bonding on the spar leading edge are shown. Following technological steps of the blade metal rear area manufacturing are reviewed: the rolled aluminum foil degreasing; the aluminum honeycomb structures manufacturing; the aluminum honeycomb core butt milling. The features of the blade rear area assembling and metal blade assembling by bonding in the jig are presented; the content of works outside of the jig for metal blade of the helicopter main rotor is given.
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Chaney, Ken, Alfred J. Eggers,, Patrick J. Moriarty, and William E. Holley. "Skewed Wake Induction Effects on Thrust Distribution on Small Wind Turbine Rotors." Journal of Solar Energy Engineering 123, no. 4 (July 1, 2001): 290–95. http://dx.doi.org/10.1115/1.1410109.
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Accurate prediction of both the center of thrust location and the magnitude of the thrust on a rotor disk are critical to satisfactory modeling of the yawing of small wind turbines to large angles to passively control overshoots in power and loads at higher wind speeds. Of the two, the prediction of the center of thrust location upwind of the center of a yawed rotor disk appears to be the most uncertain and potentially in serious error. This error is due to uncertainties in skewed wake effects on the thrust distribution on the disk. Three skewed wake models are examined to better understand the potential sources of error. First is the dynamic inflow model originally developed for helicopters, and second is a modification of this model developed for wind turbines. Third is an earlier cylindrical vortex wake model which pioneered the study of skewed wake effects for helicopters, and which can be generalized for wind turbine applications. It is concluded that this generalized model and the original dynamic inflow model are the most promising for small wind turbine applications, and their predictions of center of thrust and blade root moments are compared for an idealized rotor. The focus is on static equilibrium loads, and note is taken of the potential importance of accounting for expanding wake effects. The basic results of the study are applicable to large as well as small wind turbine rotors.
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Zilberman, Arkadi, and Natan Kopeika. "A Simple Model for Assessing Millimeter-Wave Attenuation in Brownout Conditions." Sensors 22, no. 22 (November 17, 2022): 8889. http://dx.doi.org/10.3390/s22228889.
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Flying helicopters in adverse environmental conditions, such as low heights in arid regions, can be dangerous, especially during landing and take-off, since during hovering, the rotors produce a dust cloud of particles. This phenomenon is known as the “brownout” condition. Unlike visible and infrared systems, the radar devices in the microwave or millimeter wave region offer the capability of sufficient transmission through atmospheric obscurants, such as fog, smoke, sand/dust storms, and brownout. In this work, we present a theoretical evaluation of mm-wave (85–100 GHz) attenuation/scattering and power transfer in brownout conditions. The model includes attenuation/scattering prediction and radiant flux, or power collected by the receiver. We are considering the case of sand grain clouds created by helicopter rotor airflow during landing in arid areas. The evaluated scenarios are brownout environments over ranges up to 50 m. The predicted values from the mathematical model are compared with findings in the field and the literature. A simple model for mm-wave power transfer estimation shows satisfactory agreement with the measured values.
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Pilipenko, O., D. Kolesnik, A. Berezniak, V. Kohan, and O. Pankul. "MEANS, STANDS AND MACHINES FOR TESTING GEAR WHEELS AND GEAR TRAINS OF HELICOPTER REDUCTION TRAINS." Наукові праці Державного науково-дослідного інституту випробувань і сертифікації озброєння та військової техніки, no. 9 (December 3, 2021): 97–117. http://dx.doi.org/10.37701/dndivsovt.9.2021.13.
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The production and repair of such high-tech and important products as helicopters‟ reduction trains is impossible without comprehensive testing of these products, starting with the manufacture of their individual parts and assemblies and ending with the delivery of reduction trains to the customer.
Various means for testing of gear wheels‟ rims and gear trains of helicopter‟s reduction trains, which have found application in testing equipment, are presented. Devices, testers, stands and machines for various tests are considered in order to control the characteristics of gear trains of aviation reduction trains after certain periods of their operation and repair, aimed at achieving better performance during further operation.
The considered traditional metrological means of control of gear rims, gear measuring machines and complexes, some stands and machines for testing of reduction trains, pulse controllers and roll machines give an idea of various methods and means of control of gear wheels and gear trains of helicopters‟ reduction trains.
The main method of experimental research of gear trains of reducers is stand tests both on movable gear wheels and on roll machines.
Until recently, the most common method for monitoring and diagnosing gear trains has been vibrography, however, existing techniques do not give an accurate picture of the train condition, especially the contact surface of the teeth. During the operation of the gear train as a part of the helicopter‟s reduction train, signals from other sources (rotors, blades, shafts, bearings) are superimposed on the vibration signal generated by the gear train which significantly complicates the extraction and processing of the desired vibration signal.
One of the most effective methods for monitoring and diagnosing the technical condition of kinematic chains of different complexity, which includes gear trains of helicopters„ reducers is kinematometry. The disadvantage of traditional kinematometry is the need to use high-precision sensors for the frequency and phase of the rotor rotation.
Control of vibration from the early 1990s to the present time is the most advanced control, the means and methods of which are well developed in the aviation industry.
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Mauricio, Alexandre, Linghao Zhou, Mathew Greaves, Wenyi Wang, David Mba, and Konstantinos Gryllias. "Advanced signal processing tools for helicopters’ future Health and Usage Monitoring Systems (HUMS)." MATEC Web of Conferences 304 (2019): 01021. http://dx.doi.org/10.1051/matecconf/201930401021.
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Health and Usage Monitoring Systems (HUMS) have been developed in order to monitor the health condition of helicopter drivetrains, focusing towards early, accurate and on time fault detection with limited false alarms and missed detections. Among other systems, the Main GearBox (MGB) is the heart of the drivetrain, reducing the high input speed generated by the engines, in order to provide the appropriate torque to the main rotors and to other auxiliary systems. HUMS are mounted on helicopters aiming to enhance the operational reliability and to support maintenance decision making, in order to increase the flight safety keeping in the meanwhile the overall maintenance cost low. Currently used HUMS seems to have reached their limits and the need for improvement has been recently highlighted by the post-accident analysis of the helicopter LN-OJF, which crashed in Norway in 2016. The aim of this paper is the application and further extension of recently proposed advanced cyclostationary based signal processing tools for the accurate detection of faults in helicopter gearboxes. The methodologies are tested, evaluated and compared with state of the art methods on datasets captured during experimental tests under various operating conditions on helicopter gearboxes, including a Category A Super Puma SA330 main planetary gearbox.
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Bautista-Medina, José Antonio, Rogelio Lozano, and Antonio Osorio-Cordero. "Modeling and Control of a Single Rotor Composed of Two Fixed Wing Airplanes." Drones 5, no. 3 (September 8, 2021): 92. http://dx.doi.org/10.3390/drones5030092.
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This paper proposes a simple flying rotor prototype composed of two small airplanes attached to each other with a rigid rod so that they can rotate around themselves. The prototype is intended to perform hover flights with more autonomy than existing classic helicopters or quad-rotors. Given that the two airplanes can fly apart from each other, the induced flow which normally appears in rotorcrafts will be significantly reduced. The issue that is addressed in the paper is how this flying rotor prototype can be modeled and controlled. A model of the prototype is obtained by computing the kinetic and potential energies and applying the Euler Lagrange equations. Furthermore, in order to simplify the equations, it has been considered that the yaw angular displacement evolves much faster than the other variables. Furthermore a study is presented to virtually create a swashplate which is a central mechanism in helicopters. Such virtual swashplate is created by introducing a sinusoidal control on the airplanes’ elevators. The torque amplitude will be proportional to the sinusoidal amplitude and the direction will be determined by the phase of the sinusoidal. A simple nonlinear control algorithm is proposed and its performance is tested in numerical simulations.
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Figat, Marcin. "Aerodynamics analysis of rotor’s impact on the aircraft in the tandem wing configuration." Aircraft Engineering and Aerospace Technology 92, no. 3 (October 22, 2018): 336–44. http://dx.doi.org/10.1108/aeat-01-2018-0065.
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Purpose This paper aims to present the results of aerodynamic calculation of the aircraft in tandem wing configuration called VTOL. A presented vehicle combines the capabilities of the classic aircraft and helicopters. The aircraft is equipped with two pairs of tilt-rotors mounted on the tips of the front and the rear wing. The main goal of the presented research was to find the aerodynamic impact of both pairs of tilt-rotors on aerodynamic coefficients of the aircraft. Moreover, the rotors impact on the static stability of the aircraft was investigated too. Design/methodology/approach The CFD analysis was made for the complete aircraft in the tandem wing configuration. The computation was performed for the model of aircraft which was equipped with the four sub-models of the front and rear rotors. They were modeled as the actuator discs. This method allows for computing the aerodynamic impact of rotating components on the aircraft body. All aerodynamic analysis was made by the MGAERO software. The numerical code of the software was based on the Euler flow model. The used numerical method allows for the quick computation of very complex model of aircraft with a satisfied accuracy. Findings The result obtained by computation includes the aerodynamic coefficients which described the impact of the tilt rotors on the aircraft aerodynamic. The influence of the angle of attack, sideslip angle and the change of rotor tilt angle was investigated. Evaluation of the influence was made by the stability margin analysis and the selected stability derivatives computation. Practical implications Presented results could be very useful in the computation of dynamic stability of unconventional aircraft. Moreover, results could be helpful during designing the aircraft in the tandem wing configuration. Originality/value This paper presents the aerodynamic analysis of the unconventional configuration of the aircraft which combines the tandem wing feature with the tilt-rotor advantages. The impact of disturbance generated by the front and rear rotors on the flow around the aircraft was investigated. Moreover, the impact of rotors configuration on the aircraft static stability was found too.
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Majeti, Rohin Kumar, and Stephan Benz. "Mission-based optimal morphing parameters for rotors with combined chord and twist morphing." Open Research Europe 1 (October 12, 2021): 121. http://dx.doi.org/10.12688/openreseurope.14060.1.
Full textAbstract:
Background: The fixed geometry rotor blades in today’s helicopters do not give the best performance throughout the duration of any mission. However, low-speed and high-speed flights have different geometrical requirements for the shape of the most efficient rotor blades. With advancements in morphing technologies, these can be applied to change the shape of the blades in different flight regimes. Methods: Two different helicopter rotor morphing concepts – namely, the linearly variable chord extension and the torque-tube based twist - under the framework of the European project SABRE were investigated for their optimal geometric parameters using a Particle Swarm Optimization (PSO) algorithm. Since the morphing parameters were dependent on the mission profile, three different missions representing typical helicopter applications were chosen. The optimization problem was posed both as single objective (power) and as multi-objective (power, tip elastic torsion and vibratory hub load). Based on the insights drawn from these investigations, a rotor was set up including both morphing concepts in a single blade. Results: The rotor with combined chord and twist morphing was shown to have better performance than the baseline blade, while keeping the penalty on the elastic torsion and vibration of the rotor to a minimum. Conclusions: Chord and twist are both important parameters determining the efficiency of a rotor blade. Since they have non-overlapping requirements, combining the two morphing concepts into a single blade can yield higher performance than the individual ones.
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Li, Liang, Ming Chen, Fang Wang, and Anan Xu. "The Influence of Rotor Adjustment Parameters on the Dynamic Balance of a Scale-Model Rigid Variable Speed Rotor." Applied Sciences 12, no. 23 (November 27, 2022): 12125. http://dx.doi.org/10.3390/app122312125.
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In this paper, the dynamic balance of a rigid variable speed rotor is tested and analyzed. The vibration acceleration is measured by vibration analyzer instrumentations. The rotor adjustment parameters of counterweight, pitch, and trailing-edge flap are considered. The amplitude and phase of the 1 Ω vibration acceleration are analyzed through an all-phase fast Fourier transform. The experiments are conducted using two rigid rotors with the same geometry. The accelerations of the fuselage in the x, y, and z directions are measured. Through a waterfall diagram of the auto-power spectrum, it is found that the imbalance of counterweight, pitch, and trailing-edge flap causes an obvious increase in 1 Ω and 2 Ω acceleration. The hub counterweight mainly causes the lateral and longitudinal vibration in the disc plane, and the aerodynamic factors such as pitch and trailing-edge flap mainly affect the vertical vibration. In order to achieve dynamic balance for variable speed rotors, the counterweight adjustment should be given the highest priority for the vibration in the disc plane, and the pitch and trailing-edge flap adjustment should be given the highest priority for the vertical vibration. The results obtained from this experiment may be helpful toward reasonable designs of variable speed rotor helicopters.
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Afari, Samuel, Vladimir Golubev, Anastasios S. Lyrintzis, and Reda Mankbadi. "Review of Control Technologies for Quiet Operations of Advanced Air-Mobility." Applied Sciences 13, no. 4 (February 16, 2023): 2543. http://dx.doi.org/10.3390/app13042543.
Full textAbstract:
The current technologies for developing quiet rotor noise in urban canyons are reviewed. Several passive noise control approaches are discussed with their limitations in reducing both tonal and broadband noise. Blade tip modifications are seen to be one of the more successful in reducing tonal noise, with serrations at the trailing edge useful in reducing trailing edge broadband noise. Due to the adverse performance limitations of passive control, several optimization approaches are reviewed to discuss the possible improvements in performance of rotors. Additionally, a few legacy control technologies for helicopters are discussed. Active control technologies are investigated. The overall outlook and challenges to these methods are discussed with an eye on Advanced Air Mobility Vehicles (AAM).
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Majeti, Rohin Kumar, and Stephan Benz. "Mission-based optimal morphing parameters for rotors with combined chord and twist morphing." Open Research Europe 1 (June 7, 2022): 121. http://dx.doi.org/10.12688/openreseurope.14060.2.
Full textAbstract:
Background: The rotor blades with fixed geometry in today’s helicopters do not give the best performance throughout the duration of any mission. However, low-speed and high-speed flights have different geometrical requirements for the shape of the most efficient rotor blades. With advancements in morphing technologies, these can be applied to change the shape of the blades between different flight regimes. Methods: Two different helicopter rotor morphing concepts – namely, the linearly variable chord extension and the torque-tube based twist - under the framework of the European project SABRE were investigated for their optimal geometric parameters using a Particle Swarm Optimization (PSO) algorithm. Since the morphing parameters were dependent on the mission profile, three different missions representing typical helicopter applications were chosen. The optimization problem was posed both as single objective (power) and as multi-objective (power, tip elastic torsion and vibratory hub load). Based on the insights drawn from these investigations, a rotor was set up including both morphing concepts in a single blade. Results: The rotor with combined chord and twist morphing was shown to give performance improvement of 6.8% over the baseline blade for a whole mission while keeping the penalty on the elastic torsion and vibration of the rotor to a minimum. The performance improvement was higher at 13% for hover and low speed flight of µ = 0.14. Conclusions: Chord and twist are both important parameters determining the efficiency of a rotor blade. Since they have non-overlapping requirements, combining the two morphing concepts into a single blade can yield higher performance than the individual ones.
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Flowers, G. T., and B. H. Tongue. "Nonlinear Behavior of a Rotorcraft Model During Air Resonance." Journal of Vibration and Acoustics 113, no. 2 (April 1, 1991): 141–51. http://dx.doi.org/10.1115/1.2930162.
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The term “air resonance” refers to an instability associated with helicopters in hover. It is characterized by a coupling between motions of the fuselage and the blades and is of primary concern for helicopters having soft in-plane rotors. This paper presents a study of the effects of nonlinearities on the dynamical behavior of a simplified air resonance model. In order to provide a direct comparison between the behavior of the linearized system and the nonlinear one, a linear analysis of the air resonance model is first performed. Then, the system is analyzed for the effect of selected nonlinearities on its steady state dynamical responses. Geometric nonlinearities and cubic lag damping are considered in these analyses.
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Yuki, Shoichi, Yuso Kobara, Mitsuru Nakashima, Yoshihito Ozaki, Hiroaki Yoshiyama, Kazuyasu Yuasa, Yosuke Kubota, Yukito Fujii, and Hirofumi Yamasaki. "Comparison of Test Methods for Spray Deposition and Distribution by Unmanned Aerial Vehicle for Agricultural Chemical Spraying Application between Japanese Convention Protocol and ISO 24253 Protocol." Applied Engineering in Agriculture 41, no. 1 (2025): 11–21. https://doi.org/10.13031/aea.15989.
Full textAbstract:
HighlightsSpray deposition and distribution evaluations of UAVs were conducted.Spray distributions by the ISO and the Japanese protocol showed similar trends.The Japanese test protocol is useful as an evaluation method.A great benefit is its consideration of UAV-specific downwash and crosswinds.Abstract. For this study, evaluations of spray deposition and distribution on industrial unmanned helicopters and multi-rotor UAVs were conducted, respectively, according to the Japanese convention test protocol for UAVs and the test protocol for ground boom sprayers specified in ISO 24253 part 1. Using both the Japanese conventional protocol and the ISO 24253 protocol, spraying was conducted with 8 L per hectare with commercial UAVs. The amounts of tracer captured by collectors placed on the ground surface were measured and converted to the spray application rate per area. Results found for spray distribution by the ISO protocol exhibited similar trends to those obtained using the Japanese protocol. Results obtained from comparing the spray depositions of both test protocols indicated coefficients of determination R2 of the spray deposition measured values as 0.64 and 0.85, respectively, for helicopters and multi-rotors. Under the Japanese protocol, droplets on each of the five planes of the cubic collector were examined. More than 40% of the total droplets were observed on vertical planes because of downwash from UAV rotors, despite the crosswind effect during spraying. Therefore, one reason for differences in deposition values between these test methods was that the Japanese test protocol was able to capture droplets from the lateral direction with the cubic collector, which could not be captured using the ISO test. The Japanese test protocol, which measures the amount of adhesion using cubic collectors, is a useful and promising evaluation method that takes into account the UAV-specific downwash and crosswind effects. Keywords: ISO 24253 part 1, Japanese convention test protocol for UAVs, spray deposition and distribution, UAV pesticide application.
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Tang, Peng, Fei Wang, and Yuehong Dai. "Controller Design for Different Electric Tail Rotor Operating Modes in Helicopters." International Journal of Pattern Recognition and Artificial Intelligence 33, no. 08 (June 25, 2019): 1959022. http://dx.doi.org/10.1142/s0218001419590225.
Full textAbstract:
The nonlinear aerodynamics and new kinds of operation associated with helicopter electric tail rotors (ETRs) make accurate speed tracking control under complex flight conditions a key challenge confronting designers. In this paper, we present an electric propulsion system for tail rotors that uses a high-power-density permanent magnet motor. The management of aerodynamic disturbance rejection and accurate speed control are aspects of ETR design that require particularly close attention. To this end, we have developed a speed controller that is based on an active disturbance rejection control (ADRC) technique that can handle fixed speed and adjustable pitch-angle modes. We have also applied a linear extended state observer (LESO) with a self-tuning bandwidth to estimate fluctuations in the drive system. For variable speeds, a simple controller combined with an adaptive radial basis function (RBF) observer and nonlinear state error feedback using ADRC was designed to replace LESO while avoiding any dependence on the system parameters. The stability of the controllers was analyzed and their effectiveness was verified using a simulation platform. Test results showed that the propulsion system is able to achieve fast dynamic response and aerodynamic disturbance rejection.
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Guner, Feyyaz, and J. V. R. Prasad. "Combined Momentum Theory and Simple Vortex Theory Inflow Model for Multirotor Configurations." Journal of the American Helicopter Society 67, no. 2 (April 1, 2022): 1–15. http://dx.doi.org/10.4050/jahs.67.022007.
Full textAbstract:
For conventional main/tail rotor helicopters, momentum theory-based inflow models are still popular for design trade studies and flight simulations. However, simple momentum theory-based inflow models are not readily applicable in design trade studies of multirotor configuration vehicles where complex flow interactions among rotors can have a significant impact on vehicle overall performance, and hence, can impact vehicle sizing. The use of empirically corrected ad hoc inflow models is not often satisfactory. In this study, momentum theory is combined with a simple vortex theory in the development of a combined momentum theory and simple vortex theory (CMTSVT) based inflow model that is readily applicable to generic multirotor configurations. The developed model is validated against some multirotor inflow models and experimental data from the literature through comparisons of inflow predictions and performance predictions for different dual-rotor configurations. Further, inflow predictions using the proposed inflow model for a partially overlapping quad-rotor configuration are presented to illustrate the significance of rotor-on-rotor flow interactions in multirotor vehicle configurations.