Effects of Auxiliary Lift and Propulsion on Helicopter Vibration Reduction and Trim

Sekula, Martin K.; Gandhi, Farhan

doi:10.2514/1.496

Cited by 13 publications

(7 citation statements)

References 8 publications

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“…As for the short period modes, the eigenvalues of the HCH model's heave and pitch subsidence modes are ap- (13) and (14). For a conventional helicopter in high speed flight, the derivative M w influences the eigenvalues of the short period modes, as seen in equation (12). However, for the HCH model, M w is very small due to the wing's contribution following a perturbation of angle of attack resulting in Z w and M q determining the damping of the heave and pitch subsidence modes, respectively.…”

Section: Dynamic Stability Of the Hch Modelmentioning

confidence: 99%

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Flight Dynamics Investigation of Compound Helicopter Configurations

Ferguson

Thomson

2015

Journal of Aircraft

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Compounding has often been proposed as a method to increase the maximum speed of the helicopter. There are two common types of compounding known as wing and thrust compounding. Wing compounding offloads the rotor at high speeds delaying the onset of retreating blade stall, hence increasing the maximum achieveable speed, whereas with thrust compounding, axial thrust provides additional propulsive force. The concept of compounding is not new but recently there has been a resurgence of interest in the configuration due to the emergence of new requirements for speeds greater than those of conventional helicopters. The aim of this paper is to investigate the dynamic stability characteristics of compound helicopters and compare the results with a conventional helicopter. The paper discusses the modelling of two compound helicopters, with the first model featuring a coaxial rotor and pusher propeller. This configuration is known as the coaxial compound helicopter. The second model, known as the hybrid compound helicopter, features a wing and two propellers providing thrust compounding. Their respective trim results are presented and contrasted with a baseline model. Furthermore, using a numerical differentiation technique, the compound models are linearised and their dynamic stability assessed. The results show that the frequency of the coaxial compound helicopter's dutch roll mode is less than that of the baseline helicopter and there is also greater roll damping. With regards to the hybrid compound helicopter the results show greater heave damping and the stabilisation of the phugoid due to the addition of the wing and propellers. stability and control matrices C q , C t torque and thrust coefficient C t u , C t l upper and lower rotor thrust coefficientnumber of rotor blades N p yawing moment due to roll rate (1/s) P coaxial rotor power (HP) R, R prop radius of the main rotor and propeller blade (m) U e forward speed at trim (m/s)

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Section: Dynamic Stability Of the Hch Modelmentioning

confidence: 99%

“…To optimise the compound design, most authors agree that a wing must be supplemented with auxiliary propulsion (Refs. [12][13][14][15]. The reason for this is that a wingonly compound helicopter tends to have a more pitch down attitude, relative to a baseline helicopter (Ref.…”

Section: Introductionmentioning

confidence: 99%

Flight Dynamics Investigation of Compound Helicopter Configurations

Ferguson

Thomson

2015

Journal of Aircraft

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“…These trim methods for helicopters can be found in the literature. [3][4][5][6] Padfield 7 divided the trim into three parts in accordance with the initial predicted values: the longitudinal, the lateral and the rotor speed. In this method, the damping term, also depends on the engineering experience, is constructed.…”

Section: Introductionmentioning

confidence: 99%

Helicopter flight simulation trim in the coordinated turn with the hybrid genetic algorithm

Wang

Liu

2017

Proceedings of the Institution of Mechanical Engineers, Part G:

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Helicopter trim models are multivariate nonlinear equations and it is difficult to determine these initial trim points comparable to flight conditions. To solve this question, a hybrid genetic algorithm is presented in this paper, that combines the quick convergence ability of the quasi-Newton method and the advantages of genetic algorithm, such as global convergence. The trim control vector and the constraint conditions were established in the coordinated-turn based on the helicopter flight dynamic model. The coordinated turn flight of a UH-60 A helicopter was taken as an example to simulate on the experimental platform. Comparisons were made between the trim results and flight test data and there is a good agreement among them, and the efficiency of the algorithm presented is verified. It is a general method that can be applied to trim the helicopter of different flight conditions.

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“…Whereas thrust compounding, which is supplied by a propulsive device such as a propeller, provides additional propulsive thrust in high speed, therefore divorcing the main rotor of its propulsive duties. In order to appreciably expand the flight envelope of a helicopter, the vehicle must be supplemented with both thrust and lift compounding (2,(5)(6)(7)(8) . Firstly, consider a helicopter which only features lift compounding.…”

Section: Introductionmentioning

confidence: 99%

Examining the stability derivatives of a compound helicopter

Ferguson

Thomson

2016

Aeronaut. j.

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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 conventional helicopter. One method to examine the flight dynamics of an aircraft is to create a linearised mathematical model of the aircraft and to investigate the stability derivatives of the vehicle. The aim of this paper is to examine the stability derivatives of a compound helicopter through a comparison with a conventional helicopter. By taking this approach some stability, handling qualities and design issues associated with the compound helicopter can be identified. The paper features a conventional helicopter and a compound helicopter. The conventional helicopter is a standard design, featuring a main rotor and a tail-rotor. The compound helicopter configuration features both lift and thrust compounding. The wing offloads the main rotor at high speeds whereas two propellers provide additional propulsive thrust as well as yaw control. The results highlight that the bare airframe compound helicopter would require a larger tailplane surface to ensure acceptable longitudinal handling qualities in forward flight. In addition, without increasing the size of bare airframe compound helicopter's vertical fin, the Dutch roll mode satisfies the ADS-33 level 1 handling qualities category, for the majority of the flight envelope.

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Effects of Auxiliary Lift and Propulsion on Helicopter Vibration Reduction and Trim

Cited by 13 publications

References 8 publications

Flight Dynamics Investigation of Compound Helicopter Configurations

Flight Dynamics Investigation of Compound Helicopter Configurations

Helicopter flight simulation trim in the coordinated turn with the hybrid genetic algorithm

Examining the stability derivatives of a compound helicopter

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