The compound helicopter — why have we not succeeded before?

Orchard, Matthew; Newman, S.J.

doi:10.1017/s0001924000064526

Cited by 6 publications

(4 citation statements)

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“…The compounding of a helicopter is not a new idea but the development of a compound helicopter has proven elusive for the rotorcraft community due to a combination of technical problems and economical issues [1]. The rotorcraft community is again exploring the compound helicopter design, with various manufacturers testing their prototypes.…”

Section: F Propmentioning

confidence: 99%

Maneuverability Assessment of a Compound Helicopter Configuration

Ferguson¹,

Thomson²

2016

J Am Helicopter Soc

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The compound helicopter design could potentially satisfy the new emerging requirements placed on the next generation of rotorcraft. 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 compound helicopter design can provide additional benefits in terms of maneuverability. The paper features a conventional helicopter and a compound helicopter. The conventional helicopter features a standard helicopter design with a main rotor providing the propulsive and lifting forces whereas a tail rotor, mounted at the rear of the aircraft, provides the yaw control. The compound helicopter configuration features both lift and thrust compounding. The wing offloads the main rotor at high speeds whereas two propellers provide additional axial thrust as well as yaw control. This study Presented at the 40th European Rotorcraft Forum, Southampton, U.K., September 2-5th, 2014. investigates the maneuverability of these two helicopter configurations using inverse simulation. The results predict that a compound helicopter configuration is capable of attaining greater load factors than its conventional counterpart, when flying a Pullup-Pushover maneuver. In terms of the AccelDecel maneuver, the compound helicopter configuration is able of completing the maneuver in a shorter time than the conventional helicopter, but at the expense of greater installed engine power.The addition of thrust compounding to the compound helicopter design reduces the pitch attitude required throughout the acceleration stage of the maneuver. Nomenclature

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Section: F Propmentioning

confidence: 99%

Maneuverability Assessment of a Compound Helicopter Configuration

Ferguson¹,

Thomson²

2016

J Am Helicopter Soc

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“…The compounding of a helicopter is not a new idea but the development of a compound helicopter has proven elusive for the rotorcraft community due to a combination of technical problems and economical issues (Ref. 1). The rotorcraft community is again exploring the compound helicopter design, with Sikorsky and Eurocopter both testing their prototypes.…”

Section: Introductionmentioning

confidence: 99%

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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“…The compound helicopter is a high speed design concept which aims to expand the flight envelope of the helicopter, therefore making it suitable for various roles such as ship replenishment and scouting missions. Although this is not a new concept, the development of a compound helicopter has proven elusive due to a combination of technical problems and economical issues [1]. Recently, various compound helicopter demonstrators have been developed, all of which are capable of reaching speeds that significantly surpass its conventional counterpart.…”

Section: Introductionmentioning

confidence: 99%

“…Although this is not a new concept, the development of a compound helicopter has proven elusive due to a combination of technical problems and economical issues. 1 Recently, various compound helicopter demonstrators have been developed, all of which are capable of reaching speeds that significantly surpass its conventional counterpart. For example, Sikorsky and Eurocopter, now Airbus Helicopters, are taking their compound helicopter demonstrators seriously with the flight tests of the Sikorsky X2 and the Eurocopter X 3 indicating promising results.…”

Section: Introductionmentioning

confidence: 99%

Performance comparison between a conventional helicopter and compound helicopter configurations

Ferguson

Thomson

2015

Proceedings of the Institution of Mechanical Engineers, Part G:

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The compound helicopter is a high speed design concept that is once again being explored due to emerging requirements for rotorcraft to obtain speeds that significantly surpass the conventional helicopter. This increase in speed, provided efficient hover capability is maintained, would make the compound helicopter suitable for various roles and missions in both military and civil markets. The aim of this paper is to investigate the compounding of the conventional helicopter and how the addition of thrust and wing compounding influences the performance of this aircraft class. The paper features two compound helicopters. The first configuration features a coaxial rotor with a pusher propeller providing additional axial thrust, and is referred to as the coaxial compound helicopter. The second configuration, known as the hybrid compound helicopter, features a wing and two propellers providing thrust compounding. In this study, the performance of these two compound helicopter configurations are assessed and compared with a conventional configuration. The paper presents the standard performance parameters of each configuration which include the power required in steady level flight, the maximum range, the maximum endurance and the hover ceiling of each of the aircraft configurations. Furthermore, a performance analysis of each configuration flying standard helicopter missions is conducted. The results of the hybrid configuration show that the addition of the wing to the design successfully offloads the main rotor at high speeds, however significant propulsive power is required by the propellers to overcome the airframe drag. Concerning the coaxial configuration, the power required by the coaxial compound and baseline configurations are comparable at low speeds.However, in high speed flight a significant amount of power is required by the propeller to divorce the coaxial rotor of its propulsive duties. The results also reinforce the importance of reducing airframe drag in a potential compound helicopter design.*Manuscript accepted for publication in the Journal of Aerospace Engineering KeywordsCompound helicopter, Rotorcraft and performance.

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The compound helicopter — why have we not succeeded before?

Cited by 6 publications

References 1 publication

Maneuverability Assessment of a Compound Helicopter Configuration

Maneuverability Assessment of a Compound Helicopter Configuration

Flight Dynamics Investigation of Compound Helicopter Configurations

Performance comparison between a conventional helicopter and compound helicopter configurations

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