The fundamental configuration and design of the compound helicopter

Abstract

The compound helicopter has much to offer as a means of expanding the¯ight envelope of rotorcraft. There have been signi®cant amounts of research performed, albeit disjointed, and manȳ ight demonstrator compound helicopters produced and trialled since the end of the Second World WarÐmainly with the aim of increasing the helicopter's maximum forward speed. This paper aims to pool this knowledge, along with relevant developments in other ®elds, not only to state the current level of understanding of the compound helicopter con®guration but also to use it to predict likely con®gurations and technologies that would be best suited to future compound helicopter designs. From this basis it is suggested that the most likely con®guration will be a low wing of minimized area to alleviate retreating blade stall at a minimum hover blockage, with plain¯aps for blockage reduction and control of the rotor±wing load share. In terms of propulsion a ducted fan or propeller are deemed most suitable, driven by either an advanced mechanical drive or variable cycle engine. The areas of rotor±wing interaction and advanced rotor design are also noted as subjects of signi®cant interest in the optimal design of a compound helicopter.

Maneuverability Assessment of a Compound Helicopter Configuration

“…Another reason for the choice of the Lynx is that it features a rigid rotor which is likely to be used in a compound helicopter design [27]. One primary advantage of the rigid rotor is its ability to generate powerful moments independent of the amount of rotor thrust.…”

New-Trim-Method-Based Investigation on the Cyclic-Pitch-Effected Advancing-Blade-Concept Helicopter Aerodynamics

“…Research on new configurations of high-speed helicopters has been conducted to overcome this disadvantage. The advancing-blade-concept (ABC) rotor [1] propeller-augmented compound helicopter [2,3] (also called ABC helicopter) is one of the most successful configuration; the X-2 helicopter is a representative of such configurations. The X-2 helicopter maintains and develops the technical features of conventional helicopters [1], which is an important direction for the development of future helicopters.…”

Nonlinear Modeling and Flight Validation of a Small-Scale Compound Helicopter

“…The strategies of these existing products vary but the common point is that they all use propellers to create extra thrust and a wing is required to unload the rotor, except for the X2, which makes use of coaxial rotors. A fundamental compound helicopter configuration [2] uses a wing to unload the rotor and a propeller to create forward thrust in forward flight.…”