A flight dynamics investigation of compound helicopter configurations

Ferguson, K. and Thomson, D. (2013) A flight dynamics investigation of compound helicopter configurations. In: AHS 69th Annual Forum and Technology Display, Phoenix, AZ, USA, 21-23 May 2013, pp. 1-15.

Abstract

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.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Thomson, Dr Douglas and Ferguson, Dr Kevin
• Authors: Ferguson, K., and Thomson, D.
• College/School: College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
• Copyright Holders: Copyright © 2013 by the American Helicopter Society International, Inc.
• Publisher Policy: Reproduced with the permission of the publisher