Comparing the flight dynamics characteristics of tandem and conventional helicopters for the purposes of automatic control

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Ferguson, K.
Thomson, D.
Anderson, D.
Ireland, M.
Tu, Z.
Manso, S.
Chandran, A.
Ibal, G.
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The broad aim of the collaborative research programme between the Australian Defence Science Technology (DST) Group and the University of Glasgow has been to develop a simulation framework capable for use in operational research to analyse helicopter mission effectiveness. This has involved integrating flight mechanics models of the helicopter with radar, guidance, weapons and threat models to allow typical operational scenarios to be modelled within a simulation framework designated CHOPPA. One objective of this broad aim is to develop a control system for generic rotorcraft configurations to quantify mission effectiveness. This paper presents the recent activity between the University of Glasgow and the DST Group towards achieving this goal. The starting point for developing a control system is understanding the flight dynamics of the rotorcraft that is to be controlled. As the control system will be implemented in conventional and tandem helicopter simulations, it is important to identify and compare the flight dynamics characteristics between these two rotorcraft arrangements. Consequently, the paper presents the salient flight dynamics attributes of a tandem helicopter and a conventional helicopter. The tandem and conventional helicopters of interest are the CH-47 Chinook and the UH-60, respectively. The first part of the paper focuses on the flight mechanics of these vehicles and how a control system can be developed to improve the operational effectiveness of both rotorcraft configurations. Thereafter, the basic control structure of the autopilot is introduced. Subsequently, a case study of the autopilot using a CH-47 mathematical model is presented.