Load alleviation on transport aircraft using acceleration feedback

Requirements to fly faster and farther with ever increasing payloads have resulted in aircraft with larger and more flexible airframes. Traditionally, many of the problems associated with high performance aircraft have been resolved using passive control techniques, but active control technology (ACT) methods are more versatile and can be implemented with negligible weight penalties. Furthermore, incorporation of ACT during the conceptual design stages can greatly improve performance. Noninteracting control equations (NICE) are being developed to extract the maximum benefits in an integrated flight control system. NICE was initially applied to design an aeroservoelastic control system for the Garteur wind tunnel model (which is a flutter model of a tactical aircraft) to solve a binary flutter problem. It is shown that NICE yields a highly effective integrated flight control system which can simultaneously alleviate wing loads and control the aircraft in the pitch-plane. The important of using acceleration signals for feedback is illustrated by the reduction of the important first peaks (which are also the largest) of the bending moments when the aircraft is subjected to a discrete gust. However, this feature is accompanied by an increase in the wing torque; this is a characteristic feature of the structural behaviour of the VC10 aircraft. The only adverse feature of the controller is that it slightly increases the vertical acceleration levels at the pilot station whilst the levels at the fuselage centre of gravity show little change