Stability augmentation design of a large flexible transport using nonlinear parameter optimization

Abstract

Flight control laws for commercial aircraft have traditionally been designed using classical methods. This is adequate for rigid statically stable airplanes controlled by mechanical and hydraulic means. The challenge increases as pitch stability is reduced and structural flexibility is increased. The practical application of modern linear quadratic methods to stability augmentation system synthesis for a large subsonic transport is demonstrated. Stability, robustness, handling qualities, and dynamic load requirements under discrete and random gusts are addressed. The approach evolves from the traditional linear quadratic regulator methods to the synthesis of robust low-order controllers of a given structure with parameter optimization. The design is accomplished with aeroelastic models at flight conditions ranging from a low-speed takeoff to a high-speed cruise with forward and aft center-of-gravity configurations .