STABILITY AUGMENTATION DESIGN OF A LARGE FLEXIBLE TRANSPORT USING NONLINEAR PARAMETER OPTIMIZATION

Flight control laws for commercial aircraft have traditionally been de signed using classical methods, This is adequate for rigid statically stable airplanes controlled by mechanical and hydraulic means. The cha llenge increases as pitch stability is reduced and structural flexibil ity is increased, The practical application of modern linear quadratic methods to stability augmentation system synthesis for a large subson ic transport is demonstrated. Stability, robustness, handling qualitie s, and dynamic load requirements under discrete and random gusts are a ddressed. The approach evolves from the traditional linear quadratic r egulator methods to the synthesis of robust low-order controllers of a given structure with parameter optimization. The design is accomplish ed with aeroelastic models at flight conditions ranging from a low-spe ed takeoff to a high-speed cruise with forward and aft center-of-gravi ty configurations.