Application of NDI flight control to a second generation supersonic transport aircraft

The continual drive to optimise aerodynamic efficiency has resulted in commercial transport aircraft using increasing levels of relaxed longitudinal stability, which can result in dynamic instability and degradation in handling qualities. However, a carefully designed fly-by-wire flight control system can restore stability margins, shape the aircraft´s response and optimise the handling qualities throughout its flight envelope. Advanced control law, rapid prototyping tools such as non-linear dynamic inversion (NDI), which are based on simple manipulations of the aircraft equations of motion, generate a perfect first-order response within control power constraints. In addition, NDI can be rapidly applied to any vehicle dynamic model for concept comparison, to quantify control power requirements and to provide a functional control law design. This article has applied NDI techniques to a longitudinally unstable second-generation supersonic transport aircraft on the landing approach to restore stability, to generate an ideal response and to provide desirable handling qualities.