Handling Quality Design Criteria for Advanced Supersonic Aircraft Flight Control

Abstract

Concorde’s unique low-speed handling qualities are acceptable when flown in a rigidly procedural manner by experienced pilots. However, to be commercially viable and environmentally acceptable more numerous second-generation supersonic transport (SST) aircraft would need to provide increased passenger carrying capacity, range and the flexibility to integrate with existing sub-sonic air traffic during terminal manoeuvres. Their much larger size, weight and inertia compared to Concorde’s, combined with increasing levels of relaxed longitudinal stability to improve aerodynamic efficiency, results in unconventional dynamics and degraded handling qualities on the final approach, where precise manual flightpath control is required. Modern commercial and military transport aircraft utilise increasingly complex command and stability augmentation systems to restore stability, optimise aerodynamic performance and provide the pilot with the optimum handling qualities. Provided it has sufficient control power a second generation fly-bywire SST should be capable of exhibiting similarly desirable low-speed handling qualities. Successful flight control law design requires identification of: the ideal command response type for that particular phase of flight; valid handling quality criteria and design constraints supported by pilot simulation using suitable tasks and assessment criteria. The study uses MATLABSimulink dynamic simulation and analysis software for model building, control law design and subsequent analysis. In addition to desktop PC simulation, ‘real-time’ piloted simulation is included in the design process so human factors, which do not translate easily into design criteria, can also be taken properly into account. This paper begins with a statement of the technical background to the work together with an overview of handling qualities and the selected flight control law design method. This is followed by a description of the aerodynamic mathematical model synthesized on the final approach together with an analysis of the open-loop longitudinal response. Specific handling quality design criteria are then identified together with a set of revised constraints within which the flight control laws are implemented. The aircraft’s closed loop response using the resulting flight control laws is analysed offline and then validated through piloted simulation trials using a civil aircraft engineering research simulator. Finally, conclusions and recommendations are made for further research.