Longitudinal robust controller for excellent handling qualities design of a general aviation aircraft using QFT

Handling Qualities improvement by means of active Fly-by-Wire Flight Control Systems has been applied successfully since decades. In contrast small general aviation aircraft are still missing such valuable pilot assistance in terms of the manifold benefits offered by advanced Active Fly-by-Wire Flight Control Systems featuring a wide range of functionalities and applications. In order to bring such a system to a real aircraft as well as allowing the system to be certified in future, controller design layout must be tailored to the general aviation aircraft constraints, e.g. available actuators, sensors and sensor signals, mechanical linkage design, control surface deflection limitations and aircraft dynamics. E.g. in order to minimize the number of sensor signals, the controller should be designed featuring maximum robustness and hence, to yield the capability to operate with fixed gains (not requiring any velocity/dynamic pressure based gain scheduling) both for the whole flight envelope as well as any configuration changes with respect to flaps or landing gear. For that purpose the Quantitative Feedback Theory (QFT) has been applied to the controller design in order to meet the desired handling qualities criteria, including the Control Anticipation Parameter (CAP), Neal Smith, C-Star (C*), Drop Back and others. Consequently, an integrated approach is presented which incorporates and combines all these criteria. Moreover the often neglected part of the inceptor and feel system design, respectively, is addressed in order to provide excellent handling for the pilot. The presented technology work is applied in a joint Research project of an Austrian aircraft manufacturer and the Technische Universität München.