Abstract: It this paper the optimal quadratic regulator design method is used to design the flight control systems with the robustness properties of stability and handling quality. The weighting matrix Q is successively modified to assign the close loop system poles in a desirable region at different flight conditions resulting in a simultaneously stable flight control system under different flight conditions. Then a weighting error function which is the difference between the states of a nominal system and the systems corresponding to different flight conditions is used to minimize the difference between the performances of the nominal system and the systems of various flight conditions.Such a designed flight control system has the robustness properties of stability and handling quality. The stability in whole flight envelope is proved. An example of a fighter control system is illustrated and it shows the simplicity and efficiency of the design procedure.

Key words: robustness, stability, handling quality, flight control systems