BIFURCATION-ANALYSIS OF A HIGHLY AUGMENTED AIRCRAFT MODEL

Bifurcation theory is used to analyze the dynamics of a modern high-pe rformance aircraft. An F-16 lighter aircraft model, which includes a f ull authority control system, is considered. The vehicle is a basicall y unstable configuration, and its response modes are tailored by the E ight control system according to different mission tasks. The steady s tates of the F-16 are computed by a numerical continuation method. The classical application of this technique to trace the steady states of the system as continuous functions of control deflections or control force is to be reconsidered when the use of maneuver demand control in highly augmented aircraft provides zero stick force for most of the t rimmed flight conditions of the vehicle. The practical worth of bifurc ation theory for the design and analysis of high performance aircraft is evaluated. Such aspects of the problem as the selection of meaningf ul parameters for the continuation procedure and the interpretation of the bifurcation diagrams are discussed for the different modes of ope ration of the flight control system. The behavior of the aircraft mode l at high angle of attack is predicted when the alpha limiter is disen gaged to simulate the effects of possible failure conditions.