APPLICATION OF BIFURCATION-THEORY TO THE HIGH-ANGLE-OF-ATTACK DYNAMICS OF THE F-14

Bifurcation theory has been used to study the nonlinear dynamics of th e F-14. An 8 degree-of-freedom model that does not include the control system present in operational F-14's has been analyzed. The aerodynam ic model, supplied by NASA, includes nonlinearities as functions of th e angles of attack and sideslip, the rotation rate about the velocity vector, and the elevator deflection. A continuation method has been us ed to calculate the steady states of the F-14 as continuous functions of the elevator deflection. Bifurcations of these steady states have b een used to predict the onset of wing rock, spiral divergence, and jum p phenomena that cause the aircraft to enter a spin. A simple feedback control system was designed to eliminate the wing rock and spiral div ergence instabilities. The predictions were verified with numerical si mulations.