An Examination of Wing Rock for the F-15

Abstract : Wing rock in the F-15 was examined both analytically and experimentally. Using a previously developed model for the F-15, bifurcation analysis and continuation techniques were used to map out the periodic wing rock solutions and the equilibrium solutions leading up to wing rock. this was done for four maneuvers; a 1 g stall, rudder sweeps, constant bank turns and a symmetric pullup. To supplement this research, time history simulations were used to examine. the time history of wing rock. A study of stability derivatives was also done, to determine the critical parameters in wing rock. Bifurcation was also used to study candidate feedback architectures used to suppress wing rock. It was found that feeding back roll rate was effective in delaying wing rock onset and suppressing the subsequent motion, but this made the aircraft more departure prone. The results of the 1 g stall, constant bank turns, and the symmetric pullup were experimentally tested through flight test. Wing rock onset differed 4 degrees AOA from predicted in all maneuvers but the symmetric pullup, where the flight mach number correlated with the computer model's flight condition/Wing rock was found to be highly random and non periodic, directly contradicting computer predictions and prior research. High AOA, Stability and Control, F-15, Wing Rock, Stability Derivatives Stall.