Wing rock as a lateral-directional aircraft limit cycle oscillations induced by nonlinear aerodynamics occurring at high angle of attack

Abstract

Wing rock at high angle of attack is an oscillatory lateral-directional motion phenomenon known to exist in some of today's high performance tactical aircraft. The motion has been consistently characterized as a lightly damped Dutch-Roll oscillation attributable to asymmetric wing stall. However, evidence gathered from wind tunnel simulations and at least one British study indicate that aerodynamic nonlinearit ies may be the source of wing rock. Regardless of the actual cause of the phenomenon, a study of wing rock has positive ramifications with respect to gaining a clearer understanding of the aerodynamics associated with high angle of attack flight. This report presents the results of an investigation of wing rock which centered on the premise that two distinct nonlinear aerodynamic mechanisms (aerodynamic hysteresis and a cubic nonlinearity in yawing moment) not only can cause wing rock but may drive it to a limit cycle oscillation as well.