THE DYNAMICS, PREDICTION, AND CONTROL OF WING ROCK IN HIGH-PERFORMANCE AIRCRAFT

This study is an investigation of the nonlinear aircraft behaviour kno wn as wing rock. An eight-state F-15 model is analysed by using bifurc ation theory and root-locus techniques. The wing-rock onset point is i dentified, and small perturbation analysis is used to linearize the eq uations of motion about this point. The eigenstructure of the model is analysed and is used to identify the stability modes involved in this motion. A procedure is developed to predict wing-rock onset, and the critical stability derivatives involved in this behaviour are identifi ed. The developed procedure is applied to existing F-15 data. The resu lts show that wing rock is an unstable Dutch-roll motion and the devel oped wing-rock prediction parameter is accurate to within 1 degrees of onset angle of attack (AOA). Various simple feedback control schemes are evaluated to determine how to delay the onset of wing rock. The mo st effective control scheme is found to be a combination of roll rate and sideslip fixed gain feedback to the ailerons yielding a 6 degrees improvement in the onset AOA of wing rock.