The dynamics, prediction, and control of wing rock in high–performance aircraft

Abstract

This study is an investigation of the nonlinear aircraft behavior known as wing rock. An eight–state F–15 model is analyzed by using bifurcation theory and root locus techniques. The wing rock onset point is identified and small perturbation analysis is used to linearize the equations of motion about this point. The eigenstructure of the model is analyzed 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 behavior are identified. The developed procedure is applied to existing F–15 data. The results show that wing rock is an unstable Dutch–roll motion and the developed wing rock prediction parameter is accurate to within 1 degree of onset angle–of–attack (AOA). Various simple feedback control schemes are evaluated to determine how to delay the onset of wing rock. The most 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.