Theoretical Prediction of Wing Rocking,
KANSAS UNIV LAWRENCE
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Wing rock is primarily a rolling oscillation about the longitudinal body axis at high angles of attack. It involves nonlinear interaction between flight dynamics and aerodynamics. A nonlinear aerodynamic model was proposed earlier to predict the wing rock frequency and amplitude of low aspect-ratio configurations with good accuracy. In this paper, the theory is applied to a twin-jet fighter airplane of moderate aspect ratio and to a low-speed configuration of high aspect ratio. For the purpose of predicting necessary aerodynamic derivatives, a lifting surface method coupled with nonlinear airfoil section data is developed. The results show that wing rock can be predicted with the present wing-rock and aerodynamic theories. It is also found that for configurations of high aspect ratio, the one degree-of-freedom dynamic model in the present wing-rock theory should be used for other configurations, the three degree-of-freedom model is more appropriate.