Approximate Method to Calculate Nonlinear Rolling Moment due to Differential Fin Deflection

Abstract

A new nonlinear method has been developed to predict the roll moments due to differential deflection of fins (often referred to as roll driving moment). The method utilizes the nonlinear aerodynamics currently available in the 2009 version of the Aeroprediction Code (AP09) for the horizontal wing alone and wing-body aerodynamics. Specialized treatment is given to the leeward and windward plane fins as well as engineering approximations to handle the physics associated with fin-to-fin interference, wing-tail interference, a fin in close proximity to a large wing upstream, and fins located on a boattail. Comparison of the new method to seven body tail configurations, five wing-body-tail cases with tail control and six wing-body-tail cases with canard control showed the new method followed the general trends of the experimental data for most cases. Results were quite good for most cases with the poorest agreement with experiment being for canard control cases where the tail fins were very large. Results from several of the cases where comparisons of the new theory to experiment have been made are presented in this paper.