Observations on the Effect of Geometric Nonlinearities on a Representative Civil Aircraft Incorporating Flared Folding Wingtips

Recent studies have considered the use of Flared Folding Wingtips (FFWTs) to enable higher aspect ratios - reducing overall induced drag - whilst reducing gust loading and meeting airport operational requirements. The majority of these analyses have been conducted using linear assumptions despite the presence of large wingtip deformations. This paper applies a recently developed method, utilising MSC Nastran, for modelling the geometric nonlinearities due to the large deformation of folding wingtips on two models of representative civil jet aircraft. The models are used to explore how the dynamic stability and response to gust encounters of an aircraft incorporating FFWTs are effected by large rotations of the wingtips. The results show that the effect of modelling these geometric nonlinearities is highly dependent on the entire aircraft structure, with the nonlinearites modestly affecting the flutter speed in a flutter mechanism dominated by wingtip flapping: however, in the case of more flexible aircraft, the large rotations can significantly change the dynamics of the entire structure.