Stability analysis of a scaled tiltrotor model with wing extensions and winglets

A scaled tiltrotor wind tunnel model with wing extensions and winglets has been investigated using RCAS modeling. The scaled model is based on the properties of NASA XV-15 model. The model consists of three highly twisted elastic rotor blades attached to a gimbaled hub. Wing, wing extension and winglet structures are modelled using the finite element formulation of nonlinear beam elements. Nonlinear lifting line theory is used for the aerodynamic modeling for both rotor blades and main wing and wing tip devices. The effects of wing extension and winglet on whirl flutter speeds and wing mode damping are investigated. Parametric studies of the wing extension and winglet have been conducted. The results show that wing extensions and winglets can significantly increase the wing beam mode damping, but their effect on the wing torsion mode damping is limited due to relatively high wing torsion stiffness. While various parameters of wing extensions and winglets may influence the wing mode damping, the dominate factor is the length of wing tip devices. The results also show that the structural tailoring such as main wing beam stiffness tapering and wing extension beam stiffness tuning may be more effective on the wing beam mode than on the wing torsion mode.