Tiltrotor Whirl Flutter Stability Augmentation Using Active Wing Tips

Abstract

Tiltrotor whirl flutter stability augmentation using an active wing tip is investigated. The wing tip is a small active wing segment which is attached to the outboard side of the pylon through a controllable bearing. Using a feedback control system, the tip cancels wing motion to augment whirl flutter stability. Multiple individual and combined feedback schemes and control system parameters are investigated on a scaled XV-15 model using the comprehensive analysis RCAS. The simulated small tip was shown to increase system damping and extend the whirl flutter boundary by 25–33% from 160 kts to over 200 kts by selecting the optimum control parameters for beamwise and chordwise feedback independently and then combining them. The damping resulting from individually feeding back beamwise and chordwise motion was additive when feeding both back together. The required actuation amplitude was on the order of 1 degree.