Design Studies of Transonic Flutter and Limit-Cycle Oscillation of an Aircraft Wing/Tip Store

Abstract

Abstract : This study investigates the effect of store parameters variation on store-induced flutter and limit-cycle oscillation phenomena of an aircraft wing in the transonic regime. The primary store parameters are its mass and the chord wise location of its center of gravity. The effect of including store aerodynamics on the wing/tip store configuration is also investigated. These studies are being conducted to understand the behavior of store-induced flutter and limit-cycle oscillation in the nonlinear region so as to limit the number of flutter flight tests to a few critical ones and enable in future store certification efforts. The tip store center of gravity (c.g.) has been varied and positioned at three different locations: 32.5%, 40%, and 50%, with respect to aerodynamic tip chord. Automated Structural Optimization System and Computational Aeroelasticity Program - Transonic Small Disturbance (CAP-TSD) have been used in the linear and nonlinear region to perform this research. Studies show that flutter speed increases as the store c.g. was moved forward towards the leading edge. This gives an indication that store c.g. must be placed as far forward as possible with respect to the elastic axis to delay the occurrence of flutter, while satisfying other design constraints. It was observed that the increase in tip store mass significantly reduced the flight operating speed range of the aircraft. The effect of inclusion of store aerodynamics for different wing/store configurations was found to be insignificant compared to their corresponding mass-only models in the transonic regime. LCO onset speed was found to be sensitive to store mass and varied significantly for different store mass configurations.