Body Freedom Flutter in Large Flexible Aircraft: Influence of Rigid-Elastic Coupling on Aeroelastic Stability

Abstract

Large flexible aircraft, designed with high aspect ratio wings and lightweight compliant materials, offer superior lift-drag characteristics and enhanced endurance. However, their inherent flexibility leads to pronounced elastic effects, characterized by low-frequency concentrated modes. These aircraft also possess small pitch inertia and relatively high short-period modal frequencies. Consequently, the frequency separation between rigid body motion and elastic vibration diminishes, leading to a complex interplay of structural motion, unsteady aerodynamic forces, and rigid body dynamics. This interaction gives rise to 'body freedom flutter', a novel form of aeroelastic instability. Distinct from traditional flutter, body freedom flutter often manifests at a lower critical stability point, impacting safe flight boundaries. This study investigates the dynamic modeling of aeroelastic systems incorporating rigid-elastic coupling effects. Through simulations, we examine body freedom flutter and analyze the influence of rigid-elastic coupling on the overall stability of the aeroelastic system.

Keywords: Large flexible aircraft, rigid-elastic coupling, aeroelastic instability, body freedom flutter, stability analysis.