Parametric aeroelastic stability analysis of a generic X-wing aircraft

This paper discusses the dynamic aeroelastic stability of a generic X-wing aircraft configuration. The analysis model includes rigid-body degrees of freedom and unsteady aerodynamic forces generated using the doublet lattice method. Design parameters are varied to evaluate the trends in dynamic aeroelastic stability. X-wing rotor blade sweep angle, ratio of blade mass to total vehicle mass, blade structural stiffness cross coupling, and vehicle center of gravity location were parameters considered. The typical instability encountered is "body-freedom" flutter involving a low-frequency interaction of the first elastic mode and the aircraft short period mode. In most parametric cases, those cases having the least static longitudinal stability demonstrated the highest flutter dynamic pressures. As mass ratio was increased, the flutter boundary decreased. The decrease was emphasized as center of gravity location was moved forward. As sweep angle varied, it was observed that the resulting increase in forward-swept blade bending amplitude relative to aft blade bending amplitude in the first elastic mode had a stabilizing effect on the flutter. b [B,] [C'\ [C] El [F] GJ [7] ^ [K] [Kf] L Lb [M'] mb nif mr [M] q