Effect of Aerodynamic Damping Approximations on Aeroelastic Eigensensitivities

Aeroelastic sensitivities for the flutter solution are a crucial component of the multi-disciplinary optimization methods employed in modern aircraft design. This paper derives the aeroelastic sensitivities for different aerodynamic damping approximations—the p-k method, the g method and the generalized aeroelastic analysis method—highlighting the influence of the employed aerodynamic approximation on the required derivatives. The derived formulation for the determination of aeroelastic sensitivities by means of a direct method is verified for the case of a two-degree-of-freedom typical section model, where analytical aeroelastic sensitivities can be analytically obtained. For this and for an additional model, namely the AGARD 445.6 weakened wing, the significant effect of the aerodynamic damping approximation on the aeroelastic sensitivities is shown.