Stability derivatives computed usinga panel method in the compressible, subcritical flow

This paper presents an application of a low-order panel method to the stability analysis of an aircraft in steady flight. The aerodynamic coefficients and most of the stability derivatives determined using a low-order panel method with constant singularity distributions over flat panels. The stability derivatives were computed in terms of quotients of the increments of aerodynamic forces and moments to the increments of linear and angular velocities. Compressibility of the flow was taken into account using the Prandtl-Glauert geometry transformation. Stability derivatives with respect to the pitch and yaw were calculated using a cylindrical coordinate system. Eigenvalues of the natural of oscillations were determined, using a rigid-body model of the real aircraft. The influence of each stability derivative on the of eigenvalues individual modes was determined by means of evaluation of the sensitivity coefficients of all eigenvalues with respect to the nondimensional stability derivatives. The sensitivity coefficients of natural modes offer a quick assesment of the effect of small perturbations of selected stability derivatives, and hence, enable the assesment of the influence of variations of the designgeometric parameters on dynamic of an aircraft.