Calculating single static and dynamic derivatives of aircraft with step response method

Based on step response method and rigid moving mesh techniques, the fine single static and dynamic derivatives of aircraft were simulated. Longitudinal derivatives were taken as examples to represent these methods. Firstly a constant additional angle of attack was applied on the aircraft, and the unsteady aerodynamic force was calculated during the step response process, then the static derivative can be identified from the derivation of aerodynamic force; similar to static derivative, a constant pitching angular velocity was used to force the aircraft pitching around the reference point, and also a translate speed should be considered at the same time to eliminate the effect of additional angle of attack generated from the pitching angular velocity. NACA0012 airfoil and SACCON fly wing unmanned combat aerial vehicle were used to test the methods, both the static and dynamic derivatives of the two configurations agreed well with the reference and wind tunnel test results,with the maximum error no more than 5%. The research shows that the computational time of direct single static and dynamic derivatives simulation methods based on step response is nearly 21% of the of traditional oscillation method, with relatively higher effectiveness; this can be used in analysis of lateral and directional derivatives as well as longitudinal ones, providing technical reference for aircraft stability.