Dynamic Stability Analysis of Aircraft Flight in Deep Stall

Beyond aerodynamic stall, the analysis of aircraft flight requires models accurately representing nonlinearities and instabilities. Previous bifurcation analysis studies therefore had a priori knowledge of the aircraft dynamics including dynamic damping. Yet, unlike airliners, extensive wind-tunnel tests and high-fidelity models are rarely available for small unmanned aircraft. Instead, continuous fluid dynamic simulations may provide basic insights into the aerodynamics, however limited to static conditions. In this paper, bifurcation analysis is presented as a tool to discuss the effects of unidentified pitch-damping dynamics during deep-stall transition that allows development of a nonlinear pitch-damping model for a small unmanned aircraft. By preliminary study of the static case, the model is extended based on deep-stall flight data to predict dynamics and stability. As a result, the deep-stall modes of the extended model are investigated in full envelope.