Spin Aerodynamic Modeling for a Fixed-Wing Aircraft Using Flight Data

Novel techniques are used to identify a nonlinear, quasi-steady, coupled, spin aerodynamic model for a fixed-wing aircraft from flight test data. Orthogonal phase-optimized multisine inputs are used as excitation signals while collecting spinning flight data. A novel vector decomposition of explanatory variables leads to an elegant model structure for spin flight data analysis. Results shows good agreement with validation flight data. This effort was motivated by interest in developing a flight termination system for a fixed-wing unmanned aircraft that controls a descending spiral trajectory toward a designated impact area. The design and tuning of the control law, which is described in a separate paper, benefits from a model of the aircraft dynamics and control authority in the neighborhood of a stable, oscillatory spin.