Application of New and Standard Pilot-Induced Oscillation (PIO) Analysis Methods to Flight Test Data of the C-17 Transport Aircraft

The roll PIO susceptibility of the C-17A Globemaster III during approach and landing is represented as a highly nonlinear, stochastic, and adaptive pilot closed-loop oscillatory dynamics analysis problem. Multiple well-known, industry-wide, PIO analytical methods and metrics are applied to the lateral Pilot-Induced Oscillations (PIO) flight test evaluation of the C-17A Globemaster III during approach and landing. These include Roll Axis Bandwidth and Phase Delay, Gibson’s Average Phase Rate, Gibson’s PIO Gain Limit, and Real-time Oscillation Verifier (ROVER), as well as pilot PIO ratings and comments. A new flight-test-data-matched, time-domain, pilot-model-based method has been developed to augment and extend the above analyses. This new pilot-model-based method possesses several important advantages relative to other methods. Precise quantification of flight-testvalidated pilot closed-loop oscillatory dynamics, as a function of pilot dynamics, is a direct result. Analytical extensions to asymmetric flight conditions, failures, alternate control laws, and more extreme pilot dynamics, such as the theoretical infinite-gain pilot, are easily made. With an emphasis on the pilot model method, the combination of the aforementioned analyses is used to better quantify roll PIO susceptibility of the C-17A Globemaster III during approach and landing for three different control law configurations, as a function of partially unknown pilot dynamics, for one operationally relevant flight condition. A maximum sideslip PIO analysis case is utilized to demonstrate an application of the pilot model method to a more challenging flight condition.