In-Flight Test Campaign to Validate PIO Detection and Assessment Tools

Abstract

This paper describes a joint research campaign conducted by the German Aerospace Center (DLR) and the National Research Council Canada (NRC) to explore methods and techniques to expose rotorcraft pilot-induced oscillations (PIOs) during flight testing. A flight test campaign was conducted at NRC using the Bell 205 experimental aircraft. Results show that, particularly for the lateral axis, ADS-33 tasks can be successfully applied to expose PIO tendencies. Novel subjective and objective criteria were used during the test campaign. PIO prediction boundaries of the objective phase-aggression criteria (PAC) detection algorithm were validated through results obtained. This was the first use of PAC with data recorded in-flight. To collect subjective feedback, the aircraft–pilot coupling (APC) scale was used. This was the first use of the novel scale in-flight and received favourable feedback from the evaluation pilot. Modifications to ADS-33 mission tasks were found to successfully improve the ability to consistently expose PIOs.

Suggestions for Criteria to Evaluate Lateral-Directional Nonlinear Pilot-Induced Oscillations Due to Fly-by-Wire Civil Aircraft Landing Configuration Switch

“…However, the traditional flying qualities evaluation criteria [12][13][14][15] can only be used to evaluate the PIO characteristics of an aircraft in a certain configuration, namely Category I or Category II PIOs, and cannot predict the Category III PIO phenomena caused by the change in closed-loop aircraft dynamic characteristics [16]. Therefore, it is difficult to evaluate whether a designed flight control law is suitable for the process of switching to the landing configuration, and it cannot expose flight safety hazards that may exist in the approach and landing stage of FBW civil aircraft.…”