Evaluation of Rotorcraft Pilot Induced Oscillations (PIO): Results from a DLR/NRC Collaborative Project

Pilot-induced oscillations (PIOs) still pose a significant risk to safety of rotorcraft operations, particularly as no formal evaluations are conducted during test and evaluation programs. Usually during experimental flight testing if PIOs are observed, additional testing and evaluations are conducted. This paper details results from a joint research effort undertaken by researchers at the National Research Center Canada (NRC) and the German Aerospace Center (DLR) to investigate and test novel methods and techniques to assess PIOs occurring in rotorcraft. The efforts included modifications to test processes and the use of PIO detection and prediction criteria. The research was conducted using both a ground-based simulation facility and a research helicopter. Results of the campaign showed the suitability of a novel subjective assessment scale and a PIO detection algorithm. This was confirmed through both objective and subjective assessment. Furthermore, modifications to ADS-33 mission task elements were also considered to improve the applicability to testing for PIOs.