A Time-Frequency Domain Approach for PIO/PAO Detection and Analysis

Adverse pilot-vehicle interaction is an important topic, as its impact ranges from handling qualities degradation to potential loss of control. Typical rotorcraft-pilot couplings events are intrinsically time dependent, although characterized by intrinsic frequency aspects, at least when an oscillatory behavior is involved, as in Pilot Induced and Augmented Oscillations. As such, methods capable of simultaneously capturing frequency and time domain related aspects are desirable. In this work, the computation of indicators for the identification of the insurgence of pilot-induced oscillations are revisited in terms of power spectral density, in the frame of ergodic processes. Since the assumption of ergodicity does not apply to intrinsically time-dependent phenomena, Wavelet Transform is used to compute corresponding time-dependent indicators. The suitability of this approach is checked by considering its application to the analysis of signals measured during piloted flight simulation tests in which adverse pilot-vehicle interactions were observed. The results obtained so far are quite promising, suggesting the opportunity to further investigate the approach.