Author Description

This report documents comparisons of flight and ground-based Pilot- Induced Oscillation (PIO) evaluation methods. The study was to develop and modify ground-based simulation methods to improve the likelihood of early PIO detection. The study strickly looked into the linear causes of longitudinal PIOs due to phase lag or high time delays as opposed to nonlinear PIO types such as rate limiting or mode switching. The results of the ground-based simulation were compared with data taken from the HAVE PIO flight test program. The flight test program was well documented and provided a good basis from which to establish a ground simulation. The PIO tendencies of flight test configurations ranged from none to severe. The wide range of PIO tendencies was important to preclude an evaluation process which would result in false PIO predictions. Comparisons were based on Cooper-Harper and PIO ratings which were validated by time history data and pilot comments. Trends were established which led to several proposed evaluation concept such adding gates at the offset corrections, time delays, and winds, gusts and turbulence to the model, and increasing pilot stick gain to make ground-base simulators a more effective tool for detecting PIO.