Adverse Rotorcraft-Pilot Coupling: Recent Research Activities in Europe

Unintended and unexpected oscillations or divergences of the pilot-rotorcraft system have become a critical issue for augmented helicopters with modern flight control systems. The rapid advances in the field of high response actuation and highly augmented flight control systems have increased the sensitivity to aspects that lead to complex oscillations related to unfavourable Aircraft-Pilot Coupling (APC) and Rotorcraft-Pilot Coupling (RPC) events. The understanding, prediction and prevention of adverse RPCs are demanding tasks and require the analysis and simulation of the complete feedback loop: pilot - control system - rotorcraft. Based on numerous flight events in the past, several types of RPCs have been observed differing in their frequency content as well as in the underlying physics and human behaviour. In Europe, research activities were launched in 2005 under the umbrella of the GARTEUR organisation in order to improve the physical understanding of RPCs and to define criteria for quantifying the helicopters susceptibility to RPC. This paper is intended to give an overview of the various numerical and experimental activities of the research group HC AG-16. Selected results are highlighted and discussed demonstrating the approach used to investigate different RPC phenomena in a systematic manner.