Rotorcraft-pilot coupling research in Europe: A success story in collaboration

For augmented helicopters with modern flight control systems, unintended and unexpected oscillations or divergences of the pilot-rotorcraft system have become an increasingly critical issue. Especially 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 unfavourable Aircraft-Pilot Coupling (APC) and Rotorcraft-Pilot Coupling (RPC). The understanding, prediction and prevention of adverse RPCs is a challenging task requiring the analysis and simulation of the complete closed loop system consisting of pilot – control system – rotorcraft. In Europe, comprehensive research activities were launched by the GARTEUR HC AG-16 action group (2005-2008) in order to improve the physical understanding of RPCs. Overall objectives of GARTEUR HC AG-16 were the definition of criteria for quantifying the helicopters’ susceptibility to RPC and the establishment of guidelines for preventing or suppressing critical RPC incidents in future, thus contributing to increased helicopter operational safety. The GARTEUR research was further continued under the umbrella of the 7th European Framework Programme (FP7) in the project ARISTOTEL - Aircraft and Rotorcraft Pilot Couplings – Tools and Techniques for Alleviation and Detection (2010-2013). Regarding numerous flight events in the past, several types of RPCs have been observed which can be differentiated by the frequency contents as well as by the underlying physics and human behaviour. Focus in the GARTEUR HC AG-16 group was given on the one hand to RPC phenomena in the frequency range up to approximately 1 Hz and on the other hand to coupling phenomena approximately between 2 Hz and 5 Hz. This paper presents an overview of the various numerical and experimental activities of research. Selected results are highlighted and discussed demonstrating the used approach to investigate different RPC phenomena in a schematic manner.