Development and Inflight-Evaluation of a Haptic Torque Protection Corresponding with the First Limit Indicator Gauge

The First Limit Indicator gauge of modern Eurocopter helicopters displays torque and associated engine limits to the pilot. In DLR's Flying Helicopter Simulator, based on a EC135, it was now complemented by a haptic cue on the collective controller. The system was evaluated in ground-based simulation and demonstrated and evaluated in-flight. The development included the identification of a polynomial based torque prediction algorithm and a limit blending logic. The predictive polynomial is sufficient to approximate the quasi-steady torque for the evaluated maneuvers. The evaluation showed a significant reduction in pilot workload, expressed as NASA Task Load Index. The quantitative evaluation of the flight test and simulation data showed a better use of the available power with the haptic torque protection available. Suggestions for an optimization of the system are made.