The goal of ‘RETAX’ was to explore intrinsically safe and efficient solutions for mid-size rotorcraft autonomous taxiing on ground, minimising the overall weight of the system, based on an electrically powered motorised wheel integrated with the landing gear. Subsequently to select the most promising solution and develop it into a technical demonstrator to be tested and verified.

The former experience of Michelin in electric-drive solutions for motorized cars, busses and aircraft was used and translated into a rotorcraft electric taxiing system. A high level of integration and performance was reached in order to be able to achieve an optimal solution. A key success factor was the control of the complete chain, from the power electronic to the wheel, through electrical motor and gearbox in order to reach the global optimisation customised for this specific application.

After a preliminary study to define the optimum feasible concept and architecture for the motorised wheel and power electronics, including the voltage level choice (28 Vdc or 270 Vdc), a detailed analysis and simulation of the intended solution was performed. A real demonstrator of the electric-drive system was designed, engineered and built to physically test and prove the intended performance, the fulfilment of all requirements and also to calibrate the simulation models. The protections for high-voltage human safety (270 Vdc) was included in the demonstrator, if high voltage is used. An extrapolation study towards larger size rotorcraft was performed. This feasibility demonstration of electrically driven rotorcraft ground taxiing in accordance with Clean Sky electrification objectives was a significant step towards greener rotorcraft operations, bringing this technology closer to the market, and creating European competitive advantage.