Overview
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.
Funding
Results
Executive Summary:
In the view of meeting the ACARE goals and radically reducing the impact of air transport on the environment, one concept being investigated was to move towards electrical aircraft. Innovative solutions and breakthrough technologies will have to demonstrate overall increase of efficiency and reduction of undesirable emissions. The current trend to evolve towards electrically controlled and actuated aircraft is an ongoing process. These electric systems are lighter, thus enabling to achieve significant savings in fuel consumption. Other advantages include reduced maintenance costs and easier monitoring.
On-board electrical systems are very common in the entire airplane. Electrical taxiing is just another electrifiable function; electrical braking or electrical flying controls are other examples. Electric taxiing is an alternative method of manoeuvering rotorcraft on ground, without any spinning from the rotor.
The main advantages identified consist of:
- Suppressing noise on ground generated by the high-speed turning rotor
- Improving ground personnel safety by suppressing main and tail rotor rotation
- Reducing fuel consumption during taxiing, using an efficient motion system
- Allowing autonomous on ground movement, even backward without external means
This technology is based on an electrically powered motorized wheel integrated within the landing gear, relying on an electrical energy source.
Electric ground taxiing offer an improve solution, which enables to reach simultaneously extended autonomy with the helicopter, noise and emission reduction, increasing safety on the airport.
With the RETAX project, feasibility has been demonstrated, using intrinsically safe and efficient solutions for rotorcraft autonomous taxiing on ground, minimising the overall weight of the system, based on an electrically-powered motorised wheel, integrated within the landing gear.
This has been done through testing of a complete manufacture landing gear for heavy rotorcraft including motorised wheel, and reaching a TRL4 level, demonstrating the confidence in the solution. The full system has been tested on a face to face and dyno test-bed. The critical safety aspects have been demonstrated as well, related to the undesired events.
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.