Drives and Controls Magazine
Rolls-Royce buys Siemens’ electric aircraft business
Published:  19 June, 2019

Rolls-Royce has agreed to buy Siemen’s electric and hybrid-electric aerospace propulsion activities for an undisclosed sum. The move – announced at the Paris Air Show – is aimed at accelerating Rolls’ electrification strategy and boosting its ambition to become the leading supplier of electric and hybrid-electric propulsion systems for aircraft and to play a major role in the “third era” of aviation. The acquisition is expected to complete late 2019, following a period of employee consultation.

The business – which Siemens calls eAircraft – is based in Germany and Hungary, and employs around 180 electrical designers and engineers who have been developing all-electric and hybrid-electric propulsion systems for the aerospace industry for about ten years. The eAircraft team has already worked with Rolls-Royce and Airbus (with which it entered a development partnership in 2016) on the E-Fan X project which is designed to demonstrate hybrid-electric propulsion at the scale needed to power regional aircraft.

The eAircraft business has been working with various partners to create prototypes for propulsion systems with power ratings ranging from less than 100kW to several thousand kilowatts. One example is Airbus’ CityAirbus ­– a four-seater “multicopter” that is intended to advance remotely piloted electric vertical take-off and landing (eVtol) flight. A full-scale demonstrator of the CityAirbus took off for the first time last month when it performed a “tethered jump”.

Siemens says that the eAircraft business will have substantially better growth prospects under an owner that is more closely connected to the aerospace industry. “Our eAircraft team, under the leadership of Frank Anton, has made aviation history several times in the past ten years and is a pioneer in electric and hybrid-electric systems for aircraft,” says Siemens’ chief technology officer and chief operating officer, Roland Busch. “With Rolls-Royce, we've found a perfect home for this business and have placed its expertise in the hands of one of Airbus’ close partners. We will continue to cooperate with Rolls-Royce – in particular by making our digital solutions portfolio available in order to facilitate this major step toward sustainable, lower-emission aviation."

Rolls-Royce Electrical director, Rob Watson, predicts that electrification will have as dramatic an impact on aviation as the replacement of piston engines by gas turbines. “We are at the dawn of the third era of aviation, which will bring a new class of quieter and cleaner air transport to the skies,” he says. “We have already made significant strides in realising our strategy of ‘championing electrification’ and this move will accelerate our ambitions in aerospace by adding vital skills and technology to our portfolio.”

Watson adds that the acquisition “brings us increased scale and additional expertise as we develop a product range of hybrid power and propulsion systems. I look forward to welcoming our new colleagues into Rolls-Royce and working with them to pioneer new technologies and solutions.”

Siemens' eAircraft team has been working with Airbus on this remotely controlled four-seater "electric taxi", called the CityAirbus, which took off for the first time last month.Photo: Airbus helicopters

“The electrification of flight is just one part of Rolls-Royce’s commitment to making aviation more sustainable,” points out Rolls-Royce’s chief technology officer, Paul Stein. “We are continuing to increase the fuel efficiency of our gas turbines, encouraging the development of environmentally friendly and sustainable aviation fuels, and pursuing the electrification of aviation.

“We believe that pure electric, or all-electric, propulsion will power smaller aircraft in the foreseeable future, while larger aircraft will rely upon hybrid electric solutions that combine electrification with evolutions of the gas turbine,” Stein continues. “Additionally, as our group technological portfolio becomes increasingly electrical with the development of hybrid electric trains and microgrids, the capabilities of this world-class team will be a vital part of the future Rolls-Royce.”

Rolls Royce has already performed successful ground tests of a hybrid propulsion system that can be used in smaller transport platforms including hybrid eVtols, general aviation aircraft, and hybrid helicopters. These tests are part of one of the world’s most comprehensive development and integration programmes on hybrid turbine engines, paving the way for experimental test flights in 2021.

The ground tests involved a Rolls-Royce M250 gas turbine operating in series-hybrid configuration, where the engine operates as a turbo-generator that charges an on-board battery system; as a parallel hybrid, where the aircraft’s thrust is supplied by a combination of the engine and the electrical system; and in a turbo-electric mode, where the engine operates as a pure turbo-generator supplying electric power for thrust and other power needs on the aircraft.

Last year Rolls-Royce unveiled an eVtol concept, which could be powered by such a hybrid system. It is also developing an all-electric demonstrator aircraft, as part of the Accel initiative that will attempt to break the world speed record for all-electric flight next year.