Rolls-Royce is accelerating its shift to more environmentally sustainable aviation transportation with a plan, announced at the Paris Air Show, to acquire Siemens’s electric and hybrid-electric aerospace propulsion “eAircraft” business. Terms of the agreement were not disclosed, but Rolls-Royce expects the deal to be completed late this year, “following a period of employee consultation.”

Since 2017, Rolls-Royce (Chalet 93) and the Siemens eAircraft operation have been working together along with Airbus on the E-Fan-X demonstrator, which is a hybrid-electric propulsion test program for a BAe 146 regional jet—one of the jet’s four engines is being replaced with a two-megawatt hybrid-electric powerplant.

Rolls-Royce has conducted ground testing of a hybrid system based on its M250 turboshaft in three different configurations. One is driving a generator that charges onboard batteries (series hybrid); the second is parallel hybrid, with thrust from a combined engine/electrical system; and finally as a turbo-generator, with the engine powering a generator that delivers electricity directly to electric motors and for other onboard power needs.

The impetus for the purchase, according to Rolls-Royce chief technology officer Paul Stein, is that “pressure is on us to increase the environmental performance of all our products.”

While Rolls-Royce is applying this philosophy to products other than turbine engines and not just for aviation, it is focusing on three pillars for aviation: continuing to evolve the gas turbine engine; collaborating on the use of sustainable alternative fuel; and exploring radical alternatives such as electrification. Underpinning these efforts are Rolls-Royce’s “Intelligent Engine” digital technology efforts. 

Rolls-Royce envisions a range of technologies applicable to future aircraft, from more electric architecture for large aircraft that will continue to be powered by efficient turbofan engines to hybrids for regional aircraft and eventually all-electric power for personal air mobility vehicles that will fly from 100 to 600 nm. 

Aviation remains important for Rolls-Royce as it plans on how to integrate the 180 Siemens eAircraft employees. “Flying is not bad for the environment,” Stein said. “CO2 is. Flying can be better. We have to manage emissions and CO2.”

“Electrification is set to have as dramatic an impact on aviation as the replacement of piston engines by gas turbines,” said Rolls-Royce Electrical director Rob Watson. “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.”