Airbus and Rolls-Royce are on track to start modifying a Bae 146/RJ100 airliner into the E-Fan X hybrid-electric demonstrator in 2020 as the engine maker assumes a greater role following its recent acquisition of Siemens’ eAircraft unit, a former partner in the project.

Siemens, which developed the electric drivetrain for the demonstrator, had already reverted to becoming a supplier to the demonstrator project when Rolls purchased the German company’s electric propulsion operations. Under the revised arrangement, Rolls will continue to oversee the power generation system and associated power electronics and now has complete responsibility for the electric propulsion unit, including a 2 megawatt e-motor and inverter.

Airbus is responsible for the overall integration of the hybrid electric propulsion system into the aircraft and the system’s lithium-ion battery pack as well as the 3 kilovolt AC/DC distribution network, harnesses and power distribution center. Both companies collectively take care of thermal management and the control architecture.

The 2.5 megawatt turbogenerator at the heart of the demonstrator is based on a Rolls’ AE2100 turboprop from a Saab 2000 mounted in the rear fuselage and provides electricity to the battery pack mounted under the cabin floor and an electric motor that replaces one of the aircraft’s four Honeywell LF507 turbofans. The motor will power a fan from a Rolls AE3007 which will be mounted in an inboard nacelle.

“This is an incredibly challenging task for our teams,” Airbus chief technology officer Grazia Vittadini said. Flight testing which begins in 2021, will focus particularly “on handling power transients which are critical on something like this.”

Rolls CTO Paul Stein said the E-Fan X “gets us into the megawatt class of electrical systems which is breakthrough technology for the future.”

The company is testing a full-scale, flight representative thermal rig at its Indianapolis facility and has completed testing of a hybrid-electric engine control system in Derby, UK. Testing of the 2.5 megawatt generator will be completed at Rolls’ Trondheim site in Norway.