Europe’s Distributed Electric Propulsion Testbed Flies

A subscale flight demonstrator of distributed electric propulsion for large passenger aircraft has made its remotely piloted first flight in Italy under Europe’s Clean Sky 2 public-private research program.

The aircraft was originally built under Clean Sky 2’s Scaled Flight Demonstrator (SFD) project. This started with a dynamically scaled, electrically powered model of the Airbus A320, the D03, which was flown in 2022 to validate that scaled demonstrators could be used as a lower-cost method of flight-testing unconventional configurations.

With a wingspan of 4 m (13 ft.) and takeoff weight of 140 kg (310 lb.), the 12%-scale D03 was then modified into the Scaled Flight Demonstrator-Distributed Electric Propulsion (SFD-DEP), or D08, with the maximum reuse of components, including the electrical system. Taxi tests began at the Dutch aerospace center Royal NLR in March 2023 but in May the aircraft was destroyed in a battery fire.

Designed to de-risk the handling qualities of distributed electric propulsion, including the use of differential thrust for flight control, the 167-kg D08 has six propellers mounted on the wings. The two outboard propellers are mounted on the wingtips to reduce induced drag and are smaller in diameter to improve ground clearance.

The SFD-DEP was destroyed in the ground fire, but was insured, so the project team decided to rebuild the aircraft. The electrical system was made more robust, with improved batteries and wiring as well as additional monitoring and protection. The 10-min first flight of the rebuilt aircraft was conducted May 2 in Italy by SFD project leader NLR.

Applied to a full-size aircraft, distributed electric propulsion is expected to reduce energy consumption by 20%, NLR says. Instrumented flights of the SFD-DEP will evaluate which control algorithms yield the most significant benefits and whether the aircraft can be controlled effectively using differential thrust on the propulsors.