LE BOURGET—Daher, Safran and Airbus expect to fly the EcoPulse distributed hybrid-electric propulsion demonstrator on electric power this fall.

The team has completed 30 hr. of flight testing without power to the electric propellers to collect baseline aerodynamic data on the modified TBM 700 turboprop.

Ground testing is beginning on the high-voltage propulsion system, Daher's Head of Design Christophe Robin says. The EcoPulse is equipped with six small propellers on the wing leading edge, driven by 50-kW Safran electric motors that are powered by an Airbus battery pack and a 100-kW Safran turbogenerator.

The EcoPulse is a demonstrator, and the TBM’s Pratt & Whitney Canada PT6A turboprop is retained. This thermal engine will be used for takeoff as the electric propulsion system is not sufficiently powerful, says Robin. In cruise, the turboprop will be shut down and the aircraft will fly on electric power.

Different distributed electric propulsion configurations will be tested in flight to measure their effect, Robin says: all six propellers operating, the outer pair only or the inner four only, with power coming from the battery or the turbogenerator. The inner four propellors are positioned to blow the wing to increase lift coefficient, while the outer pair are used for flight control.

Distributed electric propulsion using leading-edge propellers offers the potential to use a smaller, more heavily loaded wing to improve cruise efficiency while still meeting takeoff and landing requirements. The outboard propellers promise to cut down on cruise-induced drag and allow rudder size to be reduced.

For the team members, the demonstrator configuration allows for multiple possible configurations of electric propulsion to be flight-tested using a single platform, says Eric Dalbies, Safran's executive vice president for strategy and chief technology officer (CTO).

The EcoPulse program is supported by Corac, France’s Council for Civil Aeronautics Research, and co-financed by DGAC—France's Civil Aviation Authority—as well as the France Relance and NextGenerationEU post-pandemic economic recovery packages.

Daher is program leader and responsible for system integration and ensuring safety. Safran has developed the hybrid-electric propulsion system, including the EngineUS-50 electric motors, turbogenerator, power distribution and rectifier system and 800-volt power harnesses. DUC Helices supplied the three-blade leading-edge propellers.

Airbus has developed the high-energy-density battery system, mounted under the fuselage, as well as the flight control computer for thrust management and lateral stabilization of the aircraft. Airbus was also responsible for aerodynamic assessment of the modified TBM, Airbus CTO Sabine Klauke says.

Airbus is also leading psychoacoustic studies of noise perception as well as synchrophasing of the multiple propellers to minimize noise. Klauke says the EcoPulse tests will benefit Airbus’ work on hybrid-electric propulsion under its ZEROe program, and for its helicopters.

A total of 70 hr. of EcoPulse flight testing is planned by mid-2024, Daher CTO Pascale Laguerre says. The company's CEO Didier Kayat has set the target of proposing a hybrid-electric product to the market by 2027, with the objective of accounting for 10% of aircraft sales, Laguerre says.

Daher’s biggest market is the U.S., which is less concerned with sustainability than Europe, but Laguerre says the growth of the electric vehicle market in the U.S. shows that could change. “By 2027 we want to have a product ready if our customers want to jump to hybrid-electric,” he says.