On a chilly day in mid-December, key stakeholders gathered together at a Daher hangar in Tarbes, in southwest France, to bid adieu to the EcoPulse demonstrator during a livestream wrap-up.

A distributed hybrid-propulsion aircraft demonstrator, EcoPulse was designed and developed jointly by Airbus, Daher and Safran. Leaders from all three companies were on stage to share their perspectives on the programme, including Airbus’ own Jean-Baptiste Manchette, Head of Propulsion of Tomorrow.

The atmosphere on-site buzzed with excitement, with around 50 people gathered to watch the event live, over five years after EcoPulse was first announced at the 2019 Le Bourget Paris Air Show. But before we get into the flight test results, first let’s have a quick refresher on what EcoPulse was testing, and the technical design aspects of the aircraft.

What was EcoPulse?
The EcoPulse demonstrator was a modified Daher TBM 900 Turboprop aircraft that aimed to evaluate the potential benefits of distributed hybrid-electric propulsion, as well as the possibility of integrating certain related technology bricks into future aircraft. Distributed propulsion systems work by breaking down thrust generation between multiple small engines located along the wings. Airbus, Daher and Safran believe that this technology could unlock improved aircraft performance, particularly in regards to cabin noise and energy savings.

To assess this, the three partners divided the work of developing the demonstrator along their different areas of expertise: Safran was in charge of developing the distributed hybrid-electric propulsion system, including the six wing-mounted e-propellers, while Airbus Defence and Space contributed the 800-volt, high-energy-density battery that was used to power the propulsion system. This battery was capable of delivering 350 kilowatts of electricity, allowing it to power all six e-propellors in flight. Airbus developed the flight control computer system and handled the aerodynamic and acoustic integration of the distributed-propulsion system. Daher, for their part, integrated Airbus and Safran’s modifications into the airframe and handled all flight and airworthiness testing.

Key takeaways
The flight test campaign lasted eight months, running from November 2023 to July 2024. 50 test flights were performed, which added up to around 100 flight hours. Several different types of testing took place during flight, examining the effects of the distributed propulsion system on aerodynamics, efficiency, noise and more. Many of the results were positive, so let’s head back to the hangar in Tarbes to hear more about what we’ve learned.

A leap forward for battery technology
“The battery is one of the key parts of hybridisation, and the way to master how to design, manufacture and clear it for flight is really important for us,” Jean-Baptiste explained to the audience. The customised lithium-ion battery had to be designed entirely in-house by Airbus Defence and Space, as the technology does not currently exist on the market. Standard battery technology for aircraft is focused on low-voltage, low-energy-density batteries mainly used to start the auxiliary power unit (APU) or during emergencies. Larger batteries, like those used in the automotive industry, are too heavy and bulky for use on aircraft. Christophe Robin, Head of Aircraft Design at Daher, summarised exactly why the EcoPulse battery is such a big deal while on stage: “Usually, on a light aircraft, we use a 28-volt battery. On a commercial aircraft, we use 115-volt AC as the standard. What we are using here [on EcoPulse] is 800 volts [DC], and that is a completely different story.”

And the story has a happy ending. The battery control models were successfully validated during the flight testing, and the EcoPulse project proved that a battery of such power can be safely integrated into an aircraft and flown without compromising any safety standards.