GE Aerospace and its subsidiary Avio Aero have successfully completed the first engine restart test using hydrogen fuel under simulated altitude conditions.

The test, conducted as part of the European Union-funded HYDEA (HYdrogen DEmonstrator for Aviation) project led by Avio Aero, took place at the German Aerospace Center (DLR) Institute of Space Propulsion in Lampoldshausen, Germany.

The firms claim this is a key milestone in the development of hydrogen-powered aviation technology.

Key test establishes relight operability envelope

As GE Aerospace points out in a press statement, hydrogen fuel burns faster and hotter than conventional jet fuel. According to the firm, the new test campaign “addressed one of the most demanding requirements for flying with hydrogen: the ability to relight an engine quickly and reliably in thin, cold air at high altitude.”

For the engine restart test, engineers used a custom hydrogen sector combustor test rig equipped with a synthetic air generator. The system vaporized liquid oxygen and nitrogen to replicate the low-humidity, low-pressure conditions found at altitude.

The test campaign successfully established a relight operability envelope for hydrogen combustion. The ignition system, which was designed and manufactured by Unison (a GE Aerospace company) specifically for hydrogen operation, performed as intended.

The engineers used a multi-cup combustor configuration as it provided a more representative geometry than single-cup setups. This allowed researchers to observe flame propagation and igniter interactions with high-speed cameras. According to GE’s statement, data from these tests will inform the design of a full annular hydrogen combustor rig.

The HYDEA project supports the broader CFM International RISE (Revolutionary Innovation for Sustainable Engines) technology demonstration program, a 50-50 joint venture between GE Aerospace and Safran Aircraft Engines. It aims to demonstrate the feasibility of hydrogen propulsion for aircraft engines through ground testing by 2026.

In a parallel effort under the Clean Aviation project AMBER, teams tested a megawatt-class fuel cell system at DLR’s BALIS facility. The tests validated the system’s dynamic response from idle to maximum power and its performance under simulated short- and long-range flight conditions. AMBER focuses on hybrid-electric propulsion integrating fuel cells, power electronics, and electric drives for regional aircraft.

“Avio Aero and GE Aerospace teams in Europe are proud to be at the forefront of new technology innovation. Together with our European partners and research institutions, we’re turning ideas into real, tested capability,” said Luca Bedon, head of research and technology at Avio Aero.

Roman Seele, future of flight leader for GE Aerospace in Germany, added: “The future of flight is more electric. We’re proud to partner with DLR and others around the world to advance the building blocks to help make hybrid-electric flight a reality.”

Working towards a hydrogen future

These achievements advance multiple Clean Aviation initiatives involving GE Aerospace and Avio Aero facilities across Europe.

As GE Aerospace noted in its statement, the RISE program has accumulated more than 350 tests and 3,000 cycles, targeting over 20% fuel burn reduction compared to current engines through advanced architectures, including open fan, compact core, and hybrid-electric systems.

Hydrogen propulsion offers the potential for near-zero carbon emissions in flight, provided challenges in fuel handling, combustion, and infrastructure are addressed.

Successful altitude relight capability is critical for commercial viability, ensuring reliable engine operation across all flight phases. Further testing and full-scale demonstrations will be required before hydrogen-powered aircraft enter service.

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