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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →H2FLY’s piloted HY4 demonstrator completed four flights powered by liquid hydrogen during a September 2023 campaign in Maribor, Slovenia. One flight lasted more than three hours. The milestone was the first piloted flight of a liquid-hydrogen-powered electric aircraft, according to the European Union Aviation Safety Agency (EASA)—not a commercial airliner flight or a demonstration of a 1,500-kilometre journey.
What was the world’s first liquid-hydrogen aircraft flight?
It was a flight-test campaign by H2FLY, a hydrogen-electric aviation developer, using its experimental HY4 aircraft. The aircraft’s fuel-cell propulsion system used hydrogen stored onboard as a cryogenic liquid. H2FLY announced four liquid-hydrogen flights at Maribor, Slovenia, in September 2023; H2FLY and Germany’s aerospace center, DLR, report that the longest lasted more than three hours. EASA independently described the event as the first piloted flight of a liquid-hydrogen-powered electric aircraft.
The full European HEAVEN project campaign included seven flights: three using gaseous hydrogen and four using liquid hydrogen, according to the European Commission’s CORDIS project-results summary. The achievement was the integration of a piloted aircraft, fuel-cell electric propulsion and onboard cryogenic storage under flight-test conditions. It did not certify an aircraft for commercial service.
How does the HY4’s hydrogen-electric system work?
Instead of burning hydrogen in a conventional jet engine, the HY4 used a fuel cell to produce electricity for its electric propulsion system. The hydrogen was carried as a cryogenic liquid, rather than as compressed gas. The fuel cell’s operation also involves managing air, fuel, water and heat—systems that must meet aviation requirements for reliability, safety and weight.
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Liquid storage can reduce the tank’s weight and volume compared with pressurized gaseous storage, potentially leaving more room for range or useful payload. That potential comes with its own engineering demands: cryogenic tanks and insulation, safe handling, venting and compatible ground equipment. The HY4 campaign showed that these elements could be operated together in experimental flights; it did not settle the design or certification challenges for commercial aircraft.
How far can H2FLY’s HY4 fly on liquid hydrogen?
H2FLY and DLR reported a maximum-range comparison of 750 kilometres with gaseous hydrogen versus 1,500 kilometres with liquid hydrogen for the HY4. They presented liquid hydrogen as potentially doubling the aircraft’s maximum range. The 1,500-kilometre figure is a reported comparison for this aircraft configuration, not a distance demonstrated during the campaign, an independently verified commercial range or a general performance rule for hydrogen aircraft.
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What still stands in the way of hydrogen-electric commercial aircraft?
Fuel-cell systems and aircraft safety
HEAVEN project coordinator Maria Sol Rau told CORDIS that fuel-cell air, fuel, water and thermal management must improve to meet aviation reliability, safety and weight standards. Aircraft also need effective safeguards for cryogenic hydrogen storage and venting. A successful demonstrator flight does not by itself show that a system meets certification requirements or can be operated routinely at airline scale.
Airport operations and hydrogen supply
Aircraft using liquid hydrogen require suitable ground equipment and refuelling arrangements. CORDIS identifies airport infrastructure, along with sufficient production, storage and distribution of green liquid hydrogen, as necessary for wider use. The test campaign involved project-specific tank and ground-support equipment; it did not establish a ready-made airport network.
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- The Hydrogen fuel trolley uses zinc particles and food grade citric acid to synthesize hydrogen, and then uses the produced hydrogen and air to generate electricity to drive the trolley.
- During the experiment, please use 80℃ hot water for Combination reaction (if the water temperature is low, the amount of hydrogen and air pressure from the Combination reaction are insufficient, the fuel cell cannot be used for power generation), and then take off the plug of the vent pipe at the lower part of the fuel cell, release the gas in the rubber hose immediately, and then plug it back immediately, so that only pure hydrogen and air are in the fuel cell, so that the fuel cell can generate hydrogen air power.
Certification, scale and commercial service
Moving from a test aircraft to passenger service entails aircraft and system development, certification, operational procedures, fuel supply and commercial economics. H2FLY’s current company page describes certification-ready components as a 2028 objective and potential initial commercial flights from 2030 onward. These are company-stated plans, not guaranteed dates or proof that a commercial aircraft is certified or in service.
Does liquid hydrogen make commercial flights emissions-free?
The campaign demonstrated flight using a hydrogen-electric system; it did not establish lifecycle emissions for the hydrogen supply or the aircraft and airport system. A fuel cell’s operation produces water vapour as a by-product, as CORDIS notes, but the wider climate impact depends in part on how hydrogen is produced and delivered. CORDIS specifically identifies green hydrogen production and suitable infrastructure as requirements for broader deployment. The demonstrator’s result should therefore be read as a propulsion and storage milestone, not proof of zero lifecycle emissions for commercial flights.
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- The Hydrogen fuel trolley uses zinc particles and food grade citric acid to synthesize hydrogen, and then uses the produced hydrogen and air to generate electricity to drive the trolley.
- During the experiment, please use 80 ℃ hot water for Combination reaction
- And then take off the plug of the vent pipe at the lower part of the fuel cell, release the gas in the rubber hose immediately, and then plug it back immediately, so that only pure hydrogen and air are in the fuel cell, so that the fuel cell can generate hydrogen air power.
Who built and supported the HY4 liquid-hydrogen test?
H2FLY led the European-supported HEAVEN project. CORDIS says Air Liquide Advanced Technologies designed and built the liquid-hydrogen tank and ground-support equipment used for refuelling. Pipistrel Vertical Solutions integrated the tank into the test aircraft and carried out aircraft modifications and structural safety tests. DLR provided test facilities and infrastructure and said the experimental data would inform its work on fuel-cell control algorithms. CORDIS lists HEAVEN as closed, with a project end date of September 30, 2023.
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