H2FLY announces first successful test flight with liquid H2

In cooperation with partners, H2FLY has announced the completion of what it claims is the world's first flight of a manned electric aircraft powered by liquid hydrogen. The test flights are intended to indicate that the maximum range of the demonstration aircraft can be doubled from 750 to 1,500 kilometres.


H2FLY is known to be a Stuttgart-based company specialising in the development of hydrogen fuel cell systems for aircraft. Together with partners from the ‘HEAVEN’ project, the company now reports its first flights with liquid, cryogenic hydrogen (LH2) as fuel. This is “another important step on the way from demonstration flights operating at lower altitudes to commercial aircraft applications”, the Stuttgart-based company emphasises.

The demonstration aircraft HY4, which has been taking off regularly for test purposes with pressurised tanks since 2020, was used in the test flight campaign. Among other things, the HY4 has already completed a 124-kilometre non-stop flight with gaseous hydrogen from its home airport in Stuttgart to Friedrichshafen for the AERO. Now that the test carrier has been fitted with an LH2 tank system (H2FLY already informed about progress in the integration of liquid hydrogen tanks in the summer of 2022), the tension has increased once again. In total, the HY4, which had been converted in this way, completed four flights powered by liquid hydrogen – including one flight that lasted over three hours.

The testers found that “the hydrogen-electric ‘HY4’ demonstrator aircraft took off from Maribor, Slovenia, and saw safe and efficient operation throughout multiple flight tests,” as H2FLY wrote. From the test flights, the Stuttgart-based company deduces that by using liquid hydrogen instead of gaseous hydrogen, the maximum range of the demonstration aircraft can be doubled from 750 to 1,500 kilometres.

The background to the LH2 initiative is that the use of liquid, cryogenic hydrogen enables significantly lower tank weights and volumes compared to the storage of gaseous hydrogen under high pressure (GH2), which results in an increased range and payload of the aircraft. The results now achieved with the HY4 represent, in the view of the initiators, a decisive step on the way to emission-free, commercial medium- and long-haul flights.

“This achievement marks a watershed moment in the use of hydrogen to power aircraft. Together with our partners, we have demonstrated the viability of liquid hydrogen to support medium and long-range emissions-free flight,” affirms Josef Kallo, co-founder of H2FLY. “We are now looking ahead to scaling up our technology for regional aircraft and other applications, beginning the critical mission of decarbonizing commercial aviation.”


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