H2FLY, the Stuttgart, Germany-based developer of hydrogen-electric powertrain systems for aircraft, has successfully completed the world’s first piloted flight of an electric aircraft powered by liquid hydrogen. The H2FLY team has completed four flights powered by liquid hydrogen as part of its flight test campaign, including one flight that lasted for more than three hours. The flights were completed with H2FLY’s piloted HY4 demonstrator aircraft, fitted with a hydrogen-electric fuel cell propulsion system and cryogenically stored liquid hydrogen that powered the aircraft.
Results of the test flights indicate that using liquid hydrogen in place of gaseous hydrogen will double the maximum range of the HY4 aircraft from 466 miles (750 km) to 932 miles (1500 km), marking a critical step toward the delivery of emissions-free, medium- and long-haul commercial 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,” said Professor Josef Kallo, cofounder 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.”
The successful campaign marks a significant milestone for H2FLY, reflecting the extensive insights from the company’s research efforts. It is the culmination of Project HEAVEN, a European government-supported consortium assembled to demonstrate the feasibility of using liquid, cryogenic hydrogen in aircraft. The consortium is led by H2FLY and includes the partners Air Liquide, Pipistrel Vertical Solutions, the German Aerospace Center (DLR), EKPO Fuel Cell Technologies, and Fundación Ayesa.
Beside project HEAVEN, the work has been funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK), the German Federal Ministry for Digital and Transport (BMVD), and The University of Ulm.
H2FLY said that, compared with pressurized gaseous hydrogen storage, the use of liquified, cryogenic hydrogen enables significantly lower tank weights and volume, therefore leading to increased aircraft range and useful payload.
“Air Liquide is proud to have designed, manufactured, and integrated, together with H2FLY, the liquid hydrogen tank that powered the HY4 aircraft,” said Pierre Crespi, innovation director at Air Liquide Advanced Technologies. “Today’s success demonstrates the full potential of liquid hydrogen for aviation. Liquid hydrogen can be stored onboard and transported. Hydrogen is key to the energy transition and this new step proves that it’s already becoming a reality.”
“DLR boasts extensive expertise in electrified aircrafts, with a track record spanning more than 15 years,” said Dr. Syed Asif Ansar, head of Department Energy System Integration at the DLR. “Starting from the inaugural flight of the Antares DLR-H2 in 2009, consistent advancements have been made in fuel cells and their auxiliary systems. This progressive journey culminates in a significant present achievement in aviation history: the use of cryogenic liquified hydrogen as fuel storage for a four-seater aircraft powered by fuel cells. Collaborating with H2FLY, AirLiquide, and other project members, DLR is actively engaged in projects aimed at propelling the development of CS-23 and CS-25 fuel cell powered aircraft into the next phase.”
With the completion of the flight testing in project HEAVEN, H2FLY will focus on the path to commercialization. In June, H2FLY announced the development of its new H2F-175 fuel cell systems which will be capable of providing their full power range in flight altitudes of up to 27,000 ft. (8230 m), marking an important step on the path from lower-altitude viability flight demonstrations to real-world commercial aircraft applications.
In 2024, H2FLY will open its Hydrogen Aviation Center at Stuttgart Airport, co-funded by the Ministry of Transport Baden Württemberg. The center will become a focal point for the future of Europe’s aviation industry and its hydrogen economy, providing fuel cell aircraft integration, facilities, and liquid hydrogen infrastructure.