H2Fly is one step closer to realizing true liquid hydrogen flight

Stuttgart-based H2Fly has reached another critical milestone with the successful test refueling of its cryogenic storage for liquid hydrogen.
Christopher McFadden
Liquid hydrogen flight is now one step closer.


H2Fly, a company that makes hydrogen-powered planes, has successfully tested its cryogenic hydrogen refueling procedure on the ground. This is an essential prerequisite for the company's planned test flights in the coming months.

If the test flights also prove successful, it will be an important stepping stone towards a future of cleaner (with regards to fossil fuel emissions) long-haul flights. With so much pressure to reduce carbon emissions in the aviation industry, it would be great if hydrogen-powered planes could be made and used.

And hydrogen is the only viable solution, as other options, like pure electricity, aren't feasible, according to experts. This is for various reasons, among them being that batteries are heavy. For this reason, hydrogen power could be a sort of "holy grail."

Hydrogen has about 2.8 times the energy per unit of weight as current liquid fuels. However, even after being cryogenically cooled into a liquid, it still occupies a sizable amount of space (about 3.7 times more than jet gasoline). Since hydrogen can only remain a liquid at temperatures below -423.4 °F (20 kelvin or -253 °C ), it is light but takes up a lot of space, and some of the weight savings are lost once you consider the entire system.

For this reason, most new hydrogen aviation companies have studied it, bookmarked it, and moved on with making their planes work on gaseous hydrogen instead. Without dealing with a cryogenic liquid, there is more than enough work to demonstrate that the rest of these systems, from fuel cells and storage to electric propulsion, which are certifiably safe and ready for prime time.

But, this is where H2fly comes into its own by being willing to take on the challenge. After completing the first manned, wholly hydrogen-powered flight in 2009 and more recently conducting groundbreaking research with a gaseous hydrogen system integrated into a twin-fuselage Pipistrel Taurus G4 aircraft, the company has now equipped the same HY4 aircraft with a liquid storage system from Air Liquide and hopes to lead the charge back into the skies with liquid H2.

The statement made today concerns the accomplishment of ground-based fuel-filling tests. The cryogenic tank, which is alone in the left fuselage and is well isolated from the pilot in the right fuselage, has already undergone extensive vibration and leak testing by the business.

“The successful on-ground filling tests today mark the next milestone in our pursuit to doubling the range of our HY4 aircraft," explained Prof. Dr. Josef Kallo, co-founder and CEO of H2FLY. "It is a critical step for our upcoming flight test campaign this summer, [demonstrating] the feasibility of liquid hydrogen as a medium and long-haul flight fuel,” he added.

If the HY4 launches as scheduled this summer, it will be the first human-crewed flight of a passenger airplane powered by liquid hydrogen in history. The green transition will significantly benefit from this groundbreaking effort.

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