This week at Aero Friedrichshafen in Germany, Flight Design unveiled plans to begin test flying a hydrogen-powered version of one of its light airplanes in 2023. While the Hyfly research program prototype on display at the show is a mockup, it still gives some ideas about how the airplane could be configured.
A proof-of-concept Flight Design prototype powered by a battery-electric propulsion system has already flown, but CEO Daniel Guenther believes that whether powered by batteries or hydrogen, a minimum endurance of at least two hours is needed. Existing electric aircraft such as the Pipistrel Velis Electro and its 20-kW battery don’t meet that requirement, he said. “The benchmark is two hours,” he said. “If we achieve that, it will be a true product.”
On display next to the Hyfly mockup is a ball-shaped hydrogen tank made of carbon fiber and measuring 700 mm in diameter. It can hold seven kilograms of pressurized gaseous hydrogen.
According to business development and new products head Mattias Betsch, the HyFly's propulsion system would include a 70-kW electric motor powered by a fuel cell supplied by hydrogen at the rate of about 1.25 kg/hour. Thus a single ball tank could keep the airplane aloft for five or so hours.
A “baffle” battery would provide additional power to the motor during times when the fuel cell can’t react quickly enough. This is “because the fuel cell is not agile in controllability,” he noted. For longer range, an aircraft could carry multiple ball tanks.
Total weight of the propulsion system, not including the motor, is about 50 kg (110 pounds). If this were to become a product, the target would be to sell the propulsion system with the motor for about €50,000.
The demonstrator will seat just one pilot, even though the airplane being used is a two-seater, and it will also be heavier than the 600-kg maximum weight European light aircraft standard.
An unusual feature on the Hyfly mockup airframe is a large air scoop on the belly. This is to provide cooling air to the fuel cell and electrical components, which generate a lot of heat while operating.