On 29 September 2016, the HY4 aircraft took off on its first official flight from Stuttgart Airport. The HY4 is the world’s first four-seat passenger aircraft powered solely by a hydrogen fuel cell system. Researchers from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) developed the aircraft’s powertrain and worked on the project with industry and research partners.
The HY4 fuel cell aircraft was developed by the DLR Institute of Engineering Thermodynamics together with partners Hydrogenics, Pipistrel, H2FLY, the University of Ulm and Stuttgart Airport. DLR researchers were responsible for developing the hydrogen fuel cell power train and installing it in the aircraft.
The powertrain consists of a hydrogen storage system, a low-temperature hydrogen fuel cell and a battery. The fuel cell converts hydrogen directly into electrical energy. The only waste product from this process is water. An electric motor uses the power thus generated to propel the aircraft.
A high-performance lithium battery covers peak power loads during take-off and when climbing. If the hydrogen required for the fuel cell is generated via electrolysis using power from renewable energy sources, the HY4 can fly without generating any emissions at all. The aircraft is operated by the DLR spin-off H2FLY.
The HY4 has a motor output of 80 kW, a maximum speed of approximately 200 kilometers per hour and a cruising speed of 145 kilometers per hour. Depending on speed, altitude and load, it can achieve a range of between 750 and 1500 kilometers.
The most striking feature of the HY4 is its twin fuselages, each with space for two passengers. The maximum weight of the aircraft is 1500 kilograms.
With the HY4, we now have an optimal platform to continue developing the use of fuel cells on aircraft. Small passenger aircraft, such as the HY4, could soon be used in regional transport as electric air taxis and offer a flexible and rapid alternative to existing means of transport.—Josef Kallo, responsible for the HY4 project at DLR and a Professor at the University of Ulm