Fuel cell aircraft presented at Stuttgart Airport
Eco-friendly and silent propulsion system receives permit for test flight

Ulm University

Climate-friendly flights could soon become commonplace throughout Europe. On December 11, the latest generation of the world’s first four-seater hydrogen fuel cell aircraft, the Hy4, was presented at Stuttgart Airport in a predominantly virtual event. The alternative propulsion system consisting of a battery fuel cell system was developed under the leadership of Professor Josef Kallo, who conducts his research at Ulm University and the German Aerospace Center (DLR) in Stuttgart. The latest generation of Hy4 drives only recently received its test flight permit, allowing it to take off from Stuttgart Airport.

Andreas Scheuer, Federal Minister of Transport and Digital Infrastructure, congratulated the company on this important step towards eco-friendly flying by sending a video message. “The Hy4 hydrogen aircraft is innovative, quiet and climate-friendly. It shows that CO2-free aviation is already possible and feasible at present. This new method of flying has what it takes to change mobility in the long term. Germany is a pioneer in this high-tech field: The Hy4 is the world’s first four-seater passenger aircraft to fly entirely on electricity powered by fuel cells. This is the power of innovation made in Germany, and secures jobs and creates value in our country.”

The maiden flight of the Hy4 hydrogen passenger aircraft at Stuttgart Airport was a minor sensation in 2016. The four-seater aircraft’s most recent test flights took place in November in Maribor, Slovenia, silently and with zero emissions. The Hy4 is powered by a hybrid system that combines battery and fuel cell technology. If the energy generated in this way is not sufficient - for example, during take-off or when climbing - the lithium-ion battery kicks in. In the fuel cell, hydrogen and oxygen are converted into electrical energy for the propeller drive. The eco-friendly by-product is water. To date, the functionality of the new propulsion system has been tested and examined during more than 30 take-offs and flights of up to 2 hours. 

During the presentation at the airport, Baden-Württemberg’s State Minister of Transport, Winfried Hermann, praised the scientific accomplishments behind the Hy4: “Air traffic must become more climate-friendly as quickly as possible. With the Hy4 hydrogen fuel cell aircraft, the only one of its kind in the world, the scientific community is presenting a promising technology for emission-free flying. With this expertise, Baden-Württemberg is a globally competing pioneer in the field of hydrogen and fuel cell technology.”

The first milestone of the Hy4 project was supposed to be regionally deployable air taxis for individual passengers. But since the first flight of an aircraft with a fuel cell in 2008, Kallo and his partners from the research and industry sectors have made massive advances in the pioneering propulsion technology. “Now in its sixth generation, the system incorporates redundancy concepts for the hydrogen tank, fuel cell, power distribution and the electric propulsion system. This increased efficiency and improved safety architecture will make hydrogen-powered aircraft for up to 40 passengers and with ranges of 2,000 kilometres possible in the next 10 years,” explains Professor Kallo, director of the institute in Ulm. 

The electric motor and the energy distribution unit of the Hy4 were developed, tested under laboratory conditions and put into operation at the Institute of Energy Conversion and Storage at Ulm University. The electric motor has an output of 120 kilowatts, enabling a maximum speed of 200 kilometres per hour. Most of the basic fuel cell research and the interconnection of the components took place at the German Aerospace Center. H2FLY GmbH, in turn, is responsible for the overall system architecture comprising the hydrogen tank, fuel cell and electric drive. H2FLY is also responsible for the safe integration and operation in the aircraft.

“With Germany’s only cluster of excellence in the field of battery research and strong partners in the city of science, Ulm University has become a leading international centre for energy research. The eco-friendly Hy4 aircraft combines battery and fuel cell technology, making it an excellent application example for innovative drive concepts and the mobility of tomorrow,” emphasised Professor Michael Weber, President of Ulm University.

The partners in the collaboration firmly believe in the future of hydrogen propulsion in aviation, and this belief has now been confirmed with the permit-to-fly. Emission-free, efficient and simultaneously low-noise flying in the passenger sector is now within reach. As supporters from the very beginning, representatives of Stuttgart Airport are also pleased about this development: “The emission-free aviation of the future is making considerable progress with this project. For the sake of the climate, we must continue to vigorously pursue technology development in aviation and its launch on the market,” stated Walter Schoefer, spokesperson for the management of Flughafen Stuttgart GmbH. Future tests in Stuttgart will focus on the interaction and coupling of new, even more powerful drive components by May. 

The partners in the Hy4 project 

Ulm University, the German Aerospace Center, H2FLY and Diehl Aerospace (data communication and control hardware) are pooling their expertise in the Hy4 project. At the international level, they are supported by Pipistrel (aircraft hardware) and the research institutions Politecnica di Milano, TU Delft, University of Maribor and Cummins Canada. Sponsors include the National Organization for Hydrogen and Fuel Cell Technology (NOW GmbH), the German Federal Ministry for Economic Affairs and Energy, and the German Federal Ministry of Transport and Digital Infrastructure. Additional funding is provided by the German Aerospace Center, Stuttgart Airport and the European Commission, as well as funding from the industry sector.

Media contact: Annika Bingmann

State Minister of Transport Winfried Hermann, Hy4 Project head Professor Josef Kallo and Managing Director Walter Schoefer at the presentation of the newest generation of the Hy4 hydrogen aircraft at Stuttgart Airport
State Minister of Transport Winfried Hermann, Hy4 Project head Professor Josef Kallo (Ulm University / DLR) and Managing Director Walter Schoefer (from left) at the presentation of the newest generation of the Hy4 hydrogen aircraft at Stuttgart Airport (photo: Tom Koenig)
Hy4 flying
The world's first four-seater hydrogen fuel cell aircraft Hy4 (photo: DLR)
Video: Presentation at Stuttgart Airport