Diamond Aircraft Teams Up with Austrian Research Institutes for Hybrid Hydrogen-Electric Propulsion

Diamond Aircraft is leading an innovative project funded by the Austrian Research Promotion Agency (FFG) to enhance the understanding of gaseous hydrogen as a fuel source for hybrid powertrains in General Aviation. The 'H2EDT' (Hydrogen-based Twin-engine Electrification and Digitalization Testbed) project consortium brings together researchers from FH JOANNEUM (Institute of Aviation and Electronic Engineering), TU Graz (ITnA), HyCentA, and IESTA. They are developing an experimental hybrid testbed to investigate the challenges associated with using hydrogen as an aviation fuel. Research activities, including manufacturing and testing, will be conducted at Diamond Aircraft's facilities in Wiener Neustadt until the end of 2025.

Hydrogen represents a zero-carbon fuel that may significantly influence the future of sustainable aviation. It can be utilised in fuel cells, where electrochemical reactions generate energy from hydrogen and oxygen, yielding only water as a byproduct, or in internal combustion engines. In both applications, hydrogen does not emit carbon dioxide. However, in high-temperature reactions like hydrogen combustion, nitrogen oxide emissions may occur under certain conditions.

The zero-emission characteristics and quieter operation of low-temperature fuel cells are key factors contributing to the increasing adoption of this technology across various sectors, including automotive, maritime, and aviation. Furthermore, hydrogen powertrains provide a higher system-level energy density compared to purely electric systems, enabling greater range and endurance for zero-emission aircraft.

Relying solely on hydrogen for aircraft propulsion presents significant challenges. These challenges include the low power-to-weight ratio of hydrogen fuel cells, which could result in excessive weight, making it difficult to meet peak power demands. Additionally, the storage of hydrogen requires substantial volume due to its low density, which must be accommodated within the constraints of an aircraft's airframe. Furthermore, there are safety and certification concerns, given hydrogen's tendency to leak and its low ignition energy, as well as the safety issues associated with high-pressure or cryogenic hydrogen storage systems.

For these reasons, the research team is implementing a hybrid hydrogen-electric architecture. They see this is as key to leveraging both the high power density of batteries and the high energy density of the hydrogen fuel cell powertrain. This architecture also offers increased redundancy as an added benefit.

The testbed will be a scaled General Aviation platform, incorporating a fuselage, multiple independent battery sets, a hydrogen fuel cell, a hydrogen storage system, and up to ten electric motors and propellers. Initially, the research team intended to develop a testbed reflecting the powertrains commonly used in General Aviation twin-engine aircraft. However, due to the rapidly increasing interest in Advanced Air Mobility, the team has modified its design to facilitate testing of a VTOL (vertical takeoff and landing) platform with up to ten motors.

With the H2EDT testbed, the project has set about testing a holistic approach to energy management and heat recovery, while investigating the performance and reliability of hydrogen fuel cells and storage and distribution systems for aviation applications.

What sets the H2EDT apart is its digital power management system, implemented via a power distribution board developed by FH JOANNEUM, as well as its ‘parallel’ hybrid architecture, where batteries and hydrogen fuel cells can both directly power any motor in the system. The innovative H2EDT system leverages digital sensors and multiple power sources to automatically combine electric and hydrogen power as required, greatly improving efficiency and safety.

An essential part of the project has been the design of a digital twin assembling both detailed CAD geometry and performance simulations, the latter thanks to a model developed in cooperation with TU Graz. This model will be calibrated using test data and provide insights beyond the scope of the H2EDT testing. These will include simulations of failure modes and different environmental conditions, such as high-altitude flight or high air temperatures.

DA42

Another project goal is to define certification and design guidelines for a possible follow-up hydrogen project on a full-scale General Aviation platform, such as a DA40 or a DA42. Certification and design challenges specific to hydrogen storage and distribution systems are also being investigated.

DA40

H2EDT marks another important milestone for Diamond Aircraft in hydrogen propulsion research. Previous achievements include Boeing Phantom Works integration of a fuel cell system in a Diamond HK36 and participation in the AH2AS (Austrian Hydrogen Aviation Study) and concurrent FFG funded projects like the Austro Engine-TU Wien conversion of a diesel engine into a dual fuel Jet-A1/H2 powered engine. Presentation of the H2EDT results is anticipated for the first half of 2026.

HK36

This project has received funding from the Austrian research funding program Take Off. Take Off is a Research, Technology and Innovation Funding Program of the Republic of Austria, Ministry for Innovation, Mobility, and Infrastructure (BMIMI). The Austrian Research Promotion Agency (FFG) has been authorised for the Program Management.