While each project has its own deliverables, they will collaborate on integrated testing efforts, where the TRL5 components from Clean Hydrogen project are used to build and test the TRL4 system within the Clean Aviation project.

• Suitable test infrastructures should be used, for example by research institutions and the industrial sector to demonstrate respective technology readiness levels;
• Identify, under the Clean Aviation JU funded project, the scope of the components to be developed and tested;
• Derive the requirements for specific components (e.g. sensors, valves, monitoring systems) from the system definition provided in cooperation with Clean Aviation funded project. This ensures that the developed components will be compatible with the overall system architecture;
• Detailed component design of key components e.g. for the hydrogen feed and vent systems. This includes material selection, sizing, mechanical and thermal analysis;
• Manufacture and test prototype components to validate their performance, functionality and reliability in a cryogenic hydrogen environment;
• Develop and test control algorithms necessary to manage the operation of the components (e.g. valve sequencing for venting, pressure control). These algorithms are essential for safe and efficient system operation;

Simulation and experimental component analysis are needed. Simulations are intended to complement component development activities by providing tools and methods to derive control strategies, optimal operating conditions, optimise thermodynamic integration and assess performance impacts at the aircraft system level. They should include component, subsystems and system modelling (if necessary, from hydrogen onboard storage to hydrogen conversion in fuel cells), to analyse thermo-fluid-dynamic behaviour, dynamics and energy flows.

Therefore, the project should address the following:

• Development and validation of sizing- and simulation tools for hydrogen supply components design tailored to application specific requirements;
• Identification of mass sensitivity for hydrogen supply system components enabling further mass reduction. Exploration of potential indirect weight reductions in other systems by using cooling power availability during evaporation and heat up of liquid hydrogen;
• Reduction of aerodynamic drag associated with heat exchange surfaces for in-situ hydrogen evaporation. Consideration of secondary coolant specifications to optimise the heat exchanger in realistic conditions, while maximising potential use of the available cooling;
• Evaluation of component performance across all operating phases in connection with liquid hydrogen and fuel cell powertrains using simulation tools;
• Development of control strategies for the hydrogen supply and conditioning system relevant for the testing purpose as well as for an hydrogen powered aircraft[2] (HPA) mission profile;

The development of components shall be complemented by experimental system analysis – preferably at research facilities or with support from industrial partner – in combination with a high-power fuel cell system, within a relevant system architecture and power class. Leveraging available infrastructure is expected to provide operational experience under dynamic and mission-relevant conditions, allowing early identification of system-level challenges. These insights will inform and improve component-specific development beyond what could be achieved through systems engineering alone. In parallel, developed components are expected to undergo individual qualification to ensure performance and reliability. These activities contribute to establishing safe, certifiable, and aviation-ready subsystem maturity.

• Demonstrate hydrogen supply and conditioning component and sub-system operations under application relevant conditions and evaluate responses to system-level failure cases and dynamic constraints;
• Address the durability of materials, components and sub-systems under representative environmental- and mission relevant conditions, including cleanliness and fluid purity sensitivity of the components.

The component development work and the broader sub-system analysis (simulation and experimental testing) are expected to contribute to light weight, energy efficient and low-maintenance designs. The analysis should explore enabling factors (smart topologies, reduction of components & sensors) to achieve such designs, relevant but not limited to the component-level improvements. With system analysis and simulation, critical safety aspects (e.g. failure scenarios, leakage risks, purity effects) are also expected to be assessed.

Scientific analyses and innovation activities should aim to explore the scientific and technological foundations that support safe, certifiable, and high-performance hydrogen supply systems:

• Perform safety and failure mode, effects and criticality analysis in alignment with aviation standards;
• Consider safety requirements for liquid hydrogen supply components: perform review of available liquid hydrogen fueling safety knowledge, prioritise potential incident scenarios, identify and address safety knowledge gaps, propose safety solutions` strategies. Where appropriate based on engineering and development needs, complement these activities with a detailed quantitative risk analysis and derive applicable risk management measures (including safety devices);
• Enablement of robust and safe fuel cell operation in aviation environments;
• Validation of hydrogen leakage rates considering both safety and climate impact;
• Conduct scientific analyses of the potential cooling systems optimisation/reduction by using cooling power available during evaporation and heat-up of liquid hydrogen.

This project should build on insights from Clean Hydrogen JU projects such as ELVHYS[3], HEAVEN[4], BRAVA[5] and COCOLIH2T[6]. HEAVEN contributed to modular fuel cell and cryogenic storage solutions, while BRAVA sets the foundation to demonstrate a hydrogen-powered fuel cell system exceeding 2 MW (propulsive power for one out of several aircraft powertrains), highlighting the potential of hydrogen in future aircraft energy systems. COCOLIH2T aims to develop a safe composite and vacuum-insulated liquid hydrogen (LH2) tank for the aviation sector, using innovative fabrication technologies to design and manufacture a conformal tank. It should also leverage findings from the Clean Aviation JU projects HEROPS[7], NEWBORN[8], FAME[9], H2ELIOS[10], which explores the integration of liquid hydrogen and fuel cells in propulsion architectures for emission-free regional aircraft.

In order to secure the exchange of the necessary elements (such as, but not limited to, liability, background and foreground IP, hardware, digital and physical assets) and information (requirements, specifications, etc.) needed to perform the components testing activities at the TRL targets defined in this topic at project completion, the project selected under this topic will require an enhanced cooperation with the project(s) funded under the Clean Aviation topic “HORIZON-JU-CLEAN-AVIATION-2026-04-HPA-02: Demonstration of an integrated hydrogen fuel system for a fully electric hydrogen fuel cell powered aircraft”.

The project may also build on prior developments from earlier national or other European programs.

Development of cryogenic tank and fuel cell system are excluded from the scope of the topic.

Additional considerations:

• R&D activities should be scalable and transferable to aviation and potentially present positive spill-over effects with other heavy-duty applications.
• Projects should outline how the developed components – while tailored for fuel cell applications – could also enable positive spill-over effects for hydrogen combustion in aviation, supporting broader hydrogen use cases across propulsion technologies;
• Projects should justify proposed budgets based on component/system test size, test duration, and TRL objectives;
• Innovation activities should clearly define the novel aspects and demonstration scale;
• Collaboration across relevant stakeholders and end users (e.g., aircraft manufacturers, fuel cell and hydrogen technology developers, certification bodies) is encouraged;
• While formal certification is not required within this call, proposals should demonstrate how their results and activities support future certification processes and compliance with relevant aviation standards.