Demonstration of Advanced Low NOx H2C Propulsion System for a direct hydrogen combustion aircraft

Call HORIZON-JU (Clean Aviation Call 4) funds an Innovation Action to develop and demonstrate an advanced low-NOx hydrogen direct combustion propulsion system for aircraft. Topic budget is €15 million (up to one project expected), the funding rate is up to 70% for for-profit entities and up to 100% for non-profit entities, and standard Innovation Action consortium rules apply. Required technical outcomes are a low-NOx combustor demonstrated at TRL5 achieving at least 30% NOx reduction and an efficient hydrogen combustion engine architecture demonstrated at TRL4 with appropriate rig and subsystem validation. Submission opens 31 March 2026 and the deadline is 19 May 2026 at 17:00 Brussels time via the EU Funding & Tenders Portal.

Opportunity overview

Who can apply

Essential facts

Call HORIZON-JU (Clean Aviation CfP 04). Seeks consortia (coordinator + beneficiaries) able to develop and demonstrate a direct hydrogen combustion propulsion system focused on an advanced low-NOx combustor and an efficient hydrogen combustion engine architecture.

What it funds:Innovation Action (HORIZON-JU-IA). Demonstration of a low-NOx hydrogen direct-combustion combustor at TRL5 (min. 30% NOx reduction) and an efficient hydrogen combustion engine architecture at TRL4 to enable a viable direct-hydrogen aircraft concept.

1. 1Eligible applicants: consortia of legal entities established in eligible Member States/Associated Countries (see call). Typical partners: OEMs, engine manufacturers, combustor developers, research centres, certifying bodies and test providers.
2. 2Scope: design, test and demonstration activities leading to TRL5 combustor validation and TRL4 engine architecture demonstration, including operability, integrity and emissions verification.
3. 3Evaluation: single-stage call; proposals assessed against Excellence, Impact and Implementation award criteria under Clean Aviation rules.

Footnotes

1. 1Full topic description, application templates and specific eligibility rules (countries, financial capacity, ethics, security and model grant text) are published on the Funding & Tenders Portal topic page.

Demonstration of Advanced Low NOx H2C Propulsion System for a Direct Hydrogen Combustion Aircraft (HORIZON-JU-CLEAN-AVIATION-2026-04-HPA-03)

Programme: Clean Aviation Joint Undertaking, Clean Aviation CfP 04 (HORIZON-JU-Clean-Aviation-2026-01). Type of action: HORIZON-JU-IA (Innovation Actions). Type of MGA: HORIZON Action Grant Budget-Based [HORIZON-AG]. Opening: 31 March 2026. Deadline: 19 May 2026, 17:00 Brussels time. Submission: single-stage via the EU Funding & Tenders Portal Topic Page ¹.

Opportunity Overview and Technical Scope

This topic targets the development and demonstration of an advanced low-NOx hydrogen direct combustion (H2C) propulsion system to enable a viable direct hydrogen combustion aircraft concept. It specifically calls for:

• A low-NOx combustor demonstrated at TRL 5, achieving at least 30% NOx reduction and demonstrating operability and integrity.
• An efficient hydrogen combustion engine architecture demonstrated at TRL 4.
• Overall objective: advance the technology building blocks to support a credible direct H2 combustion aircraft pathway.

Applicants should plan experimental and validation activities that credibly reach the specified TRL targets within the project, including component and subsystem-level demonstrations and the supporting design, analysis, and test campaigns that prove operability, integrity, efficiency, and emissions performance.

Key Dates and Call Logistics

• Planned opening date: 31 March 2026.
• Submission deadline: 19 May 2026, 17:00 Brussels time (single-stage).
• Q&A publication schedule for the call: first release on 17 February 2026; second release on 17 April 2026. Updates will be posted on the call page and in the Q&A document.
• Templates and supporting documents are made available on the call page. Financial annex templates will be available around mid-March 2026.

Evaluation, Award, and Legal Framework

Evaluation criteria and thresholds follow Horizon Europe General Annexes. For Innovation Actions, the criteria are Excellence, Impact, and Quality and efficiency of the implementation; Impact is weighted by 1.5. Minimum thresholds: 3/5 per criterion and 10/15 overall after weighting. Clean Aviation JU applies its Specific Rules and a CAJU-specific evaluation template for Large Scale IA projects. The process includes individual evaluation, consensus, Topic Panel review, and may include hearings. Proposals are evaluated as submitted; budget inflation or inadequately justified costs may reduce scores.

• Admissibility and eligibility: per Horizon Europe General Annexes A–C.
• Award criteria and thresholds: General Annex D; Impact weight 1.5 for IA.
• Submission and evaluation procedures and indicative timeline: General Annex F and Online Manual.
• Legal and financial set-up: General Annex G.
• Specific Clean Aviation rules apply (submission, evaluation, selection, award, review). Editorial note clarifies references to CAJU Work Programme in the rules document.

Budget Context and Funding Rate

Indicative total call budget: €329,500,000 for the Clean Aviation CfP 04 portfolio across multiple topics. No topic-specific budget is published for HPA-03 on the call page.

• Funding rate (Innovation Action): up to 70% of eligible costs; up to 100% for non-profit legal entities, in line with Horizon Europe Annex G.
• Reimbursement of eligible direct costs plus 25% flat-rate for indirect costs, per Horizon Europe Model Grant Agreement.

Eligibility and Participation

Participation and funding eligibility follow Horizon Europe General Annex B and Clean Aviation-specific rules. Unless a derogation is explicitly stated at topic level, standard consortium composition for IA applies.

• Consortium composition (standard HE rule): at least 3 independent legal entities, each established in a different EU Member State or Associated Country; at least one in an EU Member State.
• Possible Clean Aviation derogation: CAJU rules permit, where stated at topic level and duly justified, a single legal entity established in a Member State or Associated Country or consortia not meeting Article 22(2) HE to be eligible. No such derogation is indicated on the topic page; applicants should assume standard consortium eligibility.
• Eligible countries for funding: EU Member States (including OCTs), and Horizon Europe Associated Countries. Entities from other countries may participate without funding, unless exceptional funding is justified under the Programme Guide.
• Restrictions for Innovation Actions: Legal entities established in China are not eligible to participate in IA in any capacity. Legal entities established in Russia, Belarus, or in non-government controlled territories of Ukraine are not eligible to participate in any capacity. Entities subject to EU restrictive measures are not eligible.

What Projects Should Deliver

• TRL 5 demonstration of an advanced low-NOx hydrogen combustor achieving at least 30% NOx reduction with validated operability and integrity.
• TRL 4 demonstration of an efficient hydrogen combustion engine architecture suitable for integration in a viable direct H2 aircraft concept.
• Robust system engineering, safety assessments, operability envelopes, transient response, stability and blow-off margins, start-up and altitude relight demonstrations as relevant to combustion and engine sub-systems.
• Quantified emissions assessments and test results underpinning the claimed NOx reduction versus state-of-the-art kerosene or hydrogen baselines as applicable.
• Clear validation plans, test matrices, facility readiness, instrumentation and data quality controls for combustor rigs and sub-scale or full-scale component tests.

Application Materials and Templates

Applicants must use the application form available in the Submission System (Part A administrative forms and Part B technical annex). Proposal page limits and layout are defined in the templates. For budgeting and implementation planning, CAJU provides mandatory financial annex templates and supporting models. Additional Clean Aviation-specific templates are available.

• Proposal Application Form for this topic (Part A and Part B).
• Financial annex templates: estimated budget by reporting period; Work Package description (Detailed); Work Package effort (Detailed); Cost Breakdown per beneficiary; Budget summary per applicant and work package; In Kind Contribution.
• CA JU Model Consortium Agreement.
• Clean Aviation contract template for the provision of services by EASA (for projects interfacing with EASA advisory and certification readiness tasks).
• Evaluation form templates and the CAJU Large Scale Projects (IA) template.
• Guidance documents: HE Programme Guide; Model Grant Agreements; General Annexes; Online Manual; Annotated Model Grant Agreement.

Evaluation Details and Process Specificities (Clean Aviation JU)

• Single-stage evaluation. Phases: Individual Evaluation Reports (IER), Consensus, Topic Panel Review; optional Call Panel Review.
• Hearings may be organised to clarify technical scope, synergies, and budget optimisation; hearings cannot be used to modify proposals, only to provide clarifications.
• Ranking within IA topics: Impact criterion weighted 1.5; ex aequo resolution per CAJU rules aligned with HE General Annexes (e.g., Excellence/Impact ordering, gender balance in researchers table, geographical diversity).
• Evaluation outcomes include Evaluation Summary Reports (ESR), potential recommendations for technical and financial adjustments in Grant Agreement Preparation (GAP), and possible linking of actions across CAJU portfolio.
• Ethics screening/assessment and security appraisal apply where relevant; projects must be exclusively for civil applications.

Administration, Legal, and Financial Set-up

• Grant Agreement Preparation may require adjustments for alignment with CAJU High-Level Objectives (HLOs), budget optimisation, synergies across topics, and linking of actions.
• Consortium Agreement required unless the call specifies otherwise; CA JU Model Consortium Agreement is provided.
• Gender Equality Plan requirement for certain categories of legal entities to be eligible by grant signature, per HE rules.
• Reporting: continuous reporting of deliverables/milestones; periodic technical and financial reporting; payments include pre-financing, interim (if applicable), and final payment with standard HE controls.
• Audit, review, monitoring, ethics, and security obligations follow HE MGA; records must be kept for at least 5 years after final payment (standard HE rule).

Categorisation of the Opportunity

Eligible Applicant Types

Eligible applicants include legal entities established in EU Member States or Horizon Europe Associated Countries. Typical participants are industrial companies (engine and combustor OEMs and tier suppliers), SMEs, large enterprises, universities, research and technology organisations, and other non-profit entities. Public bodies and agencies can participate where relevant. Entities from non-associated third countries may participate without funding unless exceptional funding is justified. Entities established in China are not eligible to participate in Innovation Actions in any capacity; entities established in Russia, Belarus, or in non-government controlled territories of Ukraine are not eligible in any capacity.

Funding Type

Grant under Horizon Europe (HORIZON-JU-IA Innovation Action) managed by the Clean Aviation Joint Undertaking.

Consortium Requirement

Standard Horizon Europe consortium for IA: minimum three independent legal entities, each established in a different EU Member State or Associated Country, with at least one established in an EU Member State. Clean Aviation rules allow topic-specific derogation to single applicants in justified cases; no derogation is stated on the topic page, so applicants should assume the standard consortium requirement.

Beneficiary Scope (Geographic Eligibility)

EU Member States and Horizon Europe Associated Countries are eligible for funding, per General Annex B. Some non-associated third countries may participate without funding. Restrictive measures include ineligibility of entities in Russia, Belarus, or in non-government controlled territories of Ukraine; and ineligibility of entities established in China for Innovation Actions in any capacity.

Target Sector

Aviation/aerospace propulsion; hydrogen technologies; combustion systems; climate and environment (NOx reduction); energy for aviation; aircraft systems integration; safety and certification preparedness.

Mentioned Countries

Region: European Union and Horizon Europe Associated Countries, as per Horizon Europe eligibility. Exclusions: entities established in China (for IA), Russia, Belarus, and non-government controlled territories of Ukraine are not eligible. No specific Member States are singled out for this topic.

Project Stage (Expected Maturity)

Development, validation, and demonstration. Explicit targets are TRL 5 for the low-NOx hydrogen combustor and TRL 4 for the engine architecture.

Funding Amount

Total indicative budget for Clean Aviation CfP 04: €329,500,000 across multiple topics. No topic-specific budget is disclosed for HPA-03 on the call page; applicants should size budgets consistent with Large Scale IA scope and TRL 4–5 demonstrations, ensuring cost efficiency.

Application Type

Open call; single-stage submission via the EU Funding & Tenders Portal.

Nature of Support

Financial support (grant). No non-financial services are foreseen beyond standard JU support and interfaces, including potential interactions with EASA through the provided service contract template where relevant to certification readiness tasks.

Application Stages

One stage (single-stage submission and evaluation). Hearings may be organised during evaluation for clarifications.

Success Rates

Not specified for this topic or call. Clean Aviation JU does not publish an indicative success rate for CfP 04.

Co-funding Requirement

Yes for for-profit entities: Innovation Action funding rate is up to 70% of eligible costs; beneficiaries must co-fund the remainder. Non-profit legal entities may receive up to 100% of eligible costs.

How to Structure Your Application (Templates and Content Outline)

Administrative (Part A):Participant details; contact persons; declarations; ethics and security questionnaires; budget summary by beneficiary and work package; eligible country validations; Gender Equality Plan self-declaration where applicable.

Technical (Part B) – recommended structure aligned to evaluation criteria:Excellence: Objectives; relation to the work programme; ambition beyond state of the art for hydrogen combustors and engine architectures; soundness of approach and methodology; TRL plans for combustor TRL5 and engine architecture TRL4; risk management and mitigation; open science practices relevant to data sharing of non-sensitive results. Impact: Credible pathways to reduce NOx emissions by at least 30%; contributions to Clean Aviation SRIA and HLOs; expected scientific, environmental, industrial, and societal impacts; measures to maximise dissemination, exploitation, and communication; strategy to foster standardisation and certification-readiness evidence; IP management. Implementation: Work plan with detailed work packages, deliverables, and milestones; test campaigns, facilities and instrumentation readiness; Gantt chart; management structure and decision-making; consortium roles and complementarity; resource allocation and justification; data management and ethics considerations; risk register and contingency plans.

Mandatory and supporting annexes:Financial annexes (estimated budget per reporting period; WP description and effort; cost breakdown per beneficiary; budget summary per applicant and WP; in-kind contribution plan). If applicable: Information on financial support to third parties; Information on clinical studies (unlikely relevant here). CA JU Model Consortium Agreement. Clean Aviation contract template for EASA services if engaging EASA for certification-related advisory. Any topic-specific annexes when provided on the call page.

Additional Compliance and Technical Considerations

• Civil applications only.
• Ethics self-assessment and, where applicable, security screening requirements.
• Open science: provide for sharing of non-sensitive data and research outputs as appropriate; manage IP to protect foreground and facilitate exploitation across the aviation value chain.
• Standard HE MGA obligations on communication, visibility (EU emblem and funding statement), record keeping, audits, and monitoring.
• Projects may be requested to coordinate with other CAJU actions (linked actions) to optimise synergies; cooperation agreements may be requested during GAP.

Summary and Explanation

This Clean Aviation JU opportunity funds a Large Scale Innovation Action to mature key direct hydrogen combustion technologies for aviation. The core technical outcomes are a TRL 5 low-NOx combustor with at least 30% NOx reduction and a TRL 4 hydrogen combustion engine architecture. Proposals must credibly plan and resource rig and component testing, verification of operability and integrity, emissions quantification, and system-level trade-offs that support future aircraft integration. The funding environment follows Horizon Europe, with IA cost reimbursement up to 70% (100% for non-profit entities), a single-stage evaluation weighted strongly on impact, and a robust Grant Agreement Preparation phase to align with Clean Aviation’s strategic agenda and to ensure coherence across the programme portfolio. Applicants should form consortia with strong OEMs, tier suppliers, universities, and RTOs, showing facility readiness, certification-relevant evidence paths, and clear exploitation plans. Geographic eligibility follows Horizon Europe, with specific exclusions for entities in China (for IA), Russia, Belarus, and non-government controlled territories of Ukraine. All submissions go through the EU Funding & Tenders Portal using the prescribed templates and must adhere to Clean Aviation’s specific rules on evaluation, hearings, and potential linking of actions. In short, this is a strategically important JU call to advance direct H2 combustion for aviation through rigorous, test-backed demonstrations that materially reduce NOx and de-risk integration towards a future hydrogen-powered aircraft.

Footnotes

1. 1Official topic page and submission portal: Demonstration of Advanced Low NOx H2C Propulsion System for a direct hydrogen combustion aircraft EU Funding & Tenders Portal.

Clean Aviation Call 4: Demonstration of Advanced Low NOx H2C Propulsion System for Direct Hydrogen Combustion Aircraft

Funding Opportunity Overview

This Innovation Action (IA) is part of the Clean Aviation Joint Undertaking's fourth call for proposals, launched on 17 February 2026. The opportunity focuses on developing and demonstrating an advanced low NOx hydrogen direct combustion propulsion system for aircraft. The project targets demonstration of a low NOx combustor at Technology Readiness Level (TRL) 5, delivering a minimum 30 percent reduction of NOx emissions, and an efficient hydrogen combustion engine architecture at TRL 4.

Topic Identification:HORIZON-JU

Call Deadline:19 May 2026 at 17:00 Brussels time. The submission system opens on 31 March 2026.

Funding Details

Total EU Funding Available:€15 million for this specific topic. The entire Clean Aviation Call 4 provides up to €329.5 million in EU funding, with an estimated €824 million of total research effort when combined with private sector contributions.

Expected Number of Projects:Up to 1 project is expected to be funded under this topic.

Type of Action:Innovation Action (IA). For Innovation Actions, the maximum EU funding rate is 70 percent of eligible costs, except for non-profit legal entities where the rate can be up to 100 percent.

Project Scope and Objectives

The project must develop and demonstrate an advanced low NOx hydrogen direct combustion propulsion system. Key deliverables include demonstration of a low NOx combustor at TRL 5 that achieves a minimum 30 percent reduction of NOx emissions while demonstrating combustor operability and integrity. The project must also demonstrate an efficient and hydrogen combustion engine architecture at TRL 4, enabling the demonstration of a viable direct hydrogen combustion aircraft concept.

This topic is part of the Hydrogen Powered Aircraft (HPA) thrust within Clean Aviation, which aims to mature hydrogen-related technologies while strengthening the European industrial base with regards to the hydrogen ecosystem and supply chain capabilities. The work aligns with the Strategic Research and Innovation Agenda (SRIA) and supports aircraft concepts with 100-150 passenger capacity and a design range up to 1400 nautical miles.

Eligibility and Applicant Requirements

Who Can Apply

Any legal entity can participate, including entities from non-associated third countries and international organisations. However, to be eligible for funding, beneficiaries must be established in one of the following: EU Member States, Overseas Countries and Territories linked to Member States, countries associated to Horizon Europe, or specific low- and middle-income countries as listed in the Horizon Europe General Annexes.

Consortium composition requirements apply: unless otherwise provided in specific call conditions, only legal entities forming a consortium are eligible, requiring at least three independent legal entities from different countries, with at least one from an EU Member State and at least two from different Member States or Associated Countries.

Exclusion Criteria

Applicants subject to EU restrictive measures, entities established in Russia, Belarus, or non-government controlled territories of Ukraine, and certain Hungarian public interest trusts are not eligible. Legal entities established in China are not eligible to participate in Horizon Europe Innovation Actions in any capacity, with limited exceptions for justified reasons.

Operational Capacity

Applicants must have the know-how, qualifications, and resources to successfully implement their tasks, including sufficient experience in EU or transnational projects of comparable size. Financial capacity will be assessed based on stable and sufficient resources to implement the project. Public bodies, Member State organisations, and international organisations are exempted from the operational capacity check.

Evaluation and Selection Process

Proposals will be evaluated by independent external experts against three award criteria: Excellence, Impact, and Quality and Efficiency of Implementation. For Innovation Actions, the Impact criterion receives a weighting of 1.5 in the ranking. Each criterion is scored from 0 to 5, with individual thresholds of 3 and an overall threshold of 10 points.

The evaluation process includes individual evaluation by experts, consensus group discussions, topic panel review, and optional call panel review. Proposals are ranked according to their quality scores, and successful proposals are invited to the grant preparation stage. The granting authority will provide evaluation summary reports to all applicants.

Grant Agreement and Implementation

Grant Form:Budget-based, mixed actual cost grant under the Horizon Europe Action Grant framework.

Project Duration:To be determined during grant preparation, typically aligned with the Clean Aviation programme timeline and technology maturation roadmap.

Eligible Costs:Personnel costs, subcontracting costs, purchase costs (including equipment and travel), and other direct costs necessary for project implementation. Costs must be actually incurred, identifiable, verifiable, and comply with applicable national law on taxes, labour, and social security.

Reporting Requirements:Beneficiaries must submit continuous reporting on project progress, periodic technical reports, and financial statements. Reporting is linked to payment schedules, with interim and final payments subject to approval of periodic reports.

Key Conditions and Obligations

Beneficiaries must implement the action as described in the proposal and in compliance with the grant agreement, call conditions, and all applicable EU, international, and national law. They must maintain proper records and supporting documentation for at least 5 years after final payment (or 3 years for grants not exceeding €60,000).

All communication and dissemination activities must acknowledge EU support and display the European flag and funding statement. Beneficiaries must respect fundamental rights, values, and ethical principles, including the highest standards of research integrity. Data protection must comply with Regulation (EU) 2016/679 (GDPR).

Beneficiaries must prevent conflicts of interest and immediately notify the granting authority of any situation constituting or likely to lead to a conflict. They must keep sensitive information confidential and handle classified information in accordance with applicable EU and national law.

Intellectual Property and Results

The granting authority does not obtain ownership of results produced under the action. Beneficiaries retain ownership of results and background intellectual property. However, the granting authority has the right to use non-sensitive information, materials, and documents for policy, information, communication, dissemination, and publicity purposes in the form of a royalty-free, non-exclusive, and irrevocable licence.

Beneficiaries must give each other and other participants access to background identified as needed for implementing the action. If background is subject to third-party rights, the beneficiary must ensure it can comply with its obligations under the grant agreement.

Support and Guidance

The Clean Aviation Joint Undertaking provides comprehensive guidance through the Horizon Europe Programme Guide, the Online Manual for the Funding and Tenders Portal, and the EU Grants Annotated Model Grant Agreement. Questions and technical clarifications can be submitted to CFP-2026-01@clean-aviation.eu. Two Q&A document releases are scheduled: 17 February 2026 and 17 April 2026.

National Contact Points (NCPs) provide guidance and practical information on participation in Horizon Europe. The Enterprise Europe Network offers support to businesses, particularly SMEs. The European IPR Helpdesk assists on intellectual property issues, and the Research Enquiry Service answers questions about European research and funding programmes.

Strategic Context

This funding opportunity is part of the European Union's commitment to decarbonising aviation and achieving climate neutrality. The Clean Aviation programme aims to accelerate the development of climate-neutral aviation technologies for earliest possible deployment, contributing to the European Green Deal objectives. The focus on hydrogen-powered aircraft represents a critical pathway for achieving net-zero aviation emissions by 2050, with the programme targeting technologies ready for entry into service by 2035.

The programme emphasises strengthening European industrial leadership and competitiveness in sustainable aviation technologies. Successful projects will contribute to reducing strategic dependencies and establishing Europe as a global leader in clean aviation innovation. The work integrates with complementary initiatives including the Clean Hydrogen Partnership, SESAR 3 Joint Undertaking, and other EU programmes supporting the transition to sustainable aviation.