Even as its first tranche of projects begin to really hit their stride, the EU’s Clean Aviation body is preparing the ground for its second phase of EU funding, set to begin in February 2025.
This phase will kick off with the third call for proposals, allocating €380 million ($400 million) in EU funding to advance research and innovation efforts. Unveiled on 10 December, the third call, due in February, allots: €205 million to ultra-efficient short-medium range (SMR) aircraft architectures; €145 million to ultra-efficient regional aircraft architectures; and €15 million to aircraft concept integration and impact assessment.
A further €15 million will go to what Clean Aviation calls “Fast Track Areas” which are “designed to de-risk alternative or complementary technical solutions, enabling a faster implementation process”.
Having previously provided €810 million in funding to 28 projects across two first-stage calls, this time around Clean Aviation has up to €910 million to invest in the research and innovation effort.
That figure will be more than matched by industry, giving a total budget for phase 2 of somewhere in the region of €2.3 billion.
Additionally, the third call for proposals will take the outputs from the preceding stage, which should be at technology readiness level (TRL) 4 by that point, and continue their development, bringing new propulsion concepts or aircraft architectures to TRL6 by the end of the programme in 2030 at the latest. That should allow their employment in next-generation commercial aircraft to enter service in 2035.
While the ultimate goal of the programme has not changed – ensuring aviation can meet the EU Green Deal 2050 goal of climate neutrality – the path to getting there has been subtly tweaked, says Sebastien Dubois, Clean Aviation head of unit, programme development and communications.
Reflecting both EU funding realities and technological maturity levels, Clean Aviation recently set out the revised plans in its Strategic Research & Innovation Agenda (SRIA) document, what Dubois calls the “foundation to prepare the phase 2 content”.
Although the focus remains on three distinct workstreams – regional, SMR, and hydrogen-powered aircraft (HPA) – and a goal to deliver emissions improvements of at last 30%, there have been changes over the previous SRIA iteration.
The most notable is the removal of studies into hydrogen propulsion for SMR aircraft – essentially a typical narrowbody – with Clean Aviation believing the technology will not be ready to enter service for that application by 2035.
If it seems a contradiction to move away from hydrogen power on one side while also embracing it on the other, the key thing to remember are the expected performance attributes of each platform: Clean Aviation views the HPA as being in a new category, able to carry 100 passengers on routes of up to 1,000nm (1,850km), while the respective figures for an SMR aircraft are 200-250 passengers and 3,000nm.
So while the H2-powered aircraft could either use hydrogen fuel cells or direct combustion, the size and range of the SMR concept drives it towards the latter power source “and this requires much more time to mature”, says Dubois, who believes 2045 is a more realistic service-entry timeframe.
“It’s a question of a risk-mitigation approach… for SMR we need a power density that is significantly higher than then one we have on fuel cells,” he adds.
Additionally, in its second phase Clean Aviation will not fund any projects related to wings for SMR applications, despite the presence of such research in phase 1. Instead, these activities will be pursued at national level through initiatives like the Airbus-led Wing of Tomorrow project which is backed by the UK’s Aerospace Technology Institute.
Clean Aviation, says Dubois, “does not have enough funding to cover all activities”, noting that to take all the technologies in phase 1 to TRL6 would require a budget in the order of €12 billion.
A similar caveat applies to the regional aircraft segment, where a multi-MW powertrain will be flight tested, but a new ultra-efficient wing will remain earthbound, destined solely for use as a ground-based demonstrator. There will not be, Dubois says, enough funding to flight test both.
That is the crux of the issue: to fund the rest of its hugely ambitious programme of work, there has to be prioritisation.
In phase 2, individual technologies will move from the laboratory, to integration into an aircraft-level system, and in many cases eventually to flight test.
For instance, although hydrogen is no longer part of the equation, the focus within the SMR ‘pillar’ is still on “disruptive propulsion concepts”, where three different engine architectures will be flight tested in pursuit of a 20% fuel-burn improvement at aircraft level.
Those three concepts – work on which is already under way in phase 1 – are a shrunk version of Rolls-Royce’s UltraFan architecture (project HEAVEN), the water-enhanced, hybridised turbofan being developed by MTU Aero Engines and its partners (SWITCH), and CFM International’s RISE open-rotor concept (OFELIA).
Those three projects also build on existing industry-led research activities – ensuring more bang for Clean Aviation’s EU buck – CFM for instance having previously agreed a plan with Airbus to test the RISE engine aboard an A380 flying testbed.
For the regional aircraft, the demonstration will be about combining various phase 1 technologies – energy generation, storage, and distribution, plus motors – into an integrated multi-megawatt hybrid-electric powertrain.
“We need to complement that with all the necessary modifications for flight-test demonstrations,” adds Dubois. Tests will take place using an adapted regional turboprop – likely an ATR – with one of the two thermal engines replaced with the hybrid powertrain.
And for the hydrogen-powered aircraft, Clean Aviation’s first phase has funded research on three separate 1MW-class fuel cell powertrains. “We are assessing their scalability up to 2.5-3MW for future applications on a 1,000nm, 100-passengers aircraft type,” says Dubois.
However, as Clean Aviation has “decided to really put the focus on fuel cells as a primary target for flight-test demonstrations in phase 2”, he says “no flight test of H2 burn will take place”.
Two projects under phase 1 are looking at hydrogen combustion technologies: CAVENDISH, led by Rolls-Royce, and HYDEA, led by GE Avio.
Dubois says the enabler for a Hydrogen-combustion engine is not the ability to burn the element but to master the requisite technologies further upstream: “A significant effort will be made to further mature the end-to-end fuel distribution system which is probably one of the key components to make that concept work.”
But two aircraft concepts will be studied as part of this stream: a fuel cell-powered example and one equipped with dual-fuel engines – capable of burning Jet-A-1 or hydrogen – one of project CAVENDISH’s research areas.
The third call for proposals next February will be followed by calls in each of 2026 and 2027. One notable change between phases 1 and 2 is the presence of the UK as an associated country within Clean Aviation – adding €96 million to the budget – following a post-Brexit agreement, while Canadian businesses and research bodies will also be able to participate on the back of a deal struck in July.
