Rolls-Royce intends by 2028 to be running two versions of its UltraFan demonstrator engine – one for widebodies and the other for single-aisles – with flight tests to follow by the end of the decade.
And in a sign it is serious about both use cases, Rolls-Royce has named the powerplants the UltraFan 30 and UltraFan 80 in reference to their broad thrust classes.
The propulsion specialist’s renewed development work on the geared-fan architecture comes as it looks to ready the design for future applications, whether to equip an all-new aircraft or as a potential re-engining solution. Rolls-Royce indicated last year it planned to revive the test programme.
Ground testing of the original widebody-sized powerplant demonstrator – producing thrust of around 85,000lb (380kN) – wrapped up in 2023 after almost 70h of run time, but Rolls-Royce is now in the process of rebuilding that engine with the intention of restarting tests by year-end, says Alan Newby, director of research and technology, speaking to FlightGlobal ahead of the Paris air show.
Although the UltraFan “performed extremely well on the testbed” and the engineering team is “still chewing through” the 30TB of data generated by the first campaign, “We want to go back to test and really do a bit more detailed performance mapping and understanding of it”, he says.
No significant changes have been made to the engine, although elements such as blade-tip clearances have been optimised.
But in parallel, the company has begun preliminary design work on a scaled-down version intended for future narrowbody aircraft applications, an activity that should conclude later this month.
Rolls-Royce plans to build the UltraFan 30 demonstrator through 2028 and to begin running the engine by the end of that year. Flight tests could follow towards “the end of this decade”.
Newby says it is too early to disclose the exact size of the UltraFan 30 but says the fan diameter “will be bigger than current narrowbody engines” and will be “pushing towards 90 inches”. Comparatively, a current-generation Pratt & Whitney PW1100G has an 81in (206cm) fan diameter.
Similarly, thrust will be somewhere above 30,000lb, says Newby, “in the right ballpark so we can go up or down” depending on customer requirements.
Bypass ratio will be pushed towards 15:1, up from around 10-12:1 on current-generation geared-fan engines.
“We are working closely with potential customers to understand their in-service requirements,” says Newby.
Of the big two airframers, Airbus has been most open about its intentions to develop a successor to its A320neo family through its Next Generation Single Aisle programme, for service entry around 2035.
In addition to Rolls-Royce’s own internal R&T efforts, “a lot of fundamental work” to scale the architecture has taken place through the HEAVEN programme – a Rolls-Royce-led project running since January 2023 that is part-funded by the EU’s Clean Aviation body.
Activities have included rig tests of the combustor and gearbox, alongside ”some of the preliminary design work for a narrowbody engine as well”.
That work could continue through Clean Aviation’s second phase, with a call for proposals issued earlier this year.
Newby will not say whether Rolls-Royce has replied to the call – bids were due in by 16 May – but Clean Aviation will allocate up to €70 million for ground testing of a narrowbody aircraft-sized ultra-high-bypass-ratio ducted geared turbofan engine, intended to raise the concept to technology readiness level (TRL) 5 by 2029.
But Clean Aviation is now looking beyond ground tests: “Applicants should propose and build a demonstration plan aiming to validate a propulsion architecture on ground by end of 2029 and subsequently in flight by end of 2030,” its project requirements state.
Rolls-Royce stresses it is not guaranteed any funding from Clean Aviation; project selection will take place later this year enabling work to start in late 2025 or early 2026.
Assuming the application is successful, the make-up of its consortium could indicate a route forward towards flight testing. Notably, there is no airframer involvement in HEAVEN’s first phase.
Newby says it is “looking at a range of options” for flight tests, including aboard the company’s 747-200 flying testbed or in conjunction with potential customers.
However, the route will depend “on what size [engine] we take to flight test”, he says, with the firm to prioritise the widebody or narrowbody engine in line with market requirements.
“We will be guided on flight test by where we see the market developing,” he says.
“What we are trying to do now is to develop an integrated development programme that features both small and large assets,” says Newby, who stresses that the “common architecture” between the two engine sizes will ensure certain tests do not need repeating.
Rolls-Royce plans eventually to assemble two engines for each application to ensure the full range of tests can be performed, he adds.
Rolls-Royce also continues to explore potential industrial partnerships to help de-risk the development costs of bringing the UltraFan 30 to market.
Chief executive Tufan Erginbilgic has repeatedly emphasised that strategy: “At the right time, with the right partner, we will decide the next steps,” he said during a capital markets presentation in late 2023.
Newby says multiple options are being explored, from the current model of risk- and reward-sharing partnerships “right through to an OE partner”, he says, adding: “We are talking to everyone.”
A partnership may be necessary if Rolls-Royce is to re-enter a segment it left in 2012 with the sale of its stake in International Aero Engines and the V2500 programme to P&W.
That move left P&W and CFM International – the Safran-GE Aerospace joint-venture – as the sole manufacturers of narrowbody powerplants with their respective PW1000- and Leap-series ducted-fan engines.
But while P&W is proposing a second-generation geared turbofan for future narrowbodies, CFM is pursuing a radically different approach to its Leap successor and is developing an open-rotor demonstrator engine through its RISE programme.
Newby says although there are clearly propulsive efficiency benefits from an open-rotor design “by the time you install it on an aircraft” along with the additional noise and blade-out protections required “those fundamental benefits are heavily eroded”.
