Race for Next-Gen Narrowbody Engines Heats Up as Tests Near

Pratt & Whitney tests in 2027. Rolls-Royce follows in 2028. CFM plans to fly its Open Fan on an A380 by decade’s end. The winning design will shape the jets that replace the 737 MAX and A320.

Pratt & Whitney, Rolls-Royce and CFM International laid out rival test schedules this month for next-generation narrowbody engines, each competing to power successors to the Boeing 737 MAX and Airbus A320.

The plans were outlined at and around the International Council of the Aeronautical Sciences conference, held Sept. 13-18 in Sydney, Aviation Week reported. Pratt & Whitney will ground-test a new engine in early 2027. Rolls-Royce will run its UltraFan 30 demonstrator in 2028. CFM and Airbus plan to fly an Open Fan engine on an A380 testbed in 2029-2030.

The contest comes down to one basic design question. Pratt & Whitney and Rolls-Royce are refining ducted geared turbofans, which keep the fan inside a casing. CFM, a joint venture of GE Aerospace and Safran, is betting on an unducted Open Fan, which leaves its blades exposed to the air.

Why the next engine choice matters

Engine choices made over the next decade will set the performance of the single-aisle jets that make up much of the U.S. airline fleet.

“The reason for doing that right now is we are about to change the single-aisle fleet in the next 10-15 years,” said Andrew Murphy, chief engineer for advanced commercial engines concepts at Pratt & Whitney, explaining the company’s focus on noise.

“Timing is uncertain, but when it happens, that will be really what sets the noise signature for the whole aviation fleet for the next 50 years. So we have an opportunity right now to change how the world thinks about noise in aviation,” Murphy said.

The European Union’s Clean Aviation Joint Undertaking, which funds a share of the European research, has set targets for the replacement aircraft that apply to both engine designs.

“In terms of an A320 and also a 737 MAX replacement, we are looking at a 30% CO2 reduction which, together with sustainable aviation fuel, is about a 90% net CO2 emission reduction. Focusing very much on engine, we have a target of 20% fuel-burn and CO2 reduction for both ducted and unducted engines,” said Axel Krein, the group’s executive director.

The physics behind the split is bypass ratio, the ratio of air that flows around the engine core to the air that passes through it. A higher ratio cuts fuel burn. Today’s engines run at roughly 10:1 to 12:1. Pushing that number higher inside a casing means larger, heavier nacelles that add drag. By removing the casing, CFM is targeting a bypass ratio of about 60:1.

Bjorn Fehrm, an analyst with Leeham News, has said the industry has not seen a competition with stakes this high in 50 years, comparing it to the shift from turboprops to jets. If Boeing stayed with a ducted engine and Airbus proved 5% more efficient, Fehrm said, “that will kill Boeing in the market.”

Pratt & Whitney targets noise with CLEEN III engine

Pratt & Whitney will test new fan, acoustic and combustor technology in early 2027 under Phase III of the Federal Aviation Administration’s Continuous Lower Energy, Emissions and Noise program, known as CLEEN. The engine builds on the PW1100G GTF Advantage.

“That engine is being built in Connecticut at our facility to go to test early in 2027. So, hopefully, we’ll be back talking about that success,” Murphy said.

The company is aiming for a 3 EPNdB noise reduction, 10% lower non-volatile particulate matter emissions, 5% lower nitrogen oxide emissions and an additional 0.8% cut in fuel burn. The test engine will carry additively manufactured acoustic liners, low-count guide vanes and an advanced rich-quench-lean combustor.

Murphy said the noise gain is significant because the decibel scale is logarithmic, and it comes without changing the engine’s overall architecture.

The research runs alongside Pratt & Whitney’s rollout of an upgraded version of its current engine. A powder metal manufacturing defect in PW1100G engines produced between 2015 and 2021 left some high-pressure turbine and compressor disks at risk of early cracking, grounding hundreds of A320neo-family jets as airlines worked through accelerated inspections.

The FAA certified the upgraded GTF Advantage engine in February 2025. On April 17, the European Union Aviation Safety Agency certified the GTF Advantage-powered A320neo family, Pratt & Whitney’s parent company RTX said. The engine offers 4% to 8% more takeoff thrust, and full production cutover is expected in 2028. On Sept. 24, United Airlines took delivery of the first GTF Advantage-powered aircraft, an Airbus A321XLR, RTX said.

“The GTF engine delivers the lowest fuel consumption for single-aisle aircraft. The GTF Advantage engine extends that lead—offering up to double the time on wing and enhancing aircraft capability—providing even greater value to operators of A320neo family aircraft,” said Rick Deurloo, president of Commercial Engines at Pratt & Whitney.

CFM’s Open Fan heads for an A380 flight test

CFM is developing the Open Fan under its Revolutionary Innovation for Sustainable Engines program, known as RISE. It targets a cut of more than 20% in fuel burn and CO2 emissions compared with today’s most efficient engines, at speeds similar to current turbofans.

The design uses a single row of variable-pitch carbon-fiber composite fan blades followed by a row of nonrotating guide vanes. Safran has said both rows have pitch control, giving the engine reverse-thrust capability.

Open rotors have long faced questions about noise. Safran said a one-fifth-scale Open Fan model has logged more than 400 hours of wind tunnel testing at France’s ONERA S1MA and the Netherlands’ DNW facilities, work that helped validate computer simulations of the installed engine.

“As we move toward the next generation, we’ve been able to show that the noise levels are beneath those of the Leap-1, and we’ve continued to show hybrid electric is ready for the next generation,” said Christine Andrews, executive hybrid-electric systems leader at GE Aerospace.

CFM has run more than 7,600 dust ingestion cycles on RISE turbine-blade technology, including more than 2,800 on full-scale high-pressure parts in a GE F110 military engine and the rest on scaled blades in a LEAP-1B. Andrews said early testing points to fewer engine removals in hot, harsh conditions.

“In addition to having less engine removals due to not running the core temperature so hot, we’re also seeing via early testing that there’s less dust that goes through the core, and this also yields less engine removals. In fact, in the testing that we’ve done, we have seen that the hot and harsh of today will not be the hot and harsh of tomorrow,” she said.

Full-scale ground testing of the Open Fan front module is set for early 2027, with integrated system tests in 2028. Airbus is converting the first A380 ever built, MSN1, registered F-WWOW, into a flying laboratory. The double-deck jet offers enough clearance to mount the engine away from disturbed airflow off the wing. The EU-funded OFELIA and Safran-led TAKE OFF projects support the flight campaign.

Airframe integration is another open question. Rob Stallard, an analyst at Vertical Research Partners, has noted that the open rotor’s advantages come with complex wing or fuselage integration. That could stop airlines from easily swapping engine types and push planemakers away from offering two engine suppliers on their next jets.

Certification is another hurdle because the Open Fan has no containment case. In a comment-response document, EASA acknowledged in 2023 that its engine certification rules, known as CS-E, do not yet account for open rotors and that changes would be needed to certify such engines.

Rolls-Royce sticks with ducted UltraFan

Rolls-Royce plans to ground-test its UltraFan 30 narrowbody demonstrator in 2028. The demonstrator will use a 90-inch fan. Rolls-Royce recently tested the low-speed fan from its larger UltraFan on Rig 150 at the German-Dutch DNW wind tunnel to check crosswind performance and calibrate computer models.

The first demonstrator uses a core from the Pearl business jet engine. Rolls-Royce is developing a next-generation small core and a second-generation power gearbox for a production version.

“We’ll continue to push integration, both aerodynamic and structural, but also systems. What is the right level of electrical integration? What’s the right degree of hybridization?” said Alan Newby, director of research and technology at Rolls-Royce.

Newby said the core’s cycle temperatures have to be right the first time.

“A lot of focus is on getting that right balance, particularly in the core between high-temperature operations, but also making sure we’ve got that durability. So we will be getting the cooling design right and picking the fundamental cycle temperatures, because you only get one chance at that,” he said.

Newby has argued that a ducted design leaves planemakers a possible choice of engines, while an unducted design today offers only one. Airbus and Boeing have historically wanted at least two engine options to hold down prices and limit supply risk, Aerospace America reported.

Rolls-Royce Deutschland will also lead ELEVATED, a new EU-funded project that will build a hybrid-electric system into a donor engine for testing. Partners come from France, Germany, the Netherlands, Norway, Spain and the United Kingdom. Rolls-Royce aims to bring the technology to Technology Readiness Level 6 in 2029-2030.

Europe puts €290 million behind the race

Clean Aviation announced €290 million (about $330 million) in EU funding for 19 new projects on Sept. 17, mobilizing €664 million in total public and private research effort. Short- and medium-range aircraft technology received €106 million, hydrogen-powered aircraft €101 million and fast-track projects from universities and smaller firms €40 million.

Clean Aviation’s “Call 4 projects take our most promising technologies from research into ground and flight demonstration as a decisive step towards the development of our next generation aircraft,” said Rémi Maillard, executive vice president of engineering for Airbus’ commercial aircraft business and co-chair of Clean Aviation’s governing board.

Airbus scaled back its hydrogen aircraft timeline in early 2025, but the new round still funds both fuel cell and direct hydrogen combustion work. Airbus leads the EHPIC and HERO projects. The German Aerospace Center, known as DLR, leads FLHY-SYS. GE Avio and Safran lead the combustion-focused H-ELENA and FARMAN projects.

Clean Aviation has a €4.1 billion budget, with €1.7 billion from the EU and €2.4 billion from industry. Its projects target aircraft entering service by 2035. The fast-track projects start at the end of 2026, the rest follow in early 2027, and full-scale ground and flight demonstrations are planned for 2029-2030.

MTU Aero Engines leads HEURECA, a follow-on to the SWITCH project. SWITCH paired Pratt & Whitney’s geared turbofan with Collins Aerospace megawatt-class motor-generators and a water-enhanced turbofan concept that recovers exhaust water vapor and injects it into the combustor to cut nitrogen oxides and contrails. Flight tests of ducted variants could come under a future Clean Aviation Call 5.