It began with a casual encounter in Paris and has flourished into a 40-year marriage with a remarkably successful offspring. CFM International – the union between the USA’s General Electric and France’s Snecma – is heading towards production of its 30,000th engine. But the joint venture’s start, back in the 1970s, was stuttering. The first years of the transatlantic relationship were fraught with cultural and language challenges, questions over the structure of the enterprise, and concerns within the US administration over transfer of sensitive military technology.

But these were nothing compared with a much more pressing concern as the decade ended. Five years after its creation, and eight years from the informal 1971 meeting at the Le Bourget show where the GE and Snecma presidents had begun their courtship, CFM International had one product in the market – a 10-tonne, 20,000lb-thrust (89kN) engine – but no production contract. The CFM56 looked a gallant failure and CFM may have been headed for the divorce court. Had that happened, the commercial airliner market would have turned out very differently.

The marriage was saved by Boeing. The airframer had chosen the CFM56 to power a version of the ageing 707 (later adopting it to re-engine its military tanker sibling, the US Air Force’s KC-135. Today the air force is CFM's single biggest customer). A re-engining effort for another venerable, four-engined type, the Douglas DC-8, bought the programme more time. But it was Seattle’s decision to commission the 18,500lb- to 23,500lb-thrust -3 version of the CFM56 for its 737-300 in the early 1980s that was the breakthrough for an engine that had all along been intended to power a new generation of twin-engined narrowbodies.


The Leap-1A is one of the three variants of the newest CFM engine


It was the start of arguably the most commercially successful pairing in aerospace. The CFM56 went on to exclusively power the next generation 737 from the 1990s and its Leap successor will be the sole engine type on the 737 Max. Of almost 27,000 CFM56 engines, some 14,000 have been fitted to 737s. CFM’s narrowbody dominance was consolidated later in the 1980s when Airbus selected the 22,000lb- to 25,500lb-thrust -5A to compete with the International Aero Engines’ V2500 on its new A320. Since then, more than 7,500 of the CFM engines have powered Airbus narrowbodies.

The engine found another application too in the early 1990s, this time on a widebody. The CFM56-powered Airbus A340 made its service debut in 1993. While sales of the quadjet did not set the world on fire, CFM had the benefit of exclusive supply, powering all 246 of the -200/300 variants delivered.

With the arrival this decade of new versions of the 737 and A320, as well as a flurry of new narrowbody and large regional contenders from Bombardier, China’s Comac, Embraer, Russia’s Irkut and Mitsubishi, the battle in the ever-growing single-aisle market has taken on a new dimension. What began as the TECH56 technology studies in the late 1990s developed into the LEAP56 (leading edge aviation propulsion) project and eventually the launch of the Leap engine for new generation narrowbodies in 2008.

While it seemed likely that Boeing would retain CFM as solus supplier on any new narrowbody, it was Comac that was first to select the Leap when it launched its clean-sheet C919 narrowbody, in November 2010. The following month, Airbus – quicker off the mark than Boeing with its decision to re-engine its top-selling product as the A320neo – also chose the new CFM engine, albeit as an option alongside Pratt & Whitney’s PW1000G PurePower geared turbofan, which emerged around the same time as the Leap and was chosen initially to power the Bombardier CSeries.

In 2011, after much speculation over its future single-aisle strategy, Boeing announced that it would be re-engining the 737 rather than launching an all-new narrowbody, and the Leap-1B would be its sole powerplant. Seattle’s loyalty came as little surprise. The airframer said it had been working with its propulsion partner of 30 years on configurations for both re-engined and possible new types. With just under 6,000 CFM56-powered 737s in service, a global maintenance, repair and overhaul network for the legacy engine, and hundreds of content airline customers, it was the low-risk choice.

Now with a backlog of more than 7,800 Leap engines – as well as some 4,500 CFM56s – the priority for the latest CFM president, Frenchman Jean-Paul Ebanga, seems less about securing new business and instead managing what he calls “one of the most complex supply chains in the world, but also one of the best prepared to cope with this challenge”. CFM boasts that it has never delayed an airliner delivery, and – despite a production ramp-up from 1,000 engines in 2000 to around 1,550 this year and 1,800 by the close of the decade – it is not a record Ebanga plans to let slip.

The Leap-1A for the Airbus A320neo family, which has been undertaking ground testing since September last year, is expected to be certificated in the first quarter of next year, ahead of the first flight of the Leap-powered A320neo. The -1C for the C919 is due to enter flight testing this autumn, although the engine is not expected to be certificated until the end of next year. The Leap-1B for the 737 Max was fired up for the first time at Snecma’s Villaroche plant in June and is expected to be handed over to Boeing as a certificated engine in mid-2016.

Ebanga’s team have to handle not only a rapid ramp-up, but a transition from the CFM56 to the Leap starting in 2016. Although the CFM56 product developed significantly between the original CFM56-2 and today’s -5B and -7B variants, the Leap represents a huge advance in technology and will require considerable new infrastructure. Most of the industrial investment is in place, he says. A new fanblade plant will open in France in a few months, ground was recently broken on an assembly plant in Indiana and a final assembly line in Villaroche is “very advanced”.

As with the CFM56, Snecma and GE manage their own supply chains for the elements of the Leap they are responsible for – Snecma the low-pressure turbine and fan, and GE the high-pressure compressor, combustor and high-pressure turbine that make up the engine’s core. Ebanga describes the global supply chain – that includes company owned factories from North Carolina to China as well as dozens of smaller suppliers – as a “beehive” with every member of the community focused on just-in-time manufacturing and quality.

“The Leap engine is result of hundreds of thousands of daily actions across the world, everyone producing parts to the right standards and at the right time, so that in the end you have an engine that is just produced by CFM,” he says. Ebanga admits that moving from a testing and certification regime to mass production of a new product in just a few months will be an “unprecedented challenge” , but says that “by the time we get to serial production we will have all the risks back to the level we want.”

CFM success timeline

Supporting the engine in service is also a challenge. The popularity of the CFM56 has created a global network of maintenance centres, run by Snecma, GE and third parties. But repairing the Leap – with its technologies such as 3D-woven, resin transfer moulding carbonfibre fan blades – is a trickier proposition for traditional shops. It led CFM in 2008 to launch its own unified service network, and seven in 10 Leap engines ordered come under this scheme. Ebanga says one of the biggest achievements of CFM has been transitioning from a programme-focused venture at a time when “the services business did not exist” to one where CFM can present “one face to the customer for everything”.

The agreement between GE and CFM has been renewed several times since 1974 and the latest contract signed in 2008 lasts to 2040, when the Leap will be a mature engine and production of CFM56 engines, even for spares, will have all but stopped. However, just as the CFM56 engine was improved on, so too will the Leap, insists CFM. “We have hundreds of developments in our pipeline,” executive vice-president Cedric Goubet said at July’s Farnborough air show. The current engine is just “the first step in a new generation of technologies” being worked on by both partners.

In an era of high fuel prices, shaving every possible kilogramme of weight while improving efficiency remains a holy grail for engine makers, and with GE and Snecma both making advances in composite technologies and additive manufacturing, this will be a key battleground. CFM vice-president Allen Paxson, also speaking at Farnborough, predicted that increasing use of ceramic matrix composites and additive manufactured processes – currently used for fuel nozzles – will become widespread in the coming years.

The question remains as to whether the big airframers will be content with iterative improvements such as these, or will look to a breakthrough technology such as open-rotor to replace their current narrowbodies. Rolls-Royce – absent from the narrowbody market since it pulled out of the IAE consortium, unhappy with partner P&W’s decision to pursue a geared turbofan design – has said it wants to re-enter the market in the 2020s. Snecma has been pursuing an open-rotor concept which it plans to flight test on an Airbus A340 in 2019.

Any realignment looks unlikely, however, until the 2030s at least. Would-be challengers to the Airbus/Boeing duopoly – Bombardier, Comac and Irkut – have all opted for a CFM or P&W engine. Until then, it will be hard for any new propulsion player to break in and the CFM agreement prevents GE or Snecma from going it alone or joining with anyone else in that segment, even if they wanted to. If anything, says Ebanga, the development of the Leap has pushed the two partners even closer together.

Ryanair livery

Improved fuel-burn allowed carriers such as Ryanair to increase fleet utilisation, says Ebanga


Back in 1974, a French state-owned enterprise and an American corporation, both with a heritage in military engines, might have seemed unlikely candidates to alter the face of short-haul commercial aviation, a segment utterly dominated by Pratt & Whitney at the time. But CFM has been a “unique organisation”, says Ebanga. “We brought in a new level in terms of fuel burn and reliability. This enabled guys to think about higher utilisation of these assets, and instead of flying twice or three times a day, Southwest and Ryanair were able to fly six or seven times. I’m not saying the CFM56 was the only reason they did this, but it was a key enabler in this huge change in aviation over the past 30 years.”

Source: Flight International