Powering up: How the CFM56 will keep aircrafts busy for decades

From a less than auspicious beginning, CFM International developed its CFM56 turbofan into the world’s best-selling airliner engine. Now, although its attention is turning to the new-technology LEAP, the huge CFM56 fleet is likely to keep aircraft and MROs busy for decades to come.

[This piece was originally published in 2019, an update on CFM LEAP engines can be read here and in the March 2021 issue of MRO Management]

After an executive meeting at the 1971 Paris Air Show, General Electric and SNECMA laid the foundations for a joint venture that would become CFM International (CFMI).

By 1974, the company had its first product, the CFM56, up and running, literally, but found a complete lack of customers for the new engine, even after an extensive trials programme.

Boeing recognised the engine’s potential for satisfying new, more stringent noise regulations, but its re-engined 707-700 also failed to garner interest. Ironically, United Airlines eventually chose the CFM56 to re-engine part of its Douglas DC-8 fleet, providing sufficient revenue to keep the programme alive.

CFM56 engine

Then the US Air Force decided that it needed a new powerplant for the majority of its massive KC-135 Stratotanker fleet; in 1980, it announced CFMI as contract winner with the F108 military equivalent of the CFM56 engine.

Boeing subsequently selected a modified CFM56 as its Model 737 adopted a high-bypass powerplant from the 737-300 onwards, offering the CFMI product as the only 737 engine option right through to the end of 737 Next Generation production.

There, the CFM56 success story might have ended quite gloriously, but Airbus also offered the engine, as an alternative to the IAE V2500, on its A320 Family, in direct competition with the 737.

Today, Boeing’s 737 programme is switching over to the 737MAX, powered exclusively by CFMI’s CFM56 successor, the LEAP, which Airbus offers as an option on its A320neo Family aircraft, alongside Pratt & Whitney’s PW1000G.

Around 500kg lighter than the CFM56 and 15 per cent more fuel efficient, LEAP is based on the technology developed for the core of General Electric’s GENx, designed for the 787 Dreamliner and 747-8. LEAP had already attracted more than 16,000 orders by mid-July 2018 and was galloping towards the level of success the CFM56 initially struggled to achieve.

Four decades later

After 40 years production, CFMI is now a General Electric/Safran Aircraft Engines company, but it is still selling the CFM56 to airline customers, Hongtu Airlines and Loong Air committing to the CFM56-5B at July’s Farnborough Airshow.

These were but a drop in the ocean of CFMI’s show bonanza, however, with orders and commitments for more than 850 LEAP and CFM56 engines worth, when combined with long-term services agreements, $15.7 billion at list prices.

The continuing size of the global CFM56 fleet and nascent success of the LEAP engine is also great news for the service industry. With thousands of units in operation, the CFM56 represents a rich source of revenue for MRO providers – there’s significant work to be had even from supporting specific engine models.

StandardAero focuses its CFM56 expertise on the CFM56-7B as Will Findlater, director of CFM56 Customer Programs, explains.


“We entered the CFM56 market place for a number of reasons. As we grow, we continue looking for new and larger engine platforms where we can use our decades of gas turbine expertise to add value for our customers.

“With the CFM56-7B, we recognised a niche in North America for an OEM-aligned, yet independently owned MRO provider. Through previous acquisition of component repair shops, we already had a significant compliment of -7B repairs available and by virtue of the size and relative youth of the 737NG fleet, we knew investment in a CFM56-7B business would provide stability for our workforce and a return on investment for our shareholders for many years to come.”

In excess of 8,000 -7Bs are currently installed in 737NGs, and the engine is also in the early stages of powering the 737NG-based P-8 Poseidon maritime patrol aircraft too. Considering that uptake alone, the engine might easily be in service 50 years hence, during which time StandardAero is likely to evolve its MRO offering to suit.

“We always look for opportunities to improve the level of service our customers receive,” Findlater says. “For existing customers that may mean offerings like fleet maintenance modelling, trend monitoring and work scope customisation. We also work closely with the OEM on the development of new repairs in an effort to lower maintenance costs.

“As with any engine platform, eventually the larger carriers will begin to replace the 737NG, presumably with the 737MAX or similar. During that transition, smaller operators with different maintenance philosophies will begin operating the engines, and more used materials will become available as aircraft are retired and torn down.

“In terms of growth, our goal is to diversify our customer portfolio. We’re looking to extend our CFM56 services to airline customers of our legacy Vector Aerospace businesses that might operate the 737NG, and we’ve begun working with the US Navy on engine services for its growing fleet of P-8 aircraft.”

Working hard, working long

The 737NG is a hardworking aircraft, which means its CFM56 powerplant must work hard and deliver exceptional reliability in return.

Findlater notes: “The CFM56-7B is extremely reliable and depending on an airline’s operational profile and planned lifespan of the airframe, the engines may only require two or three scheduled shop visits.”

StandardAero regularly sees engines with high hours, with an average of almost 42,000 hours across the CFM56-7Bs received for scheduled shop visits to mid-August in 2018.

“The highest was in excess of 65,000 hours, but there is no limit to engine life since individual parts can always be replaced. The question becomes one of economics – does it make sense to rebuild an older engine or is it better to replace it?

“As the engine ages, additional field level inspections come up on the fan blades and turbine rear frame. As a credit to the reliability of the CFM56-7B, a large majority of engine removals are driven by the expiration of life-limited components [LLP].

Constructing the CFM56 engine

“Indeed, customer convenience is a more common reason for removal than engine condition issues.” Otherwise, regular CFM56-7B maintenance requirements are similar to those of many other engines – including oil servicing, and borescope and visual inspections.

Surprisingly, although StandardAero has sufficient experience with the CFM56-7B to confidently predict life-related maintenance requirements as they emerge, Findlater says: “Something like 60 per cent of the installed fleet has not been through a scheduled shop visit yet, so most of our experience is on engines of a relatively young age. But should we see any conditions that might be leading indicators of a potential issue, we work closely with the OEM to report and investigate. This may result in new repair development or additional service bulletins.”

Understanding the CFM56

While LEAP is CFM’s focus product going forward, in its later variants the CFM56 remains an exceptionally reliable, fuel-efficient engine that has been subject to various technology insertion programmes.

StandardAero’s Findlater says: “Tech insertion refers to the redesigned high-pressure compressor (HPC) blades, a modified combustor, and improved high pressure turbine (HPT) and low pressure turbine (LPT) components that became the production standard for the -5B and -7B in 2007.

“The Evolution variant of the -7B engine followed in 2011, with enhanced airfoil designs, improved cooling and reduced part count. We expect to see CFM continue to develop repairs and other improvements to extend the reliability and expected TOW [time on wing] of its engines.”

Of course, even the most reliable engine will suffer consequences from operating in particularly dusty or sandy environments, while ice might cause FOD and an airline’s operational profile may even be significant. Findlater reports: “CFM recognises regional and environmental impacts to the hardware.

Work scoping for shop visits takes these into account, especially in the hot section. There are service bulletins aimed at improving the expected time on wing, which are applicable to engines that perform a majority of take-offs in these geographic regions – commonly referred to as ‘hot and harsh’ environments.

Cooler environments, including North America and Europe, are not affected.

“Engines that fly shorter routes, less than 1.5 hours:1 cycle, typically reach the expiration of their LLP before having issues with performance margins. The thrust rating of the engine and level of de-rate also seem to have a larger impact on engine condition than regular flight length.”

Global industry

CFM International has built its success around the global CFM56 market and StandardAero in turn has developed a complete service offering around the engine.

As well as scheduled maintenance and repair, it includes lease engine support, where StandardAero provides an engine to a customer, either to cover a scheduled removal or by way of AOG support, to keep an aircraft flying while the removed engine undergoes maintenance and/or repair.

“StandardAero does not currently own any CFM56-7B lease assets,” Findlater notes, “but we do have agreements with several leasing companies that allow us to sublease engines.”

With the CFM56 in service worldwide, StandardAero’s portfolio further includes global field service support. “Our Mobile Service Teams are strategically located around the globe to provide rapid response to an operator’s engine, airframe and APU needs. They bring the same technical capabilities, authorisations and quality systems used in our repair centres. AOG support is also available, from our field services teams.”

The CFM56-7B’s natural successor, CFM’s LEAP engine represents an emerging MRO requirement that StandardAero is already adding to its portfolio. In fact, the relationship goes deeper than simply maintaining and fixing the new engine, as Findlater explains: “We have a history of collaborating with engine OEMs to provide high value, reliable engine maintenance to operators.

“We expect to maintain those strategic OEM partnerships into the future, including working with CFM on LEAP, and on other new engine platforms. A number of our existing customers are adding LEAP engines to their fleets and we want to continue servicing those customers.

“Through our support of the GE Testing, Research and Development Centre in Winnipeg, StandardAero technicians are actually working closely with our GE partners to test and develop next generation engine platforms.”

Speaking in the wake of its stellar Farnborough, CFMI’s President and Chief Executive Officer, Gaël Méheust, said: “We just delivered the 1,000th LEAP engine, the fleet has logged more than 1.5 million flight hours, and we have the highest daily utilisation in this thrust class. That means our customers have the flexibility to operate their assets when they want, where they want, as often as they want.”

He’s undoubtedly correct and today’s CFM56 fleet and tomorrow’s LEAPs owe much of that availability to their inherent reliability and a mature, global MRO network.

Editor’s Note: The post was originally published in October 2018.

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