Disk Durability Has Southwest Concerned Over CFM Leap Availability

TAMPA—CFM’s decision to cap the life limit of a critical Leap-1B component has Southwest Airlines concerned about a potential engine shortage as the manufacturer works to supply an improved part in time to feed scheduled overhauls for the airline’s highest-time Boeing 737 MAX engines.

CFM has told operators that life limits of original Leap-1B high-pressure turbine (HPT) stage 1 disks will not be extended beyond their current 10,000-cycle threshold. CFM is developing a new part with the more conventional 17,500 cycle limit—equivalent to 9-10 years of flying for the busiest engines. But the improved part will not be ready before the second half of this year.

“What we’re being told is that there will be a new disk in production by the third quarter of this year, and that will be [approved] with an ultimate life of 17,500 cycles by the end of the year,” Southwest Director of Fleet Asset Management Ken Barone said at Aviation Week’s AeroEngines Americas. “It’s going to take a lot of work.”

Barone expressed confidence that the GE Aerospace/Safran Aircraft Engines joint venture company will hit its marks and deliver new, 17,500-cycle life disks in time to meet Southwest’s needs. But he’s not taking any chances, particularly given the lack of spare narrowbody lift or engine spare parts.

“That is the best-case scenario, and we hope that happens,” Barone said of CFM’s timeline. “What we would look at as an operator, though, is what is Plan B and Plan C if that doesn’t happen?

Southwest is “working closely with CFM and [GE Aerospace] and all of our partners out there to make sure that if for some reason it’s another six months, we are prepared—operationally at Southwest and as an industry—to be able to work through that,” Barone said. “That’s a concern. That’s probably our biggest focus right now is just making sure we’re communicating ... and that the industry is going to be ready.”

Engine swaps often match higher-time aircraft with lower-time engines. But given the lack of spare Leaps, engines with available green time do not stay off wing for long.

Aviation Week’s Tracked Aircraft Utilization (TAU) data suggest there are at least 150 Leap-1Bs that will reach the 10,000-cycle threshold in the next 12-24 months.

Southwest has more than 40 737-8s with at least 8,000 cycles, including six with more than 9,500, TAU shows.

Only two other carriers have more than five Leap-1B-powered aircraft with at least 8,000 cycles—Malta Air, with 22, and Brazil’s GOL, with 13, TAU shows.

A Southwest 737 MAX averages about 140 cycles per month, or 1,680 per year. GOL’s are even busier, at 150 cycles per month on average.

The scenario, combined with an already constrained supply of spare Leap engines and parts, means any delays to CFM’s plan could leave Southwest—and potentially other airlines—scrambling to keep affected aircraft in service.

Evaluating a new engine model’s performance and extending service lives to a manufacturer’s best-case targets are routine steps in every program’s maturation process. The extensions, which the FAA must approve, are validated with manufacturer data, including information from teardowns of higher-cycle engines.

In some cases, findings show a part’s life can’t be extended without improving its design. Ideally, such work is done well in advance of engines reaching the initial, conservative limits assigned to key LLPs, leaving operators unaffected.

But the Leap-1B’s maturation has uncovered several major durability issues, notably fuel nozzle coking and turbine blade wear, that required significant engineering resources and new-part development to solve. This, multiple sources confirm to Aviation Week, has slowed the engine program’s routine post-service entry evaluation and improvement process.

In the Leap-1B HPT stage 1 disk case, findings from routine shop visits prompted CFM’s decision to develop an improved version rather than seek a life extension. CFM’s plan is to align disk swaps with scheduled engine overhauls, which the manufacturer manages for Southwest and many other carriers under power-by-the-hour agreements, to minimize operational disruptions.

The company declined to elaborate on specific issues found that prompted its decision or discuss the new part’s development timeline. The Leap-1A, which competes with the Pratt & Whitney PW1000G geared turbofan (GTF) on the Airbus A320neo family, has its own life-extension process and is not affected by the Leap-1B findings.

“At CFM International, we know durability and reliability are top priorities for our customers, and we are continuously looking for ways to improve time-on-wing to better serve our customers’ needs,” the company said.

Sources with knowledge of the situation tell Aviation Week that the Leap disk issues are not related to contaminated powder metal (PM).

CFM’s problems have been overshadowed by a series of durability issues on the PW1000G GTF, followed by a quality control issue that led to thousands of parts made of contaminated PM being installed on A320neos, A220s, and Embraer EJet E2s. The resulting years-long inspection and part-swap program has jammed Pratt’s overhaul shops and grounded hundreds of aircraft as engines queue up, awaiting induction.

While CFM’s problems have been less disruptive, they are a major contributor to a disappointing track record for current-generation narrowbody engines. The issues have added stress to an already brittle supply chain and driven demand for services on older engines to help operators keep up with strong passenger demand.