CFM International on 22 April started building the first parts for the common Leap-1A and -1C engines selected to power the Airbus A320neo and Comac C919 families.

The General Electric and Snecma joint venture also is approaching the firm configuration milestone on the Leap-1B engine for the Boeing 737 Max.

In the duel of next-generation narrowbody engines, Pratt & Whitney has a nearly one-year head start due mainly to its earlier position on the Bombardier CSeries programme. P&W delivered the first PW1100G engine for the A320neo family to its internal ground test team last October.

But CFM is following as planned 11 months later and so far remains on schedule, as the twin challenges of airworthiness certification and a steep production ramp-up still loom ahead.

Neither process is made easier by CFM's plan to introduce several new technologies in a narrowbody-class engine, including the first uses of ceramic matrix composites in the turbine section, additive manufacturing techniques for fuel nozzles in the combustor and five stages of blisks in the compressor section. CFM corporate member GE has used composite blades and fan cases in previous engine models, but the scale of demand for Leap engines means production levels dwarf all previous efforts.

Gareth Richards, CFM's Leap project manager, notes that each Leap engine contains 18 composite blades, meaning that Snecma must produce 32,000 3D-woven composite blades at full-rate production of 1,800 engines per year after 2020.

"Nobody will have ever accomplished composite manufacturing, except maybe for people who make golf clubs which are not of aerospace quality, to that scale," Richards says. "That's kind of staggering."

At the same time, CFM also downplays the scale of the production ramp-up. Deliveries of CFM56 engines have doubled to 1,500 over the last decade, while the jump to 1,700 mostly Leap engines by 2019 represents only a 13% increase over the next six years.

However, the complexity of several critical parts, such as the fan blades, rises to a new level on the Leap engine.

Snecma is planning to build two new factories for assembling the blades. How the factories will support blades for all three variants is still being decided, but CFM officials are discussing the possibility of dedicating one factory to producing only blades for the Leap-1B. CFM is the exclusive engine supplier for the 737 Max, while it expects to split engine orders for the A320neo and build an incremental number of engines for the C919.

"That's just because for volume and for lean and simplicity, you give that factory only one part number to worry about," Richards says.

Discussions are also underway with regulators in the USA and Europe. A preliminary type board meeting was held on 19 March with CFM, the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA). CFM submitted separate proposals to both agencies during the meeting, outlining how it intends to meet thousands of individual certification requirements.

CFM officials believe it is possible to achieve FAR 33 certification on all three Leap engines with the imposition of no more than a few special conditions, despite the new technologies being introduced.

"Special conditions normally arise where we're taking an exception to a regulation," Richards says. "There's very, very few of those in our submission."

The FAA and EASA are expected to respond to CFM's proposals within 60 to 90 days of the 19 March meeting, Richards says. Their responses will set the rules for the year-long series of ground testing that are expected to begin on the Leap-1A in September. Flight testing will begin on GE's Boeing 747 flying testbed in June next year, using the Leap-1C engine for the C919. That's because the Leap-1C must be delivered to Comac a year ahead of the Leap-1A, to support first flight of the C919 in 2014.

CFM has not yet reached a decision whether to build the Leap-1C in China. Such a step would require applying for a new production certificate with Chinese authorities or applying Snecma's existing production certificate.

"The regulatory and quality aspects get very complicated," Richards says.

Source: Air Transport Intelligence news