CFM finalises LEAP-X engine architecture

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CFM International partners General Electric and Snecma have finalised the architecture of their LEAP-X turbofan, which is under development to equip the next generation of narrowbody airliners from Airbus and Boeing.

The engine is being designed for a possible service entry in 2016, offering a 16% reduction in fuel-burn compared with the best-selling CFM56, which it will eventually replace. However there are widespread expectations that the airframers will not bring their new 150-seat aircraft to the market before the end of the next decade.

"As the entry into service date moves to the right, we get the benefit of that additional time to put more efficient components into the engine," says LEAP-X programme manager Ron Klapproth.

The LEAP-X will have a bypass ratio of around 10, compared with 5-6 for the CFM56 family, and a core pressure ratio double that of the current engine, at 22. The powerplant will also feature a two-stage high-pressure turbine driving a 10-stage compressor, and the low-pressure turbine blades will be produced using ceramic matrix composite (CMC), says CFM International executive vice president Olivier Savin.

"Last year we didn't talk about CMC even though we were working on it, because we didn't want to promise something that was not mature enough," says Savin. This year...we think that it's achieveable and it's useful."

The LEAP-X core will undergo bench tests starting in mid-2009, and the first run of the full powerplant demonstrator is scheduled for 2012.

"We need to have the core on test a minimum of seven years before certification," says Klapproth.

The first phase of performance tests of LEAP-X's 18-blade, 1.8m (71in) diameter composite fan mounted on a CFM56-5C core at Villaroche in France are around two-thirds complete, with results "in line with predictions," says chief engineer Jerome Friedel.

The fan demonstrator will be shipped to GE's Peebles facility later this year for acoustic and crosswind trials, before being returned to Villaroche for 5,000 cycles of endurance testing.

The composite fan and casing, produced using three-dimensional resin transfer molding, are expected to yield more than 450kg (1,000lb) in weight savings per aircraft, says Savin. The CMC low-pressure turbine will save a further 150kg.