CFM targets leap in line replaceable unit reliability

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CFM International is planning especially gruelling tests to ensure promised line replaceable unit reliability for its next generation turbofan, the Leap-X1C.

"We've had a real focus on improving the reliability of the externals," says programme director Ron Klapproth. "The biggest challenge is to deliver all of this technology at the same level of reliability that the customers expect. They're very clear on that."

Destined for service entry on the Comac C919 single-aisle jetliner in 2016, the Leap-X1C is designed to provide 15% lower fuel burn compared with today's CFM56-5B and -7B engines as well as being quieter and producing significantly lower NOx.

"You can talk about fuel burn and emissions all you want," says Klapproth, "but you have to bring the reliability of today's CFM product."

Although CFM has not yet chosen vendors for the 60 or so line replaceable units that will be needed for the engine, the 50/50 joint venture between General Electric and Snecma is already designing engine-level tests to expose any lurking life expectancy issues in the equipment during the engine certification programme, expected to be complete in 2014.

"We will dedicate a series of engine testing in the certification programme to prove out the reliability of components," says Klapproth. "We will intentionally put an imbalance in an engine and do thousands of cycles to shake all the external components to make sure they can take it."

Behind CFM's push in part are lessons learned from the CFM56-7B engine. Introduced in December 1997 on Southwest Airlines Boeing 737-600/700/800s, the -7B engine experienced issues with its hydromechanical fuel control unit (HMU) in its first year in operation. The problem led to a 1998 airworthiness directive from the Federal Aviation Administration after reports of three uncommanded engine acceleration events, one of which resulted in an in-flight shutdown of an engine. CFM later identified the problem and began retrofitting the engines with an improved HMU in 1999.

Klapproth says CFM will begin the request for proposal process for the line replaceable units in 2011, noting that there is likely to be a high level of interest from vendors. "When you look at the volumes of aircraft and volumes of engines [coming], there's going to be a lot of interest to get on board."

Along with the C919, for which Comac is expecting to sell nearly 4,000 aircraft in the first 20 years of production, the Leap-X engine was also recently selected by Airbus as an option for its A320neo narrowbody, a re-engined aircraft the company says has a market potential of 4,000 aircraft over 15 years.