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Originally published December 6, 2012 at 9:57 PM | Page modified December 10, 2012 at 11:05 AM

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Corrected version

737 MAX engine will push the envelope

Seattle Times business staff

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In the heated sales battle between Boeing’s 737 MAX and Airbus’ A320 neo, one neutral arbiter can blow some cool air on the claims of superior performance by both sides.

For this next generation of narrowbody airplanes, it’s all about the engines.

CFM International, a joint venture between GE and Snecma of France, makes an engine that powers today’s 737s and A320s. It also is developing a new, super-efficient engine — called the LEAP — for both the MAX and the neo.

In a briefing in Seattle this week, LEAP program managers Gareth Richards and Francois Bastin outlined their technology.

They also offered a calmer take on how the two airplanes may stack up than Airbus did in recent trade- press ads showing the 737 MAX with a Pinocchio nose.

The engine-makers’ assessment? “The relative improvement over today’s product is the same in both cases,” Richards said.

With the Boeing plane lighter than the Airbus, the MAX version of the LEAP is much smaller than the neo version — 69 inches vs. 78 inches in diameter.

Yet, CFM is contractually guaranteeing that the MAX and the neo engines will each be 15 percent more fuel-efficient than current models.

That sounds like a recipe for maintaining today’s status quo, in which Airbus and Boeing split the narrowbody market roughly evenly.

Yet there is risk. Improving today’s already breathtaking engine technology entails some big ... leaps.

Snecma is making the LEAP’s fan and fan casing from advanced composites instead of metal — each of the fan’s 18 blades is woven from miles of carbon fiber.

The total weight savings from using composites in the fan system alone is 500 pounds.

Snecma’s debris rejection system ensures that sand or other runway detritus that is sucked in by the fan is centrifuged out to the edges and bypasses the engine core.

GE’s expertise is in the hot, high-pressure core of the engine, where the air is squeezed until its volume is reduced by a factor of 22 — twice the compression ratio in today’s 737 engine.

As the compressed air flows into a combustion chamber that can reach a temperature of more than 3,000 degrees F, only a separate streaming layer of cool air prevents the metal from melting.

The hot gas flow then turns a high pressure turbine, around which is a shroud made from a ceramic composite, strengthened with metallic threads — just thousandths of an inch away from the fast-spinning turbine blades.

Both the spinning and the static components expand with heat, so a flow of cooling air, precisely adjusted on the fly, must be used to tweak the temperature and maintain the tight clearance.

With so much that’s new, can the LEAP be as reliable as CFM’s current engines?

That’s a tough standard. Earlier this year, an engine on a 737 flown by German charter carrier TUIFly passed the record milestone of 13 years on the wing: more than 50,000 flight hours without coming off for maintenance.

Bastin said the LEAP’s new elements have been developed and tested over years. “It’s an evolutionary approach to introduce revolutionary technology,” he said.

Both executives said CFM is on schedule to test the first complete LEAP engine for the neo next year and fly it in 2014, with the MAX version following about a year later.

“We are right where we want to be,” Richards said.

Dominic Gates: (206) 464-2963 or

The original story was published on Dec. 6, 2012, and was corrected the next day. An earlier version of this story incorrectly stated that the LEAP engine fan blades are hollow. It also incorrectly stated that a ceramic composite shroud surrounds the fan at the front of the engine. In fact, this shroud surrounds the high pressure turbine further back. The original also said incorrectly, based on information from CFM, that a CFM engine had flown nine years without coming off for maintenance. The correct period is 13 years.

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