General Electric is emphasizing the maturity of the advanced technology to be introduced in the GE9X engine for Boeing’s 777X, designed to provide a 10% lower fuel burn than the GE90 powering today’s 777-300ER.

“We will run the high-pressure compressor five years before certification,” says Bill Fitzgerald, GE Aviation vice president and general manager of the commercial engines operation.

The first version of the high-pressure compressor (HPC) is complete and will begin tests in July and two more iterations are planned before design of the 102,000-lb.-thrust GE90X is frozen in 2015.

With a 27:1 pressure ratio, 20% higher than that in the GENx (in turn 20% higher than in the GE90), the HPC is one of the key changes being introduced in the GE9X, which will exclusively power the 777X.

Others are a “fourth-generation” composite fan with wider, thinner (and fewer) blades, and lightweight, uncooled ceramic matrix composites (CMC) for high-pressure turbine (HPT) nozzles, shrouds and blades.

“We have a rigorous technology maturation program on all the parts that change,” says Bill Millhaem, GE90 general manager. “The first 4-5 years are about demonstrating technology..and producibility.”

The 132-in.-diameter fan will use a new lighter, higher-strength carbon-fiber material system, enabling a thinner blade with wider chord and more sweep. Blade count will reduce to 16 from 22 in the GE90.

A composite front fan-case, used in the GENx, will save more than 700 lb. per aircraft over the aluminum case in the GE90, Millhaem says.

The HPC alone will provide 2% fuel-burn reduction, and will feature new powder-metallurgy disk alloys to cope with 80-100-deg. higher temperatures at the back end of the compressor, he says. The HPC will have 11 stages, one more than in the GE90 and GENx.

CMCs will be used for inner and outer combustor liners, high-pressure turbine nozzles, first-stage shroud and uncooled second-stage blades. “We are doing testing to determine their feasibility,” Millhaem says. “We will run CMCs in 2014 in GENx demonstrator engines,” says Fitzgerald.

CMCs are a third the weight of high-temperature superalloys, have two times the strength and 20% greater temperature capability, reducing the cooling air required, Millhaem says.

Use of CMCs in the hot section accounts for another 2% fuel-burn reduction. GE has a back-up plan “that will keep the impact relatively small,” he says, if CMC blades prove not to be workable.

Titanium-aluminide blades will be used in the low-pressure turbine. Additive manufacturing is being looked at for fuel nozzles, where it is used in the smaller General Electric/Snecma Leap-1. The GE9X will have a so-called TAPS 3 combustor, rebalanced for the higher pressure and temperature of the air from the HPC.

“We are looking at active clearance control in the engine and evaluating other new technologies,” says Millhaem, stressing that everything in the engine “will be at TRL 6 [technology readiness level] and MRL 6 [manufacturing readiness level] at tollgate 6 [design freeze in 2015].”

The first full core engine is planned to run in 2015, and the first full engine in 2016. The GE9X is scheduled to get airborne on a GE flying test bed in 2017, with certification planned for 2018.

GE has “no plans” to put GE9X technology back into the GE90, but because it will first test the changes in GENx demonstrators, the experience “will allow us to define ways to take technologies back into the GENx,” says Fitzgerald.