GE Aviation started testing its fourth-generation composite fan blades for the new GE9X turbofan, the company announced last week. Chosen to power the Boeing 777X, the 100,000-pound-thrust-class engine promises a 10-percent fuel burn improvement over the GE90-115B–the engine that powers the Boeing 777-300ER.

GE expects to spend $200 million this year on “maturation testing” of technologies for the new engine. A first round of tests in June at the ITP Engines UK facility in Rugby, UK, centered on validating the new carbon-fiber composite material GE plans to use to manufacture the fan blades. A second round of testing this summer will “further validate” the composite material and a steel alloy chosen for the blades’ leading edge. In the fall, GE plans to run fan performance tests on a Boeing fan rig in Seattle, Washington.

The GE9X uses 16 fan blades, fewer than the GE90-115B and Boeing 787 GEnx engines use, and a 132-inch-diameter composite fan case, the largest of any GE engine. The company said the lower blade count and composite blade material allow it to increase the fan tip speed, thereby improving the efficiency of the engine’s low-pressure turbine and delivering a fuel efficiency improvement of 1.5 percent over the GE90-115B.

This month, the company plans to start testing a GE9X high-pressure compressor at the GE Oil & Gas facility in Massa, Italy. Next year, its schedules call for it to begin testing hot-section components made from advanced ceramic matrix composites.

At the Paris Air Show in June, GE said it plans to freeze the engine design in 2015 and build the first test engine the following year. The company expects to flight-test the engine on a Boeing 747 testbed beginning in 2017 and aims to certify it in 2018.