B777X motoren testes på B747 - AW&ST

GE9X For Boeing 777X Delivered For Final Flying Testbed Certification Guy Norris Providing graphic proof of aviation’s never-ending drive for higher bypass ratios and greater propulsive efficiency, General Electric’s gargantuan GE9X, the largest turbofan ever to fly, is poised to return to the skies in November for a final evaluation campaign on the company’s Boeing 747-400 flying testbed. Ready for flight test in its definitive production configuration, the 105,000-lb.-thrust GE9X is in development for Boeing’s new 777X twinjet flagship, about to enter the closing stages of an intense and broad-ranging process that began with core tests in late 2015. The effort will clear it for the start of flight tests of the 777-9, the initial 777X-family variant, in March 2019, followed shortly by certification of the engine itself. GE9X enters certification flight-test phase in November First compliance engines for initial 777-9 flight test aircraft in assembly CMC ramp-up key element of production readiness for GE9X The flight-test engine, which is due to be attached to the 747-400 at GE’s Victorville, California, flight-test operations facility in the second half of October, is one of eight GE9X development units in the baseline program. A further batch of eight compliance engines, plus two spares, are also under assembly, with the first expected to arrive at Boeing’s Everett, Washington, site in November for completion with buildup units and accessories prior to installation on the first 777-9. Rebuilt for the flight-test program, Engine 004 is the same unit that was used for the initial flight phase between March and May. The rebuild adds stronger variable stator vane (VSV) actuator lever arms, which in the original design failed during runs of the second ground-test engine as it was being used to demonstrate extreme performance conditions required to pass the official FAA 150-hr. block test. During this intensive test, the engine was run at triple red-line conditions (maximum fan speed, core speed and exhaust gas temperature) to evaluate the engine at its operational limits.

The flaw in the lever arm, which moves the VSVs to modulate flow through the GE9X’s 11-stage high-pressure compressor section, led to a pause in the program and contributed to a roughly three-month delay to the start of flight tests. Despite this, and the resulting schedule impact, Boeing and GE say the knock-on effect has been minimal and the initial 777-9 remains on track to complete the bulk of tests in 2019 and enter service in 2020. The follow-on 777-8 variant, also powered exclusively by the GE9X, is set to debut in 2022.

Though limited in extent by the non-production-standard lever arm issue, initial flight tests showed performance at altitude was on target. Credit: GE Aviation