General Electric GE9X

In February 2012, GE announced studies on a more efficient derivative of the GE90, calling it the GE9X, to power both the -8 and -9 variants of the new Boeing 777X. It was to feature the same fan diameter as the GE90-115B with thrust decreased by to a new rating of per engine. In 2014, the fan diameter was increased another to , slightly increasing thrust from . The first engine was expected to be ground-tested in 2016, with flight testing to begin in 2017 and certification happening in 2018. with certification expected in late 2019. Ground testing The first engine to test (FETT) completed its first run in April 2016. This engine completed 375 cycles in 335 hours run-time, which validated the engine design in terms of aerodynamic performance, mechanical system behavior and secondary air system heat management. Eight additional engines were involved for certification, as well as one for ETOPS certification installed in the aircraft nacelle. In February 2018, the GE9X's first flight was delayed by problems discovered in the high-pressure compressor (HPC) variable stator vanes (VSV) lever arms. By January 4, 2019, eight test flights and 55 hours of run time had been completed. At the end of January, the turbine case and rear frame strut were damaged during the blade out test and relevant components were redesigned. In early May, the flight test program was completed after 320 hours run time, during which high-altitude cruise fuel burn was established. Engines were modified to a final certifiable configuration standard before the maiden flight of the 777X, delayed beyond the previously expected June 26 by a stator problem at the front of the 11-stage high-pressure compressor. Before certification, final tests included a full durability block test, replacing the usual "triple redline" test at maximum EGT and both rotor speeds, as modern high-bypass ratio engines cannot achieve all maximum conditions near sea level. The high-pressure compressor stator redesign delayed engine certification into autumn, which delayed the 777X first flight until January 2020. In 2022, a different issue with the GE9X paused testing of the 777X. ==Design==

The GE9X increases fuel efficiency by 10% over the GE90. Its 61:1 overall pressure ratio should help provide a 5% lower thrust specific fuel consumption (TSFC) than the XWB-97 with maintenance costs comparable to the GE90-115B. The initial thrust of will be followed by derated variants. Most of the efficiency increase comes from the better propulsion efficiency of the higher-bypass-ratio fan. The fan is housed in diameter case. Fourth generation carbon fiber composite materials, comprising the bulk of the fan blades, make them lighter, thinner, stronger, and more efficient. The GE9X also uses a carbon fiber composite fan case, first developed for the GEnx, to further reduce weight. The high pressure (HP) compressor is up to 2% more efficient. The first-stage HP turbine shroud, the first- and second-stage HP turbine nozzles and the inner and outer combustor linings are made from CMC, only static components, operating hotter than nickel alloys with some cooling. 3D printing is used to manufacture parts that would otherwise be impossible to make using traditional manufacturing processes. prototype flying with the GE9X. ==Specifications==