A first-flight milestone for the GE9X turbofan is only weeks away after GE Aviation completed installing the 339cm (133.5in)-diameter turbofan on the Boeing 747-400 testbed.
A photo released by GE show how the 105,000lb-thrust powerplant for Boeing's 777X fits snugly under – and slightly over – the wing of a 747.
With a fan diameter 55% wider than the 747-400's three other CF6-80C2 engines, the GE9X forced GE and Boeing to make several modifications, including a strengthened wing and pylon.
The upcoming flight tests will be used to validate how the GE9X conforms to a promised 10% fuel-burn reduction relative to the GE90-115B, the engine used to power the 777-300ER.
It is the fourth test engine in the GE9X programme.
The first engine to test was fired up initially in April 2016. GE ran the second engine to test last May.
GE has started certification testing on the GE9X, with plans to achieve airworthiness certification next year. The first 777-9 test aircraft is scheduled to fly in 2019, followed by certification and entry into service before the second half of 2020.