GE understandably doesn't want the test engine to be the only one keeping an aircraft in the air. So it has a testbed plane, a four-engined Boeing 747, with one of its engines replaced by the new one. The "GE Propulsion Test Platform" has three standard CF6 engines, a workhorse that GE has been making since the 1970s in various, often modernized versions — and one giant GE9X. The three older engines provide enough power to keep the plane in the air in case the new one fails.
You need only look at the image below to see how ridiculously large the GE9X looks compared to the older engines. That's because it is the world's largest turbofan engine, measuring 134 inches (11 feet, 2 inches) in diameter. For reference, the internal cabin diameter of a Boeing 737 is 139 inches. So, yeah, it's a massive engine.
Despite being able to generate 105,000 pounds of thrust it is, according to its maker, the quietest GE engine ever produced, and will have the least NOx emissions of any GE engine, per pound of thrust produced. It will be slightly less powerful than the GE90-115B that powers the current Boeing 777-300ER aircraft, but it will be 10% more efficient, so the 777X will be able to fly farther than today's 777s. And because the new 777s will be partially made with lighter, composite materials, its engines don't need to be as powerful, even though the planes themselves will be larger.
The GE9X program is a couple of months behind schedule due to a design flaw found late last year, but GE already has almost 700 engines on order.
GE Aviation released a video of the takeoff and landing of the first flight:
