A few decades ago, engineers at GE Aviation approached customers about what they wanted to see in an ideal jet engine. The engineers came up with a wish list of around 300 items, with one wish firmly at the top: fuel efficiency. No wonder, given that fuel s for nearly one-fifth of an airline's operating costs. Those engineers got to work and created the GE9X engine. Together, the engine and the plane for which it was designed, Boeing's 777X widebody enger jet, are 20% more efficient than its predecessor, the Boeing 777-300ER, powered by a pair of GE90 engines. Efficiency isn't the only thing this machine has going for it. It is also the most powerful jet engine in existence at 105000 pounds.
In September, the Federal Aviation istration certified the engine, meaning GE can start building engines for commercial service. But building the world's biggest and most powerful commercial jet engine also means having to design ways to transport it, test it, and hang it under the wing of GE's flight test bench.
How exactly do you shut an engine that is as big as the body of a Boeing 737 under the wing of a Boeing 747? And what happens if the engine is too big for the state roads leading to a test site?
Here are some of the fascinating technical challenges that GE Aviation engineers faced in order to achieve certification for the world's most powerful engine.
With its FAN reaching over 11 feet in diameter, the GE9X engine required a uniquely designed carrier that would allow the engine to be road loaded while remaining below the maximum height requirements so the engine would not snag power lines, railroad trestles and other transportation challenges. The team designed a nested trailer allowing the GE9X to cross country to Boeing's facility in Everett
Every engine program creates its own challenges, and nowhere was that clearer than the roads around GE Aviation's Peebles Test Operation in Peebles, Ohio, a village of less than 2.000 people 65 miles east of Cincinnati. Although the transport vehicle was not very different from the one used for the GE90, more than one GE9X engine was entering or leaving the test site at the same time. For safety reasons and to give transport vehicles more room, Ohio State Routes 73 and 32 were widened so that trucks carrying the GE9X had enough room for two engines to each other.
While the video above is from the Peebles test range, it does give you an idea of how big the engine is traveling on the road.
At a whopping 18 feet in diameter and 15 feet long, the bellmouth inlet to the GE9X is the largest in the world. When it was transported to Ohio, the Highway Patrol measured the shipment at a weigh station because it took the “broad load” concept to a new level.
Engineers and aviation enthusiasts marveled at how peculiar the gigantic GE9X looked on the flight test wing, especially compared to the three CF6 engines next to it. Given the GE3,3X's 9-foot diameter, many have also asked: How do engineers for ground clearance?
The engine is mounted on a unique pole that swings the engine in front of the wing and tilts it upwards by approximately 7 degrees. Additionally, engineers extended the landing gear struts to provide an additional 4 inches of space. The result is about 18 inches of space between the bottom of the nacelle and the ground when the test aircraft is stopped on the runway.
Given the relatively small clearance, flying in crosswinds presents another challenge. The balance of weight on the wings is offset by the fuel in the tanks. GE's test 747 was modified, the fuel transfer between the tanks is manual, thus making the pilot control from the cockpit. The GE9X has 105.000 pounds of thrust, the CF6 69000 pounds of thrust, on takeoff both CF6s are used on one wing and only the GE9X on the other.
According to GE test pilot Jon Ohman, Boeing provides performance calculations for the 747's unique configuration with the variety of test engines it flies. With the GE9X producing significantly more thrust than a CF6 engine, takeoff and climb performance is excellent. With the GE9X and full takeoff thrust, we have to reduce the #1 engine thrust to ensure proper directional control in case of #4 engine failure. Cruise performance relative to overall fuel consumption is slightly higher than normal , mostly due to the added drag of our asymmetric setup.
