Two decades ago, GE engineers fanned out across the aviation industry, asking their customers what they wanted to see in a jet engine. The list they came back with was lengthy, comprising some 300 items, but it was topped by a simple request: fuel efficiency. Fuel costs, after all, account for close to a fifth of an airline’s operating expenses.
The engineers got to work with Boeing and they gave airlines what they asked for: an engine called the GE9X. The GE9X engine and the plane it was designed for, the Boeing 777X, will be 20% more fuel-efficient than their predecessors. On Friday, that powerfully efficient engine got one step closer to service when the Federal Aviation Administration certified it. The certification, a key milestone, means GE can start making GE9X engines for commercial service.
The GE9X also happens to be the most powerful jet engine in the world, incorporating technologies the world barely knew at the turn of the century. “We've developed an aircraft-engine combination that I honestly think is going to be unbeatable in the marketplace,” says Karl Sheldon, a senior engineering executive at GE Aviation who was involved in the project.
Sheldon, a mechanical engineer who’s spent nearly two decades at GE, knows what he’s talking about. He started out at GE Research, where scientists developed lightweight but heat-resistant materials called ceramic matrix composites. CMCs allow core parts of the GE9X to withstand temperatures as high as 2,400 degrees Fahrenheit — where even the most advanced alloys grow soft. At these searing temperatures, the engine can burn fuel more efficiently, generating more energy and fewer emissions.
Another key innovation is the engine’s 134-inch fan, made from sinuous carbon fiber composite blades. Driven by the efficient turbine, the fan is designed to ingest as much air as possible to propel the jet forward. The blades may look alien, but the GE9X will actually use the fourth generation of the GE technology. Composite blades have been serving for two decades on the GE90 and also the GEnx, the engine that the company developed for Boeing’s 787 Dreamliner jets.
By the time Sheldon joined GE Aviation in 2007, the company was already experimenting with 3D-printing parts from metal, an approach also known as additive manufacturing. In the last few years it introduced 3D-printed parts in the GE90 and the GEnx as well as the LEAP, a revolutionary engine for single-aisle jets developed by CFM International, a 50-50 joint company between GE Aviation and Safran Aircraft Engines. The just-certified GE9X engine has more than 300 3D-printed parts, including a nozzle designed to further reduce fuel use. “We piggybacked on a lot of technology development that came before us,” Sheldon says. “We were really able to capitalize on lessons learned from what was new only a few years ago.”
That development also includes big data and analytics. “With every generation of engines that we've introduced over the last decade, the digital connectivity of it has become more and more pronounced, and it culminates with the GE9X and the sensor suite that we have on it,” Sheldon says. “The telemetry that will be available to provide data back to us as an engine manufacturer is really going to be unprecedented. We will have the ability to monitor engine pressures, temperatures, flows. The predictive capability of that engine will exceed anything that we've got out there today.”
Data and software will also help keep maintenance costs low. “We’re within striking distance of a GE90 maintenance cost,” Sheldon says, adding that it’s “one heck of a technological feat to get that kind of performance with an engine that is much more complex.”
The certification process involved nine different engines, the first of which GE Aviation began testing on land in Peebles, Ohio, in 2017. Precisely prescribed by regulators, the regimen involved water, hail and bird ingestion, as well as a so-called blade-out, where the team exploded a blade inside the engine while it was running at high speed. The engine torture culminated in the “triple redline test” design to push, overheat and shake the engine as hard as possible — and beyond anything it would encounter in service. “We try to accelerate any type of fatigue mode that might be there and really push the engine beyond where it would ever expect to be in the field, just to make sure we got everything figured out,” Sheldon says.
After pushing a test engine through thousands of simulated takeoffs and landings in various conditions, the team took it apart to inspect each component, down to individual nuts and bolts. “We lay out everything that can be physically separated,” Sheldon says. “Imagine an area almost as large as a football field where every little part is put on a table, cleaned, inspected and reported on.”
After Peebles, one of the engines was loaded onto a truck and driven across the country to Victorville, California. There in the high Mojave Desert, it went through further tests on GE Aviation’s flying testbed. Finally, last year, GE started shipping the engines to Boeing, where they powered the planemaker’s four 777X test planes — which will also require their own certification. The 777X, which in one configuration will be able to carry more than 420 passengers, is scheduled to enter service in the first half of 2022. GE has received orders and commitments for more than 600 GE9X engines.
“There are things inside this engine that have never been done anywhere on the planet,” Sheldon says. “And this team figured it out. They are truly inventing the future of flight. I mean, they are really pushing the boundaries of the industry. I couldn't be more thrilled to be on this team. Honestly, I'm amazed at their ability.”