Groundhog Day 1995 will go down in the history books, and not just because Punxsutawney Phil cast no shadow. While the sky was cloudy in Pennsylvania on Friday, Feb. 2, 1995, a new chapter in commercial aviation was dawning by the Ohio River.
It happened in the Cincinnati suburb of Evendale, home to the headquarters of GE Aviation, where a crowded conference room filled up with GE engineers and executives and officials from the Federal Aviation Administration (FAA). On the table were certification documents for a giant high-bypass turbofan aircraft engine called the GE90, which the company had spent the previous decade developing. Without certification, the engine couldn’t fly on Boeing’s 777 airplane.
The GE90 was a big bet by Brian Rowe, the GE unit’s CEO at the time. Rowe believed in Boeing’s concept that large jetliners flying long-distance, international routes could be powered by just two engines, instead of four as was typical, reducing both fuel and maintenance costs. But getting there meant supersizing the engines and developing parts from materials never used in civilian aviation before. “The GE90 will be the engine that will lead the way to the 21st century,” Rowe said.
The tension in the room turned into relief as FAA representatives leaned forward and signed the documents, declaring the GE90 engine officially airworthy. But there was no time for champagne or celebration. “We put the certificate straight on the fax machine and sent it to Seattle,” remembers Phillip Rambo, who was present in the room as a senior engineer on the GE90 program.
Over in the Pacific Northwest, a team of technicians was standing by. They immediately printed an aircraft nameplate for a twin-engine Boeing 777 that was waiting on the runway. That plate gave the 777 the all-clear to fly. “It made its first test flight with the GE90 engine that same afternoon,” says Rambo, now a chief consulting engineer with GE Aviation.
The rest, as they say, is history. The GE90 and the 777 went on to reinvent the logistics, economics and aesthetics of jet travel, enabling an era of twin-engine airplanes and smooth, cost-efficient, long-haul flights.
A quarter of a century may have passed since Groundhog Day 1995, but the GE90 is still the benchmark against which other modern jet engines are measured. It reigned supreme as the world’s largest and most powerful aircraft engine until another GE Aviation product, the GE9X, dethroned it last year. Much of the cutting-edge technology that’s now standard in modern jet engines — such as lightweight, composite fan blades and 3D-printed parts — began in the GE90 family. “It all started with this engine,” says Jim Elliott, a principal engineer at GE Aviation. “It has exceeded all expectations and become the envy of the industry.”
The numbers tell one part of the story. Close to 3,000 GE90 engines have rolled off the production line since 1995, recording approximately 28 million flights and nearly 90 million flight hours between them. British Airways was the first airline to fit its Boeing 777 fleet with the GE90 in 1995; today more than 70 carriers operate over 2,500 of the engines, most of which are the higher-thrust variant, the GE90-115B. Emirates, Qatar Airways, Cathay Pacific and Air France all operate over 100 of the engines, principally on the best-selling Boeing 777-300ER, where “ER” stands for “extended range.”
Range and efficiency were one set of attributes that made the engine attractive to airlines. Another one was the GE90’s raw power. The engine held the record as the world’s most powerful jet engine for nearly 15 years, clocking in at 127,900 pounds of sustained thrust in 2002. This was on a par with the solid-fuel rockets used by NASA in the 1960s space exploration. Together, efficiency, reliability and power boosted the extended operations (ETOPS) of a Boeing 777-300ER to around 345 minutes, meaning that the airplane could, if needed, fly for nearly six hours on a single engine from the nearest airport where it could safely land. “That really opened up the southern hemisphere and stretched the legs of twin-engine operations,” Rambo says.
For Boeing, going from four engines (used by planes like the iconic Boeing 747) to two was not a case of showing off. It allowed airlines with the 777-300ER in their fleet to cut expenses by lowering fuel bills — fuel amounts to as much as 20% of an airline’s operating costs — and also by lowering its maintenance bill since it’s easier and faster to take care of two engines than four. This improved the economics for passengers as well as freight, Rambo explains.
Over the years, the GE90 also became a symbol of innovation as well as power. The engine has served as a petri dish for all the cutting-edge jet engine technology that is commonplace today. Rambo says the recent successful test flight of the Boeing 777X, which uses the GE9X engine, may have felt like the dawning of a new era, but it was really the continuation of a dynasty. That’s because the GE9X contains composite, rather than metal, fan blades, and several 3D-printed parts. “Those both started with the GE90,” he says.
Made from light and tough carbon-fiber composites, the huge fan blades were such an engineering breakthrough that to this day, no other engine maker has been able to catch up. Before the GE90, engines used fan blades made from titanium, a silvery metal with relatively low density and high strength. But GE Aviation engineers began experimenting with other materials with the objective of reducing the total weight of the engine and its fuel burn, while boosting its power and performance. The solution was a material discovered by GE co-founder Thomas Edison: carbon fiber.
Starting with the GE90, all of GE’s large new engines boast fan blades made from carbon-fiber composites, thin sheets woven from carbon fibers and fused together like phyllo dough with a special resin. This has helped to reduce the weight of jet engines by hundreds of pounds, which allows blades to be bigger. That’s crucial, because larger blades can move more air, which boosts the GE90’s all-important bypass ratio — or how much thrust comes from the fan at the front of the engine compared to its core. The bypass ratio on the GE90 is 9:1, which means the engine is sending nine times more air around the core and through the fan than through the core. (The GE9X is 10:1).
The blade’s design was also ahead of its time. Rambo says the blade manufactured for the base engine in 1995 was “pretty straight,” but over the years it took on an increasingly flared shape that more efficiently captured and accelerated airflow. That blade had aesthetic, as well as aerodynamic, value. New York’s Museum of Modern Art has a fan blade from the GE90 engine in its collection. “I also had one in my living room,” Rambo says.
Although the blades are now manufactured in San Marcos, Texas, by CFAN, a joint venture between GE Aviation and Safran Aircraft Engines, the first ones were made in Cincinnati. “They weren’t cheap,” says Rambo. “I remember walking past a Porsche 911 in the parking lot and thinking a single blade was worth more than the car.”
The blade may now be a design classic, but back in 1995 it was the subject of many 5 a.m. meetings, recalls Rambo. He said one of the biggest challenges was ensuring that the airfoils could easily deal with that perennial bugaboo for pilots: bird strikes. And all those early mornings have paid off over the decades. Over the course of 25 years and millions of flights, bird strikes have not damaged or deformed a single fan blade, according to GE. “That’s actually amazing when you think about it,” Rambo says.
Advances pioneered by the GE90 have served as a springboard for innovations that led to engines like the new GE9X. Where the GE90 had 22 composite fan blades, the GE9X has just 16. The GE90 was the first jet engine to host a 3D-printed part, a temperature sensor, back in 2015. Jonathan Clarke, a GE90 program manager, explains that the technology allowed the engine to quickly overcome the issue of ice buildup on the sensor. “3D printing allowed us to design and produce a new part six months earlier than conventional casting technologies,” he says. “Since the design was introduced, we haven’t had one ice accumulation issue. It’s a huge win.”
The GE9X now holds a number of parts made by 3D printing, also known as additive manufacturing. Engineers were able to use additive manufacturing to combine more than 300 engine parts into just seven 3D-printed components, including the fuel nozzle tip, which precisely sprays a mixture of fuel and air into the combustion chamber, low-pressure turbine blades and heat exchanger.
But Clarke, who has worked on the GE90 program for eight years, says it’s important to remember the GE9X’s heritage and origins. “I’m just a newbie here compared to Phil and Jim,” he says. “But I know that continuation is absolutely key.”