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The General Electric GE90 is a family of high-bypass turbofan aircraft engines built by GE Aviation for the Boeing 777, with thrust ratings from 81,000 to 115,000 lbf (360 to 510 kN). It entered service with British Airways in November 1995. It is one of three options for the 777-200, -200ER, and -300 versions, and the exclusive engine of the -200LR, -300ER, and 777F.
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Design and development
Developed from the NASA 1970s Energy Efficient Engine, the 10-stage high-pressure compressor develops an industry record pressure ratio of 23:1 and is driven by a 2-stage, air-cooled, HP turbine. A 3-stage low-pressure compressor, situated directly behind the fan, supercharges the core. The fan/LPC is driven by a 6-stage low-pressure turbine. The GE90 series are physically the largest engines in aviation history, the fan diameter of the original series being 123 in (310 cm), and the largest variant GE90-115B has a fan diameter of 128 in (330 cm).
The GE90 engine was launched in 1990. GE Aviation teamed with Snecma (France, 24%), IHI (Japan) and Avio (Italy) for the program.
As one of the three available engines for the new Boeing 777, the GE90 was an all-new $2 billion design meant to handle transoceanic routes; the offerings from Pratt & Whitney and Rolls-Royce were modifications of existing engines. It is the world's largest and the most powerful jet engine.
Higher thrust variant
For Boeing's next-generation 777 long-range versions (later named 777-200LR and 777-300ER), greater thrust was needed to meet the specifications. General Electric and Pratt & Whitney insisted on a winner-take-all contract due to the $500 million investment in engine modifications needed to meet the requirements. GE received sole engine supplier status for the higher-thrust engine variants for the 777-200LR, -300ER, and 777F.
These higher-thrust variants, GE90-110B1 and -115B, have a different architecture from the earlier GE90 versions, with one stage removed from the HP compressor and an extra stage added to the LP compressor. A net increase in core flow was achieved. General Electric performed a similar re-staging exercise when they upgraded the CF6 from the -6 to the higher-thrust -50. However, this thrust growth route is expensive, since all the downstream components (e.g. turbines) must be larger for flow capacity. The fan is an advanced, larger diameter unit made from composite materials and is the first production engine to feature swept rotor blades.
The GE90-115B is powerful enough to fully operate GE's Boeing 747 testbed on its own power, an attribute demonstrated during a flight test.
Operational history
The first General Electric-powered Boeing 777 was delivered to British Airways on November 12, 1995; the aircraft, with two GE90-77Bs, entered service five days later. Initial service was affected by gearbox bearing wear concerns, which caused the airline to temporarily withdraw its 777 fleet from transatlantic service in 1997. British Airways' aircraft returned to full service later that year.
Problems with GE90 development and testing caused delays in Federal Aviation Administration certification. In addition the GE90's increased output was not yet put to use by airlines and it was also the heaviest engine option, making it the least popular choice while Rolls-Royce held the top spot. British Airways soon replaced the GE90 with Rolls-Royce engines on their 777s.
GE90 engines can only be air freighted in assembled form by outsize cargo aircraft such as the Antonov An-124, presenting unique problems if, due to emergency diversions, a 777 were stranded in a place without the proper spare parts. If the fan is removed from the core, then the engines may be shipped on a 747 Freighter.
The GE90-equipped Boeing 777s have been the best-selling long-range large wide-body aircraft in the 2000s, at the expense of the four-engine Airbus A340 that is less fuel efficient.
The -94B for the -200ER is being retrofitted with some of the first FAA-approved 3D-printed components.
It has an in-flight shutdown rate (IFSD) of one per million engine flight-hours. It accumulated more than 8 million cycles and 50 million flight hours in 20 years.
Records
According to the Guinness Book of Records, at 127,900 lbf (569 kN), the engine holds the record for the highest thrust (although rated at 115,300 lbf (513 kN)). This thrust record was accomplished inadvertently as part of a one-hour, triple-red-line engine stress test. To accommodate the increase in torsional stresses, a new steel alloy, GE1014 was created and then machined to extreme tolerances. The new record was set during testing of a GE90-115B development engine at GE Aviations' Peebles Test Operation, which is an outdoor test complex outside Peebles, Ohio. It eclipsed the engine's previous Guinness world record of 122,965 lbf (546.98 kN).
In October 2003, a Boeing 777-300ER broke the ETOPS record by being able to fly five and a half hours (330 minutes) with one engine shut down. The aircraft, with GE90-115B engines, flew from Seattle to Taiwan as part of the ETOPS certification program.
On November 10, 2005, the GE90 entered the Guinness World Records for a second time. The GE90-110B1 powered a 777-200LR during the world's longest flight by a commercial airliner, though there were no fare-paying passengers on the flight, only journalists and invited guests. The 777-200LR flew 13,422 mi (21,601 km) in 22 hours, 42 minutes, flying from Hong Kong to London "the long way": over the Pacific, over the continental U.S., then over the Atlantic to London.
Incidents
On May 28, 2012, an Air Canada 777 taking off from Toronto en route to Japan suffered failure of a GE90-115B at 1,500 feet (460 m) and returned safely. Engine debris was found on the ground.
On September 8, 2015, a GE90-85B powering a Boeing 777-236ER on British Airways Flight 2276 suffered an uncontained failure during take-off roll leading to a fire. NTSB and FAA investigations were begun to determine the cause; initial findings were reported in September 2015.
On June 27, 2016, a GE90-115B powering a Boeing 777-300ER, on Singapore Airlines Flight 368, received an engine oil warning during flight and returned to Singapore Changi Airport. On landing the malfunctioning right engine caught fire, leading to fire damage to the engine and the wing.
Transfer gearbox failures
The FAA issued an Airworthiness Directive (AD) on May 16, 2013, and sent it to owners and operators of General Electric GE90-110B1 and GE90-115B turbofan engines. This emergency AD was prompted by reports of two failures of transfer gearbox assemblies (TGBs) which resulted in in-flight shutdowns (IFSDs). Investigation revealed that the failures were caused by TGB radial gear cracking and separation. Further inspections found two additional radial gears with cracks. This condition, if not corrected, could result in additional IFSDs of one or more engines, loss of thrust control, and damage to the airplane. The Airworthiness Directive requires compliance by taking remedial measures within five days of receipt of the AD.
GEnx
The GEnx engine, that has been developed for the Boeing 787 Dreamliner and 747-8, is derived from a smaller core variant of the GE90, but features a fan with swept rotor blades.
GP7000
GE Aviation has also set up a cooperative venture with Pratt & Whitney, named Engine Alliance, under which the companies have developed an engine for the Airbus A380, called the GP7000, based on an 0.72 flow scale of the GE90-110B/115B core.
GE9X
In February 2012, GE announced studies on a more efficient derivative, dubbed the GE9X, to power the new Boeing 777-8X/9X aircraft. It was to feature the same 128 inches (330 cm) fan diameter as the GE90-115B with an overall thrust decreased by 15,800 pounds-force (70 kN) to a new rating of 99,500 pounds-force (443 kN) per engine with a 10% increase in fuel efficiency. The -8X engine was to be derated to 88,000 pounds-force (390 kN), the bypass ratio was planned for 10:1 and the overall pressure ratio for 60:1 with a new 11-stage high-pressure compressor developing a pressure ratio of 27:1.
In 2013, the fan diameter was increased by 3.5 in (8.89 cm) to 132 in (335 cm). In 2014, thrust was increased from 102,000 lbf (450 kN) to 105,000 lbf (470 kN) and fan diameter to 133.5 in (339 cm). The new engine has the largest front fan at 134 in (340 cm) in diameter with a composite fan case and 16 carbon fiber composite fan blades, it completed its first test run in April 2016. The GE9X has only 16 blades where the GE90 has 22 and the GEnx 18, making the engine lighter and spinning faster to better match the low-pressure fan and turbine.
As it is larger than the GE90, for testing it fits only the 747-400 with larger main gear struts and bigger tires and not the previous -100 GE testbed, and the tested engine is tilted 5° more than the original CF6. Its type certification is planned for the fourth quarter of 2018.