General Electric GE90

The General Electric GE90 is a family of high-bypass turbofan aircraft engines built by GE Aerospace for the Boeing 777, with thrust ratings from 81000 to 115000 lbf. 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. It was the largest jet engine, until being surpassed in January 2020 by its successor, the 110000 lbf GE9X, which has a larger fan diameter by undefined in. However, the GE90-115B, the most recent variant of the GE90, is rated for a higher thrust (115,000 lbs) than the GE9X.

Background
In the early 1980s, GE began to develop an unducted fan (UDF) engine, which was thought to be a more fuel-efficient option to propel short-haul airliners, a compelling proposition after the 1979 oil crisis. NASA gave GE a grant in February 1984 to continue its research, eventually building the experimental GE36. One of the major innovations for the engine were its carbon fiber composite fan blades, which were both lighter and stronger than traditional materials. However, the UDF was less reliable than the turbofans of the era, lower fuel costs made the cost of developing the engine less attractive, and the company was worried the GE36 would cannibalize sales of the highly successful CFM56 engine it had co-developed with Snecma of France.

Development
The GE90 engine was launched in 1990 to provide a large turbofan engine for the Boeing 777, a wide-body, long-range, twin-engine jet airliner. GE Aviation teamed with Snecma (France, 24%), IHI (Japan) and Avio (Italy) for the program. The GE90 would face stiff competition as Pratt & Whitney and Rolls-Royce would also offer engines for the 777, the PW4000 and Trent 800, respectively.

The major innovation of the GE90 was that it used 22 carbon fiber composite fan blades, technology first developed for the GE36. These blades provided double the strength at one-third the weight of traditional titanium fan blades. The 22 fan blades were a significant reduction from the 38 blades used in GE's prior large turbofan, the CF6, despite the 30 in greater diameter of the GE90. Having fewer fan blades reduces the engine weight and improves aerodynamic efficiency.

With the stiff competition to equip the 777, GE tried to branch out and use the GE90 for other aircraft. Then-CEO Brian H. Rowe went so far as to offer to pay for the development of the GE90 for the Airbus A330, but Airbus rebuffed the plan, instead choosing to focus on the four-engine A340 for the long-haul market.

In the late 1990s, Boeing began developing ultra-long-range variants of the 777, the 777-200LR and 777-300ER. For these aircraft a more powerful engine in the thrust class of 100000 lbf was required, leading to talks between Boeing and engine manufacturers. General Electric offered to develop the GE90-115B engine, while Rolls-Royce proposed developing the Trent 8104 engine. In 1999, Boeing announced an agreement with General Electric, beating out rival proposals. Under the deal with General Electric, Boeing agreed to only offer GE90 engines on new 777 versions. The GE90-115B had its first run at the GE facility in Peebles, Ohio in November 2001.

Design


The GE90's 10-stage high-pressure compressor developed a then-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 higher-thrust variants, GE90-110B1 and -115B, have a different architecture from that of the earlier GE90 versions. General Electric incorporated an advanced larger diameter fan made from composite materials which enhanced thrust at low flight speeds. However, GE also needed to increase core power to improve net thrust at high flight speeds. Consequently, GE elected to increase core capacity, which they achieved by removing one stage from the rear of the HP compressor and adding an additional stage to the LP compressor, which more than compensated for the reduction in HP compressor pressure ratio, resulting in a net increase in core mass flow . The higher-thrust GE90 variants are the first production engines to feature swept rotor blades. The nacelle has a maximum diameter of 166 in. Each of the 22 fan blades on the GE90-115B have a length of 4 ft and a mass of less than 50 lb.

Operational history
As one of the three available engines for the new Boeing 777 long-range airliner, the GE90 was an all-new $2 billion design in contrast to the offerings from Pratt & Whitney and Rolls-Royce which were modifications of existing engines.

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 thrust was not yet required by airlines and it was also the heaviest engine of the three available choices, making it the least popular option while the Rolls-Royce engine was the most popular. British Airways soon replaced the GE90 with Rolls-Royce engines on their 777s.



For Boeing's second-generation 777 long-range versions (later named 777-200LR, 777-300ER, and 777F), greater thrust was needed to meet the aircraft requirements. 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. The improved version entered service with Air France in May 2004.

The higher thrust GE90-110B1 and -115B engines, in combination with the second-generation 777 variants -200LR and -300ER, were primary reasons for 777 sales being greater than those of the rival A330/340 series. Using two engines produces a typical operating cost advantage of around 8–9% for the -300ER over the A340-600. The 777-300ER was also seen as a 747-400 replacement amid rising fuel prices given its 20% fuel burn advantage.

Until passed by its derivative, the GE9X, the GE90 series held the title of the largest engines in aviation history. The fan diameter of the original series being 123 in, and the largest variant GE90-115B has a fan diameter of 128 in. As a result, the GE90 engine can only be air-freighted using an outsize cargo aircraft such as the Antonov An-124, which restricts shipping options if, due to an emergency diversion, a 777 were stranded needing an engine change. If the fan and fan case are removed the engine may be shipped using a 747 Freighter.

The -94B for the -200ER was retrofitted with some of the first FAA-approved 3D-printed components.

In 2011, its list price was US$ million, and it had an in-flight shutdown rate (IFSD) of one per million engine flight-hours. Until November 2015, it accumulated more than 8 million cycles and 50 million flight hours in 20 years. In July 2020, the fleet of 2,800 engines surpassed 100 million hours, powering over 1,200 aircraft for 70 operators with a dispatch reliability rate of 99.97%. A complete overhaul costs more than $12 million.

Records
The GE90-115B provided enough thrust to fly N747GE, GE's Boeing 747-100 flying testbed with the other three engines at idle, an attribute demonstrated during a flight test.

According to the Guinness Book of Records, at 127900 lbf, the engine held the record for the highest thrust achieved by an aircraft engine (the maximum thrust for the engine in service is its rated thrust 115300 lbf). This thrust record was reached inadvertently as part of a one-hour, triple-red-line engine stress test using a GE90-115B development engine at GE's outdoor test complex near Peebles, Ohio. It eclipsed the engine's previous Guinness world record of 122965 lbf. On November 10, 2017, its successor, the GE9X, reached a higher record thrust of 134,300 lbf in Peebles.

The initial GE90 fan shaft design loads were greatly increased for operational torque and the fan blade-off condition. To accommodate the increase in fan-shaft torsional and bending stresses, a steel alloy, GE1014, not previously used in aircraft engines was required. A significantly longer fan shaft spline-coupling was required and maintaining the required high machining accuracy was challenging.

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 13423 mi in 22 hours, 22 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 August 11, 2004, a GE90-85B powering a Boeing 777-200ER on British Airways flight  2024 suffered an engine failure on takeoff from George Bush Intercontinental Airport, Houston. The pilots noticed a noise and vibration on takeoff but continued the rotation. At 1500 ft AGL they noticed smoke and haze in the cockpit and cabin crew advised cabin was filling with smoke. They returned to the airport for an immediate emergency landing. Findings were a stage 2 turbine blade had separated at its shank damaging the trailing blades causing the vibration. The debris was contained in the engine casing.

On May 28, 2012, an Air Canada 777-300ER taking off from Toronto en route to Tokyo suffered failure of a GE90-115B at 1500 ft 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 at Las Vegas McCarran Airport, 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. This through the combined effect of manufacturing process and operating stresses. 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. All affected modules have been replaced.

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, also featuring a fan with swept rotor blades.

GP7000
GE Aviation set up a cooperative venture with Pratt & Whitney, named Engine Alliance, under which the companies have developed an engine for the Airbus A380, named GP7000, based on an 0.72 flow scale of the GE90-110B/115B core.

GE9X
In February 2012, GE announced studies on a 10% more efficient derivative, dubbed the GE9X, to power the new Boeing 777-8X/9X aircraft.

LM9000
The LM9000 is an aeroderivative gas turbine available in two options; the LM9000 without water augmentation outputting 66 MW at a 42.4% efficiency before cogeneration, and the LM9000 with water augmentation outputting 75 MW at a 42.7% efficiency before cogeneration. The engine's 33:1 pressure ratio comes from a 4-stage low pressure compressor followed by a 9 stage high pressure compressor, driven by a 2 stage high pressure turbine and a 1-stage low pressure turbine, powering a 4-stage free turbine.