GE redesigns GE9X compressor part for 777X engine

GE Aviation is redesigning a static compressor part for the in-development GE9X engine, to power the Boeing 777X, after the component showed premature deterioration during the test programme.

The engine maker’s chief executive David Joyce said during a briefing today that extended block cycle tests showed that the part “near the [compressor’s] front end” proved to be less durable than expected and that this issue would, if unaddressed, lead to premature shop visits.

The problem was detected in late May when exhaust gas temperature readings were outside an expected range.

GE will install a re-engineered, “more robust” part in all eight engines involved in the GE9X test programme, Joyce says.

The part in question is being produced by GE rather than an external supplier, he notes.

Ground tests with the re-engineered part are being conducted, but the findings suggest a delay in the 9X programme.

Vice-president of commercial engines Bill Fitzgerald says that the manufacturer is still in the process of determining a flight test schedule for the modified engine.

He expresses confidence that the GE9X will be certificated “later in the fall” and that Boeing will still conduct the 777X’s first flight this year.

The durability issue was determined during the last module of ground tests. That module – comprising around 250-300h of testing – will need to be completed prior to certification.

Fitzgerald foresees that the repeat test will “probably” begin in August.

Thus far, the GE9X programme accumulated around 2,700h of ground tests and an additional 450h across two flight-test campaigns on the manufacturer’s 747 test bed, across a total of 71 sorties.

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GE Aviation addresses GE9X issue after lengthy flight test phase

GE Aviation still anticipates completing GE9X certification testing this year after a lengthier-than-planned round of flight tests and recently discovered “anomaly” in an engine’s high-pressure compressor.

GE Aviation completed a second round of certification flight testing for the 777X’s engine in May, during which it completed 53 test flights and logged more than 300 flight hours.

The engine maker had told FlightGlobal late last year that it anticipated “making about 18 flights or so” during the second round of testing.

That was about the same number as in the first testing round, which concluded in May 2018.

The company says additional flight tests in the second phase reflect changes to the massive, 105,000lb-thrust (467kN) GE9X’s “variable stator vane lever arm”.

The arms set the pitch of stator vanes, which are inside the compressor and slow airflow, increasing its pressure. GE Aviation redesigned the arm prior to the second phase of test flights after determining the initial design wore out faster than expected.

“Since the engine for phase two had the new variable stator vane lever arm in the high-pressure compressor, we wanted to get the engine performance data on this configuration at altitude,” GE Aviation says.

It also repeated some tests conducted in the first phase of flight testing. “The engine performed extremely well on the flight tests,” GE Aviation says.

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GE Aviation tests the GE9X on its 747-400 flying test bed

GE Aviation

The company is making other changes to improve the GE9X’s durability.

“During a recent test, GE detected an anomaly in the engine data from the high-pressure compressor,” GE Aviation says. “After data analysis and additional testing, our engineers saw an opportunity for a durability improvement in the front of the compressor.”

“GE anticipates completing its certification testing this year,” it adds.

The company does not provide specifics, but says the anomaly is “mechanical in nature — and is not related to the design or performance of the high-pressure compressor”.

“GE is taking a proactive approach and working the improvement so it can be incorporated into the flight test engines at Boeing as well as incorporated into our engines that will take part in our remaining ground tests,” the company says.

GE Aviation has completed about 85% of the GE9X’s certification testing, including aerodynamic, bird-ingestion, loss-of-blade, hailstorm and icing tests.

“The engine’s performance at altitude was great,” GE Aviation says. “Just a handful of tests remain, including emissions and block test.”

The block test involves running the engine for 25, six-hour cycles, accumulating 150h of run time during which the engine is at “redline” – its max core speed, fan speed and exhaust gas temperature, GE Aviation says.

The company conducts GE9X flight testing on its 747-400 test bed.

Last week Boeing chief financial officer Gregory Smith said Boeing was waiting on the GE9X to advance the 777X programme.

“Long-pole in the tent right now is [the] GE engine. There are some challenges. They’re working through their own testing,” Smith said of GE Aviation during an investor conference hosted by investment bank UBS. “We’re having to do some retesting. And they’re working their way through that.”

“We still expect to fly this year and entry into service in 2020,” Smith added.

Boeing installed GE9Xs on its first flight-test 777X in January. The engine’s 3.4m-diameter (134in) fan, composed of 16 carbonfibre blades, makes the GE9X the world’s largest jet engine, GE Aviation says.

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Boeing installs GE9X engines on 777X test aircraft

Boeing’s first flight-test 777X is powerless no more.

In recent days, the company hung two massive GE Aviation GE9X turbofans from the aircraft’s wing, in a milestone bringing Boeing closer to its goal of a 2019 777X first flight.

The move also marks another step toward to the entry-into-service of an engine with the largest fan ever produced for a commercial aircraft, according to Boeing and GE.

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The first 777X test aircraft’s left-side GE9X, recently installed by Boeing in Everett


That GE9X’s fan, composed of 16 whirling carbonfibre blades, measures 3.4m (134in) in diameter – slightly wider than the 3.3m-diameter fan on the GE90-115B, which powers the first-generation 777.

The GE9X’s compressor has a 27:1 pressure ratio, and the engine has an overall pressure ratio of 60:1, which GE says are the greatest ratios for any of its engines.

Those pressure differentials are among reasons why the GE9X uses 10% less fuel than the GE90, which has an overall 40:1 pressure ratio and powers first-generation 777s, according to GE.

Boeing released a video showing photographs of the engine installation process.

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Boeing, Twitter

Now fitted with its 105,000lb-thrust (467kN) GE9X engines, the first flight-test 777X – a 777-9 variant – remains inside Boeing’s Everett hangar, awaiting a roll-out that Boeing has said could happen by March.

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Boeing’s first 777X, now with engines, awaits rollout from the company’s Everette hangar


Boeing expects first flight in 2019 followed by certification and first delivery in 2019.

The Seattle-based airframer has made steady progress assembling several 777X test airframes in the last year.

It began assembling the first two 777-9 flight test aircraft in mid-2018. The first of those aircraft came together by November, when Boeing joined the aircraft’s nose with its mid and aft sections. Boeing powered that aircraft’s electric systems for the first time in December.

In addition to two flight-test aircraft, Boeing last year assembled a 777X fuselage that will be used exclusively for static ground-based testing.

Meanwhile, GE has continued parallel testing of its 105,000lb-thrust (467kN) GE9X.

GE is well into a second round of GE9X flight testing that kicked off on 10 December. The engine had completed eight test flights and logged 55h of run time during the second round as of 4 January, GE tells FlightGlobal.

GE expects the second round will involve roughly 18 flights and include evaluation of the GE9X’s software and performance in hot-and-high conditions.

“The campaign is moving ahead exactly on target, with very efficient testing,” GE says. “The plan is to complete this campaign in the first half of the year.”

GE conducts the tests with a GE9X hung from the wing of its 747-400 flying testbed, which operates out of Victorville, California.

GE’s first round of flight tests were delayed several months after the company discovered unexpected wear on “lever arms” that alter the pitch of the GE9X’s compressor vanes, GE has said.

Eventually, GE started the first round of testing in March using an engine in the original configuration as it worked on a fix. GE completed the first flight-testing round in May, also after 18 flights.

As of mid-December, GE had subjected the GE9X to water-ingestion, over-temperate and crosswind tests, but had not completed blade-out, hailstone, bird-ingestion or endurance testing, it said at the time.

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GE begins second round of GE9X flight testing

GE Aviation’s GE9X turbofan returned to the skies on 10 December, kicking off a second round of airborne testing during which the engine maker will evaluate the powerplant’s software and performance in hot-and-high conditions.

The latest round of testing will involve roughly 18 flights on GE’s flying Boeing 747-400 testbed, which will carry the massive GE9X turbofan under its wing, GE says.

The 105,000lb-thrust (467kN) GE9X will power Boeing’s 777X.

GE9X flight tests will stretch into the first quarter of next year, bringing GE closer to achieving its goal of receiving in 2019 certification of the engine by the Federal Aviation Administration, according to the Ohio-based engine maker.

“During the second round of testing, GE will continue software development testing that began in the first round, perform hot-and-high starts and fill in remaining gaps from the first round of testing,” says GE.

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GE’s GE9X turbofan goes to work on the wing of the company’s 747-400 flying testbed.

GE Aviation.

The company’s first round of GE9X airborne testing was delayed more than two months earlier this year after engineers discovered unexpected wear on “lever arms” that alter the pitch of vanes inside the engine’s compressor.

The engine finally got airborne in March when GE began an initial round of airborne tests that lasted until early May. That round involved 18 flights and 105h of flight time, allowing GE to study high-altitude performance and to compare performance during cruise to ground-test data, GE has told FlightGlobal.

With the initial round complete, the company transported the test engine to Ohio, where it was modified into the final configuration expected for production, GE says.

“The engine is more than halfway through the certification testing programme and [has] completed various tests during the last few months,” GE says.

Those tests have included evaluation of performance during water ingestion, overheating and crosswinds, it says.

“Tests that remain include blade out, hailstone, bird ingestion and block or endurance testing,” GE says.

The GE9X-105B variant of the engine will power the 777-9, which Boeing expects will achieve first flight in 2019 and enter service in 2020.

GE also plans to develop versions of the turbofan with 102,000lb-thrust and 93,000lb-thrust, according to regulatory filings with the FAA. Those engines could power other 777X variants.

GE operates a flight test center in Victorville, California, but also performs airborne testing from Colorado Springs in Colorado, Seattle, Fairbanks in Alaska and Yuma in Arizona, it says.

The company acquired its 747-400 flying testbed from Japan Air Lines, then modified and strengthened the aircraft’s wing and strut to accommodate test engines, it says.

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GE9X enters flight test phase

GE Aviation’s GE9X turbofan flew for the first time on 13 March, launching a months-long engine certification campaign for the largest turbofan engine in history.

The 340cm (134in)-diameter fan mounted on the inboard station of the left wing of GE’s Boeing 747-400 flying test bed took off from Victorville, California.

“Today’s flight starts the beginning of the GE9X flight test campaign that will last for several months, allowing us to accumulate data on how the engine performs at altitude and during various phases of flight,” says GE programme manager Ted Ingling.

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GE Aviation

The GE9X will power the Boeing 777-9 and 777-8, which are scheduled to enter service in 2020 and 2022, respectively.

The 105,000lb-thrust engine produces less thrust than the older 115,000lb-thrust GE90 for the 777-300ER, but is 10cm wider. The additional width increases the bypass ratio to about 10:1, a key metric in GE’s plan to reduce fuel burn compared to the GE90 by about 10%.

The first flight comes more than two months behind schedule. GE planned to begin flying the first flight test engine – designated within the programme as the No. 4 engine – by the end of last year.

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GE Aviation

GE decided in mid-December to redesign the external lever arm that actuates to move the variable stator valves. The redesign of the lever arm is ongoing, but flight test has started using the previous design, GE Says.

The GE9X programme also has completed icing tests at GE’s facility in Winnipeg, Canada. Crosswind tests are continuing at the Peebles Test Operation in Ohio.

Meanwhile, Boeing has started assembling the first 777-9 aircraft in Everett, Washington. In addition to the GE9X engines, the 777X family will feature a 71.8m-span composite wing with folding wingtips and a longer fuselage.

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