Defect found in Boeing GE engine not isolated
The engine installed on every Boeing 787 built in South Carolina so far has a problem.
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The beginning: The second Boeing 787 built in South Carolina experienced a fiery engine failure on July 28 that prompted a National Transportation Safety Board investigation and international headlines.
Since: Two other GEnx engines have been found to have a similar problem with their drive shafts, and now the Federal Aviation Administration appears poised to require regular inspections of all such engines.
What’s next: Affected 787s and 747s will have to be inspected regularly for cracks in their engines’ fan midshafts and, according to one expert, the shafts will have to be replaced in every engine.
The first sign something was wrong came on a Saturday afternoon in July when the second locally made Dreamliner experienced a pre-flight engine failure as it accelerated down the runway at Charleston International Airport.
A month and a half later, the extent of the defect has become clearer — and bigger.
The North Charleston incident was not isolated, as had been the original hope. Instead, two other General Electric-made GEnx engines have been found to suffer from a similar defect in the drive shaft.
And the concern is that the problem could be even more widespread, inherent to the make-up of the engine itself.
That news came Friday afternoon as the National Transportation Safety Board, which has been investigating the July 28 incident, issued a pair of urgent safety recommendations regarding the fan midshafts of GEnx engines.
The NTSB called on the Federal Aviation Administration to require ultrasound inspections of all GEnx-powered 787s and 747s not already inspected before any further flight.
The NTSB also recommended that the FAA require repetitive inspections of the fan midshafts of all GEnx engines “at a sufficiently short interval that would permit multiple inspections and the detection of a crack before it could reach critical length and the FMS fractures.”
That’s what happened in Charleston in July and on Tuesday as a Boeing 747-8F cargo jet was preparing to take off from Shanghai.
The FAA released a statement Friday saying it “will soon issue an emergency airworthiness directive and will take appropriate action.” The FAA statement noted that Atlas Cargo Airlines is the only operator with two affected U.S.-registered aircraft.
“We understand one inspection was completed (Friday) with no findings and the second aircraft will be inspected over the weekend,” the FAA said.
The 787 has been delivered to only five foreign airlines so far, including Air India, which took delivery of its first Dreamliner from Boeing South Carolina this month.
In addition to the recommendations, the four-page NTSB document also revealed for the first time that there had been a third engine that had a fan midshaft problem.
On Aug. 13, ultrasound inspection of a GEnx engine installed on a 787 built in Everett, Wash., revealed a similar crack to what caused the fracture of the shaft in Charleston.
Neither the Everett nor the Charleston 787s had ever flown, and the Air Bridge Cargo 747 that failed in China had flown just 240 times.
“Because of the short time to failure and the fact that all of the engines on any single airplane, whether the 787 or the 747-8, have all operated for the same period of time, the NTSB is not only concerned about the potential for further fractures occurring, but also the possibility that multiple engines on the same airplane could experience an FMS failure,” the agency wrote.
As fatigue had clearly not been a factor in the fractures and crack, the NTSB report suggested that what had happened was “environmentally assisted cracking,” caused by galvanic corrosion in a moist environment.
Shortly after the NTSB released its recommendations, General Electric released a statement, concurring with the NTSB, pledging further cooperation and noting a new preventive measure.
“As a result of findings to date, GE has introduced changes in the production process that address environmentally assisted cracking, including changes to the dry-film coating applied to the mid-shaft, as well as changes to the coating lubricant used when the retaining nut is clamped to the mid-shaft,” the statement said.
Boeing, whose 787 program has been plagued by supply chain and technical problems for years, also issued a statement pledging to work closely with the NTSB, FAA and GE.
Hans Weber, a California aviation consultant who has advised the FAA on jet-engine inspection procedures, said he is surprised such a defect could have eluded testing at GE, which he described as “the world’s most experienced jet-engine maker.”
“This sort of thing happens, but it is unexpected. To have a shaft fail is very unexpected,” Weber said. “The shafts are made of high-strength steel, and [GE] likely developed what they thought was a better type of high-strength steel. And it’s biting them.”
Weber said the NTSB-recommended inspection regime is likely not the end game here.
“This looks like something where they have to replace the shaft, and in the meantime, the NTSB takes the classic approach that you have to inspect them,” he said.
According to GE, 10 GEnx-1B engines and 108 GEnx-2B engines have been delivered to customers. Weber said all of those engines might have to come off their respective 787s and 747s to be outfitted with new fan midshafts.
He said GE will also have to look at any other parts of its engine with the same metallurgy as they could be vulnerable to cracks, too.
“Those questions are there and are being addressed there’s no doubt about it,” he said. “If they see a problem with metallurgy, that’s a systemic problem.”
Reach Brendan Kearney at 937-5906 and follow him on Twitter at @kearney_ brendan.