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Metal fatigue in the fan blades may be the cause of a Boeing’s engine failure in Denver this weekend, the U.S. National Transportation Safety Board said.
The Pratt & Whitney engine caught fire shortly after take off on a United Airlines Boeing 777-200, on a Denver-Honolulu flight, with 231 passengers and 10 crew on board. The pilots issued a Mayday appeal and returned to Denver.
The next day, dozens of 777 planes were grounded after Boeing said those with Pratt & Whitney PW4000 engines should not be used until full inspections could be carried out.
National Transportation Safety Board (NTSB) Chairman Robert Sumwalt said Monday that a preliminary assessment suggested the damage was consistent with metal fatigue and that the blade would be examined Tuesday at a Pratt & Whitney lab under the supervision of NTSB investigators. .
Sumwalt said it was not clear whether Saturday’s PW4000 engine failure was consistent with another engine failure on another United flight to Hawaii in February 2018, attributed to a fatigue fracture in a blade. fan.
“What’s important is that we really understand the facts, circumstances, and conditions surrounding this particular event before we can compare it to any other event,” Sumwalt said.
In another incident with the same type of engine on a Japan Airlines 777 in December 2020, the Japan Transportation Safety Board reported finding two damaged fan blades, one with a metal fatigue crack.
The Federal Aviation Administration (FAA) has plans to issue an Emergency Airworthiness Directive soon that will require intensified fan blade inspections for fatigue.
After the United engine failure of February 2018 was attributed to fan blade fatigue, the FAA ordered inspections every 6,500 cycles.
Sumwalt said the United incident was not considered an unconfined engine failure because the containment ring contained the parts as they took off. There was minor damage to the plane’s body, but no structural damage, he said.
The NTSB will look into why the engine cowl separated from the plane and also why there was a fire despite indications that the engine fuel was cut, Sumwalt added.
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