NEW YORK: Initial investigations confirm metal fatigue was a factor in panic last month when a Boeing 777 engine caught fire and rained down on homes, a key US safety regulator said on Friday.
But the National Transportation Safety Board (NTSB) said it had not reached a final conclusion on the causes of the accident involving the Pratt & Whitney engines.
The United Airlines flight to Hawaii returned to Denver shortly after disembarking after the engine caught fire and began to fail.
No one was injured in the accident, but the accident raised questions about aircraft maintenance.
The NTSB update confirmed that the engine’s fan blades had failed, and said “the fracture surface corresponds to fatigue”.
This confirms the agency’s initial discovery of metal stress, which is a weakening of the material due to stress after repeated use.
The NTSB said the maintenance data for the blade with breaking fatigue showed it had gone through 2,979 cycles – Take off and landing – Since its last scan, which means it has been far from the next scan requiring all 6,500 trips.
The agency continues its investigation and has sent the damaged propeller blade “to the Pratt & Whitney Minerals Laboratory for further investigations led by one of the NTSB’s senior metallurgy experts.”
In the wake of the recent accident, same-engine Boeing 777s have been grounded worldwide, and the Federal Aviation Administration (FAA) has ordered inspections of all Pratt & Whitney engines similar to those that crashed.