Investigators suspect that metal fatigue was the cause of a recent engine failure of a United Airlines Boeing 777 aircraft that departed Denver where engine parts debris were found scattered.
The incident lead to the grounding of dozens of Boeing 777 series 200 around the world.
US officials said that even prior to the Denver incident, air safety regulators considered undertaking stricter inspections on the aircraft that had Pratt & Whitney engines, following a December 2020 incident in Japan.
The Federal Aviation Administration (FAA) earlier reviewed inspection records and maintenance history of Japan Airlines’ fleet of Boeing 777s after an engine fan blade incident last December 4, 2020 “to determine the cause of the fracture and was evaluating whether to adjust blade inspections,” an FAA spokesman said. The Japan flight landed without injury.
While no one was injured in the Denver incident, the incident is the latest setback for Boeing which had just resumed deliveries of the long-grounded Boeing 737 MAX following two fatal crashes of that airliner.
The incident resurrected doubts on the FAA which was harshly criticized for its oversight of Boeing in the certification of the 737 MAX.
Aviation experts had said the Denver airplane engine failure — and earlier incidents involving Boeing 777s with the same Pratt & Whitney engine — raised questions about plane maintenance practices.
A video shot from inside the United flight —which had 231 passengers and 10 crew —showed the right engine in flames and wobbling on the wing of the Boeing 777-200.
Residents in the Denver suburb of Broomfield found large pieces of the plane scattered around their community.
National Transportation and Safety Board (NTSB) officials said it is too early to determine if the cause in the Denver incident was similar to those in the Japan Airlines flight, or to a February 2018 incident involving another Boeing 777 and Pratt & Whitney engine.
“A preliminary on-scene exam indicates damage consistent with metal fatigue,” NTSB Chair Robert Sumwalt told a briefing.
He said two fan blades fractured on engine number 2 of the Boeing 777-200, one of them was later found on a soccer field, the other remained lodged in the engine.
The NTSB intends to look at the inspection record on the United airplane to see “who knew what when, what could have been done and what should have been done,” Sumwalt said.
Following the February 2018 incident on another United jet, the FAA reviewed 9,000 fan blade inspection reports and issued an airworthiness directive setting new rules on inspections.
Boeing declared that all 128 of the 777s with Pratt & Whitney engines have been grounded. Of the 128 planes, only 69 were in service while 59 were in storage.
Besides United, which removed 24 planes from service, affected airlines included Japan Airlines, All Nippon Airways, Asiana and Korean Air.