Metal fatigue was a factor that led to a Pratt & Whitney engine failure aboard a United Airlines flight over Denver, according to federal investigators.
A preliminary exam at the scene of fallen debris in Broomfield, Colo., following the incident Saturday found a fan blade fractured at the root “indicates damage consistent with metal fatigue,” said Robert Sumwalt, chairman of the National Transportation Safety Board.
The loose blade apparently struck another blade that also was fractured, he said at a news conference Monday evening.
Investigators also want to know why a cowling, which covers part of the fuselage, broke away. “We don’t expect a cowling to separate like that,” Sumwalt said.
The NTSB also will investigate why the engine was on fire after the crew cut off the fuel, he said.
The Boeing 777-200, with 229 passengers and 10 crew aboard, suffered a failure in its right engine and flames erupted under the wing as the plane began to lose altitude. Following a “loud bang,” the airline crew declared an emergency with air traffic control and made a “safe, single-engine landing” at Denver International Airport 20 minutes after the engine failure, Sumwalt said.
Pratt & Whitney, the East Hartford, Conn.-based unit of Raytheon Technologies Corp., said hours after the accident it dispatched a team to work with investigators.
In February 2018, a United Airlines 777-200 outfitted with Pratt and Whitney PW4077 engines, the same type involved in Saturday’s incident, suffered engine failure over the Pacific near Hawaii, after a fan blade fractured, according to an NTSB report released in June.
In another incident in December, an engine failed on a Japan Airlines flight on a 777-200 headed to Tokyo. Authorities in Japan and the Federal Aviation Administration issued directives requiring more regular inspections of planes and fan blades involving the PW4000 engine.
As part of the investigation, the NTSB will try to “find out who knew what when,” Sumwalt said.
“We’ll be looking at that to see what could have been done, what should have been done if anything at all,” he said.
United temporarily removed Boeing 777 aircraft powered by Pratt & Whitney 4000 engines from its schedule.©2021 Hartford Courant. Visit at courant.com. Distributed by Tribune Content Agency, LLC.