US National Transportation Safety Board (NTSB) Chairman Robert Sumwalt said Monday that damage to a propeller blade in a Pratt & Whitney engine that malfunctioned on a United Airlines Boeing 777-200 was consistent with metallic fatigue, according to a preliminary assessment.
In a press release, Sumwalt said it was unclear if the PW4000’s engine failure on Saturday shortly after takeoff corresponded to another engine failure on another flight to Hawaii in February 2018, which was attributed to a fatigue break in the fan blade.
In another engine-type accident on Japan Airlines Flight 777 in December 2020, the Japan Transportation Safety Board reported that it had found two damaged propeller blades, one of which had a crack due to metal fatigue.
United’s fan blade will be examined on Tuesday after being airlifted to Pratt & Whitney Lab where it will be examined under the supervision of NTSB investigators.
“It is important that we really understand the facts, circumstances and circumstances surrounding this particular event before we can compare it to any other event,” Sumwalt said.
The Federal Aviation Administration plans to issue an emergency airworthiness directive soon that will require extensive inspections of propeller blades for fatigue.
The Federal Aviation Administration (FAA) in March 2019 after February 2018 engine failure attributed to propeller blade stress ordered inspections every 6,500 revolutions.
Sumwalt said the United incident did not consider an unseated engine failure because the containment ring contained the parts as they were flying.
He said there was minor damage to the fuselage, but no structural damage.
Somwalt added that NTSB will be looking into why the bonnet split from the aircraft and also why a fire broke out despite indications that the fuel in the engine has been shut down.