WASHINGTON (Reuters) – President of the National Transportation Safety Council (NTSB), Robert Sumwalt, said on Monday that damage to a fan blade of a Pratt & Whitney engine that failed in a Boeing 777-200 from United Airlines is consistent with metal fatigue, according to a preliminary assessment.
At a news conference, Sumwalt said it was unclear whether the PW4000 engine failure on Saturday with a “crash” four minutes after takeoff is consistent with another engine failure on another United flight to Hawaii in February 2018 , which was attributed to a fracture fatigue in a fan blade.
The engine that failed on the 26-year-old Boeing Co 777 and dropped parts in a Denver suburb was a PW4000 used in less than 10% of the global fleet of 777 widebody jets.
In another incident at Japan Airlines (JAL) 9201.T 777 with a PW4000 engine in December 2020, the Japan Transport Safety Council reported finding two damaged fan blades, one with a fatigue metal crack. An investigation is underway.
The focus is more on engine maker Pratt & Whitney and analysts expect little financial impact on Boeing, but the problems with the PW4000 are a new headache for the aircraft maker as it recovers from the much more serious 737 MAX crisis. Boeing’s main jet was stranded for almost two years after two fatal accidents.
The United fan fan blade will be examined on Tuesday after being transported to a Pratt & Whitney laboratory, where it will be examined under the supervision of NTSB researchers.
“The important thing is that we really understand the facts, circumstances and conditions surrounding this particular event before we can compare it to any other event,” said Sumwalt.
Boeing recommended that airlines suspend the use of airplanes while the FAA has identified an appropriate inspection protocol, and Japan has imposed a temporary suspension of flights.
The Federal Aviation Administration plans to issue an emergency airworthiness directive soon, which will require intensified inspections of the fan blades to check for fatigue.
The FAA in March 2019 after United’s engine failure in February 2018 attributed to fan blade fatigue ordered inspections every 6,500 cycles. A cycle is a takeoff and landing.
Sumwalt said the United incident was not considered to be an unrecognized engine failure because the retaining ring contained the flying parts.
There was little damage to the aircraft body, but no structural damage, he said.
The NTSB will investigate why the bonnet detached from the plane and also why there was a fire despite indications that the engine’s fuel was turned off, Sumwalt added.
Pratt & Whitney, which is owned by Raytheon Technologies Corp, said on Sunday that it is coordinating with regulators the review of inspection protocols.
Nearly half of the global fleet of 128 planes operated by airlines, including United, JAL, ANA Holdings, Korean Air and Asiana Airlines, had already stranded amid falling travel demand due to the coronavirus pandemic.
Reporting by David Shepardson in Washington and Jamie Freed in Sydney; additional reporting by Tracy Rucinski in Chicago. Editing by Kim Coghill and Gerry Doyle