(Adds details of South Korea inspections)
By David Shepardson and Jamie Freed
WASHINGTON, February 22 (Reuters) – Damage to the fan blade of an engine that failed on a United Airlines Boeing 777 flight is consistent with metal fatigue, based on a preliminary assessment, said the president of air crash investigators. from the US on Monday.
The Pratt & Whitney PW4000 engine failed on Saturday with a “crash” four minutes after the takeoff from Denver, Robert Sumwalt, president of the NationalTransportation Safety Board (NTSB), told reporters after an initial analysis of the flight datarecorder and flight recorder voice of the cabin.
There was minor damage to the aircraft body, but non-structural damage, he said.
He said it is still unclear whether the incident is consistent with an engine failure on a different flight bound for Hawaii in February 2018, which was attributed to a fatigue fracture in a fan blade.
“What is important 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.
The engine that failed on the 26-year-old Boeing Co777 and dropped parts in a Denver suburb was a PW4000 used on 128 planes, or less than 10% of the global fleet of more than 1,600 delivered 777 widebody jets.
In another incident on Japan Airlines (JAL) 777 with a PW4000 engine in December 2020, Japan’s Transport SafetyBoard reported finding two damaged fan blades, one with a metal fatigue crack. An investigation is underway.
The focus is more on engine maker Pratt and analysts expect a small financial impact on Boeing, but the problems with the PW4000 are a new headache for the aircraft maker as he recovers from the much more serious 737 MAX crisis. Boeing’s flagship has been idle for almost two years after two fatal accidents.
The United fan blade will be examined on Tuesday after being transported to a Pratt laboratory, where it will be examined under the supervision of NTSB researchers.
The United States Federal Aviation Administration (FAA) said on Monday that it was already considering whether to adjust fanblade inspections after the December incident in Japan, after reviewing maintenance records and conducting a metallurgical examination of the fanblade fragment.
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.
Pratt & Whitney, owned by Raytheon Technologies Corp., recommended to airlines an increase in inspections at a factory being reviewed by the FAA, sources with knowledge of the matter said. Pratt did not immediately respond to a request for comment.
The FAA said it plans to issue an emergency safety directive soon, which will require more intense inspections of the fan blades to check for fatigue.
“United Airlines has landed all affected planes with these engines, and I understand that the FAA is also working very fast as Pratt & Whitney has reiterated or revised a service bulletin,” said Sumwalt. “It looks like action is being taken.”
In March 2019, after the United 2018 engine failure attributed to fan blade fatigue, the FAA ordered inspections every 6,500 cycles. A cycle is a takeoff and landing.
South Korea’s Ministry of Transport said on Tuesday that it had instructed its airlines to inspect the fan blades every 1,000 cycles, following Pratt’s directions after the United incident.
Sumwalt said the United incident was not considered an unrecognized engine failure because the retaining ring contained the parts while they were flying.
The NTSB will investigate why the bonnet detached from the plane and also why there was a fire despite indications that the engine was shut down, Sumwalt added.
Industry sources said that while the engine is made by Pratt, the fairing, or frame, is manufactured by Boeing. Boeing referred questions to the NTSB.
Nearly half of the global fleet of Boeing777 jets equipped with PW4000 and operated by airlines, including United, JAL, ANAHoldings, Korean Air and Asiana Airlines, had already been stranded amid falling demand for travel due to the coronavirus pandemic. (Report by David Shepardson in Washington and Jamie Freed in Sydney; additional reporting by Tracy Rucinski in Chicago, JoyceLee in Seoul and Tim Hepher in Paris; editing by Kim Coghill and Gerry Doyle)