United Boeing 777 engine injury because of steel fatigue: NTSB By Reuters

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© Reuters. United Airlines flight UA328 returns to Denver International Airport with its starboard engine burning after it set off a Mayday alarm

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By David Shepardson and Jamie Freed

WASHINGTON (Reuters) – Damage to an engine fan blade that failed on a United Airlines Boeing (NYSE 🙂 777 flight is consistent with metal fatigue, based on a preliminary assessment, the U.S. aviation accident investigator chairman said Monday .

The Pratt & Whitney PW4000 engine failed four minutes after takeoff in Denver with a “loud bang,” said Robert Sumwalt, chairman of the National Transportation Safety Board (NTSB), to reporters after an initial analysis of the flight data recorder and cockpit -Voice recorder.

He said it remained unclear whether the incident was consistent with an engine failure on another flight to Hawaii in February 2018 that was due to a fatigue fracture in a fan blade.

“What is important is that we really really understand the facts, circumstances and conditions surrounding this event before we can compare it to any other event,” said Sumwalt.

The engine that failed in the 26-year-old Boeing Co. 777 and scale parts over a suburb of Denver were PW4000s that were used on 128 aircraft, or less than 10% of the global fleet of more than 1,600 777 wide-body jets shipped.

In another incident on Japan Airlines (JAL) 777 with a PW4000 engine in December 2020, the Japanese Transport Safety Board reported finding two damaged fan blades, one with a metal fatigue crack. An investigation is still ongoing.

The focus is more on engine maker Pratt, and analysts expect little financial impact on Boeing. However, the PW4000 issues are causing new headaches for the aircraft manufacturer as it recovers from the far more severe 737 MAX crisis. Boeing’s flagship narrowbody jet was on the ground for almost two years after two fatal crashes.

The United engine’s fan blade will be examined Tuesday after it was flown to a Pratt lab where it will be examined under the supervision of NTSB investigators.

The U.S. Federal Aviation Administration (FAA) said Monday it had already examined whether to adjust fan blade inspections after the December incident in Japan, after reviewing maintenance records and conducting a metallurgical examination of the fan blade fragment.

Boeing recommended that airlines cease using the aircraft while the FAA put an appropriate inspection protocol in place, and Japan imposed a temporary suspension of flights.

Pratt & Whitney, owned by Raytheon Technologies (NYSE 🙂 Corp., has recommended airlines step up inspections in a plan that is being scrutinized by the FAA. Pratt did not immediately respond to a request for comment.

The FAA has announced that it will shortly issue an emergency airworthiness policy that will require increased inspection of fan blades for fatigue.

“United Airlines has grounded all affected aircraft with these engines, and I understand the FAA is also very fast and Pratt & Whitney has re-run or revised a service bulletin,” said Sumwalt. “It looks like action is being taken.”

In March 2019, after the United engine failed in 2018 due to fan blade fatigue, the FAA ordered inspections every 6,500 cycles. A bicycle is a take-off and a landing.

Sumwalt said the United incident was not viewed as uncontrolled engine failure as the safety ring contained the parts when they flew out.

There was minor damage to the aircraft body, but no structural damage, he said.

NTSB will investigate why the hood parted from the aircraft and why a fire broke out despite signs that the engine was turned off fuel, Sumwalt added.

According to the industry, the hood or case is made by Boeing, although the engine is made by Pratt. Boeing referred questions to the NTSB.

Almost half of the global fleet of PW4000-equipped Boeing 777 jets operated by airlines such as United, JAL, ANA Holdings, Korean Air and Asiana Airlines had already ended up in a decline in travel demand due to the coronavirus pandemic.

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