Engine on United Boeing 777 showed signs of metal fatigue: Investigators


The damaged starboard engine of United Airlines Flight 328, a Boeing 777-200 after an engine failure.


Damage to a fan blade on an engine that failed on a United Airlines Boeing 777 flight is consistent with metal fatigue based on a preliminary assessment, the US 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 and spilled parts over a suburb of Denver on the 26-year-old Boeing Co 777 was a PW4000 that was 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 & Whitney, 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 nearly two years after two fatal crashes.

The United engine fan blade will be examined Tuesday after it was flown to a Pratt & Whitney 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 stop using the aircraft while the FAA established an appropriate inspection protocol, and Japan imposed a temporary suspension of flights.


The FAA plans to issue an emergency airworthiness policy shortly that will require increased inspection of fan blades for fatigue.

The FAA ordered inspections every 6,500 cycles in March 2019 after the United engine failed in February 2018 due to fan blade fatigue. 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 plane and why a fire broke out despite signs that the engine was turned off fuel, Sumwalt added.

Pratt & Whitney, owned by Raytheon Technologies Corp., said Sunday it had lined up with regulators to review inspection logs.

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.

(Except for the headline, this story was not edited by GossipMantri staff and published from a syndicated feed.)


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