Damage to Boeing 777 fan in conformity with metal fatigue: NTSB

The chairman of the National Transportation Safety Board said preliminary assessments showed that damage to a fan blade in the engine that failed on the United Airlines Boeing 777-200 is consistent with metal fatigue.

The Pratt & Whitney PW4000 engine failed with a “loud bang” four minutes after takeoff from Denver on Saturday, causing minor damage to the torso, NTSB President Robert Sumwalt said on Monday of early analysis of flight data and caucusit voice recorders Later told reporters.

He said it was unclear whether the accident was consistent with an engine failure on the air-bound United Flight in February 2018 that was responsible for a fatigue in a fan blade.

“It is important whether we really understand the facts, circumstances and situations surrounding this particular incident,” Suwalt said in a news briefing.

The 26-year-old aircraft used the engine involved in Saturday’s incident on 128 aircraft – or less than 10 percent of the worldwide fleet of more than 1,600 Boeing 777s, according to Reuters.

According to the Transport Safety Board of Japan, in a December 2020 incident, two damaged fan blades with a PW4000 engine were reported in the Japan Airlines Boeing 777. That investigation continues.

The Federal Aviation Administration said on Monday that it was already evaluating whether to adjust the fan blade inspection in view of the December incident in Japan.

The combined engine fan blade will be examined after being sent to the Pratt on Tuesday, where it will be tested under the supervision of NTS investigators.

Boeing recommends that airlines suspend the use of 777 aircraft while the FAA has identified an appropriate inspection protocol.

The agency has said it plans to issue an emergency airworthiness directive that would require inspection of fan blades for fatigue.

“United Airlines has fielded all affected airplanes with these engines, and I think the FAA is working very quickly and at the same time Pratt & Whitney has repeated or revised a service bulletin,” Sumwal. he said. “Looks like action is being taken.”

He said the combined incident was not considered an unsupervised engine failure because the control ring had parts as they were flying out.

The NTSB will look into why the coupling was separated from the jetliner, and also why the fire was set off despite indications that the engine had stopped fueling, Suvalav said.

Industry sources said that although the engine is made by Pratt, Kauling is manufactured by Boeing, which referred questions from the NTSB.

Pratt & Whitney, which is owned by Raytheon Technologies Corp., has recommended airlines extend oversight to a plan that is being reviewed by the FAA, Reuters informed of the matter.

With post wires

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