Damage to engine fan blade led to Boeing incident: Investigator

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 chairman of the US air accident investigator said on Monday.

The Pratt & Whitney PW4000 engine failed on Saturday with a “loud bang” four minutes after takeoff from Denver, national transportation safety board (NTSB) chairman Robert Sumwalt told reporters following an initial analysis of the flight data recorder and cockpit voice recorder.

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

He said it remained unclear whether the incident is consistent with an engine failure on a different Hawaii-bound United Airlines flight in February 2018 that was attributed to a fatigue fracture in a fan blade.

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

The engine that failed on the 26-year-old Boeing 777 and shed parts over 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 safety board reported it found two damaged fan blades, one with a metal fatigue crack. An investigation is ongoing.

The focus is more on engine maker Pratt and analysts expect little financial impact on Boeing, but the PW4000 issues are a fresh headache for the planemaker as it recovers from the far more serious 737 MAX crisis. Boeing’s flagship narrowbody jet was grounded for nearly two years after two deadly crashes.

The United engine’s fan blade will be examined on Tuesday.