WASHINGTON (Reuters) – The chairman of the US National Transportation Safety Board (NTSB), Robert Sumwalt, said on Monday that damage to a fan blade in a Pratt & Whitney engine that failed in a United Airlines Boeing 777-200 corresponds to metal fatigue, according to a preliminary assessment.
At a news conference, Sumwalt said it was not clear whether the failure of the PW4000 engine on Saturday with a “loud bang” four minutes after takeoff was consistent with another engine failure during another Hawaii flight in February 2018 attributed to a fatigue. break in a fan blade.
The engine that crashed on the 26-year-old Boeing Co 777 and shook parts over a suburb of Denver was a PW4000 used on less than 10% of the global fleet of 777 wide-body aircraft.
In another incident on Japan Airlines (JAL) 9201.T 777 with a PW4000 engine in December 2020, the Japan Transportation Safety Board reported that two damaged fan blades had been found, one with a metal fatigue crack. An investigation is underway.
The focus is more on engine manufacturer Pratt & Whitney and analysts expect little financial impact on Boeing, but the PW4000 issues are a fresh headache for the planner as it recovers from the much more serious 737 MAX crisis. Boeing’s flagship narrow-gauge aircraft was on the ground for almost two years after two fatal accidents.
The United engine’s fan blade will be examined on Tuesday after being flown to a Pratt & Whitney laboratory, where it will be examined under the supervision of NTSB investigators.
“What’s important is that we really need to understand the facts, circumstances and conditions surrounding this particular event before we can compare it to any other event,” Sumwalt said.
Boeing recommended that airlines suspend the use of the aircraft while the FAA identified an appropriate inspection protocol, and Japan temporarily suspended flights.
The Federal Aviation Administration plans to issue an emergency airworthiness directive soon that will require stricter inspections of the fan blades for fatigue.
The FAA ordered in March 2019 after the February 2018 engine failure attributed to fan blade fatigue every 6,500 cycles. A cycle is one takeoff and landing.
Sumwalt said the United incident was not considered an unintentional engine outage because the containment ring contained the parts while it was flying out.
There was minor damage to the aircraft, but no structural damage, he said.
NTSB will investigate why the hood separated from the aircraft and also why there was a fire, despite the indication that the fuel was switched off at the engine, Sumwalt added.
Pratt & Whitney, which is owned by Raytheon Technologies Corp., said Sunday they are coordinating with regulators to review inspection protocols.
Nearly half of the global fleet of 128 aircraft operated by airlines, including United, JAL, ANA Holdings, Korean Air and Asiana Airlines, were already grounded amid high demand for travel due to the coronavirus pandemic.
Reporting by David Shepardson in Washington and Jamie Freed in Sydney; additional reporting by Tracy Rucinski in Chicago Editing by Kim Coghill and Gerry Doyle