WASHINGTON – United States National Transportation Safety Board Chairman Robert Sumwalt on Monday said damage to a fan blade of a failed Pratt & Whitney engine in a United Airlines Boeing 777-200 is consistent with metal fatigue, based on a preliminary assessment.
At a press briefing, Sumwalt said it was not clear whether Saturday’s PW4000 engine failure with a “loud bang” four minutes after take-off was consistent with another engine failure on another flight. United to Hawaii in February 2018, attributed to fatigue. fracture in a fan blade.
The engine that broke down on the 26-year-old Boeing Co 777 and lost parts over a Denver suburb was a PW4000 used on less than 10% of the world’s 777 widebody fleet.
In another incident on Japan Airlines (JAL) 777 with a PW4000 engine in December, the Japan Transportation Safety Board reported finding two damaged fan blades, one with a metal fatigue crack. An investigation is underway.
The focus is more on engine maker Pratt & Whitney and analysts expect little financial impact on Boeing, but the PW4000 issues pose a new headache for the aircraft maker as it is recovering from the much more serious 737 MAX crisis. Boeing’s flagship narrow-body aircraft was grounded for nearly two years after two fatal crashes.
The United motor’s fan blade will be examined on Tuesday after being transported to a Pratt & Whitney lab where it will be examined under the supervision of NTSB investigators.
“What is important is that we really understand the facts, circumstances and conditions surrounding this particular event before we can compare it to any other event,” Sumwalt said.
Boeing has recommended airlines suspend aircraft use while the FAA identifies an appropriate inspection protocol, and Japan has imposed a temporary flight suspension.
The Federal Aviation Administration plans to issue an Emergency Airworthiness Directive soon that will require intensified fan blade inspections for fatigue.
In March 2019, the FAA after the February 2018 United engine failure attributed to fan blade fatigue ordered inspections every 6,500 cycles. A cycle is a takeoff and a landing.
Sumwalt said the United incident was not considered an unconfined engine failure because the containment ring contained the parts as they flew away.
There was minor damage to the plane’s body, but no structural damage, he said.
The NTSB will look into why the engine cowl separated from the plane and also why there was a fire despite indications that the engine fuel was cut, Sumwalt added.
Pratt & Whitney, which is owned by Raytheon Technologies Corp, said Sunday it was coordinating with regulators to review inspection protocols.
Nearly half of the global fleet of 128 aircraft operated by airlines such as United, JAL, ANA Holdings, Korean Air and Asiana Airlines had already been grounded amid falling travel demand due to the pandemic of coronavirus.