Engine on a United Airlines jet Breakup due to Denver Federal investigators said Friday that such accidents occurred in 2021 because fan blades were not adequately inspected for signs of cracks.
The National Transportation Safety Board said manufacturer Pratt & Whitney did not require frequent enough inspections, which allowed tiny cracks to grow undetected until the fan blades broke.
The NTSB said the design and testing of the engine’s air intake contributed to the severity of the incident, while other factors made the engine fire more severe than it should have been.
The Boeing 777’s right engine failed shortly after taking off from Denver International Airport, raining parts across the suburbs. Twenty-four minutes after takeoff, the pilot declared an emergency and landed safely.
Debris from engine inlets, fan shrouds and thrust reversers fell in parks and residential areas. There were no reports of injuries on board the plane or on the ground.
Shortly after the February 2021 incident, the Federal Aviation Administration Grounded All US-registered aircraft have been equipped with the same PW4000 series engines for more than a year.
Less than three years after the Denver emergency Southwest Airlines passenger dies When a different model of fan blade cracked and part of the engine casing turned into shrapnel and hit the aircraft. Other fan blade failures occurred on a United Airlines flight to Hawaii in 2018 and a Japan Airlines Boeing 777 in 2020.
The series of events has raised concerns that long-held assumptions about fan blades were wrong – that they were failing much earlier than expected.
At that time, the blades in the PW4000 engine needed to be inspected every 6,500 flights and did not need to be replaced as long as they passed the inspection. The FAA later began requiring more frequent inspections.
The blades that failed in Denver were overhauled at the Pratt facility in 2014 and 2016. During the second repair, the software found two “low-level signs” in the blades, but the inspector dismissed them as camera “noise” or loose grit.
The NTSB said the blade should have been stripped, repainted and inspected again, or “equivocal signs” should have been submitted to the team for more review. The National Transportation Safety Board said neither scenario appears to have occurred.
Pratt, a unit of RTX Corp., did not immediately respond to a message seeking comment.
Boeing, which supplies the engine casings, said it has worked with the FAA to make design improvements to the air inlets and fan shrouds of the affected engines and has provided progress on the work to the FAA, Pratt & Whitney and airlines.
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