The National Transportation Safety Board stated on Friday that the United Airlines Boeing 777 engine failure in Colorado in February 2021 was caused by a crack in a fan blade and pointed to insufficient inspections as a contributing factor.
The Federal Aviation Administration (FAA) immediately required examinations of 777 aircraft with Pratt & Whitney 4000 engines prior to further flights following the accident, which resulted in the planes’ being grounded for more than a year.
After taking off from Denver, the Boeing 777-200 headed for Honolulu scattered debris over adjacent communities, but no one was hurt, and the plane made it back to the airport without incident.
According to the NTSB, “the inadequate inspection of the blades, which failed to identify low-level indications of cracking, and the insufficient frequency of the manufacturer’s inspection intervals, which permitted the low-level crack indications to propagate undetected and ultimately resulted in the fatigue failure.” An RTX subsidiary, Pratt & Whitney, declined to comment right away.
In a statement released on Friday, United stated that it has “closely collaborated with the NTSB, FAA, Boeing, and Pratt and Whitney on each step of the investigation and are pleased to have these aircraft back in our fleet.”
Following three documented in-flight fan blade failures, including the Colorado event that called for increased inspections and modifications, the FAA finalised new safety directives in March 2022. In reaction to the events involving fan blades, the FAA announced on Friday that it had issued the safety instructions.
Following the incident, according to Boeing, it “has identified appropriate design changes to improve the structural integrity of the engine inlet and cowling and has been communicating with the FAA, Pratt & Whitney and airline customers on its progress.”
As of 2022, United was the only U.S. airline operating 777s equipped with the PW4000 engine.
According to the NTSB, as of January, 17 confirmed broken fan blades had been discovered; the first one was discovered in December 2004. This does not include the three fan blades that experienced full-blade separation while in use.