Incident · 2021-02-20

What the record says

Event date

2021-02-20

Event type

Incident

Highest injury level

No injuries

Aircraft

BOEING 777-222 (N772UA)

Operating rule

Part 121

Operator

UNITED AIRLINES, INC. Operator named in NTSB report

Operated by (per NTSB report)

United Airlines

Probable cause

The fatigue failure of the right engine fan blade. Contributing to the fan blade failure was 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. Contributing to the severity of the engine damage following the fan blade failure was the design and testing of the engine inlet, which failed to ensure that the inlet could adequately dissipate the energy of, and therefore limit further damage from, an in-flight fan blade out event. Contributing to the severity of the engine fire was the failure of the “K” flange following the fan blade out, which allowed hot ignition gases to enter the nacelle and imparted damage to several components that fed flammable fluids to the nacelle, which allowed the fire to propagate past the undercowl area and into the thrust reversers, where it could not be extinguished.

Flight crew

Certification and experience as recorded in the NTSB accident database for this event. The NTSB records these facts about the crew's flying history; GroundCheck shows them as filed, without names or identities.