United 328 Engine Failure: Two Blades Broken, Metal Fatigue Implicated (Updated)

NTSB chairman Robert Sumwalt updated the agency’s investigation of the incident involving United Flight 328, which lost an engine on departure and made an emergency landing back at Denver. While stressing that the investigation is in the very early stages, Sumwalt said that the indications are that metal fatigue led to the failure of one of the Pratt & Whitney PW4077’s first-stage fan blades, of which there are 22. 

“Two blades found fractured," he said. “One at the root while the adjacent blade was fractured at mid span. The indications are consistent with the blade [broken at mid span] is that it was hit by the other blade.” Portions of one blade were found in the engine containment ring at the 1 o’clock position. As widely reported, the 777 left a debris field a mile long; Sumwalt says that the NTSB is working with local law enforcement to recover as much of the missing engine and airframe as possible.

Sumwalt commented on the other damage visible. “There was damage to the composite wing-to-body fairing, and there were dings and nicks in other places on the wing.” Sumwalt stressed that at this stage is appears the damage is limited to nonstructural components and that no systems appear to have been in jeopardy nor was the Boeing’s pressure vessel breached. 

United 328 had departed Denver for Honolulu and had been cleared to 23,000 feet. About 4 minutes after takeoff, climbing through 12,500 feet and going 280 knots, “there was a loud bang and increased vibration from the #2 engine,” Sumwalt said, based on a preliminary read on the cockpit voice recorder and flight-data recorder. Sumwalt also confirmed that the fire handle for the right engine had been activated and both fire bottles discharged. Video of the aircraft returning to Denver shows the engine power section glowing, though Sumwalt confirmed that the fuel supply had been shut off as part of the shutdown procedure.

The 777-200 landed without further incident. The crew decided that an emergency egress was not needed back at Denver so the 229 passengers deplaned normally.