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

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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. 

Image: NTSB. Damage to the belly of the 777-200 appears to be limited to the wing-to-fuselage fairing.
Image: NTSB.

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.

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7 COMMENTS

  1. “Portions of one blade were found in the engine containment ring at the 1 o’clock position.”

    How fortunate. Unsolicited engineering advice: the occurrence of good fortune is very unreliable.

    These engines are amazing. Their containment aparatus? Not so much. Time for a re-think.

    • And again, you want “a re-think”. I suppose an engine could be built to withstand every rare thing that happens to it, at more cost and more weight, for a safety improvement that couldn’t even be quantified.
      Get a job designing, certifying, and manufacturing jet engines, and get out of your armchair.

  2. I don’t think they said that containment failed and I have not seen a hole through the containment ring. When you lose a couple of blades that large it makes for a large imbalance and high vibration that seems to have caused the engine fairing to disintegrate.

  3. Unfortunately, accidents (and other mishaps) aren’t that rare. Moreover, they are indeed quantifiable.
    That is why Lee Iacocca refused to alter the design of the Ford Pinto, after cost-benefit analysis showed
    that facing wrongful death suits would be less expensive than retooling the undercarriage of the vehicle.
    This is the norm in American business, so much so that we don’t even notice it, except when there’s an
    “incident” that no one can ignore, be it a near-miss, the death of someone famous, or a catastrophe so
    enormous that it cries out for investigation. Otherwise, it goes unchallenged, except for those willing
    to lose their jobs, even with whatever legal protection being a whistleblower may afford. Boeing isn’t
    exactly renowned for its safety record, especially in light of the 737-MAX, the 787 Dreamliner, and an
    ever-tightening budget, causing layoffs and severe reductions in their workforce. Faced with loss of
    revenue, plant closures, and trouble securing favorable loan rates for capital investment, what to do
    when a problem arises, be it on the assembly line, at the drafting table, or during the testing phase?
    My suspicion is that Boeing fudged it–on advice of counsel, and after consulting with their CFO. In this
    as in most cases, the armchair rules; those who believe in their bosses are corporate tools, while pilots,
    passengers and the public are simply played for fools. Denver was fortunate; don’t press Boeing’s luck.