It's a small miracle nobody was hurt or killed in Colorado over the weekend after an engine blew on a United jet and rained huge pieces of debris on neighborhoods near the Denver International Airport. In fact, one of the engine's fan blades came down on a soccer field in Bloomfield. As the investigation unfolds, here is the latest:
- Metal fatigue: The investigation could take more than a year, but an early report by the NTSB suggests that "metal fatigue" caused one of the engine fan blades to break, reports CNN. The blade then apparently sheared off a second one, and the engine caught fire. "My daughter was sitting on the window and ... I was just like, 'Don't look, like ... let's close it up and let's just pray,'" passenger Brenda Dohn recalls. The engine on the Boeing 777 is made by Pratt & Whitney, part of its PW4000 series.
- Other incidents: That same day, a Boeing 747 in the Netherlands with similar engines—from the PW4000 series, though a different model—suffered a similar fate, reports Reuters. In December, a Japan Airlines jet with engines from the PW4000 series also had to return to the airport because two fan blades broke on one of them. And three years ago, a fan blade broke on a United jet with a PW4000 series engine out of San Francisco, per NBC News. As in Colorado, all the flights landed safely.
- Now what? The AP reports that 69 planes in use, plus 59 in storage, have been grounded in the US, Japan, and South Korea, the only nations to have jets with this type of engine. FAA chief Steve Dickson says inspections will be increased "for the hollow fan blades that are unique to this model of engine," per NBC.
- Questions: "What's being missed? Is it an inspection cycle? Are they doing proper types of inspections? Are there commonalities between the three failures? Those are the kinds of things that the investigators are going to be looking at now," John Cox, an accident investigator and the head of aviation consulting firm Safety Operating Systems, tells the New York Times. The manufacturing process also will be examined.
- Context: All of this is playing out in the wake of the 737 Max fiasco, which "resonates throughout the industry," an aviation attorney tells the Wall Street Journal. NTSB chief Robert Sumwalt says investigators will also be reexamining the December incident: "We'll be looking at that to see what could have been done, what should have been done, if anything at all."
- Silver lining: The engine blew and started on fire, and yet the jet landed safely. "The FAA requires that the manufacturer of a two-engine plane like this certify it so it can fly on one engine, which it did," an aviation expert tells NBC.
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