That 777 Incident In Denver


They (and those on the ground) were very lucky. If that shrapnel had angled up a little more, it would have hit the fuel tank in the wing, and they’d have probably been a fireball. I wonder if the engine was still providing thrust?

20 thoughts on “That 777 Incident In Denver”

  1. That is not the fuselage…not the pressure vessel. That is the wing to body fairing. Usually made from fiberglass honeycomb. Not exactly strong stuff.

    1. The fuselage is on the other side of it. And you’re correct, the composite fairing is not especially strong…but the fan blade is, and had considerable velocity.

      As far as proving thrust, with a fan blade gone the fan would have been wildly out of balance, and the procedure would be to shut the engine down. Considering the aircraft was preparing to land, maybe they did, or at least pulled the power back to zero thrust, maybe they didn’t.

      The report (thankfully, not from the NTSB since no one was killed) will let us know.

  2. Those parts landed about three miles north of here. I vaguely remember a plane that was noisier than usual about that time, but the Boulder airport (BJC) is about the same distance to the northwest from here, so we get noise all the time.

    As for what could’ve happened on the ground, I thought of PSA 182 in San Diego in 1978.

      1. Heh. I was in the Army Guard at the time, and we were convoying through the area…The police stopped us and asked if we had any body bags.

    1. Yeah, that could have been an issue, but it didn’t appear to me that the drag would be altered that much. Would it fly slower and lower on a single engine? I wonder if that would make the drag better, or worse.

      1. Well, I figure that ETOPS standards are set so that the plane, if flown properly for single-engine out conditions, will have enough range to stay dry. They’re only going to put enough fuel on board to meet all those relevant standards, so if you add a bunch of extra drag on top of the normal engine-out condition, it might come up short.

        Meanwhile, a 747-400 taking off from Maastrict just dumped PW4000 turbine blades all over people’s cars. Two injured, one a child whose parents apparently hadn’t taught them not to pick up smoking hot jet engine components.

        Now I’m worried about putting my Pratt & Whitney reliable-engine coffee mug in the microwave.

        1. The standards may be set that way, but at least at United they take off at the maximum safe fuel load anyway. (I live in Hawaii, and have often waited for takeoff while they burn off enough fuel to meet takeoff weight)

      2. Yes it would have flown slower, possibly not able to climb as much. But the engine not windmilling freely would have created considerable drag.

        In order for an airliner to receive ETOPS (Engines turn or passengers swim) certification, it has to be able to lose an engine and fly for 90 or 120 minutes on one engine. Would they have made it to Hawaii? Probably, or turned back for the west coast.

  3. AgentJZ, a jet engine tech who runs an excellent Youtube channel, has a video up suggesting that the broken blade was contained, only the aerodynamic engine cowling was lost, not the actual engine case itself, and that the fire was likely oil, not fuel. It was windmilling, not under power–and even at that much lower speed, the imbalance of the lost blade was sufficient to cause the shaking seen in the passenger videos.

    1. Yes, but the media would rather get expert commentary from hack aviation journalists then actual people with deckplate experience. Kinda like watching the defense experts trotted out to comment on the Japanese submarine collision a week ago than going to Aaron Amick (SubBrief) on Youtube.

  4. Yes, wait for the report and all of that. But if what failed was a fan blade, it appears that the containment and fire suppression arrangements did the job (along with a composed, trained air crew) in bringing this plane back home.

    I would gladly request United Airlines (or United Technologies) to buy me a replacement living room in exchange for bringing all those people home.

  5. Thanks Rand. Some passengers reported feeling an impact under their feet at the time the engine exploded. This explains it.

  6. I did some ballistic tests for my jet glider conversion project. Two 40 Kgf drone/large R/C aircraft engines. A turbine blade is about the same mass and velocity as a standard velocity .22 bullet. Had fun shooting at bits of stainless steel/4130 steel and multiple layers of 170 gm kevlar. 7 layers will stop the bullet completely, as will 1 mm of 4130, nice dent though. About 4 layers of kevlar behind 0.55 mm stainless will also stop the bullet from 4 meters.
    Lots of firewall, fire detection and fire suppression installed. Turbine manufacturer tells me they’ve never had a turbine blade fail. It is a blisk.

    Obviously a large turbofan is a different kettle of fish.

  7. So I am just wondering. How many of use here, if we were sitting on the side of the jet near a window and could see that partially disassembled nacelle and the dull orange glow of burning engine oil in the thrust reverser section would have only one thought?


  8. While at FAA/AST, I tried to get the flight safety analysts going on using actual data from flight incidents like this one to see what the expectation of casualties (Ec) would be using the methodology (and AST’s RRAT software) required of space launch license applicants. My objective was to see whether the methods and software would predict greater or less than 1E-4 casualties, thus helping to test the model validity.

    The project never got any traction, though it wasn’t for lack of interest on the part of the flight safety analysis group. We just didn’t have the time, given the tremendous workload back then (which, I imagine, is even greater now).

    Airplanes shed parts more regularly than most people realize, up to and including entire engines. A wide-body jet engine can weigh upwards of 18,000 pounds. Yet I have never been able to find an account of an injury among people on the ground. Even plane crashes seldom result in ground casualties – the Concorde crashed into a hotel, for gosh sakes, and only killed four employees. That’s not to minimalize their loss, far from it. But the Concorde represented every bit as big a hazard as any commercial launch vehicle, and even crashing into a hotel didn’t result in the kind of carnage AST fears.

    Fact is, AST has no idea whether its methods and models bear any relationship to the real world, because they’ve never been tested. That was what I wanted to do, but the manpower and budget constraints prevented it.

    In my opinion, we way, WAY overconstrain the commercial space launch industry from a safety perspective. Elon has griped about it, and I wholeheartedly agree with him.

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