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Continental crash in Denver | Broken Wing

Continental crash in Denver

Posted on 23. Dec, 2008 by in Featured

737-crash1

Saturday a Continental Airlines Boeing 737 left the runway, shearing off its main and nose landing gear as well as the left engine nacelle. It then caught fire and was destroyed; miraculously no one was killed. I always hesitate to comment on aviation accidents because it is an opportunity to put foot in mouth. I’ll always remember the aviation “expert” I watched on TV adamantly insist that the DC-10 in the Sioux City accident could not have had a total hydraulic failure; “impossible”. Never say never in aviation; the United Airlines DC-10 did in fact have a total hydraulic failure.

So what do we know? The 737 aborted its take off and left the runway. Reports today say the NTSB has found that the engines were running and the brakes functioned properly; included in the report and very telling was the loud sound of something banging around in the back ground of the cockpit voice recording.

First: Abort equals bad, high speed abort very bad! My last post I wrote about a missed approach and how it was the most crew intensive NORMAL procedure a crew can perform. The abort, especially the high speed abort, is the most intensive EMERGENCY procedure. The crew has to get the throttles to idle, the spoilers and thrust reversers deployed and the brakes on to the maximum extent possible. All done simultaneously while keeping the aircraft on the runway, radioing the tower and ensuring any automated features function properly. It is not easy! Oh, and by the way you have to make the decision on whether to abort or continue in the first place as the aircraft hurls toward the end of the runway.

To help in the decision process we have a decision speed that is calculated for every flight. That speed is called V-1. V-1 is the decision speed for aborting, over-simplified; if you are below that speed you have enough runway to decide and perform an abort without running off the end. Above you “probably” don’t. Probably you ask? There are few absolutes in aviation, the crew, specifically the Captain must decide what the best option is. For example: if an engine fire light illuminates with secondary indications, and you are at DFW with 15,000 feet of runway and an over run, and flat prairie beyond that. Most Captains would abort above V-1rather than take a confirmed fire into the air. If you were at LGA, runway 4, no over run just river? Probably not. The human element, and experience counts, computers can’t do it.

Denver is like DFW lots of runway and flat over run. IMO the choice to stop the take off process with an obvious material failure was a good one. A contributing factor was a very strong cross wind, some reports up to 33 knots, near the maximum demonstrated ability for the 737. My educated guess, but still a guess, is that the crew heard the sounds of a mechanical failure. No pilot I’ve ever met would take an airplane into the sky with a known/suspected structural failure. For it to be so loud in the cockpit I suspect it was a failure in the nose gear area, possibly disabling the nose gear steering. One of the automated systems in modern aircraft are auto brakes. On abort they will activate when the throttles are pulled to idle, and they will apply equally. In the strong wind the aircraft would have weather-veined into the wind (swerve left). If the audible failure bound the controls (rudder pedals) or caused nose wheel steering failure, or even a structural failure of the nose gear, then it’s probable that the yawing moment could not be overcome by the crew. At that point all you can do is to try and decelerate as fast as possible and keep the wings from digging in and flipping the aircraft. IMO they did a good job keeping the 737 upright. But, again, it will be a while before we know for sure.

9 Responses to “Continental crash in Denver”

  1. lavonne 23 December 2008 at 20:55 #

    Fascinating analysis. You should think about becoming one of those TV ‘experts’!

  2. Chip 24 December 2008 at 09:19 #

    LaVonne;
    I’d would be one ugly talking head!

  3. Rick 30 December 2008 at 14:31 #

    I suspect one of the tires on the nose gear failed. That would have made the racket plus could have effected steering control. I have had this happen to me once landing a C172…lost left main gear tire and plane went off the runway to the left because of the drag. I can see this happening to a two tire nose gear also.

  4. chip 31 December 2008 at 13:02 #

    Rick;
    That is a sound theory. A Captain I’m currently flying with thinks it could also be the main gear skipping side ways on the runway caused by the strong wind and/or not enough aileron into the wind or a mechanical failure. There are also some rumors circulating about problems w/the new wing tips in a strong cross wind. I’ve been looking through some manuals for cross wind limits for take off. I have not found any yet, just for landing. It is looking like this could prove to be a series of problems that linked up to cause the crash.

  5. Rick 31 December 2008 at 15:29 #

    Chip,
    I saw the Airnav website posted winds gusting 280 degrees at 33 knots. Since this was runway 34R, it seemed to me that just a quartering left front crosswind that should not have that adverse of an impact on a 737. That’s why I’m inclined to believe it’s a blown tire (perhaps debris on the runway?). Do you know were they actually at V1 when they aborted? That taxiway they went off at is about 1/3 of the way down the runway…approx 4000 feet. Is that enough runway for a 737 to reach V1? I’m not a 737 pilot, just private, so I don’t know myself.

  6. Rick 31 December 2008 at 15:36 #

    I also noticed that NBC, MSNBC, and CNBC constantly kept using an animated strip that showed the plane on takeoff roll on the parallel taxiway to 34R, not actually on 34R. They ran it for 4 days With all their aviation experts, that’s an embarrassment.

  7. chip 2 January 2009 at 13:36 #

    Rick;
    Great questions; I decided to answer them in a new post.
    BTW: I think had there been a tire failure we would have heard about it, or seen the debris on the runway in pictures.

  8. Rick 3 January 2009 at 09:26 #

    Chip, I went back to the old “crosswind wheel” and saw that 280 degrees at 33Kts on a runway 34 does still give a high crosswind “factor” of 30. That’s pretty high, I agree. Regarding the debris on the runway, I have looked and looked and can not find any photos of the runway’s entire length just after the accident. All of the news choppers were concenrating on the hull only, and not much on the runway.

  9. tyty 10 July 2012 at 14:39 #

    wat was the flight number


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