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This one's for Bob Parks -

Discussion in 'Aviation Chat' started by Gatorrari, Mar 31, 2019.

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  1. Gatorrari

    Gatorrari F1 World Champ
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    Jim Pernikoff
    #1 Gatorrari, Mar 31, 2019
    This newly posted video simulation is about a Dan Air Boeing 707 crash in Zambia in 1977 that was due to an apparent design defect in the stabilizers of the 707 Intercontinental versions that I had never heard of before.

    Bob, are you familiar with this? Do you have any comment?

    http://www.youtube.com/watch?v=_MHyryL4q40

    My only complaint about the video is that it does not state what action was taken as a result of the crash investigation. I assume that some fix was applied to 707s still in service, as well as the military equivalents.
     
  2. Bob Parks

    Bob Parks F1 Veteran
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    Robert Parks
    #2 Bob Parks, Mar 31, 2019
    I am not familiar with the one, Jim. I don't think that I was back with the company at that time. I have heard the structures guys discussing the transmission of loads through the structure in an even and flexible manner without any stiff points.
     
  3. Ferrari27

    Ferrari27 Formula Junior

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    #3 Ferrari27, Apr 1, 2019
    Here is a link to the accident investigation report.

    https://reports.aviation-safety.net/1977/19770514-0_B703_G-BEBP.pdf
     
  4. Bob Parks

    Bob Parks F1 Veteran
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    #4 Bob Parks, Apr 1, 2019
    Unrelated to the thread, I recalled an assignment to "work out" a potable water tank installation in the overhead of a cargo version. I seem to remember 40 gallons. It had to withstand a 13G crash load. I had enough structural stuff to contain it but the load was too concentrated and it had to be spread out more. So, we spread things more into adjacent structures so that the tanks wouldn't crush the crew that would have already expired from the crash.
     
  5. Gatorrari

    Gatorrari F1 World Champ
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    Jim Pernikoff
    #5 Gatorrari, Apr 1, 2019
    The key to this is that both strength and stiffness need to be accounted for in design. Strength is fine, but structure that is either not stiff enough or too stiff can still fail.

    In the case of the Lockheed Electra, the outboard nacelle structure was strong enough, but not stiff enough to stop whirl-mode flutter, which caused two wings to fail in harmonic vibration. Apparently, in the case of these 707 stabilizers, the revised structure was too stiff, which promoted metal fatigue that was hard to detect. If this was the only 707 to crash because of that, Boeing and the airlines were very lucky.
     

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