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Aerospace Resistence of wings on commercial airliners

  1. Sep 20, 2004 #1
    How much force are wings designed to resist on commercial passanger planes such as Boeings and Airbusses and even Learjets before they actually tear off?

    I would also like to see if we can factor in the speed these planes are traveling at versus the counter force of water, air, concrete and steel.

    Another point is if the fuel traveling to the turbines will affect wings resistence.

    If there are sites with this information, maybe my googling skills are inferior because I haven't really found anything.

    thanks
     
  2. jcsd
  3. Sep 21, 2004 #2

    russ_watters

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    Well, at cruising speed, engine output equals drag...

    And the strength of a wing vertically at the wing root has to be enough to hold up the fuselage (and pull 2+ gees).
     
  4. Sep 21, 2004 #3

    Cliff_J

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    Concrete and steel?

    I think you misunderstand how the wings are constructed. While they may very well have a failure point at say 4Gs (which is many many tons of force for a large aircraft) this force is distributed over the entire surface area of the wing and handled by the internal structure as a system. But a bridge upright weighing less than one percent of the plane's takeoff weight could potentially rip off a large part of a wing just a takeoff speed (much less cruising speed) simply because the forces would be localized. And while that bridge may be constructed to handle hundreds of tons of load, a single failure point like that may lead to the structure collapsing under its own weight. So two very large, well engineered, high-load capacity structures could destroy each other with very little energy input compared to their maximum capabilities.

    So its more than just a simple force number, its also a function of how that force is applied to the structure.

    Cliff
     
  5. Sep 21, 2004 #4
    I know Boeing tests all their wings to destruction. But I think they only do it in bending, since that is the weakest failure mode of the wing. Search Boeing's site, and I think you'll have better results with getting information.
     
  6. Sep 21, 2004 #5

    enigma

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    Plus they're designed to resist flutter and wing divergence, both of which are dynamic properties and become worse with speed.

    The way that they're sized is they calculate the absolute highest force that they are expected to see, and then they multiply it by a safety factor. IIRC for most aeronautical applications that number is between 1.5 and 2
     
    Last edited: Sep 21, 2004
  7. Sep 21, 2004 #6

    russ_watters

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    I ignored that part, but wait - this isn't a 9/11 thread, is it?
     
  8. Sep 21, 2004 #7

    Cliff_J

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    I'd hope not but wanted to make sure the poster was aware that a simple cantilever force calculation wouldn't suffice to give them an answer. While things like moment can be calculated around the cg when the model is simplified, a little bit of reality couldn't hurt either when talking about an aluminum skinned structure engineered to handle predetermined loading where impacts of non-deforming objects are not part of that plan. A 4lb bird is tested but has a much lower compressive and tensile strength. Road signs and light poles are engineered for automobile accidents, etc.

    I'd think the calculations of the energy that would need to be dissapated within the structure for a plastic collision would alone point out that the wing would not likely survive as a lift producing device. As I remember from a TV show, the original Airbus prototype that crashed on a touch-n-go while demonstrating fly-by-wire did not fare very well at all in the forest it ended up in.

    So I'd hope the intent of the post is in terms of how to design a structure to be strong enough to handle what is expected of it, and not about destruction. Discovery Wings channel had a program that showed the history of flutter and as I sat there open jawed at a model twisting wildly (and I thought all the FEA simulations exaggerated!!) I remebered the plane that flew into the turbulence from the plane ahead and lost its tail rudder a couple years ago just after takeoff in NY. The dynamics of flight encompasses an incredibly wide range of forces....

    Cliff
     
    Last edited: Sep 21, 2004
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