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Stress in aircrafts landing gear

  1. Feb 12, 2008 #1
    Hi I am doing a physics coursework presentation, and i need to calculate the stress in the landing gear of an aircraft. It can be any aircraft I just need some figures, for instance the force on the landing gear as it lands, and the cross-sectional area of the landing gear.

    The formula for stress = force / area
    so does anyone know a particular aircrafts force when it lands, and the area of the landing gear? If you know a website with data on this or other helpful info. please let me know what it is.

    I could state the stress on the landing gear whilst on the ground stationary, but this would require the area. For the boeing 747 i know the maximum takeoff weight is 396890kg so i could use this figure but still need the area. Many thanks in advance
     
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  3. Feb 12, 2008 #2

    mgb_phys

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  4. Feb 12, 2008 #3
    Hi thanks for the reply, do you know which chaper or page I should look at? thanks for this though its useful.

    I also found a few other figures out now:
    max weight of B747 = 396890, so max force would be this x9.8 so i got 3889522N

    for the area i found a website http://www.malabar.com/pdf/product/axle/sd65P10AR.pdf stating cyclinder diamater is 8 inches, which is about 20cm. So therefore the cross-sectional area would be about 0.0314159265 msquared

    so now one divided by the other gives about 123,807,330 Pa. But this would be across the 5 main landing gear sets so the stress on landing gear of B747 when stationary is about 24761466 Pa or about 25MPa. Does this seem an appropriate figure?
     
  5. Feb 12, 2008 #4

    mgb_phys

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    Another ball park estimate is that the tire pressure is about 150psi which is 1Mpa so 25Mpa in the gear seems reasonable.

    Generally there is almost no weight (5%) on the nose gear - just enough to provide some friction for steering.

    Boeing provide detaile dspecs on their aircraft and the airport and servicing requirements start here http://www.boeing.com/commercial/overview/overview3.html
     
    Last edited: Feb 13, 2008
  6. Feb 13, 2008 #5
    hm ok thanks, I decided I would use a B737 now instead, but the cyclinder diameter is supposed to be the same as the website http://www.malabar.com/pdf/product/axle/sd65P10AR.pdf states it is used in main landing gear. A B737 only has 2 main landing gears sets and a nose gear. If i took the max weight to be about 70080kg, and the area of the cylinder at 0.032365 Meters squared, then the stress would work out at

    21219649.797Pa, or about 21MPa, but this is across the two main landing gear so approximate stress would be 10.5MPa

    so firstly does this number seem more accurate for the landing gear?
    do my calculations make sense?
    and are my choices of the cyclinder Cross-sect-area best to look at stress of landing gear?

    Thanks for all your help let me know any suggestions or whatever ... thanks
     
  7. Feb 13, 2008 #6

    mgb_phys

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    The pdf is for a jack not the actual landing gear, the 737 probably has smaller diamter cylinders than a 747.
    And it would be more normal to say that the stress is 70t / 2*0.3m^2, and use the total area.
     
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