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  • Climb Gradient calculation...

    It seems like a easy question but I can't find the correct answer...

    A 4 jet-engined aeroplane (mass=150000kg) is established on climb with all engines operating. The lift-to-drag ratio is 14. Each engine has a thrust of 75000 Newtons. The gradient of climb is: (g=10m/s?)

    a) 1.286%
    b) 12.86%
    c) 27%
    d) 7.86%

    Climb Gradient (%) = (T - D)/W . 100
    = (30.000kg - D)/150.000kg x 100

    So we have to find Drag...

    The only thing we know is D = L/14

    and
    L = W . cos X
    L = 150.000kg . cos X

    We still have to know... the climb angle.
    Dreams hang in the air...
    CPL/IR/ME/GI
    http://www.steventaildeman.be

  • #2
    hi Steve
    Convert the mass into Newtons 150,000kgs x 10m/s2 = 1,500,000Newtons
    The drag is 1,500,000 / 14 = 107,142.85N
    Substitute known values into formula
    T-D/W = SIN theta x100
    300,000-107142.85/1,500,000 = 0.1285714 x 100

    = 12.86%

    Cheers
    Colin

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    • #3
      If fact you assume L = W...
      (but its in climb, so i used L = W . cos X)

      Nevertheless I know we're I went wrong.

      Thanks!
      Dreams hang in the air...
      CPL/IR/ME/GI
      http://www.steventaildeman.be

      Comment


      • #4
        In performance should we not take 3 engines operative instead of 4?
        If we do the answer is 7.86% which is also in the answers but 7.86 is wrong. So when should we use 3 engine instead of 4?

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