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Homework Help: Calculate the density at which the available thrust is equal to the minimum drag

  1. Oct 31, 2012 #1
    Calculate the density at which the available thrust of a jet propelled aeroplane is equal to the minimum drag for the full fuel load case. Use the simplest assumption for the variation of engine thrust with density.

    Wing area, S = 29.5
    Weight, W = 88000
    CD,0 = 0.02
    k = 0.044
    Max thrust (at sea level) = 16000N
    CT = 1.7*10^-4

    I use the formula Dmin = 2((CD,0*k)^0.5)*W = 5221N

    The problem I have is that I can't work out the density without the velocity but there is no way to relate velocity to drag without density. Where do I go from here?
  2. jcsd
  3. Nov 1, 2012 #2


    User Avatar

    Staff: Mentor

    If you care to revise your posting, supplying the units and explaining what each of the three co-efficients is, I'll take a look at your problem.
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