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

[liam1992]

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
C_D,0 = 0.02
k = 0.044
Max thrust (at sea level) = 16000N
C_T = 1.7*10^-4

I use the formula Dmin = 2((C_D,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?

 

[NascentOxygen]

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.