Question

An aircraft with elliptic wing planform has parasite drag coefficient as 0.9. Lift coefficient of wing is 1.8 and aspect ratio is 8.5. Find total drag coefficient for the wing.

(a) 1.021

(b) 0.9

(c) 0.121

(d) 0.25

This question was addressed to me in class test.

The query is from Wing Geometry-2 topic in section Airfoil and Geometry Selection of Aircraft Design

Answer 1

Right choice is (a) 1.021

To elaborate: Given, elliptic wing, parasite drag coefficient CD0 = 0.9

Lift coefficient CL = 1.8, Aspect ratio AR=8.5

Now, Total drag coefficient = Parasitic drag coefficient (CD0) + induced drag coefficient (CDi)

CDi = CL*CL / (ᴨ*e*AR) = 1.8*1.8 / (ᴨ*1*8.5) = 0.121

Hence, Total drag coefficient = CD0 + CDi = 0.9 + 0.121 = 1.021.