Question

Cambered wing has minimum drag coefficient of 0.05 and constant K of 0.023. If CL is 0.8 then find the value of CD. Given minimum drag occurs at CL of 0.1.

(a) 0.06127

(b) 6.1

(c) 61.2

(d) 0.6721

The question was posed to me in class test.

The query is from Aerodynamic Coefficients topic in chapter Aerodynamics of Aircraft Design

Answer 1

Right choice is (a) 0.06127

To elaborate: Given, minimum drag coefficient CDmin = 0.05, constant K of 0.023, CL is 0.8 and minimum drag occurs at CL of 0.1. Hence, CLmindrag = 0.1.

Now, CD is given by,

CD = CDmin + K*(CL – CLmindrag)^2

= 0.05+0.023*(0.8-0.1)^2

= 0.06127.