Question

Find the value of lift coefficient to ensure power required minimum condition for cruise if CD0/K is given as 0.480.

(a) 1.2

(b) 2.1

(c) 1.7

(d) 7.5

I have been asked this question in a job interview.

The origin of the question is Flight Mechanics topic in portion Performance and Flight Mechanics of Aircraft Design

Answer 1

Right option is (a) 1.2

Easiest explanation: Lift coefficient = [3*CD0/K]^0.5

= [3*0.480]^0.5 = 1.2.