Question

If thickness ratio t/c is less or equal to the 0.05 then, the wetted area is ____

(a) Swet = 2.003*Sexposed

(b) Swet = 2.003*4*Sexposed

(c) Swet = 2/Sexposed

(d) Swet = 2*Sexposed

I had been asked this question in an interview for job.

My question is taken from Configuration Layout in section Configuration Layout and Loft of Aircraft Design

Answer 1

The correct answer is (a) Swet = 2.003*Sexposed

Explanation: Thin body has thickness tends to negligible. For a paper thin body wetted area is twice of the exposed or true planform area. However, for finite thickness of t <= 0.05*c wetted area is approximated as Swet = 2.003*Sexposed.