Question

What is the angle of attack of lift producing airfoil?

(a) Angle of attack less than zero

(b) Angle of attack greater than zero

(c) Angle of attack is zero

(d) Angle of attack remains the same

I have been asked this question during an interview.

This is a very interesting question from The Kutta-Joukowski Theorem topic in section Inviscid & Incompressible Flow of Aerodynamics

Answer 1

Correct choice is (b) Angle of attack greater than zero

To explain: A lift producing airfoil either has camber or is translating in a uniform fluid at an angle of attack greater than zero. Moreover, it must have a sharp trailing edge. An airfoil generates lift by exerting a downward force on the air as it flows past.