Question

A thin airfoil is defined as NACA 0009 is at ɑ = 5°. What is the value of lift curve slope?

(a) 2ᴨ per rad

(b) 2ᴨ per degree

(c) 4 per degree

(d) 0.4 per degree

This question was posed to me during an interview for a job.

My query is from Airfoil Selection-2 topic in division Airfoil and Geometry Selection of Aircraft Design

Answer 1

Right answer is (a) 2ᴨ per rad

Best explanation: Given, NACA0009 airfoil,

AOA ɑ = 5°

As mentioned the airfoil is thin. Hence, thin airfoil theory can be used.

According to thin airfoil theory, for thin airfoil,

Lift curve slope = 2π 1/rad = 0.11 1/degree.