Question

Consider a NACA 2812 airfoil. It is operating with flow velocity of 900m/s with chord of 1m. What should be the maximum thickness of this airfoil?

(a) 0.12m

(b) 0.21m

(c) 0.9m

(d) 28.12m

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

Query is from Airfoil Selection-1 in chapter Airfoil and Geometry Selection of Aircraft Design

Answer 1

Right choice is (a) 0.12m

For explanation: NACA-4 digit series is used to define certain airfoil characteristics.

Here, velocity = 900 m/s, chord = 1m

From NACA-4 digit,

Maximum thickness = last two digits in percent of chord=12% of chord = 0.12*1 = 0.12m.