Question

An aircraft is to be designed to have max lift coefficient as 2.8 and at q=10Pa. If maximum load factor n=5 then, what will be the stall speed?

(a) 1.80m/s

(b) 1.80mph

(c) 2.80mph

(d) 2.80m/s

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

I would like to ask this question from Selection of Thrust-Weight and Wing Loading in chapter Thrust-Weight Ratio and Wing Loading of Aircraft Design

Answer 1

Right option is (a) 1.80m/s

The explanation: Given, lift coefficient = 2.8, q=10Pa, n=5

Since density is not given we will take as sea level.

Load factor n = q*CL/(W/S)

(W/S)/CL = q/n = 10/5 = 2.

Now, stall speed V is given by,

V = \(\sqrt{2*(\frac{W}{S})/(\rho*CL)}\)

= \(\sqrt{2*2/1.225}\) = 1.80m/s.