Question

How can we say that the aircraft has initial tendency to return to its original equilibrium position after being disturbed?

(a) If aircraft generates some restoring force or/and moment without any external help

(b) If restoring force is not generated to oppose the disturbance

(c) If lift is same as weight always

(d) If thrust loading is always unity

I had been asked this question during an online interview.

My question is from Longitudinal Static Stability and Control-1 topic in chapter Stability, Control, and Handling Qualities of Aircraft Design

Answer 1

Correct answer is (a) If aircraft generates some restoring force or/and moment without any external help

For explanation I would say: If some disturbance is given to the aircraft and aircraft has initial tendency to generate some restoring force or/and moments without any external means then, we say that the aircraft has initial tendency to return to its original equilibrium position after being disturbed. Hence, it has static stability.