Question

At which cases does descent of flow occur?

(a) By flying the aircraft at airspeed less than minimum drag speed

(b) By flying the aircraft at airspeed more than minimum drag speed

(c) By flying the aircraft at airspeed less than maximum drag speed

(d) By flying the aircraft at airspeed more than maximum drag speed

I have been asked this question in a national level competition.

Asked question is from Descent Performance in Aircraft Operations topic in section Climb and Descent Performance of Aircraft Performance

Answer 1

Right choice is (a) By flying the aircraft at airspeed less than minimum drag speed

Easy explanation: The descent of an aircraft can happen at flying the aircraft at airspeed less than minimum drag speed. In this case the minimum rate of descent occurs at the minimum power speed and minimum gradient occurs at the minimum drag speed.