Question

At what rate does the minimum sink rate occur in a gliding flight?

(a) It occurs at minimum power speed

(b) It occurs at maximum power speed

(c) It occurs at minimum airspeed

(d) It occurs at maximum airspeed

The question was asked by my college director while I was bunking the class.

My question is from Climb and Descent Performance with Power-Producing Engines topic in portion Climb and Descent Performance of Aircraft Performance

Answer 1

Correct answer is (a) It occurs at minimum power speed

The explanation: The minimum sink rate occur in a gliding flight at minimum power speed. The rate of climb is given by λ-\(\frac{1}{2}\)[u^3+u^-1]=Emaxv where λ is dimensionless power, u is airspeed and Emax is endurance.