Question

The minimum drag speed is given by ___________

(a) \(\big(\frac{2W}{\rho S}\big)^{\frac{1}{2}}\big(\frac{K}{C_{Dz}}\big)^\frac{1}{4}\)

(b) \(\big(\frac{2W}{\gamma \rho S}\big)^{\frac{1}{2}}\big(\frac{K}{C_{Dz}}\big)^\frac{1}{4}\)

(c) \(\big(\frac{2W}{\rho S}\big)^{\frac{1}{2}}\big(\frac{K}{C_{Dz}}\big)^\frac{1}{2}\)

(d) \(\big(\frac{2W}{\gamma \rho S}\big)^{\frac{1}{2}}\big(\frac{K}{C_{Dz}}\big)^\frac{1}{2}\)

I have been asked this question in semester exam.

Question is from Aerodynamic Relationships topic in chapter Aircraft Force Systems and the Equations of Motion of Aircraft Performance

Answer 1

Correct choice is (a) \(\big(\frac{2W}{\rho S}\big)^{\frac{1}{2}}\big(\frac{K}{C_{Dz}}\big)^\frac{1}{4}\)

Easy explanation: The correct formula for minimum drag speed is given by \(\big(\frac{2W}{\rho S}\big)^{\frac{1}{2}}\big(\frac{K}{C_{Dz}}\big)^\frac{1}{4}\) where W is weight, ρ is density, K is constant, S is span area and CDz is coefficient of lift dependent drag.