Question

An aircraft has maximum lift to drag ratio of 15. If we want to fly aircraft for best range then, find the best value of aerodynamic efficiency to achieve above mentioned result.

(a) 12.9

(b) 13.5

(c) 15

(d) 12.1

This question was addressed to me at a job interview.

My question is based upon Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design

Answer 1

Correct option is (a) 12.9

For explanation I would say: Aerodynamic efficiency for best range = 0.866*[maximum lift to drag]

= 0.866*15 = 12.9.