Question

A jet aircraft has maximum lift to drag as 12. Find the value of the thrust loading at the cruise.

(a) 0.096

(b) 0.0069

(c) 0.96

(d) 0.0096

The question was asked in an interview for job.

Question is taken from Thrust Weight Ratio-2 in chapter Thrust-Weight Ratio and Wing Loading of Aircraft Design

Answer 1

Right choice is (a) 0.096

To elaborate: Given, maximum lift to drag = 12.

Thrust loading at cruise T/W = 1 / (L/D at cruise)

For, jet aircraft cruise lift to drag = 86.6% of maximum lift to drag = 86.6% of 12 = 0.866*12 = 10.392

Now, thrust loading at cruise,

Thrust loading at cruise T/W = 1 / (L/D at cruise)

= 1/10.392 = 0.096.