Question

The total thrust force assumed in the derivation of equations of motion is ___________

(a) FN=T cosα+DM

(b) FN=T cosα-DM

(c) T cosα=DM-FN

(d) DM=T cosα+FN

The question was posed to me in unit test.

This is a very interesting question from Equations of Motion for Performance topic in chapter Aircraft Force Systems and the Equations of Motion of Aircraft Performance

Answer 1

Correct option is (b) FN=T cosα-DM

The explanation is: The total thrust force assumed in the derivation of equations of motion is FN=T cosα-DM where FN=net thrust force, T is thrust force, cosα is lift component and DM is drag force acting downwards.