Question

Which of the following is not the additional assumption taken in the derivation of the equations of motion?

(a) Gross thrust acts in aircraft body axis

(b) Thrust component is small compared to lift component

(c) Aircraft is in symmetric flight

(d) Rate of change of mass is neglected

The question was posed to me in an interview for job.

This key question is from Equations of Motion for Performance in section Aircraft Force Systems and the Equations of Motion of Aircraft Performance

Answer 1

Correct answer is (c) Aircraft is in symmetric flight

Easy explanation: The aircraft is symmetrical flight during the derivation of equations of motion.The other assumptions taken are:

Rate of change of mass is neglected

Aircraft is in symmetric flight

Gross thrust acts in aircraft body axis

Total net thrust is T cosα-DM

Thrust component is small compared to lift component.