Question

Excess thrust in the longitudinal equations of motion is given by ____________

(a) FN+D

(b) FN-D

(c) D-FN

(d) FN*D

This question was posed to me during an internship interview.

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

Answer 1

Right answer is (b) FN-D

Easiest explanation: Excess thrust in the longitudinal equations of motion is given by FN-D where FN is net thrust force and D is drag force. This excess thrust provides the increase in potential energy and kinetic energy.