TABLE OF CONTENTS In the formulation of flight dynamic problems, we need to introduce several coordinate systems for specifying the position, velocity, acceleration, forces, and moments acting on the vehicle. Why do we need so many axes systems? Because, we do not have a single axes system that is suitable for specifying all these quantities. Further, the choice of a particular coordinate system in which the equations of motion are written and solved is also a matter of convenience to the analyst. In flight dynamic studies, it is customary to choose the so called "moving" axes system for the solution of equations of motion as discussed later in this chapter. In the following, we will discuss some of the most commonly used axes systems in flight dynamics and present relations for transforming vectors from one axes system into another.
For every flight dynamic problem, it is necessary to specify an inertial frame of reference because Newton's laws of motion are valid only when the acceleration is measured with respect to an inertial frame. In other words, the acceleration of a body in Newton's second law of motion, F = ma, is the acceleration with respect to an inertial frame of reference, which is actually at rest in the universe. While it is a difficult task to find such an inertial reference system, for most of the flight dynamic problems, a nonrotating reference system ( Ox i y
