B.1 Aircraft Nomenclature

To understand aircraft dynamics and the equations of motion, it is essential to become familiar with the aircraft nomenclature. The universally accepted notations to describe the aircraft forces and moments, the translational and rotational motions and the flow angles at the aircraft are shown in Fig. B.1. The axis system is assumed fixed at the aircraft centre of gravity and moves along with it. It is called the body-axis system. The forces and moments acting on the aircraft can be resolved along the axes. The aircraft experiences inertial, gravitational, aerodynamic and propulsive forces. Of these, the aerodynamic forces X, Y and Z, and the moments L, M and N are of importance as these play the dominant role in deciding how the aircraft behaves.

Figure B.1: Body-axis system

Figure B.1 also shows the aircraft primary control surfaces along with the normally accepted sign conventions. All surface positions are angular in deflection. The aileron deflection causes the aircraft to roll about the X-axis, the rudder deflection causes the aircraft to yaw about the Z-axis and the elevator deflection causes it to pitch about the Y-axis.

The three Euler angles describing the aircraft pitch attitude, roll angle and heading angle are illustrated in Fig. B.2 [1].

Figure B.2: Euler angles

The body-axis system notations are put together in Table B.1 below for better understanding.