AIRPLANE REFERENCE AXES

In order to visualize the forces and moments on the aircraft, it is necessary to establish a set of mutually perpendicular reference axes originating at the center of gravity. Figure 4.4 illustrates a conventional right hand axis system. The longitudinal or X axis is located in a plane of symmetry and is given a positive direction pointing into the wind. A moment about this axis is a rolling moment, L, and the positive direction for a positive rolling moment utilizes the right hand rule. The vertical or Z axis also is in a plane of symmetry and is estab­lished positive downward. A moment about the vertical axis is a yawing moment, N, and a positive yawing moment would yaw the air­craft to the right (right hand rule). The lateral or Y axis is perpendicular to the plane of symmetry and is given a positive direction out the right side of the aircraft. A moment about the lateral axis is a pitching moment, Л1, and a positive pitching moment is in the nose – up direction.