z is the vertical axis about which yaw takes place.
Courtesy of Wiki
Coordinate systems
The position (and hence motion) of an aircraft is generally defined relative to one of 3 sets of co-ordinate systems:
- Wind Axes
- X Axis - Positive in the direction of the oncoming air (relative wind)
- Y Axis - Positive to Right of X Axis, perpendicular to X Axis
- Z Axis - Positive downwards, perpendicular to X-Y plane
- Inertial Axes (or Body Axes) - based about aircraft CG
- X Axis - Positive forward, through nose of aircraft
- Y Axis - Positive to Right of X Axis, perpendicular to X Axis
- Z Axis - Positive downwards, perpendicular to X-Y plane
- Earth Axes
- X Axis - Positive in the direction of North
- Y Axis - Positive in the direction of East (perpendicular to X Axis)
- Z Axis - Positive towards the center of Earth (perpendicular to X-Y Plane)
For flight dynamics applications the Earth Axes are generally of minimal use, and hence will be ignored.