Lateral/directional rigid body modes: Dutch roll, roll, spiral

1. The Dutch Roll mode is a coupled, oscillatory second order mode that provides a rolling-yawing motion. This mode can be excited by providing a momentary rudder input, due to the fact that an increase in side force on the vertical tail causes a roll as well as a yaw.

2. The Roll mode is a convergent non-oscillatory first order mode which describes the motion about the X-axis. When the pilot applies an aileron input, this is the mode that primarily responds.

3. The Spiral mode is non-oscillatory first order long period roll-yaw motion. It can be characterized by that aircraft