The associated yaw damper must be switched on before the autopilot can be engaged using the switch located on the centre pedestal. The associated power switch (labelled AP DISCONNECT) must also be in the on (up) position.

Engage yaw damper 1 (YD-1) and then engage autopilot 1 (AP-1), or engage yaw damper 2 (YD-2) and then engage autopilot 2 (AP-2). 

The autopilot can also be engaged using the keyboard assignment ('Z' by default).