Bendix/King KAP140 Autopilot
The default Cessna 172 has a "Bendix/King KAP140 Two Axis with Altitude Preselect" autopilot. It controls the elevator and the ailerons.
The Pilots Guide can be downloaded here
To activate the autopilot in wings level (ROL) and vertical speed (VS) modes press the AP button. The autopilot will try to keep the wings level by keeping the turn rate at zero. The autopilot will also try to maintain the vertical speed at activation. Use the UP and DN buttons to set the desired vertical speed.
With the autopilot active you can use the HDG button to toggle between wings level (ROL) and heading select (HDG) modes. In heading select mode the autopilot will try to maintain the heading selected by the heading bug on the directional gyro.
Use the ALT button to toggle between vertical speed (VS) and altitude hold (ALT) modes. In altitude hold mode the UP and DN buttons change the altitude by 20 feet per press.
Press the AP button to deactivate the autopilot. The horizontal and vertical modes can not be activated independently.
Please read the Pilots Guide for complete instructions on the use of the KAP140 Autopilot system.