The basic autopilot is found in the Cessna 172 SP and the Baron 58 aircraft. It features a bank and heading hold, turn to selected heading, navigation follow, pitch hold, vertical speed hold, altitude hold and approach modes as well an altitude pre-select function.
The autopilot can stabilize the heading, airspeed, altitude as well as the vertical speed. The autopilot cannot be switched on/off and will disengage when one of the following limits is exceeded:
When the autopilot is turned on it will maintain the current pitch and bank attitude. These modes are indicated with the text “ROL” and “PIT” for roll and pitch respectively.
In this mode the autopilot will attempt to keep the wings level (ROL). The autopilot switches to heading hold mode once the wings are leveled to offer a long term constant flight path but this is not shown to the pilot.
In the bottom right of the horizontal situation indicator (HSI) or heading indicator you can find the heading bug. Rotate this knob to select a target heading on the compass rose.
The autopilot can track a VOR or ILS signal. For this you need to tune a station first and then set the course and arm the capture.
Once captured the autopilot will try to center the course deviation indicator (CDI) needle.
The pitch attitude hold (PIT) mode maintains the pitch angle at the time of engagement.
You are still in control of your airspeed, make sure to add enough power if you want to climb and reduce power for the descent.
When engaged the vertical speed mode (VS) holds the current vertical speed.
You are in control of airspeed, make sure to adjust power.
This mode maintains the altitude at the time of engagement. The autopilot will pitch up and down to try and stay at that altitude.
The autopilot will automatically switch to the altitude hold mode when you reach the selected altitude in pitch hold (PIT) or vertical speed hold (VS) mode.
The approach mode has to be armed and captured similarly to the lateral only NAV mode. The key difference is that the autopilot will also try and capture the vertical steering from the NAV1 receiver and follow the glide slope of the ILS.
After capturing the localizer signal the autopilot arms the glide slope capture. Monitor the engagement of the lateral and vertical LOC and GS modes and reduce power to maintain the desired airspeed once the glide slope is activated.