Hopefully the following information will prompt a more specific question (or series of questions):
I looked up S-TEC autopilots because they have an STC (supplemental type certificate) for their autopilot system for over 1,600 models of aircraft.
An autopilot is an avionics system designed to serve two primary purposes:
- Enhance a pilot’s flight control capabilities
- Reduce cockpit workload by putting the airplane in an automatic flight mode
An autopilot consists of three basic components:
Mode selector/programmer (The device that allows the pilot to program the autopilot to achieve the intended flight profile. This may interact with other avionics, such as a GPS unit)
Computer (This receives the information from the programmer or avionics and sends the appropriate signal to the actuators)
Actuators (The servos or motors which physically move the aircraft's control surfaces)
An autopilot system can be either position-based or rate-based.
Position or attitude autopilots typically use the pilot’s attitude indicator as a gyroscope signal source.
Rate-based autopilot systems use rate gyros and/or accelerometers as primary sensors.
There are many features and functions of an autopilot which are outlined in the referenced PDF file below, but to give you an overview:
- Wing Stabilizer (Wing Leveler).
- Heading Mode.
- Course Tracking and Coupling.
- Course Deviation Warning.
- Dual Mode Intercept.
- Roll Steering.
- Altitude Hold.
- Vertical Speed.
- Pre-Selected Altitude Capture.
- Glideslope Coupling.
- Control Wheel Steering.
Fundamentally, autopilots typically perform the following tasks:
- Maintaining Assigned Altitude and Heading.
- Holding a heading
- Tracking a VOR, GPS, LORAN or LOC signal
- Intercepting the course
Each one of these aspects of an autopilot could provide several ideas for questions that could help you get a fuller picture of all the technologies involved in autopilots, and perhaps help you limit the scope of your question to something that might not require textbook-length answer :)
Hope this helps in your quest!
S-TEC Autopilot Overview:
S-TEC Pilot Operating Handbooks:
Garmin also makes a GA autopilot called the GFC 700 which integrates into their Garmin 1000 flight deck. More info here: http://www8.garmin.com/learningcenter/training/gfc700/