How exactly does a pilot engage the autopilot? I have a number of questions about auto-pilots but rather than deluge you with a long prose here let me break them down into separate questions over the next little while.

From playing around with simulators I know that the pilot has the ability to enter desired altitudes, climb rates, heading etc into the auto-pilot. However, and forgive me, whenever I see a pilot engage the auto-pilot in movies etc, it is simply a flip of the switch.

So that got me wondering how the transition is made in actuality. 

Does the pilot need to enter the current altitude, heading etc before flicking the switch or does the AP take the current numbers and hold those automatically.

If it is the latter and the aircraft is in say a climbing turn when the switch is clicked.. then what? Does the aircraft continue in that pattern or what?
“One Switch” to operate the Autopilot is not true. That’s just the movies.

Autopilot systems vary in each aircraft. Larger jets have it divided into two: Auto-Throttle and Auto-Pilot. Smaller aircraft/piston aircraft don’t really have auto-throttle capabilities.

The Autopilot is not just to “maintain” current flight path. It really can fly the entire flight from take-off to touchdown. This includes flying a departure procedure, en-route navigation, arrival procedure, an approach and touchdown. 

Theoretically, it is possible for a pilot to not touch the aircraft controls (yoke/stick/throttle) after liftoff all the way until touchdown even if the mission is a complex IFR flight. Realistically, pilots love to fly and they will fly.

Many settings exist for each autopilot system, and these include (but are not limited to):

Lateral Navigation


Heading Mode (fly the “selected” heading”)
Nav Mode (fly the “selected” nav course)
Roll Mode


Vertical Navigation


Altitude Select Mode (Maintain the selected altitude)
Vertical Descent with a fixed speed
Vertical Descent with a fixed rate
Approch Mode (Vertical Descent with Glideslope)


Auto-Throttle


Maintain Selected Airspeed
Accelerate/Decelerate to Selected Airspeed


However, there is that master AP Switch that’ll disable all things related to the AP.