Plain English Meaning

The numbers you set on the autopilot ahead of time so it knows what altitude, heading, course, or speed to fly once you turn it on or switch modes.

Full Definition

The values a pilot dials into the autopilot and flight director system before they are needed — typically the initial altitude, heading, course, and airspeed — so that when the relevant autopilot mode is engaged, the system flies to and holds those preset targets.

Context Anchor

Seen during the before-takeoff check, when the pilot confirms that the autopilot is set up correctly before departure.

Derivation

From 'pre-' (before) and 'select' (to ). A preselect is a chosen in advance — set now, used later when the autopilot mode that uses it becomes active.