Definition
In a flight director system, the state in which the autopilot is electronically connected to the flight director's command bars so that the autopilot flies the airplane to satisfy those commands automatically, rather than the pilot hand-flying to match them.
Plain English
When the autopilot is 'coupled,' it is hooked up to the flight director and is doing the flying for you, following the same guidance the flight director is showing on the attitude indicator.
Context Anchor
Seen in instrument flying when the flight director, autopilot, or approach guidance is being used.
Derivation
From the Latin 'copula,' meaning 'a link or tie.' In aviation systems, two things are 'coupled' when they are linked so one drives the other — here, the flight director's commands drive the autopilot's actions.
Why Pilots Care
Allows the autopilot to fly precise instrument procedures hands-off, lowering workload and improving accuracy on approaches.
Intuition Check
Coupled does not just mean two things are near each other. In this cockpit context, it means the automatic control system is actively connected to selected guidance and can follow it.
Example Sentence 1
Once established on the localizer, the captain coupled the autopilot to the flight director for the approach.
Example Sentence 2
Once coupled to the flight director, the aircraft maintained the glideslope without further control inputs.