Plain English Meaning

A button or switch setting that tells the autopilot or flight director, "fly the approach." Once armed, it locks onto the approach guidance signals and follows them down toward the runway.

Full Definition

A selectable mode on a flight director or autopilot that commands the aircraft to capture and track a published instrument approach, typically following both the localizer (lateral guidance) and glideslope (vertical guidance) of an ILS, or the lateral and vertical paths of another approach type the system supports.