Definition
A selectable mode on an autopilot or flight director that arms and then engages the system to capture and track an instrument approach guidance signal — typically a localizer and glideslope for an ILS, or the lateral and vertical guidance of an RNAV/GPS approach. Once armed, the system monitors for the appropriate signals and automatically transitions from en route or intermediate guidance to precise approach tracking when the aircraft intercepts the final approach course.
Plain English
A button or setting that tells the autopilot, 'we're flying an approach now — follow the approach guidance into the runway.' Once armed, it waits for the approach signals and then takes over flying the aircraft along them.
Context Anchor
Seen when using an autopilot, flight director, GPS, or instrument landing guidance during an instrument approach.
Derivation
Approach comes from an old French word meaning “to come nearer.” Mode comes from a Latin word meaning “manner” or “way.” Function means what something is set up to do. Together, the term means the way the equipment operates when the airplane is coming in to land.
Why Pilots Care
It reduces workload and improves accuracy during low-visibility landings by automatically following precise guidance signals.
Intuition Check
Do not read “approach” here as just “getting closer.” In this term, it means the specific landing-guidance phase where the equipment is set to track a runway approach accurately.
Example Sentence 1
After being cleared for the ILS, the pilot armed Approach Mode and watched the autopilot capture the localizer and then the glideslope.
Example Sentence 2
With approach mode engaged the airplane maintained the correct glide path without further manual adjustments.