Definition
An aircraft radio navigation instrument that automatically points to the bearing of a selected non-directional beacon (NDB) or commercial AM broadcast station on the ground. The needle on the ADF indicator shows the relative bearing from the aircraft's nose to the station being received.
Plain English
A cockpit instrument with a needle that always points toward a chosen ground-based radio transmitter. Whichever way the aircraft turns, the needle keeps pointing at the station, so the pilot knows which direction it is.
Context Anchor
Seen in instrument flying when using older radio navigation, including holding patterns and timed approaches from a holding fix.
Derivation
Called 'automatic' because earlier direction finders required the pilot to manually rotate a loop antenna to find the station. The ADF does this electronically, so the needle finds and tracks the bearing on its own.
Why Pilots Care
Provides a reliable backup navigation method to NDBs when VOR, GPS, or other systems are unavailable or unreliable, directly supporting safe execution of certain instrument approaches.
Analogy
Think of it as a compass whose needle is pulled toward a specific radio station instead of north, always showing the shortest path to that station.
Intuition Check
Do not read an ADF as a full position display. It points toward a selected station; by itself, it does not tell you how far away the station is.
Example Sentence 1
After crossing the holding fix, the pilot tuned the ADF to the outer beacon and watched the needle swing to confirm station passage.
Example Sentence 2
While holding at the fix, the ADF needle provided constant bearing updates that helped the pilot time the outbound leg accurately.