Definition
A radio navigation technique in which a ground station determines the bearing of an aircraft by detecting the direction from which the aircraft's radio transmission is arriving. Air traffic controllers use this bearing information to guide a pilot toward the airport or to a safe landing area, often during emergencies when the pilot is lost or has limited navigation equipment available.
Plain English
A way for someone on the ground to figure out which direction your radio signal is coming from, so they can tell you which way to fly to reach them.
Context Anchor
Seen in emergency and lost-aircraft procedures when a pilot may need help from air traffic control to determine the aircraft’s location or a safe direction to fly.
Derivation
Plainly named for what it does: the equipment finds the direction of an incoming radio signal. The term dates from early radio navigation when ground stations literally rotated antennas to detect the strongest signal direction.
Why Pilots Care
Provides an immediate heading to safety or allows ground stations to guide an aircraft when other navigation has failed.
Intuition Check
Direction finding does not mean simply choosing which way to fly. In this context, it means using radio signals to figure out the direction from which the aircraft’s transmission is coming.
Example Sentence 1
After becoming disoriented in deteriorating weather, the pilot declared an emergency and requested DF assistance to be guided to the nearest airport.
Example Sentence 2
Search aircraft used DF to locate the downed plane's emergency beacon.