Definition
An older generation of Airport Surveillance Radar used by terminal radar facilities to detect and display the position of aircraft within roughly 60 nautical miles of an airport. It provides azimuth and range information but does not provide altitude data on its own.
Plain English
An early model of the radar system that air traffic controllers at a busy airport use to see where airplanes are around the field. It shows direction and distance from the radar, but not how high the aircraft is flying.
Context Anchor
Seen in instrument flying material when discussing TRACON facilities and the radar equipment controllers use near busy airports.
Derivation
ASR stands for Airport Surveillance Radar. 'Surveillance' comes from the French surveiller, meaning 'to watch over.' The '-3' is simply the model number, indicating an earlier generation of this equipment. Later models (ASR-7, ASR-8, ASR-9, ASR-11) replaced it as technology advanced.
Why Pilots Care
Knowing the type of radar a facility uses gives a pilot a sense of its capabilities and limitations. An older radar like the ASR-3 has less range, lower resolution, and no altitude readout from the radar itself, which affects how controllers can sequence and separate traffic.
Intuition Check
Do not read the “3” as meaning three radars, three-mile range, or three-dimensional radar. Here, “3” is just the model number of the Airport Surveillance Radar equipment.
Example Sentence 1
The smaller terminal facility was originally equipped with an ASR-3, which limited coverage to aircraft within about 60 miles of the airport.
Example Sentence 2
Although still in limited use, ASR-3 supplies only range and azimuth data without altitude information.