Definition
The frequency with which a radar antenna sweeps its coverage area and updates the position of detected aircraft on the controller's display. A faster scan rate means target positions are refreshed more often, giving the controller more current information.
Plain English
How often the radar takes a fresh look at where each aircraft is. A faster scan rate means the picture on the controller's screen updates more often.
Context Anchor
Seen in PRM radar discussions for monitoring aircraft on simultaneous approaches to parallel runways.
Derivation
From 'scan,' meaning to look over an area systematically, and 'rate,' meaning how often something happens per unit of time. So 'scan rate' literally means how frequently the radar looks across its area.
Why Pilots Care
A higher scan rate gives controllers faster, more precise position data so they can issue immediate corrections if an aircraft drifts off course, keeping parallel approaches safe.
Analogy
It is like the difference between a map that refreshes every second and one that refreshes only every few seconds. The faster refresh gives a more current picture.
Intuition Check
Scan rate does not mean how quickly the pilot looks around the cockpit. Here it means how often the radar system updates the aircraft positions it is showing.
Example Sentence 1
PRM radar uses a faster scan rate than standard approach radar so controllers can spot a deviation almost as it happens.
Example Sentence 2
Because of its high scan rate, the controller noticed the slight deviation and issued a heading correction before the aircraft left the No-Transgression Zone.