Definition
A high-resolution ground-based radar system used by air traffic control to provide highly accurate course and glidepath guidance to a pilot during a final approach to landing. The controller monitors the aircraft's position relative to the runway centerline and the ideal descent path, and issues continuous voice instructions to keep the aircraft aligned in both azimuth and vertical path until reaching the decision height or the runway threshold.
Plain English
A very accurate radar that lets a controller watch exactly where the aircraft is on final approach and tell the pilot, by voice, how to steer left or right and how to adjust the descent so the aircraft arrives correctly lined up with the runway.
Context Anchor
Seen in instrument procedure and STAR discussions where the FAA explains what can substitute for an inoperative or unusable navigation component.
Derivation
Precision comes from the Latin praecisio, meaning 'a cutting off' or 'exactness.' In this term it signals that the radar is accurate enough not just to locate the aircraft, but to guide it down a defined glidepath — a sharper, more exact form of radar than standard surveillance radar.
Why Pilots Care
It permits a precision approach to continue safely when primary landing aids fail, avoiding a missed approach or diversion.
Intuition Check
Precision does not mean perfect or error-free here. It means the radar is accurate enough for close ATC guidance, within the limits of the equipment and procedure.
Example Sentence 1
After losing the onboard glideslope receiver, the crew requested a precision radar approach and followed the controller's heading and descent calls down to minimums.
Example Sentence 2
The controller provided glidepath corrections via precision radar until the aircraft broke out of the clouds.