Definition
A high-update-rate radar system used by air traffic control to monitor simultaneous independent approaches to closely spaced parallel runways in instrument conditions. It provides controllers with very fast position updates and a clearly defined no-transgression zone between the approach courses, allowing them to detect and respond to any aircraft drifting toward the adjacent approach path before a conflict develops.
Plain English
A special radar that watches aircraft very closely when two planes are landing at the same time on parallel runways that are near each other. It updates so quickly that controllers can spot any drift toward the other runway and tell a pilot to break off the approach in time.
Context Anchor
Seen on certain instrument approach charts and in ATC procedures for busy airports with closely spaced parallel runways.
Derivation
Precision means high accuracy. Runway monitor describes the system's job: watching aircraft as they fly the final approach to the runway. Together, the name reflects a radar built specifically to track approaches with enough precision and speed to safely separate parallel traffic.
Why Pilots Care
Allows airports to run simultaneous landings on parallel runways in instrument conditions, increasing capacity and reducing delays while preserving required separation.
Intuition Check
PRM does not mean the runway is more precise or that the aircraft is guided by the runway. It means controllers have a precise monitoring system to watch aircraft spacing during certain parallel approaches.
Example Sentence 1
The crew reviewed the PRM approach procedures before accepting the simultaneous parallel approach into the airport.
Example Sentence 2
Pilots flying a PRM approach must be prepared to respond immediately to any breakout instructions issued by the controller.