Definition
A high-update-rate radar surveillance system used by ATC to monitor independent simultaneous instrument approaches to closely spaced parallel runways. It provides controllers with rapid position updates and predictive alerts so that aircraft straying toward the protected airspace of a parallel approach can be turned away before a conflict develops.
Plain English
A special radar that watches planes landing on two close parallel runways at the same time. It refreshes very quickly so controllers can spot any aircraft drifting toward the other runway and steer it back to safety.
Context Anchor
You may encounter this term in approach procedures, airport notes, or ATC discussions for airports that conduct simultaneous approaches to parallel runways.
Derivation
‘Precision’ here means highly accurate position information. ‘Monitor’ comes from the Latin monere, ‘to warn’ — fitting, because the system’s job is to warn controllers the moment an aircraft begins to deviate.
Why Pilots Care
It increases airport arrival capacity while maintaining safe separation between aircraft on parallel approaches.
Grounding Statement
Picture two airplanes lined up for two side-by-side runways; this system helps controllers make sure each airplane stays on its own side.
Intuition Check
Do not read “Precision Runway Monitor System” as a landing aid in the cockpit. It is mainly an ATC monitoring and alerting system used to watch aircraft during closely spaced parallel approaches.
Example Sentence 1
Because the airport had parallel runways spaced under 4,300 feet apart, simultaneous approaches were only authorized when the Precision Runway Monitor System was in operation.
Example Sentence 2
Pilots flying into airports equipped with the Precision Runway Monitor System must brief the possibility of receiving an immediate missed approach clearance.