Definition
Under ICAO usage, Precision Approach Radar (PAR) is primary radar equipment used to determine the position of an aircraft during final approach, in terms of lateral and vertical deviations relative to a nominal approach path, and in range relative to touchdown. The ground controller uses this information to issue guidance instructions to the pilot by radio, allowing the aircraft to be flown down to the runway threshold.
Plain English
A ground-based radar system, defined by international standards, that watches an aircraft on final approach and tells the controller exactly how far left, right, high, low, or far out from the runway it is. The controller then talks the pilot down to the runway using that information.
Context Anchor
Seen in instrument approach and air traffic control terms, especially where a controller provides spoken guidance to an aircraft approaching a runway.
Derivation
ICAO stands for the International Civil Aviation Organization, the United Nations body that sets worldwide aviation standards. The label 'ICAO Term' in the AIM glossary signals that this is the international definition, which may differ slightly from the standard U.S. FAA usage. 'Precision' here points to the radar's ability to measure the approach path accurately in three dimensions (left-right, up-down, and distance).
Why Pilots Care
It provides an independent means of conducting a precision approach when ILS or other onboard systems are unavailable or unserviceable.
Intuition Check
Precision does not just mean “very accurate” in a casual sense here. In this term, it means the radar can support guidance both side-to-side and up-or-down during the approach to the runway.
Example Sentence 1
Operating into a foreign military field, the crew briefed an ICAO-standard Precision Approach Radar approach as their backup to the ILS.
Example Sentence 2
Because the airport lacked an ILS, the crew requested a precision approach radar procedure to complete the landing in fog.