Definition
The minimum altitudes and visibility values published for a radar-controlled approach (such as an ASR or PAR), below which the pilot must not descend unless the required visual references for the runway are in sight and the aircraft is in a position to make a normal landing.
Plain English
The lowest altitude and visibility allowed when a controller is guiding you in by radar. You can't go below those numbers unless you can actually see the runway environment and are set up to land normally.
Context Anchor
Seen in radar approach procedures and approach chart information for radar-guided instrument approaches.
Derivation
Radar comes from “radio detection and ranging,” meaning the aircraft’s position is found by radio energy reflected back to radar equipment. Minimum comes from the Latin word meaning “smallest.” Together, the term points to the smallest allowed approach limits when radar is used to guide the aircraft.
Why Pilots Care
They tell the pilot exactly how low radar guidance alone can safely take the aircraft before visual contact is required.
Intuition Check
Do not read “minimums” as a goal to aim for or a suggestion. In this context, minimums are the lowest authorized limits; going below them without the required visual references is not allowed.
Example Sentence 1
Before accepting the ASR approach, the pilot reviewed the radar minimums to confirm the reported visibility was at or above the required value.
Example Sentence 2
We reached radar minimums and acquired the runway lights at two miles.