Definition
Ground-based instruments installed near a runway that automatically measure how far a pilot can see along the runway surface. They sample the clarity of the air and feed that data into the Runway Visual Range (RVR) system, which converts it into a distance value reported to pilots and controllers.
Plain English
Devices placed beside the runway that constantly measure how clear the air is, then turn that into a distance figure showing how far a pilot would be able to see down the runway.
Context Anchor
Seen in runway visual range discussions for instrument approaches and low-visibility airport operations.
Derivation
Visibility comes from a Latin word meaning “able to be seen.” Sensor comes from a Latin word meaning “to feel or perceive.” Together, the term means devices that detect how well things can be seen.
Why Pilots Care
These sensors provide the precise RVR numbers that determine whether a pilot can legally begin or continue an approach or takeoff in low-visibility conditions.
Intuition Check
Do not think of visibility sensors as a person looking down the runway. They are fixed instruments that measure the air near the runway and feed that information into the RVR system.
Example Sentence 1
The tower reported the RVR as 2,400 feet, based on readings from the visibility sensors near the touchdown zone.
Example Sentence 2
Maintenance crews checked the visibility sensors after noticing inconsistent RVR values during morning fog.