Definition
A Runway Visual Range (RVR) value of 300 feet, representing the horizontal distance a pilot can see down the runway from the approach end. In OpSpecs, 300 feet RVR is the lowest takeoff minimum authorized for properly equipped operators on runways meeting specific lighting, marking, and surface requirements, and only when the flight crew and aircraft are qualified for that minimum.
Plain English
It means a pilot can see only 300 feet down the runway. This is the very lowest visibility a specially approved operator is allowed to begin a takeoff in.
Context Anchor
Seen in OpSpecs, low-visibility instrument approach procedures, and airport weather reports that give runway visual range values.
Derivation
RVR stands for Runway Visual Range. It is measured by transmissometers or forward-scatter sensors placed alongside the runway, which estimate how far a pilot in the cockpit could see along the runway surface. The value is reported in feet (in the U.S.) rather than statute miles because at very low visibilities, feet give a more useful, finer-grained number.
Why Pilots Care
Sets the actual minimum visibility a flight crew may use for takeoff or landing under their specific OpSpecs; going below it is not authorized.
Grounding Statement
Picture looking down the runway and seeing only a short stretch of lights or markings before everything disappears into fog or heavy precipitation.
Intuition Check
300 feet RVR does not mean general airport visibility is 300 feet in every direction. It means the reported seeing distance along the runway is 300 feet.
Example Sentence 1
Our OpSpecs authorize takeoffs down to 300 feet RVR, but only on runways with operating centerline lighting and centerline markings.
Example Sentence 2
With the reported RVR at 300 feet, the flight was cleared for the Category III approach authorized in their OpSpecs.