Definition
The Runway Visual Range value reported from a transmissometer or visibility sensor located near the touchdown zone of an instrument runway, representing the horizontal distance a pilot can expect to see down the runway from the approach end. TDZ RVR is the controlling RVR value for most precision approach minima, including CAT I, CAT II, and CAT III operations.
Plain English
It is a measurement of how far a pilot can see down the runway, taken by a sensor placed near the spot where the aircraft will touch down. This is the visibility number that usually decides whether an approach can be flown to its minimums.
Context Anchor
Seen in Category II and Category III instrument approach minimums and in tower or airport weather visibility reports during low-visibility operations.
Derivation
Touchdown Zone refers to the first 3,000 feet of runway beyond the threshold, where aircraft are expected to land. RVR (Runway Visual Range) is a measured visibility value specific to the runway, not the general airport visibility. Combining the two specifies which RVR sensor's reading is being used.
Why Pilots Care
It tells the crew whether they have enough runway visibility to continue or must go around.
Grounding Statement
Picture lining up with a runway in fog: TDZ RVR is the reported seeing distance right where the landing begins.
Intuition Check
TDZ RVR is not the visibility for the whole airport. It is the reported seeing distance for the touchdown-zone area of the specific runway being used.
Example Sentence 1
Tower reported TDZ RVR 1800, which was above the CAT II minimum, so the crew continued the approach.
Example Sentence 2
When the TDZ RVR dropped below 1200 feet, the crew executed a missed approach.