Runway Visual Range (RVR) is the maximum distance over which a pilot can see and identify runway lights or markings from the touchdown zone. It is reported in feet and serves as the official visibility standard for low-visibility approaches and landings.
How It Works#
RVR is measured by an instrument called a transmissometer (or forward scatter meter on newer systems). This device sits beside the runway and measures how much light scatters through the air. It converts that reading into a distance value, expressed in feet.
Most airports with instrument approaches have transmissometers at up to three points along the runway:
- Touchdown Zone (TDZ): The first 3,000 feet of the landing runway.
- Midpoint (MID): The center of the runway.
- Rollout (RO): The far end of the runway.
The TDZ value is the primary number used for approach legality. ATC reports RVR values to pilots during approach briefings and in real time on final approach.
RVR differs from meteorological visibility, which is a general weather observation covering the surrounding area. RVR is specific to a single runway and accounts for runway lighting intensity. Higher lighting settings produce a higher RVR reading for the same atmospheric conditions.
Example in Aviation#
A flight crew is shooting an ILS CAT II approach into Chicago O'Hare. Their aircraft and crew are CAT II certified. The published minimums require an RVR of 1,200 feet in the touchdown zone.
ATC reports TDZ RVR at 1,400 feet. The crew is legal to continue the approach. If RVR drops below 1,200 feet before the decision altitude, they must execute a missed approach.
Why It Matters#
RVR directly determines whether a pilot can legally begin or continue an approach in low-visibility conditions. Instrument approach procedures (IAPs) list RVR minimums, not general visibility, for precision approaches in poor weather. A pilot who ignores RVR minimums risks descending below decision altitude without adequate visual reference.
Understanding RVR also helps pilots make accurate go/no-go decisions before departure. FAA regulations under 14 CFR §91.175 and §135.225 define exactly when RVR governs approach legality versus standard visibility values.
Key Takeaways#
- RVR measures visibility along a specific runway, not general weather conditions.
- Transmissometers at up to three runway positions feed RVR data to ATC.
- The Touchdown Zone RVR is the primary value used for approach legality.
- Higher runway lighting intensity increases the reported RVR reading.
- RVR values, not meteorological visibility, govern precision approach minimums.