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RVR – Runway Visual Range

Runway Visual Range: RVR means the maximum horizontal distance, as measured by an automated visual landing distance system and reported by an ATC unit or an FSS for the direction of takeoff or landing, at which the runway, or the lights or markers delineating it, can be seen from a point above its centre line at a height corresponding to the average eye level of pilots at the range over which a pilot of an aircraft on the centerline of the runway can see the runway surface markings or the lights delineating the runway or identifying its centerline.

To compute RVR, three factors must be known. The first is the transmissivity of the atmosphere as provided by a visibility sensor. The second is the brightness of the runway lights which is controlled on request by the ATC controller. The third factor is whether it is day or night, since the eye can detect lights easier at night than during the day. There is a period during twilight where there is a problem similar to that with prevailing visibility when neither day, nor night conditions prevail.

RVR is normally expressed in feet or metres.

RVR is used as one of the main criteria for minima on instrument approaches, as in most cases a pilot must obtain visual reference of the runway to land an aircraft. The maximum RVR reading is 2,000 metres or 6,500 feet, above which it is not significant and thus does not need to be reported. RVRs are provided in METARs and are transmitted by air traffic controllers to aircraft making approaches to allow pilots to assess whether it is prudent and legal to make an approach.

Instrumented Runway Visual Range or IRVR, which is measured by devices called transmissometers which are installed at one side of a runway relatively close to its edge. Normally three are provided, one at each end of the runway and one at the mid-point.

Runway Transmissometer

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