Runway Visual Range (RVR)

Runway Visual Range or RVR is one of the most critical numbers a pilot looks for before deciding to make an approach.

RVR is different from "General Visibility". General visibility tells you how far you can see across the airport as a whole, while RVR tells you exactly "how far the pilot can see the runway lights and markings while sitting in the cockpit during landing?".

How is RVR Measured?

It is measured automatically using precise instruments called (Transmissometers) installed next to the runway at 3 points (touchdown, mid-point, and stop-end). RVR is included in METAR reports when general visibility drops below 1500 meters.

How to Read an RVR Code in a METAR?

The code always begins with the letter R followed by the runway number, then a slash /, then the visibility distance in meters, and finally a letter indicating the trend.

Basic Example: R05L/0400N

Analysis:

R05L: Runway 05 Left.
0400: Visibility on this runway is only 400 meters.
N: No change in visibility.

Meaning of Additional Letters (Trends & Limits)

1. Trend Direction (Forecast for the next 10 minutes):

U (Upward): Visibility is improving. (Example: R23/0600U).
D (Downward): Visibility is deteriorating and fog is thickening. (Example: R23/0300D - A severe warning for the pilot).
N (No Change): Visibility is stable.

2. Instrument Limits (When fog exceeds the instrument's capability):

M (Minus): Visibility is less than the instrument's lower measurement limit. (Example: R09/M0050 means visibility is less than 50 meters!).
P (Plus): Visibility is greater than the instrument's upper measurement limit. (Example: R09/P2000 means visibility is more than 2000 meters and the situation is excellent).

3. Varying:

When visibility changes significantly and rapidly, the two numbers are written with the letter V.

Example: R27/0400V0800U
Meaning: Visibility is fluctuating between 400 meters and 800 meters, and the general trend is upward/improving (U).

Operational Impact

The RVR value dictates whether an aircraft is allowed to land or not, based on the Instrument Landing System (ILS) Category:

CAT I: Requires RVR not less than 550 meters.
CAT II: Requires RVR not less than 300 meters.
CAT III: Requires a very low RVR (less than 300 meters, and can be as low as 50 meters in CAT IIIc).

⚠️ The Golden Rule (Approach Ban): If the reported RVR is below the minimum allowed for the aircraft or the crew, the pilot is legally prohibited from descending below 1000 feet above the airport, and must divert the flight to an alternate airport.