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You've probably seen the letters "RVR" in a METAR report before. You may have also noticed that they only appear when the visibility is low. So what is RVR, and how does it work?
Runway Visual Range (RVR) describes the horizontal distance you can expect to see down a runway, based on seeing High Intensity Runway Lights (HIRL) or other things on the runway that have visual contrast.
RVR equipment is typically found at larger airports, and RVR visibilities can be reported for up to four designated runways at an airport. It's calculated using sensors like this:
The sensors are located along the runway, and they're approximately 14 feet higher than the centerline of the runway.
On most runways equipped with RVR, there are three sensors: a touchdown sensor, a mid-point sensor, and a rollout sensor.
While it's good to know about the sensors, it's even better to be able to actually read RVR. So let's jump into that.
RVR is only reported at airports that have RVR sensing equipment, when the visibility is 1 statue mile or less, or when RVR for an instrument runway is 6,000 feet or less.
In a METAR, RVR starts with the runway, coded with the letter "R", followed by the runway number. In this example, "R18R" means RVR is being reported for runway 18 Right.
(Screenshots taken from our Aviation Weather Products online course)
RVR visibility is coded using four digits, representing RVR distance in feet. In this example, "1600" indicates the RVR for runway 18R is 1600 feet.
The increments that RVR visibility is described in also changes as the visibility gets lower. The lower the visibility, the smaller the increments that RVR is reported:
If visibility is less than the lowest reportable RVR value, an "M" is placed in front of it. Here, "M0600" indicates the RVR for runway 18R is less than 600 feet.
And if the visibility is greater than the highest reportable value, a "P" is placed in front of it. Here, "P6000" indicates the RVR for runway 18R is greater than 6000 feet.
And when RVR varies by more than one reportable value over a 10-minute period, the lowest and highest values are paired with a "V" between them. In this example, "0700V1000", indicates the RVR for runway 18R is varying between 700 feet and 1000 feet.
Because RVR is only reported when the visibility is very low, it's most often used by corporate and airline pilots when they're determining if they need to shoot a CAT II or CAT III approach, or what their takeoff visibility minimums are.
But GA pilots like us can use it too. While there aren't any visibility minimums under Part 91 to begin an approach, RVR can give you a general idea if you're going to be able to see the runway or approach lights at minimums. In the chart below, the blue highlighted "24" is short for 2400 feet RVR minimum visibility for the approach.
If the RVR reported at your landing airport is lower than the minimums on the approach chart, you need to be thinking about where you're going for you alternate airport, because your chances of seeing the runway at minimums aren't that good. You might also want to consider skipping your approach altogether, and heading to your alternate.
Again, you don't need to meet the RVR minimums to shoot an approach and land, but you do need these three things:
While "flight visibility" is different than RVR (it's what you see out your windscreen), the RVR is going to give you a general idea of what you can expect to see at the end of your approach. And if the reported RVR is below what's on your approach chart, you're probably going to have a hard time landing from the approach.
While RVR doesn't play the same role in GA flying as it does to 135 and 121 operators, it's still a good tool to use when the visibility gets low. Knowing what the RVR is for your runway and comparing it to your approach minimums gives you a good idea of what you can expect to see (or not see) on your approach. It's also a good indicator of whether or not you should be trying the approach in the first place.
Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed development of numerous commercial and military training systems. You can reach him at firstname.lastname@example.org.