Given an airport with RVR 1800, variable 1800-2800, and tower visibility 1/2 SM, is an IFR takeoff authorized?

• A. no, your RVR needs to be at least 2600 to takeoff
• B. yes, minimum RVR needs to be 1200 for takeoff
• C. yes, because ground visibility is 1/2 SM
• D. yes, because the higher end of the variable RVR is more than regular takeoff minima

Answer: (C)

Takeoff minimums can be expressed in two ways: by Runway Visual Range (RVR) or by prevailing (tower) visibility. The controlling factor is whether the published minimum for takeoff has been met by any of the available visibility measurements. In this scenario, the published minimum is 1/2 mile (0.5 SM). The tower visibility is exactly 1/2 SM, so the required minimum is satisfied. The RVR value of 1800 feet does not negate that, since the takeoff minimum is already met by the prevailing visibility. The fact that the RVR can vary up to 2800 feet doesn't change the decision here—the relevant criterion is meeting the published minimum, which the tower visibility does.