What should be substituted for 2,400 RVR if it is not reported?

When 2,400 RVR (Runway Visual Range) is not reported, the appropriate substitute for visibility is 1/2 statute mile (SM) of ground visibility. This guideline is rooted in aviation regulations and standards that help ensure safety during operations.

Using 1/2 SM ground visibility as a substitute for 2,400 RVR aligns with the RVR to visibility conversion rules, as it provides a conservative estimate of the visibility conditions. This estimation aids pilots in making informed decisions regarding approaches and landings, especially in scenarios with low visibility.

In contrast, other choices involve different visibility conditions which might not provide the same level of safety or could lead to underestimating the actual conditions. For instance, substituting with a lower visibility measurement, such as 1/4 SM, could represent inadequate conditions for safe flight operations. Similarly, selecting 1 SM ignores the specific context of 2,400 RVR, which is less than 1 SM, and thus does not appropriately reflect the assumed visibility when no RVR is available.

In summary, opting for 1/2 SM ground visibility as a substitute for 2,400 RVR when it is not reported is the best practice, as it facilitates safety and adherence