Originally Posted by
Big Pistons Forever
The weather was reported as fog with 375 meters vis and the cloud base was 100 ft.
375m VISIBILITY or 375m RVR? There is a BIG difference.
If a measured RVR is not available then the "equivalent" RVR is calculated by multiplying the measured met vis by a factor of 1.5. So, 375m VIS becomes a factored met vis of 562m "RVR" (equivalent). But if the measured RVR was 375m then that is a different story.
As for cloudbase, the acceptable minimum on an ILS approach is 0'. Therefore, the only weather criterion that you need consider (legally at least) for an approach ban on an ILS is RVR.