Originally Posted by
sonicbum
oggers,
(a) A conversion from meteorological visibility to RVR/CMV should not be used:
(1) when reported RVR is available;
(2) for calculating take-off minima; and
(3) for any RVR minima less than 800 m.
point 3) in intended after a conversion i.e. with a Vis of 400 m and a conversion factor of 2.0 you would get a CMV of 800m, but with, let's say a min RVR of 550 you could not do the conversion with a Visibility of, let's say 300m.
SonicBum (nice nickname!),
In EASA land when you're at the
planning stage, you cannot apply the conversion, because of point (3), when you're
in flight and the visibility drops below 800m and you want to shoot an ILS approach, RVR should be provided. Therefore point (1) prohibits you from doing the conversion.