For reference only, EASA starting point is CAT.OP.MPA.185 Planning minima for IFR flights — aeroplanes. Then it follows to CAT.OP.MPA.110.
If,
A conversion from meteorological visibility to RVR/CMV should not be used .... for any RVR minima less than 800 m. [AMC 10 (a)(3)]
and by definition any TAF will only have VIS
then anywhere CAT I is required, RVR 550 must be disregarded and VIS 800 used.
That's different from
sonic's suggestion. Thoughts?
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.
this leaves me perplexed.