In our outfit
CAT 2 requires a minimum DH of 100'
CAT 3A requires a minimum DH of 50'
CAT 3B requires a minimum DH of 0' ( ie no DH )
These are regulatory minimums and will vary between Airports as required.
For CAT 2 and CAT 3A touchdown and midpoint RVR's are controlling ( there are allowed exceptions for system failures )
For CAT 3B all 3 RVR zones are controlling ( this can be reduced to 2 in some circumstances as well )
Last edited by nitpicker330; 10th Aug 2012 at 10:10.