Originally Posted by
TotalBeginner
Ooops, sorry I see how that reads. Obviously clearance is always required to commence the approach, but provided "LVP's in force" can be heard on the ATIS, then it's ok for the crew to conduct that approach in accordance with CAT II/III operations, correct?
Not necessarily nor systematically, although it is (nearly) true in Europe.
Most airport will declare LVO when the Wx is at or near Cat I minima.
If RVR is still Cat I, Cat I crew and craft will land normally; Would one want to do a Cat II, or Cat III with these conditions, he would have to request it, as it requires extra separation between approaching aircraft and extra protections and redundancies on the airport equipment.
Then the RVR goes Cat II and the Cat I folks are banned. Cat II/III pilots now have to "declare" they are authorized Cat II to be cleared for the approach. Same at Cat III RVR where Cat II are banned and Cat III have to be authorized to be cleared.
Just to confuse you a bit, once in Cat III, you still have to consider
Cat IIIA, CatIIIB with DH and CatIIIB without DH.
More confusion? In Cat IIIB, crew will have to remember the alert height and, whereas in usual IFR, the lower the authorized DH gives the better chance to land, the higher alert height will provide the better chance to land; figure that out!
And do not forget that if the airport is declared Cat III, and the RVR increases to Cat II or even I, no one under Cat III authorisation will be cleared to approach; one of the main reason being that in Cat III, the VASI/PAPI are switched off. Why would that be?