A Cat 2 manual approach (flight directed) requires the aircraft to be certificated for the operation and the clearance and limits be published in the AFM. More recently for aircraft types that have autoland, the manufacturers are reluctant to spend additional time and money on achieving a Cat 2 manual certification. The tests require proof that the FD guidance and pilot technical error are satisfactory; this is similar to the certification required for auto approach and HUD (Ref JAR-AWO).
The RVR limits for manual landings in low visibility are conservative and should not require extensive additional training. One good simulator period should give crew sufficient confidence and demonstrate that the general principles for landing still apply.
Cat 2 minima were historically 100 ft, 400m RVR, but with increased accuracy of flight guidance systems this has been reduced to 350m. Some operators have 300m, but this is normally associated with an auto coupled approach to 80% of the DH. Who has procedures for an autopilot failure between 100 ft and 80 ft? Are you allowed to continue or do you GA?
Research in the UK by the Blind Landing Experimental Unit (BLEU) in the late 70’s showed that it was feasible to land from 50ft in 200m RVR and from 35 ft
in 150m RVR; most operational limits are based on these data (old refs, ECAC Doc 17 and CAA computer model of landing in fog).
Thick fogs associated with Cat 3 RVR < 300m are generally stable with little variability. Thus where a pilot sees sufficient cues for a land decision then they should remain in sight and the visual scene generally improves as altitude decreases. Cat 2 conditions are much more variable and are often caused by adverse weather as well as fog. Cat 2 fog generally occurs during the fog formation or dispersal and thus is variable. A Cat 2 decision based on a visual scene does not necessarily mean that the conditions will improve below DH, thus crew should be aware that a GA below DH may be required. i.e. You can decide to land in Cat 2, but your decision could be mistaken or have to be reversed.
When flying Cat 2 HUD approach, who actually dispenses with the flare guidance and lands on the visual scene? How do you judge if the conditions deteriorate?