172 “…but that doesn't really make sense either.”
With my cynical hat on you might expect too much from the regulations, particularly harmonisation between AWO and OPS.
As you probably realise AWO looks after the equipment/safety standards, whereas OPS regulates the operation. In between there are many gaps, and where ‘unusual’ operations are approved you have to specify the context, aircraft, equipment, and/or the approving authority.
Europe may seek harmonisation in theory, but in practice … ….
My understanding of roll out guidance is that it refers to the system elements which are only used on the ground; thus it would be feasible to use a non-automatic ground roll system. One example of this was the use of para-visual displays, e.g. Trident, Tristar, and some 747s?
Re Cat 2 RVR etc. IMHO This area is a black art steeped in the mystery of pre JAR operations where operators/national authorities argued for the lowest acceptable minima irrespective of aircraft type, or to keep what they already had to be used in JAR-OPS. This was fraught with danger as each aircraft has unique attributes (e.g. glare shield cut off angle) or handing characteristics which can affect the practicality of operating in low visibility.
The European AWO regulations evolved from ECAC Doc 17. Each national authority developed their local approval systems. The UK CAA led the way on certification (Trident), and recognising operational issues, developed a reputable computer model of fog, airfield lighting, and aircraft characteristics, which provided a minimum value RVR.
This was rejected by JAA and the ensuing ‘tabular’ mess continues. JAA/EU-OPS AWO working groups have struggled (unsuccessfully) for many years to rationalise the situation, which is not aided by rigid ICAO definitions and the rapid introduction of new / novel guidance systems.
Cat 2 minima used to be what-ever the operator could argue for. More recently this has been bounded by EU-OPS tables, but there still is opportunity for variability amongst regulators in their interpretation of ‘workload’, crew skill, etc, etc, or just in understanding the rules / safety of the operation.
IMHO Cat 2 is the most risky area of AWO, in that the nature of the reduced visibility can change with altitude, fog / snow / dust. Thus having made a decision to land, this might be incorrect at a lower altitude – from experience(s).
Fortunately, the prevalence of reliable autopilots and the high cost of Cat 2 certification, most operations choose the safer auto-approach options; but now operators argue to extent Cat 2 auto systems into Cat 3 conditions – back to #1.