Slight drift: how many airlines have CAT 1 reversion from a CAT 2/3a ILS? It's a similar scenario to what Denti is discussing. I flew triple A/P Boeing with a auto land annunciator. Easy. I then flew for double A/P operators with CAT 3a fail passive. No auto land annunciator. Some operated CAT 1 reversion for an autloand system failures, other did not. I could never achieve an answer; perhaps they felt it too dodgy. Can't think why.
Regarding Alert Height; what, when & how do guys use this for a Fail Passive (2 A/P) approach?