The decision altitude/height. Note that at 800 feet the LDG INHIBIT message appears which means all non essential failures are suppressed so crew can concentrate on landing. Presumably because if you loose the other RA the aircraft will then downgrade to direct law so you want that extra safety margin to be able to see the runway in time incase it does happen. You’re also relying on single source for quite a lot of information going to a lot of systems. Only failures not inhibited in flight phases 7+8 will appear so I'm presuming an engine failure/fire is one of them. For testing reasons I would like to know which failure (that can be simulated) could be used to test the Alert Height logic. So I am searching for a failure that is indicated below the LDG INHIBIT message threshold, but not below the AH.