...that with 'BUSS' option, AOA is always available...
Always? I believe someone posted info that the ADR's have to be physically disabled thru the switches on the overhead before the BUSS is enabled.
BUSS 'appears' to be an 'on demand' EFIS displayed AOA indexer, the first 'S' in BUSS being a misnomer.
In any case this is not full time AOA.
I think the idea there was that they'd bring the FD back once the data was good, it would then be up to the crew to either use, disregard or disable them.
(my bold)
The 'disregard', as a matter of intent to operate that way, is just not done by any carriers west of Atlantis these days. 'Good' data can translate to inappropriate lateral, & particularly inappropriate default vertical steering commands. In the wild west, they're either 'on' providing pilot selected steering guidance in the 'appropriate' mode as confirmed by the FMA or 'OFF'.
PRM breakout procedures are a another prime example of the validity this requirement in order to preclude unintended vertical guidance commands. (This is not to say that an inappropriate steering command should not be recognized for whatever reason it should occur.)
He has stated very compactly the state of general airline pilot knowledge in the period leading up to AF447.
That may be a little 'broadbrushish'.
EDIT: I guess semantically with BUSS, AOA
is always 'available' just not always viewable.
