But the STALL warning stopped already passing 350 on the way down and BUSS is
not to be used above 250.
The AoA data connection with IR part of ADIRU (aside the normal data connection with ADR part) is definitive and doesn't need the BUSS to be selected on.
it requires also the FWC to be modified to filter and handle the IR AoA stall warning.
IIRC the highest ADR AoA is taken to trigger the stall warning and for IR AoA the median value is the one to trigger a stall warning.
Also, if the BUSS is the solution, why is it not basic, or made mandatory, for
all except the 380 ?
For the BUSS option more related computers needs to be modified (e.g. SDAC, DMU).
A certain EIS 'CRT' mod level is also required to be able to display the BUSS image (EIS2 'LCD' is capable).
In fact you have the see both issues apart, BUSS requires the IR AoA but one can have IR AoA without the BUSS option.