After I did post the ‘BUSS’ article last week, I realized that when you’ve lost all the speed signals this Back-Up Speed Scale wouldn’t work either.
So went into the books again and found out that modified ADIRU not only send its AOA through IR bus i.s.o. ADR bus (crew needs to switch of ADR part of all ADIRU’s to activate ‘BUSS’) but also the AOAc signal is always present (even if CAS < 60Kts !!!!), only the SSM remain set to NCD if CAS < 60Kts.
Aural Stall Warning:
In Normal Law: Max AOAc = 23 surface degrees.
In Direct Law (think this is a typo error in the docs and should be 'Alternate & Direct'?)
This is the sum of S/F term, a Mach term and a Mach term when Speed brakes are extended. Clean Config base angle is 10.8 and M correction is summed.
There are 4 tables given for all S/F positions and several M numbers. Too complicated to type it over and can’t make copies or duplicate any other way.
Table interpolation in clean config results in:Mach Corr AOAc
M 0.22 = 0 (10.8)
M 0.28 = 0 (10.8)
M 0.35 = -0.9 (9.9)
M 0.53 = -3.2 (7.6)
M 0.75 = -5.6 (5.2)
M 0.82 = -7 (3.8)
Aural Stall warning is inhibited on ground (except in functional test mode) and above M 0.866.
If all ADR’s are switched off to engage ‘BUSS’ a backup stall warning table is used based on S/F only.
Clean Config value = 8.6 AOAc.
(‘BUSS’ was not installed in this A/C)