The reason why ADR 1(2)(3) or ADR 1+2, 2+3 or 1+3 FAIL messages were absent is because the ADRs didn't fail.
They did send (CAS < 30Kts) a SSM(System Status Matrix) signal NCD and a value output of 0 Kts.
The SSM for digital on bus signals (Bit 31,30) of the ARINC word can have 4 states:
- NO (Normal Operation)
- FT (Functional Test)
- NCD (No Computed Data)
- FW (Failure Warning)
If a ADR failed (as detected by its own fault detection logic) the SSM is set to FW.
The FWC composes the exact ECAM warning, e.g. when ADR 1 and ADR 2 outputs a FW SSM then the FWC will send the warning NAV ADR 1 + 2 FAIL.
Since there is no crosstalk between ADRs, an ADR DISAGREE; ADR IAS DISCREPANCY or any other air data discrepancy can only be detected by a system which receives all 3 ADR ouputs, e.g. EFCS/AFS.
When all 3 ADRs signals are in NCD SSM state the value output is 0; so no difference between ADRs but also NO failure.
The logic I did post before did already show why the IAS discrepancy message was inhibited. (any ADR in NCD, dual ADR in NCD for 'frozen 'pitot)
Question is what will the FCPC do with the received NCD state of ADR?
Will it take the value of 0 Kts in account or ignore this ADR?
Maybe later today an answer?