Originally Posted by A33Zab
ADR Single and ADR Dual faults are detected by ADR itself.
A Triple ADR Failure message (ADR 1+2+3 FAULT) only exist if the BUSS option is installed, this is a level 3 (Red & Master Warning).
This Triple ADR monitoring was NOT installed on the A/C.
A local ADR fault without ECAM message doesn't seem logical to ECAM protocol.
1) PROBE-PITOT fault is not the result of this ADRs self-testing (two by two), it is the result of EFCS and AFS functions monitoring their respective CAS imputs. They are working with imputs from all 3 ADRs. CAS was rejected by those functions, triggering the following ACARs sequence by pointing to this PROBE-PITOT fault (total pressure imput).
2) My concern about ADR self-monitoring is to explain why ADR DISAGREE wasn't triggered following the PROBE-PITOT fault even if the three CAS were rejected by those monitoring functions. My explanation is that it was a "triple ADR fault"; hence, it was not detected at internal level. No "outlier" ADR could be rejected, being all erroneous while passing (or failing) the comparative test two-by-two.
This test condition required to reject the first ADR (CAS) is: 16 kt difference during 10 seconds.
It means that ADR 1+2 / ADR 1+3 / ADR 2+3 all passed or failed this test when CAS dropped. Hence, ADR2 was also affected like the two other recored CAS from ADR1 and ADR3; all 3 speeds went down from coherent and valid values to erroneous values:
- passing succesfully the test, hence staying consistent (c)
- failing the test, hence being inconsistent (d).
Example (CAS_1, CAS_2, CAS_3); T_1 = T_0 + 10 seconds:
.... T_0 -> (274, 275, 275) => all valid and coherent values
a).. T_1 -> (61, 275, 275) => ADR_1 ("bad") would be rejected due to ADR 1+2 and ADR 1+3 test.
b).. T_1 -> (61, 275, 77) => ADR_2 ("good") would be rejected due to ADR 1+2 and ADR 2+3 test.
c).. T_1 -> (61, 70, 77) => all values consistents (no fault) but 3 ADR erroneous.
d).. T_1 -> (61, 99, 150) => all values inconsistents (triple fault) and 3 ADR erroneous.
In case of (d), ECAM messages (FLR) are compiled into Current Flight Report (CFR) sent by ACARS when they are linked to the same fault (having the same ATA). The priority would simply be PROBE-PITOT fault over ADR fault during the correlation window.
In this case, ADR 1+2+3, being not displayed (no BUSS), it would nonetheless trigger three ECAMs:
- ADR 1+2
- ADR 1+3
- ADR 2+3
3) FCOM:
"If one ADR is correct but the other two ADRs provide the same erroneous output
or if all three ADRs provide consistent and erroneous data:
The systems will reject the “good” ADR and will continue to operate using the two “bad” ADRs."
Like I said before about this quote, something is obviously missing here:
The system could only reject the "good" ADR in the first case (one is "good", two "bad").
In the second case, the system will continue to operate using the three "bad" ADRs. This should have been added to this sentence. The consequences are the same in both case (erroneous output could be used), but the logic would be restablished.
It should be our case to be considered excepted that CAS was rejected by external monitoring functions => CAS monitoring (EFCS) and ADR monitoring (AFS).