Extract from BEA Final Report ...
STALL WARNING ...
...this warning should have continued until about 2 h 10 min 15.5, and then have been triggered again between 2 h 10 min 17 and 19. The disabling of this warning was probably due to the fact that, between 13.4 and 15.5 and then between 17 and 19, and possibly at other times, the three Mach values were abnormally low (three Pitot probes iced up). The warning triggering threshold then suddenly increased to values of about 10°, much greater than the recorded angles of attack, which led to the warning stopping.
Thanks
RetiredF4 for highlighting this anomaly, and it once more brings to the fore the hazards of "common mode" failures, especially those that then rely on faulty air-data to provide a warning function.
One can only hope that Airbus Industrie will look at using IR data as the point of reference when double or triple ADR disagreements are identified. In this case when ADR Mach values disagreed and the equivalent IR sourced value(s) was higher, then it should be used. This of course leads to the adoption of Vsyn or similar as dealt with earlier in this and other threads.