Originally posted by Graybeard ...
... nobody ever gave a good explanation for the TCAS Fail in the ACARS message. Everybody just dismissed it as due to the pitot fails.
I seem to remember that was dealt with by the BEA in Interim Report #2. From memory, the TCAS has an inbuilt function which checks that the static port pressure is valid and that the calculations that result fall within predetermined values. Should the TCAS detect erroneous values, it fails.
I need to check the report for accuracy, but the above is near to it.