VicMel:
1 NAV TCAS FAULT Message.
As indicated in the BEA report (page 50) the cause is unclear. I suspect that the most vital parameter derived by TCAS is the relative velocity with respect to other aircraft. As well as a BITE check on max and min, I would expect the rate of change of such a vital parameter to be checked. A rate of change of more than about 20 knots per second for say ten samples might be considered as out of spec and hence warrant a maintenance fault message.
What other aircraft? The one 80 miles in trail? TCAS has no airspeed input. Relative velocity with targets depends on tracking them via TCAS/transponder link, and not onboard data. Altitude difference, rate of closure, and time to CPA, closest point of approach, are the TCAS triggers.
I'm with BEA that this fail remains unanswered, and unrelated to the other faults, which can be tied back to faulty airspeed.
GB