GB;
The TCAS Fail message from AF447 remains unexplained, and not in concert with the other reported failures that can all be explained by erroneous airspeed.
Hm, it may be "unexplained" but I don't think it is inexplicable. I think the TCAS indicated "failed" because of the absence of good data from ADIRS 1. I don't think it's more complex than that.