Agreed on the inputs to TCAS, Plastic Bug. I believe the TCAS Fail came before the IR Fail, though. Not so?
I'm from the planes of separate DADC and IRU, where the failure of one, or a component of one would not condemn the output of the remainder. Is that still not true? Can you not get Airspeed Fail out of the ADIRU without Altitude Fail? If not, it's a giant step backward.
I suppose it's possible for the airspeed word to go Fail Warn, with Altitude reporting Normal (condition), and getting lumped together in the ACARS message as ADR Fail. After all, MTC just needs to know which box to change..
GB