Hi TD!
I've read the shadow, and more than once. As to a gradual packing up of the Pitots (and three apace), the a/c would trim ND/NU with ThrottleUp and/or THS/N/U/D. This would satisfy the computer, and completely bollox up the actuals. At some stage, and not necessarily due ICE, the a/p would quit (cannot hold 'Altitude'), or for any of a number of easily understood reasons. If so, and prior to "Disagree", the a/c may simply handover the goods and continue in NORMAL LAW. If agreement then degraded to the extent of AD needing "Timeouts", there is a separate kettle of fish, eh? That is UAS, certainly, but as a follow on, not as a priori. I am not sure if this mode is represented in the prior incidents of UAS, but I also do not know if our crew had experienced an actual UAS of the garden variety either.
I am amazed that so distinguished a group as this one hasn't thought the PF was indeed acting on bad data (not his "fault"), and was doomed to a guessing game either way, No?
nice to meet up again, my friend.
Can we call this mode: "Triply redundant bogus airspeed, but who knew?"
TRBA/bwk........