Originally Posted by
Graybeard
We also know that the computers were not robust enough to accommodate erroneous airspeed.
OK - one very-last post then...
You can't make a computer perform tasks with data that it known to be erroneous, it's just a logical impossibility. As such, the design of the system - on paper, before a single line of code was written - clearly defined that in a case where it is unable to do its job, the best hope lies with the pilots. So issue a "stop" command to the relevant module (beyond which nothing other than a full reset can bring it back up again), notify the pilots of the failure and leave the flying to them.
As soon as "Alternate (NO PROT)" mode was triggered, the pilots were effectively in control of a regular airliner with no protections and full control authority in the pitch axis. What isn't clear at this point (and what I suspect the BEA will be spending months trying to determine) is how the crew reacted to the situation they found themselves in, and what their intent was.
Just so we're clear - one last time.
Based on the evidence we have so far, flight control protections and the software that defines them are unlikely to be directly relevant in this accident sequence, because they were disabled very early on in that sequence, precisely as they were designed to.