Originally Posted by
RetiredF4
Exactly on that, not having thrustworthy values.
With thrustworthy values the protections would stop the trim reaching special values , without those values it will continue to trim also it can cause harm.
Where is the logic?
Logic is that when computer is half-blind and/or confused, it will hand over the responsiblity for staying inside flight envelope to the usually superior analysis and decision making skills of the real pilots.
It cannot logically limit trim to "safe" values if it no longer knows what those values are.
Autotrim didn't down this a/c - it was stalled by elevator alone and elevators were held nose-up all the way down. There was no diagnosis of stall let alone recovery attempt.
In contrast, the cessation of autotrim when things start to go wrong is a least a contributory factor in some crashes, if not a killer.