Hi Smilin Ed,
I generally share your views about autotrim but we have to acknowledge that many pilots love it and find the bus safe, easy and pleasant to fly.
When I was teaching pilots converting from Airbus to the 777, they had to adjust during the first sim sessions about having to trim and a few lesser handling problems. To those who complained I said from now on they would have to earn their living honestly
. Whilst I am sure manual trim is right with a classical control column and wheel, I cannot say it’s the same with a sidestick controller a la Airbus.
Choosing “C*” law implied autotrim: you cannot rely only on elevator to compensate for speed, configuration, or thrust changes while maintaining a constant path stick free. Besides, streamlining THS and elevator improves aerodynamic performance. The 777 uses a “C*-u” law in normal mode and does silently autotrim when compensating for configuration or thrust changes but you have to “trim to speed” to compensate for speed changes. In another design, Gums had to trim the Viper to “gee”. None of these designs preclude implementation of powerful protections at both ends of the flight envelope.
For Airbus, longitudinal static stability (LSS) is restored by software in normal law when approaching the limits. I believe this was one of the Special Conditions of certification and was called “proof of concept” at the time. The problem which I think was disregarded is the lack of LSS in ALT2 law. Imagine the THS could not move further up as soon as the stall warning activates: most probably, even with consistent full back stick, the AoA would not increase enough to the point where the stall alarm is silenced.
It is Dozy Wannabe’s opinion that the THS rightfully moved to 13 deg up in AF447 because it’s what the PF requested. It is apparently not Dozy’s opinion however that the THS should continue to trim up in normal law when high AoA protection is active and the pilot pulls on the stick, since the software prevents it. Where is the logic?