Originally Posted by
roulishollandais
said in common but acurate language "the input is not the human command, but the difference between the command and the output", and that input is not human but computed.
I'd say that's not entirely accurate. The *output* of the autotrim system is computed based on three primary inputs - elevator position, THS position and command from the flight controls. When hand-flown, the last of these inputs is indeed human.
So I suggest to use here in PPRuNe the word "automation" for the autotrim, which is more similar from the common sense from "stupid" pilots !!!
"Common sense" is by its very nature subjective, and if the discussion here is any guide there seems to be no significant barrier to pilots understanding the terminology.
That statement is loaded anyway - no part of the Airbus FBW system, and that goes for the PFC design, digital flight control system and the protections exists because anyone thought pilots were "stupid". The press liked to play that angle up because stirring up distrust between pilots and engineers means controversy, and controversy means more column inches. It exists in part because technology reached a point whereby the more mind-numbing aspects of aviation could be performed reliably, thus reducing workload on a two-man crew, and that in the case of a non-technical emergency, the pilot could perform manoeuvres safely without worrying about staying within the envelope. For management there were commercial benefits too, but that's outside the scope of what we're discussing here.
Anyway, that aside - I think autotrim should be considered distinct from the more traditional definition of automation because when under human control it simply determines the optimum placement of the THS based on the inputs it is given. Unlike autoflight it does not attempt to alter flightpath on its own. An admittedly rough analogy would be like power steering on a car.