Originally Posted by
DozyWannabe
Given that the sticks are not backdriven, they wouldn't feel it anyway, unless you're talking about in their bodies through the motion of the aircraft - in which case I'd say even if it could be felt, is it not preferable to use the ADI and thrust settings to make sure you're at a safe AoA?
Dozy,
Without judging what is better I would like to try and point out the difference:
With the THS at a given position there is a speed to which the aircraft will return by itself if you let go the yoke, even no matter what thrust you set.
If we assume that during cruise the trimmed speed is 270kts, and you command a Pitch Up, if you let go the yoke, the aircraft will lower the nose and finally settle again at 270kts, albeit at a slightly lower FL and after a couple of nice and accentuated phugoids.
You can only overcome this by constantly pulling the yoke or by deliberately changing the trim.
With any kind of Autotrim (be it AP or FBW) you do not have this constant point to which the AC will revert by itself. The Aircraft will follow a demanded flight path.
It needs clever logic (elaborated C*) in the FCS to deal with the fact that you could demand a flight path that could not be sustained by the AC.
This is done by blending over from 'g' demand to pitch demand. This makes sure the AC doesn't try to chase 1g at all costs.
Edit:
Caveat for any one who wants to bash Airbus Autotrim now: An AP mistrimming slowly and quietly and then disconnecting and handing back to the pilots can be equally bad or even worse as you cannot fix it just by applying ND on the Yoke, which would work on an AB as long as you have Autotrim.
It just has to be noted that trim is a very important aspect of flight in any aircraft and not clearly poinitng that out and training it is a clear mistake.