Do I understand this feature correctly as a pitch trim that is activated automatically whenever an extended pitch input (up or down) is commanded through the sidestick?
I believe it essentially alters the "THS" (Horiz Stab) to automatically align with the elevators - much as can be done on a 1950s jet fighter
So as you say:
In other words if I command a pitch up from the sidestick, it trims in a nose up to relieve back pressure on the elevator not unlike when you fly a conventional aircraft in manual when using the electric trim or basically the same way an aircraft on AP would trim itself?
If so what is the big deal behind this feature on the Airbus?
None whatsoever to you & me - but to the Airbus bashers, it means it was the Airbus' fault that when a pilot held the stick back and flew to a crazily low speed (AF447 & Perpignon), and the aircraft duly trimmed back, it meant when the pilot let go and/or belatedly tried to recover, it was trimmed back in a way that did not assist recovery.
There is the aspect, which is true, that if the aircraft then drops into Direct Law (as happened in Perpignon), the auto-trim stops, so your:
If the pilot would have just inputed a full nose down on the sidestick, wouldn’t the THS trimmed nose down too?
would not happen in this case. In AF447 I don't think it dropped to Direct law, so yes, stick forward and trim forward would have happened...
Assuming you are in cruise at FL370 in an Airbus 320 and all is working properly, you then encounter some mountain wave turbulence or something similar to it, what usually happens at first in an increase in speed with a tendency in an increase in altitude usually compensated by the AP.
In the above scenario in a very conventional aircraft with a basic AP without AT, if left unchecked and if the power is not reduced, the aircraft may overspeed but it should hold altitude. In an aircraft with AT, the FADECs should automatically reduce to a power setting as to avoid overspeed.
However it seems from reading on here that the Airbus might want to pitch up to avoid overspeeding, is this correct? At what point will the Airbus reduce power to keep it within the normal parameters?
To be precise, it does not pitch up to prevent overspeed, but minimise the extent when it has oversped. First the AP disconnects, then further into overspeed it pitches up a small amount (which you can override) until eventually even full forward stick will not counteract it. It does not reduce power - albeit if ATHR is on, that should have selected idle.
The ATHR is not great, and in Mountain Waves it can be almost hilarious as speed oscillates between Min and Max, and Power between full & idle, but out of phase. Disconnect ATHR, set sensible power and leave, and the speed oscillations are far lower
I suspect it would be fair to say that in the well known overspeed events, poor monitoring or inappropriately high cruise speeds may have been factors. Certainly my experience on the line is poor choice of speeds with regard to conditions - any excuse to go faster seems the aim
