Dozy,
there is no situation in cruise, where autotrim is improving a situation in ALT2 like that encountered by AF 447. If you can think of one, let me know. As we know, autotrim is inhibited in ALt1 at V-prot anyway and in direct law as well.
Then letīs look at it from the other way around.
How difficult would it be to expand the present feature from ALT1 to situations in ALT2 maybe with different and independent values? Is it rocket science?
Concerning your graceful degradation explain this degradation with autotrim of the THS:
In Normal LAW autotrim (a rally nice feature)
In ALT1 Law autotrim prohibit at VC-prot (looks sound to protect from entering unknown territory)
In ALT2 Law autotrim (that is your part to explain)
In Direct LAW autotrim off (looks sound to protect from entering unknown territory)
I would name that one non linear degradation (far off from gracefull).
Concerning your naming manual trim again, please do not push aside the inputs made to that issue from Clandestino.
http://www.pprune.org/6770409-post394.html
Quote:
Originally Posted by RetiredF4
Manual THS trim (nowhere mentioned in the books except in direct law, and never trained)
Clandestino:
Rest of youth post is spot-on, I just have to comment on this. It is not trained because it doesn't work. You can forcibly move the wheel to position of your choice but the FBW will return it to the position it deems to be necessary once you loose your grip and all the while will try to combat the trim with elevator to satisfy G demand.
There's no use and no need for manual trim while auto-trim is working.
.
That should straighten up the manual trim option once and for all. Itīs even worse, because the functioning autotrim in ALT 2 prevents manual trim in its original sense of implementation.
There might be pilots insane enough to pull on the yoke or sidestick in conventional and FBW aircraft until the aircraft stalls, but no one would trim while pulling.
To understand that above statement let me explain normal trim behaviour. With the intention to climb the pilot uses the yoke to change the pitch, once that change is reached he uses the trim to get rid of the pressure on the yoke. The trim comes into play when the change is achieved and not in the timeframe, where the change takes place.
In case of AF447 without autotrim the pilot would never ever have tried to achieve the desired flight path change with manual trim, because that is not the way to do it.