Originally Posted by
gums
@ Doze Yeah I know the three modes, but feel that the "alternate" should be more basic and eliminate the THS auto-trim feature. old ground, I know and we had a good discussion on the pro's and con's two years ago.
As we discussed two years ago, I believe the autotrim shouldn't be the issue because it is one of the things that Alternate Law has in common with Normal Law and as such would feel more natural to a FBW Airbus pilot who has spent 99% of their time flying in that mode.
The only reason autotrim became a factor here was because the PF commanded inputs which were way in excess of what should have been expected in Alternate reversion. The setup in the case of dropping out of Alternate Law is to give the pilots full authority, which makes perfect sense as long as the pilots understand the situation and make their inputs accordingly.
Interestingly (if the sim session was anything to go by) the A320 does have hard limits on autotrim in Alternate Law - which required manual intervention from the TRE to match the trim state of AF447 during our session. Why this was not carried forward onto the widebodies is a question for Airbus themselves, but I wouldn't be surprised it if was a reaction to the perception that the A320 was excessively limiting - if this was the case then the lesson should be "be careful what you wish for".
The point that I still stand by is that a drop from Normal Law means that you cannot rely on the protections and more care must be taken when making control inputs. Alternate Law does make sense, as does the requirement for at least two data sources for protections to be active - I hope you can at least follow my reasoning there even if you don't necessarily agree. The role autotrim played in moving the THS made their lives more difficult - that's a given. But the inputs that caused the autotrim to command that deflection should never have been made in the first place.