Originally Posted by
CONF iture
That must be part of the complexity of the system, laws, protections, stability ... In the mean time, can we presume that if under Low Speed Stability in ALT2, autotrim does not operate ?
I don't
think that is correct - I think autotrim is
always active outside of direct law (or manual backup)
except in abnormal attitude law. Abnormal attitude law could, I guess, co-incide with low speed stability activation, but would not automatically follow from it.
If no autotrim never under manual flying, at least a pilot knows trim is under his watch always - No ambiguity.
It's a good theory, but there are incidents (more than one 737 I can think of) where it hasn't held up in practice. In situations where the automatics dump the plane back in the pilots' lap unexpectedly (perhaps trimmed up to the limit) it can only add to the workload.
Also, I think autotrim is effecitively requried for C* control law, so without it you are looking at direct law, and no protections/limits whenever A/P is out. Not sure that is going to be an improvement.
You could reduce the number of laws/transitions to simplify things - as others have suggested. Go straight to direct law, and hence manual trim, when things start to go wrong. I'm ambivalent on that - I can see from a design & engineering point of view that the current laws are a nice graceful degradation, which should make things easier....
however, all the different laws, sub-laws, caveats and footnotes add up to a lot of combinations to learn and fit in training on. It's arguably little use having intermediate graceful degradation modes if pilots are never trained on them.
Be careful what you wish for though - there are reasons why non-normal laws get latched, and the A/P doesn't handle direct law, so you could be looking at hand-flying a long way when stuff goes wrong. On the other hand, maybe if the previous UASs had been a bit more of an "event" the **** pitots might have got fixed sooner (like when AB suggested it, or earlier).