Originally Posted by
rudderrudderrat
Normal Law removes it, but adds Alpha Prot & Alpha Max.
Alternate Law removes it and has no such "protection" or "Limit".
Direct Law would restore it. Ask any conventional aircraft pilot - they would understand it.
I've been asking a few people about it behind the scenes, but the answers I got back were too technical for me to comprehend easily (my brain has an annoying habit of shutting down when presented with algebra)... there's a pile of emails/PMs looking suspiciously at me as I type.
Let me see if I understand what you're getting at, and if I'm wrong please correct me. Prior to this I got the impression from your post that it related to the presence of autotrim - that is, when manually trimmed (with the THS at a fixed angle), the aircraft will tend to stabilise at a certain pitch angle and speed will remain more-or-less in the required ballpark. The presence of autotrim means that the THS is correcting itself based on sidestick input, and as such the trim angle is changing. In Normal Law, Alpha Prot and Alpha Max keep the trim settings within certain limits, but in Alt 2 those are not there, so there's nothing to stop the trim getting the aircraft into difficulty if the sidestick input is on the aggressive side.
Am I following you OK?
If I am, I think it's important to recognise that it takes a significant amount of input to cause the THS to get itself to such an extreme angle, and it's also important to recognise that autotrim has other benefits as well. It's pretty clear that Airbus FBW training at a basic level instructs pilots to be more careful with their sidestick inputs when law degradation has occurred. It's also worth bearing in mind that if you're in that situation and don't like what the trim is doing, all you have to do is set the manual trim as desired and avoid making large and consistent pitch inputs on the sidestick - this should cause the autotrim, when it kicks back in, to maintain a pitch angle at or near where you've just manually set it.
If I've read the "note" correctly, this isn't a case of a slight back-stick input in combination with (presumably corrective) roll input causing the THS to move to the 13deg nose-up angle in a matter of seconds, this is a case of the elevators causing the zoom climb in response to input, followed by the THS moving over the course of around a minute as repeated full or near-full backstick was held on the way down. From what I've read, THS movement from the autotrim is not particularly sensitive, nor is it likely to come into play with inadvertent sidestick deflection - the pilot *really* has to command it to be at that kind of angle for it to have got there, which is why the initial nose-down commands weren't enough to get the THS moving.