Laws, functions, protections, limiters
Sorry if I appear to harp on "too many" laws. It comes from reading and examining all the Airbus manuals I have gotten courtesy of this forum. And I thank you all.
I am gonna take a pic of the FLCS ( flight control system) I flew with back in 1979 and you will see many "laws". Will post it soon. The "laws" were those small graphs of impact pressure versus control deflection, body rate limits, AoA limits, etc.
I am also gonna show my problem with all the "modes" and "laws" and "protection". Let's face it, I flew a very simple jet and it had vastly different operational requirements.
That being said, we never used the word "protections". We used "limits". Maybe it was psychological to provide we dweebs some reason that our piloting skills were relevant, but it worked. Heh heh.
Before I take the pics and upload them, I am compelled to comment upon the THS mechanization. I know, one mo' time Gums, when will you let go? Nevertheless I feel it is more important than the pilot action to correct a roll after the AP disconnected.
With unreliable airspeed (think impact pressure, dynamic pressure, CAS/IAS), I look at some of the alternate laws and still see clues that the confusers are trimming the THS. So without airspeed, the jet is still trimming to maintain one gee. It does not care about the pilot aft stick input other than to keep the stick deflection about the same angle regardless of speed. How does it do this? It uses the accelerometers that are the major players for the basic control concept of a gee command versus an AoA command system. You don't need airspeed for the accelerometers to work. Same for body rates. Saw this on one of our accidents when a pelican wiped out pitot tubes, hemispherical air data gizmo and AoA vanes.
So a constant, even a small aft stick, that is commanding maybe 1.1 gee could result in the confusers increasing the THS angle to maintain the same stick angle for the commanded gee. No air data required. This might explain the THS increasing angle.
REMEMBER: The pilot is not commanding an AoA or pitch rate or attitude. The final command to the control surfaces utilize some of those inputs, but the primary output is related to gee. Clever addition of AoA, speed, body rates and such can make the jet "appear" like the last one the pilot flew. But down deep, the control laws are very different.