from a recent contributor:
In this case it's simply:
Normal Law -> All systems go, you can rely upon the protections
Alternate Law -> There's something wrong - protections will try to help you but if you need full authority it's there.
Alternate Law 2 -> You're missing data required for the protections to work, but you've got full pitch and trim authority via your sidestick and thrust authority via the levers.
Direct Law -> Exactly what it says on the tin.
First of all, I do not know of a single FBW system that acts in the same manner as the "old" hydraulic control systems we got used to starting in the 1950's. No mechanical connection to control surfaces, and the only feedback was body rates ( your own skinny butt, not an inertial or rate gyro). So the manufacturers did their best to give we lowly pilots a sense of feedback via springs, pneumatic bellows, etc. They also added things between we pilots and the actual control surfaces such as pitch and roll and yaw dampers, as we were moving from the old days to new designs operating at high speeds and aero effects the older planes dealt with, like Gooney Bird, P-51, Aeronica Champ, et al. Those in-between things helped to keep the pointy end forward and really helped in turbulence or near-stall conditions.
The big difference with the Airbus and the Viper FBW system compared to "simplistic" descriptions of FBW is you can never get "direct" control of the control surfaces via the computer. Well, not so fast, Gums. In the Viper, we DID HAVE A WAY to bypass the computer corrections and gains via a manual pitch override function. That thing acted like the "old" hydraulic control stick/rudder. Not recommended for the heavies, and only reason we got it was we found out we had an unusual flight condition that the computers couldn't handle. We still were at the mercy of the computers for directional stability and lateral stability. And for the "faithful" believer in the reliability of a well-designed computer system, how come they did not allow for this in the beginning?
The Airbus FBW, as in the F-16, F-22 and F-35 do not "simply" provide electrons to command the hydraulic actuators. The computers use air data, body rates, known aero characteristics, etc. to "tailor" the control surface movement in both rate and amount of movement. So this is vastly different than the "old" systems most pilots are used to and the skills they mastered.
What is this fascination with "protection"?
Beats the hell outta me, but I would rather educate the pilots that the jet "allows" this and that, and it will limit your inputs according to "its" idea of what you should be commanding.
The Airbus reversion sequences and all the "protection" and various control laws could be appropriate for a pinball wizard or drone operator. But they need better human engineering and human education as to what happens when this system goes south and what aerodynamic conditions require less "protection".
This discussion prolly needs to be moved to a separate thread in order to allow others to question who was in what seat, what pilot actions could have resulted in roll or pitch angles, what time the ACAR's transmitted a message, the bad weather in the area, etc.