Gee sensing for FBW systems
As with Chris, I too wonder what does Doze think the "system" uses to sense and use Nz.
I don't have the box specs in front of me, but I doubt that the confusers use the basic inertial and attitude system data for anything other than the plethora of "protections" and all the approach, cruise, climb, descent, flare and other stuff that enables a pinball wizard to fly the jet ( sorry for the rant).
The system likely uses its own accelerometers and rate sensors. That is the core of the entire flight control system, fer chissakes. No shabby sensors to freeze up, no cosmic autopilot or flight phase inputs, just the basics.
We tried various core principles 40 years ago. AoA, body rates, attitude, mixes of all..... The Nz control law is the one that allowed humans to fly the FBW systems when compared to older systems, and it was very easy to implement internally, without a lotta data inputs from the outside. A basic FBW system would only emulate the hydraulic pressures to the control surface actuators via servos. Big deal. Kinda sounds like the 'bus "direct law". However, we then had the opportunity to control deflection rates and total surface movement and such that we didn't have with the systems that went back to the early 1950's. We could also use a few bits of outside data like dynamic pressure and AoA to provide some "limits", not "protections". Could also use those bits of external data to keep the jet smoother and less susceptible to PIO's and overstress and STALL!!!! We could also adjust the lag of AoA and body rate inputs to make rolling into a turn smooth, but "freeze" the rate command more quickly when relaxing stick pressure. Same for pitch/gee.
For the life of me, I can't understand why the core principle for the 'bus is not an AoA versus Nz principle. A gee command that uses AoA to limit the gee command. So you can pull as hard as you want, but your command will be reduced when at an AoA limt. In other words, work back up from a well-defined control philosophy and add bells and whistles along the way. The existing system starts the other way, and it's hard to figure out what HAL decides is necessary or will do that the human does not anticipate or fully understands.
Same goes for the "gains" that go south when the sensors freeze up. Good grief, use a fixed value for "q" and keep HAL happy. If and when the air data comes back, the humans can enable it for a smoother ride and such. That is one feature lacking that I cannot fathom about the 'bus design. And that lack of feature seems to have played a role in several instances. AoA is a different story, and the design should have a sufficient bias by body rates to keep the jet flyable if the humans use airspeed as an aid, kinda like the old days.
sorry for the rant.....