Thanks to 'nuts and Rouli for bring up one aspect of the control laws that is independent of all the "autopilot" functions.
Part of the quote mentioned by Rouli strikes home, as it was inplemented operationally years before the shuttle entered drop tests and so forth:
Originally Posted by a) Alpa FBW Primer
C Star
C* (pronounced "C Star") is the popular name for a control law in which Nz (g) and pitch-rate feedback are blended. (In the late 60s and early 70s, Nz feedback was called the C law. NASA space shuttle approach studies added pitch-rate feedback, which was called C*.) At low speed in a C* airplane, pitch rate is primary;at higher speeds, g is primary. The changeover is transparent and occurs at about 210 knots in the A320 ("Fly-By-Wire for Commercial Aircraft: The Airbus Experience," C. Favre, 1991).
C*U ("U" represents forward velocity in flight equations) is a modified C* control law used in the B-777 to provide apparent speed stability. The trim switches set a reference speed that is summed with the actual speed in the feedback loop in such a way that the pilot feels conventional control force cues as speed changes. You "trim a speed," not the stabilizer (weight off wheels). Because the max trim reference speed is 330 knots, you would have to push on the control wheel to further increase speed toward Vmo. This provides a tactile high-speed cue.
The biggest thing we did not have was the airspeed feedback loop. The Nz and body rates ruled! Only thing dynamic pressure did was provide values for the "gains" that determined how much the control surfaces moved to produce the commanded Nz or roll rate ( gear up). AoA was much more important than speed, and it limited us from about 15 deg to 27 degrees with respect to gee. Figure about 15 degrees at 9 gees and 27 degrees at 1 gee ( draw the line yourself). Gear down blended AoA with the gee command and body rates. Gains were still a function of dynamic pressure. So we had the "feeling" that we were trimming for speed or AoA and not Nz as with gear up. Wasn't a real strong "feel" compared to conventional control systems, but better than a pure body rate or gee command.
Interestingly, if dynamic pressure was lost or deemed unreliable, the system used "standby gains". So gear up was 300 knots or so, and gear down was 180 knots. Simple deal, and landing gear handle switch provided the changeover. The biggest thing was the system used AoA intil the bitter end. The one example I provided was the guy who lost most of the radome due to a bird strike. This included the AoA probes. So he flew for 7 or 8 minutes using nothing but Nz and body rates and standby gains.
I am glad to see that some of our primitive control laws were improved for the Shuttle and later FBW planes.