Gee sensing deux
Thanks a33Z, shows a variation of design philosophy as well as implementation.
Our FLCS ( flight control system) folks were paranoid about using anything but their own data/sensors. Their data was shared by other systems, but if it came down to "us or them", then "them" had to do their own thing. Although we had the best system flying, autopilot inputs were not even treated with the same respect as pilot stick inputs. Very limited AP capabilities, which surprised many of us.
Our attitude display came from the nav inertial system, and we could fly without the inertial even turned on. HAL didn't care, as he had Nz and body rates of his own.
The deal with rate and accel sensing for the FLCS is you want the displayed attitude and such in the cockpit to be independent of the FLCS system. It is very easy and more redundant/reliable to have gee/rate sensors for each FLCS conmputer, and let the ADIRU equivalent be displayed and used for the autopilot inputs. In our case, we had four confusers - one in "standby", and the middle value of the other three for commanding the servo-actuators. If it got down to two, then the most benign value was used.
Not all sensor inputs were quad reduntant. AoA was supplied by two cones and an aero probe with all kindsa holes in it ( hemispherical probe). Q and static pressure was also dual, but FLCS had priority and other stuff got the leftovers. However, the system had the "standby gains" feature in case the air data was deemed unreliable or simply went to lala land. IMHO, this feature should have been incorporated in the 'bus FLCS. Easy and very safe. Stick might be more sensitive if at a very high "q", but would also be less sensitive below the chosen "stby gain" value. Wioth gear down, values were reduced to typical approach "q" values.
sorry for design philosophy, but the final report may get into this aspect of the Airbus implementation.