Originally Posted by
turbidus
I understand how they did this, as it is easier to compare one FCC to another as the AOA vanes are wired one right and one left. What concerns me is this seems like reducing redundancy in some ways, as now you have lost the redundancy of 2 independent FCC's. There must be a whole Fton of cascading scenarios by tying the 2 together.
Doesnt it seem much more difficult to trace a fault through 2 FCC's? Comparing 3 versus 2 seems like far better redundancy and error trapping. Still the same with comparing 2, which one do you pick?
If all the design does is compare two sources without anything independent for verification, you shouldn’t pick one. Functionality should require agreement between the two, otherwise shut it down. While triplex architecture compares three and disregards the outlier, there have been cases where the outlier was most correct. It’s called having a bad day. And when it happens there’s typically a common cause or condition that made the two wrong. Not a high probability, but it has happened with air data sensors. One reason that it’s useful to have independent and dissimilar system(s) to verify.