Originally Posted by
DaveReidUK
A bit more digging reveals that it's a little more complicated than that. The AOA DISAGREE annunciation worked as intended on the aircraft of operators who had opted for the PFD AoA indicator (a notable example being American Airlines), but was non-functional on aircraft without that option (i.e. most other airlines' aircraft).
That's what I said. It was incorrectly tied to the optional indicator package, so only operated if you had the extra package. It was supposed to be active w/o the package. Simple configuration mistake, probably in the build stage. I don't know how Boeing controls the options. Different software builds would be my guess, but it could be controlled by something similar to a license file. But deactivated code is a pain to certify. Much easier to do build options so the code just doesn't get included.