Quote:
Originally Posted by
MurphyWasRight 
It is important to remember that the AoA miscompare alert
was not an option.
It is a
standard feature that Boeing knew was not working unless the optional AoA display was installed.
Boeing knew this for a significant amount of time -before- the Lion Air accident.
Had it been working on the penultimate Lion Air flight it might have led to fixing AoA sensor system before the accident flight.
Originally Posted by
Peter H
Does this indicate that the MAX maintenance procedures failed to detect that this "standard" feature wasn't working?
Working from memory, since I don't have time to track original posts at the moment, I believe this was reported by Southwest and possibly others.
I don't think we know if this was discovered by Boeing testing before it was reported, possible it was missed since it does work if the optional AoA display is pressent.
It was deemed non critical and was scheduled to be fixed in a standard SW upgrade cycle.
It would actually be a bit unusual to notice that a disagree warning was not working unless there was a case where an AoA failure happened (bird strike/whatever) and someone noticed the lack of warning. A human factors factor is that it is usually harder to notice something missing than an an unexpected occurrence.
Since it is implemented in software I doubt it would be a line item in a maintenance check unlike the old days when a similar alarm might have relays and light bulbs in the mix there would be nothing specific to the AoA disagree alarm that could fail. With a big 'assuming' it worked at all of course.