Originally Posted by
WhyByFlier
What if all ADRs give the same wrong indication after the pitots have been left covered from maintainance or hitting a flock of birds? Then the system assumes all are correct, incorrectly.
OK - if the pitot tube covers have been left on by maintenance then you won't see the airspeed come "alive" during takeoff roll, which to the best of my knowledge results in a mandatory RTO/"STOP". The same should apply if any one of the airspeed indicators disagree on the roll.
The odds of a birdstrike blocking all three pitot tubes simultaneously and with the same density is infinitessimally small, and in any case you'd notice a very definite change in the reading - even in the case of AF447 there was enough time gap inbetween the three pitot tubes clogging for the systems to detect UAS DISAGREE and drop to Alternate Law. Remember the systems are checking and cross-checking tens or hundreds of times per second.
Originally Posted by
vilas
a software expert like you
Heh. I do (a much simpler kind of) Software Engineering for a living - I wouldn't call myself an expert by any means!
but in a dynamic environment it is very difficult to decide how much is too much or too little.
That's why they spent tens of thousands of hours flight-testing the systems and tweaking them in the years before the A320 was put into service!
Since every one is not a software expert it leaves certain areas which are not well understood or for that matter cannot be completely understood which gives rise to fear resulting in suspicion of the systems and lack of faith. That is what I see in numerous posts.
Understood, but the truth is that pilots have been reliant on engineering calculations since the days of the Wright Brothers, and the systems were growing in complexity continuously as aircraft started going higher and faster. The FBW systems were just the latest iteration of that trend.