Originally Posted by
Winnerhofer
NCD? What is it?
No
Computed
Data - i.e. the value is invalid and cannot be used for further processing.
Originally Posted by
Peter H
IIRC it shut off the stall warning horn until the measurements recovered.
That was a secondary consequence (or "side effect" in engineering-speak) of the systems design as a whole. The SW ceased because it was no longer receiving valid data from upstream - there was no design intent to "shut off" the SW directly.
Shutting off the stall warning cannot have helped the pilots understanding of the situation.
Undoubtedly.
IIRC the stall warning came back on again just after somebody had tried nose-down, a combination of events which could be considered positively misleading.
Yes - but we've got to remember that what we're talking about with AF447 is a scenario which would have previously been considered a massive outlier on the probability curve. Namely that the crew would deliberately put the aircraft into a stall condition, hold it there through almost a minute of stall warning and continue to pull up until the airflow over the sensors rendered the information nonsensical.
We've been over this many times in earlier threads, and the fact is that if you latch stall warning for one scenario, it runs the risk of giving false information in several other scenarios. It's a very difficult system to make completely failsafe across the board - and as I repeated above, the silence from other airframers does tend to suggest that their systems would have behaved in a similar manner.
(And as an aside - a pilot with any basic knowledge of aerodynamics should be able to work out that a SW triggered by a nose-down input means something hinky is going on...)