Originally Posted by
Ranger One
Yes, absolutely. But I think the question GY was asking, and I know the question I was asking, related to the interaction between IAS data and the stall warning being disabled below 60kts.
If you have unreliable data (sources disagree more than trivially) or NO data (all pitots stuffed) I would hope the system is smart enough NOT to inhibit the stall warning, irrespective of the (erroneous) IAS!
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Note that the BEA report states the indicated airspeeds in the initial problem "fell to 60kt". It appears that the control system does this so that any protection that may be disabled if <60kt are not. Is it correct that this speed is so far below that required for flight this isn't mentioned in any manuals?
At least 2 out of 3 speeds recovered before the actual stall, and assuming they stayed in synchrony it is quite likely they reported a valid Indicated airspeed below 60kt at high angles of attack/ sideslip. Pitot tubes are designed to be work without significant error over at least +/- 20 degrees AoA, but they do roll off sharply above +/25 degree, and if the nonlinearity is based on the amount of air directly impinging cos (60 degrees)=0.5