3 ms·

> The AoA invalidation logic ("mark AoA measurements as invalid if airspeed is less than 60kt") made the stall warning turn off as the stall became even deeper,

> The AoA invalidation logic ("mark AoA measurements as invalid if airspeed is less than 60kt") made the stall warning turn off as the stall became even deeper, making diagnosis of the stall more complicated. Worse, the BEA report states that the appropriate (nose down) control input led to the stall warning reactivating (since such an input would increase airspeed above the 60kt threshold -- inherent to a proper stall recovery), leading the pilot flying to reverse their control inputs and return the aircraft into a worse stall This sounds extremely confusing indeed. Having this kind of inconsistencies under high pressure is something that would need a really experienced and steel-nerve person to handle.

zkms 9y ago
> This sounds extremely confusing indeed. Having this kind of inconsistencies under high pressure is something that would need a really experienced and steel-nerve person to handle. It's made even more confusing by the fact that the usual/sensical pilot approach to guesstimating AoA in an aircraft with a stall warning that is boolean (can only be sounding or quiet, nothing else) is to see where its threshold is. When you're right on the threshold (modulo some hysteresis) where the horn turns on and off, that's your stall angle, and pulling the stick back makes it stall more, pushing it forwards recovers from the stall. Flipping the sense/polarity of the stall horn's semantics -- the effect of the 60kt invalidation threshold -- certainly contributed to making the upset recovery harder and more confusing. In an aircraft that has multiple AoA sensors, I (and the BEA concurs) maintain that it is pointlessly cruel and baroque to make the humans try to guess what the AoA value is. AoA is no obscure technical parameter of interest only to avionics engineers, it's amongst the most crucial instrument readings, and it should be presented to pilots right next to their airspeed and attitude indicators.

zkms 9y ago

> This sounds extremely confusing indeed. Having this kind of inconsistencies under high pressure is something that would need a really experienced and steel-nerve person to handle. It's made even more confusing by the fact that the usual/sensical pilot approach to guesstimating AoA in an aircraft with a stall warning that is boolean (can only be sounding or quiet, nothing else) is to see where its threshold is. When you're right on the threshold (modulo some hysteresis) where the horn turns on and off, that's your stall angle, and pulling the stick back makes it stall more, pushing it forwards recovers from the stall. Flipping the sense/polarity of the stall horn's semantics -- the effect of the 60kt invalidation threshold -- certainly contributed to making the upset recovery harder and more confusing. In an aircraft that has multiple AoA sensors, I (and the BEA concurs) maintain that it is pointlessly cruel and baroque to make the humans try to guess what the AoA value is. AoA is no obscure technical parameter of interest only to avionics engineers, it's amongst the most crucial instrument readings, and it should be presented to pilots right next to their airspeed and attitude indicators.