Originally Posted by
MechEngr
The flaw I can see is that in a fully automated plane the secondary mode for primary sensor failure should be secondary instruments, which the pilots are supposed to rely on already - a pitch and power schedule. If they are good enough in a black-out instrument only flight for the pilots why would they not be sufficient for the automation? Add in some monitoring of the altitude to close the loop on power and it should do better than the pilots can.
Certainly at some point the ice melted to give reasonable airspeed values and then the descent rate can be combined with it to give an approximate AoA to validate against the AoA sensors; was there some reason Airbus chose not to do this? Instead of WoW perhaps a non-zero descent rate could be the way to validate the AoA?
How would the automation know when the ice had melted though? You can only use automation to back up automation so far.
The design flaw I hinted at was that it’s practically impossible to know what the other pilot is doing until the airplane has responded. By the time the PM found out, their fate had already been sealed.
I haven’t reviewed the report recently, but if I recall, the PM recognised the stall and was the only one to apply forward pressure. By that point, they were below 60kt, and the stall warning sounded again. I’ll pardon him for being thoroughly confused at that point, as I’m sure most of us would be.