Originally Posted by
Recidivist
I understand - what I was thinking of was not the complexities of flight as the pilot sees them, but purely focussing on the automation aspect - why allow an automatic system to operate the airplane when AoA and pitch gyro are indicating different things? Sure, it's possible both are correct, but the pilots are there to make those decisions. Why allow the automation to continue to pitch down when the altimeter is showing accelerating loss of height? A pilot may indeed do this to recover from a stall, but surely it would be rare to rely on autopilot to get you out of a stall?
I gather there are situations where the pilots are presented with a message that indications disagree, and the automatics effectively hand the matter over to the pilot - I'm just exploring why that isn't the case when to continue with the automatics could result in catastrophe.
Edit: Replying to predictorM9
For the AoA sensor and the pitch angle, these are not the same and so they disagree in general (the difference between the two is the angle of climb or descent, which is not always zero).
Even if you have an accelerating loss of height, you can not know if you are out of the stall or not, so the automation relies only on the measurement of the angle of attack to determine that. They don't reconciliate the data from all sensors to check what sensor is ok and what sensor is faulty, the logic to do that would be a bit complex and probably not certifiable.