Originally Posted by
Lyman
Whether or not the a/c was reporting it, we are only sure of the crew's cognizance at 2:10:16. That is eleven seconds to be in the dark as to what is wrong.
Loss of Autopilot does NOT mean fly "PITCH AND POWER". It means fly...
It also means "don't pull up". The correct response was to observe and then correct as necessary.
You continue to studiedly ignore what RR and myself, among others, have pointed out, that the a/c was not clearly indicating that UAS was the problem, and that the computers did not necessarily include the crew from the outset of suspected duff speeds.
Even with RR_NDB's DSP algorithm, it would take time to work it out. Whether the system reported UAS or not is not the issue, the issue is and has always been the tendency to pull up when startled
The reference is to what the a/c displayed, RESULTS of bad data.
The PNF had a handle on things at approx 02:10:15 though - as I've said before this flatly contradicts the idea that the aircraft was providing confusing information. I don't believe the PF pulled up because he believed in the protections, nor because he was unaware that UAS was the problem - he did it because he freaked out under pressure.
Question. If the a/c had ceased displaying IAS from the outset of suspected bad speeds, would not the pilots have had obvious cue of loss of Airspeed (literally)
An instant appraisal cannot be done - even RR_NDB's hypothesis would still take a few seconds in order to work reliably. There's nothing to indicate that the PF's pitch inputs were an attempt to regulate airspeed - except for the response to the PNF's "Watch your speed" comment, which could have been taken from groundspeed. At that point, the PF actually briefly put the nose down, but then pulled it up again within a few seconds.
Displaying any cue that is known to be false is counter to good design, if said cue can be left out.with impunity.
Detecting UAS is difficult, and the Airbus system is more conservative than most, disconnecting AP at the onset of the potential problem. Compare this to the Birgenair B757 where the autopilot continued to try to fly on the bad data.
Why waste precious time in a situation that is easily remedied with Pitch and Power?
In this case, it looks like the startle effect took precedence.
The fact that pilot started handling the a/c demonstrates his belief it needed handling, period, speeds or not.
But it doesn't mean his belief was correct. The right thing to do was to monitor the aircraft's attitude and correct *only if* the attitude started to creep towards abnormal.