Originally Posted by
Machinbird
Dozy, have you considered that the one size fits all roll direct control gain became more appropriate as the aircraft decelerated?
It's possible, but given the situation I'm inclined to give the PF the benefit of the doubt and think that he was indeed bringing the roll under control.
As for startlement effects, the initial strong control input that started the roll PIO could have been from startlement ... it was an unfortunate response to a situation that merely required minimal control inputs.
Or no control inputs at all! The A330 is a very stable platform - and whatever one may think of Learmount, I'm inclined to agree with his opinion that with no further inputs the aircraft would have simply ridden out the turbulence as best it could, and after 30 or 40 seconds the ice would have melted from the pitot tubes and the speed indicators come back online.
I'm basing my "startle effect" call on previous similar incidents where pilots made an erroneous initial call on the problem (in some cases because the warning systems were giving misleading signals). Those incidents are Birgenair 301, ColganAir, NWA6231 and West Caribbean 708. In the Birgenair case, the Captain as PF seemed to fixate on the first warning he received, which was an erroneous overspeed. In the case of West Caribbean, the Captain thought he was dealing with a dual engine flameout. In both of those cases, the F/Os correctly diagnosed a stall and inappropriate attitude, but the Captain did not respond.
The other reason I suspect the AF447 pitch input to have been inadvertent is because the two F/Os had been discussing not being able to exceed their present altitude for safety reasons only a few minutes before. At AP disconnect they had well over 30,000ft to play with and they knew that to climb would increase risk. To initiate a climb would therefore be completely illogical, and I suspect this is (at least in part) why the PNF was initially so incredulous as to what seemed to be happening.
Originally Posted by
gums
I also go with 'bird that the "startle factor" should not have been the primary cause of later control inputs. There was even a call about "alternate" law early on, wasn't there?
There was an "Alternate Law" call from the PNF to which the PF did not respond - we therefore don't even know if he heard it (which - if he didn't - to my mind supports the "startle" theory)
BTW, I can't seem to find when the pitot system came back on line. If it did, did the input to the FLCS have to be enabled by the crew?
You can see the speeds coming back online in the DFDR traces at about 02:10:35 - at that point the aircraft is established in the climb at around 37,000ft.
No, there was no need for the crew to perform an action to bring them back online.
Originally Posted by
Machinbird
A number of Airbus pilots have remarked in the past that it would have taken a lot of work to make the lateral control inputs that were made due to the viscous damper in the lateral channel.
Did they? Must confess I don't remember so well. As far as I know the primary damping mechanism in the sidestick is actually spring-driven, and the simulator version I had a chance to get to grips with was actually very responsive and not too difficult to deflect once you had it going. The springs do centre the SS, and there is a small degree of 'breakout' force, but once deflected it offers enough resistance to let you know it's deflected, but not enough to cause physical issues.