Good morning Bear,
I do believe one has to look at the two minutes before AP/AT disconnect and at the moment there is no information from time of 2 h 08 min 07 and 2 h 10 min 05. The speed was reduced to about Mach 0.80 and the turn to the left was initiated at the start of this time period. Although the BEA never specifically has said the pitots became clogged with ice crystals (nor should they at this stage of the investigation), it is apparent they are strongly looking at this as the starting point of the total event. I also think the clogging was not one where in one-second the pitots were clear and then poof, in another second they were clogged. It probably happened on a gradual but ever increasing basis over these couple of minutes or so.
Speed
So as the pitots began to clog, the sensed airspeed by the computers began to go down. Now I can't imagine the computers observing this degrade in speed sat there and did nothing, but perhaps Takata can provide the computer reasoning and logic in this situation while in AP/AT. I would think they would signal the engines to spool-up and increase the speed to maintain level flight the AP was attempting to do at that time. Unfortunately, the sensed speed degrade was wrong and the aircraft was gaining speed it didn't probably require in level flight. I would assume that when the AT dropped and thrust lock occurred, the thrust was locked at a higher N1 setting than perhaps the PF thought it was at?
Pitch
I am not going to comment on this aspect as to what the computers were doing or not doing. But rather, some questions about an observation I noted in reading the reports regarding aircraft balance. In the very first BEA Interim Report, dated June 1, 2009, at the time of the beginning of the incident, the aircraft weight was estimated and reported at 205 t and an aft balance between 37.3% & 37.8%, controlled within 0.5% of MAC. The second BEA Interim Report mentioned nothing in this respect.
However, in the BEA Update, dated May 27, 2011, The weight of the aircraft was again reported at around 205 t, but the balance was changed to 29%, or in other words moved forward 8% or so. I thought the aft balance (37.3% - 37.8% reduced drag and improved overall efficiency.
So my questions are: How did this happen? Why did this change happen? Does this have any effect on maintaining pitch either by the automatics or in a manual fly mode?
Just curious...