ACARS Messages on AP reconnect
Having worked on fault detection/management on Avionics sub-systems I find difficult to comprehend how there could be such a sudden 'burst' of ACARS messages, 15 (or more) of them, in a minute, from diverse sub-systems. Such a sudden burst suggests that some messages would have been generated by different sub-systems at the same time. There may not have been time for the pilot to reconnect the AP before all of these other warnings came up on his screens; the AP would probably have been the least of his worries!
Considering that the pitots are all in the same environment (and located in the same area!), it is quite possible that two (or all 3) pitots iced up in a similar fashion. However, I would not expect them to ice-up in synch. Instead, I would expect that one pitot would provide 'bad' data before the other and the degradation (warnings from other sub-systems) to be a more gradual process. As a comparison, the data derived from QF72 FDR (Table 3 in www.atsb.gov.au/publications/investigation_reports/2008/aair/ao-2008-070.aspx) shows:-
1. The first event at 04:40:28 as AP1 disconnect
2. Some other warnings that perhaps resulted in a few (a lot less than 15, I would think) ACARS messages over the next minute.
3. Another minute before the first pitch down event occurred
4. Nearly another 3 minutes (04:45:11) before Flight Control went to Alternate Law
This is in a situation where 9 parameters from ADIRU 1 were recorded in the FDR as having “spikes”, with one (AoA) having a recorded 42 “spikes”, with probably other spikes not recorded.
In comparison on AF447, only a single sensor/parameter is seen as being the prime suspect in supplying 'bad' data, but the Flight Control Alternate Law Warning was just two messages later, probably occurring somewhere between 0 and 12 seconds after the first event (also AP disconnect). Is it really possible that pitot icing could have caused such 'instant chaos'?