The first BEA Interim Report organizes the ACARS messages by "Time of Reception" by Inmarsat. In that sequence, the message AUTO FLT AP OFF is received at 02:10:10. About a minute and a half passes before the PROBE-PITOT 1X2 / 2X3 / 1X3 (9DA),HARD message is received at 02:11:49, with other serious messages (like F/CTL ALTN LAW and AUTO FLT A/THR OFF) arriving in-between. The report notes that "the order in which these messages are transmitted does not necessarily correspond to the associated sequence of events."
The second BEA Interim Report reorganizes the messages based simply on their one-minute time stamp window (see aguadalte's post
http://www.pprune.org/5772547-post1602.html), and the pitot disagreement message stands out as the only "fault" message to occur in that 20:10 window.
While there seems to be a sensible agreement that blocked pitot tubes may have precipitated this upset, I'm wondering if there are other scenarios or sequences that might contain a "ring of truth." Remembering that the PROBE-PITOT message is NOT about ice or blockage but about disagreement:
From 1st report pg55 english
This message, transmitted by the FCDC2 (EFCS2), means that the FCPCs (or PRIMs) triggered one of the speed monitoring processes: they have detected a decrease of more than 30 kt in one second of the “polled” speed value. The three ADRs were considered valid by the EFCS2 at the time the monitoring was triggered, because the prior rejection of an ADR would have generated a class 2 fault message and there would therefore have been an asterisk in front of the source. In this case, the “polled” value is the median value.
By way of revisiting some of the discussion on the earlier thread, is it then possible that the aircraft was upset by really bad (severe turbulence being an inadequate description) up- down- shear forces at 02:10, stalled (easy in the coffin corner), and entered a developed and unrecoverable flat spin. In such a spin, would there not be greater than 30 kt disagreement between port and starbord pitots as the a/c rotated about its CG? Sufficient difference to trigger the PROBE-PITOT ACARS message?
It is important to note that not all aircraft are recoverable from a spin. The vast majority of large aircraft become inertially locked in a developed spin and are unrecoverable without a drag chute or other test-flight spin recovery devices (if recoverable at all)... [
Link]
How would a 205t stalled A330 fall from FL350 to finally enter the water almost flat, in the line of flight? I'd like to see that animation from the Airbus aerodynamics team.
The Flight Path Vector (FLAG ON CAPT PFD FPV and FLAG ON F/O PFD FPV) at 02:11 could have been triggered by the "measured calibrated airspeed lower than 60 kt" criterion.
It's a little difficult to understand why the ACARS message transmit times have been discounted. If the pitot disagreement preceeded the Cavalry Charge (AUTO FLT AP OFF received at 02:10), why was the PROBE PITOT message buffered in the computer (and not sent) for one minute thirty-nine seconds? One would think that if the ACARS messages were
intended to be grouped into unsequenced one-minute packages (as presented by the 2nd BEA Report), the system programmers would have designed a buffer and burst transmit routine... One would also think that sequencing could be inferred from the way the source code is written.
GB