Au Sud?
So Seabed Worker has been stood-down, and is en-route north-eastwards to the Cape Verde islands. Dommage! How disappointing for everyone concerned. The BEA is quoted as saying that AF447 was never (to be found) "to the south". I wonder. Ignoring human influence, one would indeed expect the flight to continue roughly in the original direction. But the aeroplane was already about 3nm left of track at its last-known position, and that is unlikely to have been due to a position-error in the FMC.
Assuming the deviation at that instant was the result of crew intervention, there are many possible scenarios, perhaps the least likely being a deliberate track offset of 3nm to reduce the risk of colliding with opposite-direction traffic as they approached the Dakar UIR boundary. Most crews would choose to fly right of track. It is more likely that they had either been avoiding wx for about five minutes (might even have been regaining track); and/or they were just starting to make a turn to avoid a cell recently identified on wx radar, or perhaps to negotiate a passage they had identified between clusters of cells. Finally, they might have been caught unprepared, suddenly encountering precipitation/St-Elmo's-fire/lightning-strike/moderate-to-severe-turbulence.
Perhaps it is not inappropriate, at this pause in the search, to remind ourselves of some of what this crew was up against in the next minute or so. What we do know is that, whatever they were doing, they would have been aware of that fairly rare event in the cruise, an AP disconnect − even if they did it themselves (unlikely). It's a familiar but noisy one, with a suitably-loud audio-warning, aptly called the cavalry charge; quickly cancelled by pressing the AP disconnect button on either sidestick.
Zeroing our stopwatch at AP disconnect, here are the known problems during the next 71 seconds:
T+06 − ECAM warning of windshear-detection fault. Master Caution (i.e., amber W/L illuminates) plus single chime. ECAM drill (when time permits), but not in itself a worry.
T+13 − ECAM warning that flight-controls (FBW) have degraded to Alternate Law, with most flight-envelope protections lost (attitude displays annotated with amber crosses). Master Caution + single chime. ECAM drill (urgent). Sinister event, but normal control straightforward.
[By this time, it is likely that the crew would be aware of ASI anomalies, probably indicating serious loss of airspeed. Descent may be under way.]
T+19 − Speed Limit flag appears on captain's ASI, confirming loss of underspeed and overspeed protections, and removing certain (valuable) reference-speed annotations.
T+31 − Ditto on F/O's ASI.
T+37 − ECAM warning of A/THR failure. Master Caution + single chime. ECAM drill. If descending steeply at this stage, throttles can be closed to ensure idle thrust.
T+44 − ECAM warning of TCAS fault. Master Caution + single chime. ECAM drill (when time permits). Irrelevant.
T+50 − Flag on captain's FD. Flight Director has failed. Realistically, he cannot be using it.
T+65 − Ditto on F/O's FD.
T+71 − ECAM warning of rudder-travel-limiter fault. Master Caution + single chime + Systems Display switches to the F/CTL page. ECAM drill... Use rudder with care. Who would be using rudder in this situation?
Would the handling pilot have continued straight ahead into this developing hell, or tried to turn the aeroplane away from it? Could he have turned as much as, say, 180 degrees?
Chris
PS: mm43, why would the aeroplane be stalled early-on, when the ASIs were UNDER-reading?