Ladies and Gentlemen,
According to some of the data that Air France maintenance received in the last 4 minutes of AF447, I believe that the first ECAM that the crew may have received was NAV ADR Disagree. This would have been a level 2 warning. This particular ECAM warning would have had serious implications and would have been followed by a series of warnings.
When you have a NAV ADR Disagree, the ECAM action will ask you to check your airspeed and if it is erroneous then you should proceed with the ADR Check Procedure. But more ECAM warnings will now follow.
The next ECAM should have been Flt CTRL Alternate Law (Prot Lost). This would have been picked up by one of the Prims and the result of this now is that the Autopilot will disconnect. With the disconnection of the autopilot the priority of the ECAM will place Auto Flight AP OFF at the top and in red. Note that that the ACARS sent back Rudder Travel Limiter Fault, well this is one of the inop systems in the Alternate Law which follows the ADR Disagree.
If this was the sequence that the ECAM presented itself to the crew, the situation would have been very confusing and even for the most experienced of Airbus Pilots it would be difficult to handle correctly.
Assuming that this was the sequence, the Auto pilot was now disconnected and not recoverable at this time. Applying the ECAM action correctly is critical. After the auto pilot is cleared from the ECAM the next would be the NAV ADR disagree. But you would now have to check to see which ADR or ADRS are causing the problem. Remember the ECAM does not tell you Unreliable Airspeed so if there is a discrepancy then the next thing to apply is the memory item for unreliable airspeed.
AP/FD OFF
Auto Thr OFF
They were in level flight so the rest of the items need not be mentioned. Next would be to check what the GPS is showing as speed and altitude. Now you can proceed with the ADR Check procedure.
With the Alternate Law situation which resulted in the NAV ADR Disagree, Alternate Law is latched and resetting the Prims will not change the aircraft back to Normal Law.
Did ice cause this? Let us look at a case which only happend a year ago to QR somewhere in Asia. Airbus was well aware of a phenomenon of supercooled water droplets which exists in CBs and in areas around the CBs. These supercooled water droplets can adhere to an airframe/engine even at temperatures below -40C. QR suffered a dual engine flameout as a result of this. And Airbus has now mapped out particular areas of the world where this phenomenon is known to occur. It lies along the ITCZ, Sri Lanka and near the Philipines. Heavy icing is known to exist in these parts of the world.
The action of the crew with the erroneous airspeed is the most important thing that everyone needs to know. In the memory items the auto thrust would have been OFF and now the real speed of the aircraft would increase and be well beyond the turbulence penetration speed of .80. The MMO is .86 and the MD would be at .90. Did the crew set the correct N1 on the engines as indicated in the unreliable airspeed tables? Did they retard the thrust and stall when they were in Alternate Law? There are too many variables here to pinpoint exactly what occurred. But I do believe that Airbus is now on the right track.