New elements
More details of the ACARS messages have become available on June 5th and suggest following events while the airplane was in cruise (note, there is no message regarding electrics, hydraulics or engine problems):
02:10Z: Autothrust off
Autopilot off
FBW alternate law
Rudder Travel Limiter Fault
TCAS fault due to antenna fault
Flight Envelope Computation warning
All pitot static ports lost
02:11Z: Failure of all three ADIRUs
Failure of gyros of ISIS (attitude information lost)
02:12Z: ADIRUs Air Data disagree
02:13Z: Flight Management, Guidance and Envelope Computer fault
PRIM 1 fault
SEC 1 fault
02:14Z: Cabin Pressure Controller fault (cabin vertical speed)
There have been at least two similiar incidents preceding AF-447 (dates of both flights are unknown):
First incident: An Air France Airbus A340-300, registration F-GLZL performing flight AF-279 from Tokyo Narita (Japan) to Paris Charles de Gaulle (France), was enroute at FL310, when the airplane went through a line of thunderstorms. The captain's air speed indication suddenly dropped to 140 knots, the systems issued an alert regarding disagreeing speeds (NAV IAS DISCREPANCY), the navigation display showed a tail wind component of 250 knots. The captain released control of the airplane to the first officer and tried to switch his display from ADIRU1 to ADIRU3. 2 minutes later autopilot and autothrust disconnected and the fly by wire changed into alternate law. The crew noticed icing conditions (static air temperature [SAT] -29 degrees Centigrade) and switched anti ice including pitot heating systems from automatic to on. The speed indications became normal again and agreed again, the autoflight systems were reengaged and ATC informed of severe icing. ATC reported, that two flights had just passed the location without problems. When the crew attempted to reset and reengage ADIRU 1 two times, the system again brought the message "NAV IAS DISCREPANCY" on both attempts, although the speed data appeared consistent. The crew suspected polluted pitot tubes.
Maintenance found, that the drainage holes of all three pitot tubes had been clogged, rendering it very likely that weather combined with the clogged drainage holes caused the incident. Maintenance had reported more clogged drainage holes on A330 and A340 aircraft in the past to Airbus Industries. Airbus Industries was aware of the problems, changes had already been introduced to the pitot tubes on the A320 family, where similiar problems had occured. A modification of the A330/A340 pitot tubes was already planned by AI.
Second incident: An Air France Airbus A340-300, registration F-GLZN performing a flight from Paris Charles de Gaulle (France) to New York JFK,NY (USA), encountered brief turbulence while enroute. The autoflight systems dropped offline, "NAV IAS DISCREPANCY", "NAV PRED W/S DET FAULT" and stall alerts were repeatedly issued during the following two minutes. The airplane continued to JFK without further incident. A review of the policy of retrofitting pitot tubes was recommended and authorities informed.