BEA (Bureau d’Enquete Aviation) maintain these units will reveal their secrets after 2 years at the bottom of the Atlantic ocean. At a depth of 4000 metres the condition of these boxes is remarkably good. Thoeries abound concerning the cause of the crash, where all hands dieds. Initially the cause was focussed on the pitot heads that collect the ram air and compress it through pipes to provide an electronic equivalent signal that drives airspeed indicators and supply many other computers that use the airspeed and altitude signals to attenuate outputs to autopilot, flight directors, flap computers, mach speed indicators, pressurisation, air conditioning and many other systems including download parameters for ATC. The theory is the pitot heads froze up and delivered spurious signals to all these systems. They are picked up on a pulsed basis by ATC downloads. However due to the pulse sequencing the airliner was already lost by the time the signals were monitored on ground. My own theory is the cause of the aircraft loss of contol occured before the spurious signals were transmitted. The most common manufacturer of pitot haeds worldwide is Rosemount in USA. They are generically caled Rosemount probes so common is the term. Many world airlines and aircraft have Rosemount probes installed without problems. They have internal heating elements prevent icing and on many aircraft have double elements with both AC and DC supplies. The A330 have 4 pitot heads to ensure redundancy capabilites and balanced airspeed signals in turns. The possibility of all 4 probes losing heating capabilities is extremely remote. The operating airline changed all pitot probes on all their fleet aircraft following the aircraft loss.
It is generally accepted the aircraft flew into severe turbulance precipitating the loss of control. This could be a fault of the weather radar as a theory is the Wx radar revealed an area of condensed precipitation, the aircraft avoided this but apparently the displayed picture on the screen masked a region of severe turbulance which the aircraft flew into. this in itself is difficult to understand as there was other air traffic in the area that avoided this turbulance.
Another theory is the aircraft fuselage was damaged on the ground in Rio by a service vehicle (catering, cleaning, fuel truck) that went unreported. When the aircraft pressurised the possibility is the weakened fuselage failed catastrophically. If this happened it was instantly and without warning thereby resulting in the passengers unprepared in how the recovered bodies were found.
ATC in Brazilian airspace is notoriously bad. It will be interesting to see if the ATC service are culpable. The TCAS will reveal if there was other traffic (manned or unmanned) involved!
On verra.
