The spotlight in the AF447 crash investigation has been applied to the three pitot tubes on the outside of the A330-200 which were being replaced world wide because of a history of faults.
The tubes generate air speed data, and it has already been revealed that the pilots of the jet were getting incorrect or ‘disparate’ speed indications while flying the jet with the autopilot disconnected through severe turbulence.
Blockage of at least one of these pitot tubes by ice had been mentioned to the media in France by sources in the airline on 4 June but it is not clear if this had been deduced from the automatic ACARS service messages being received at the operations base in Paris up to last contact with the jet at 2.14 am GMT on 1 June or from something a pilot said during radio calls made around half an hour earlier.
Air France says it had not yet complied with the year old Airbus recommendation to replace the tubes as the work was not the subject of an urgent airworthiness directive.
The airline says the pitot replacement program will be completed ‘in coming weeks’ and would have included the jet that crashed waiting its turn.
In earlier reports it was revealed that faulty speed data was suspected of causing the jet to fly too slowly or too fast in the violent weather conditions, in turn leading to either a stall at high altitude or causing air frame damage that would have quickly spread and lead to loss of control and break up.
Blocked pitot tubes were blamed for two Boeing 757 disasters in 1996.
On 6 February 1996 all 189 people on board a Birgenair flight died when it crashed into the Atlantic shortly after taking off from Puerto Plata in the Dominican Republic.
The investigation found that incorrect data from the blocked tubes fooled the control system on the Boeing into generating false and conflicting warnings and readings to the pilots.
The most likely culprit was an infestation of wasps inside the tubes of the jet which had been parked for 25 days at the airport, which was experiencing a wasp plague.
On 2 October 1996 a similar accident killed all 70 people aboard an Aeroperu 757 when it crashed into the Pacific Ocean after departing Lima.
Masking tape had been left in place over its pitot tubes during aircraft cleaning. The crew were attempting to return to Lima in darkness using airport radar readings of its airspeed, altitude and direction when they skimmed into the water, and attempted to regain altitude, only to have the jet turn upside down and hit the sea for the second and last time.
Sunday updates. Several bodies have been found on the surface of the sea in the crash zone as well as Air France cabin fittings and travel papers. If the bodies have worked free from wreckage on the sea floor the chances of finding the ‘black box’ flight recorders in the immediate vicinity will have been improved.
Qantas has been asked if it is carrying out the pitot replacement recommendation and for the status of any program to that effect. Answers pending.
