Their different positioning could be the explanation

Measure of precaution, or will cut short the controversy While several pilot unions threatened to call their members not to fly on Airbus A330 and A340, Air France reported yesterday that all of the probes speed Pitot, implicated in the crash of AF447 Rio-Paris flight, will be replaced within a period of ten days. All A330 and A340 have already received two new probes on three. Dysfunction of these small tubes, used to measure the external air pressure to determine the speed of the aircraft, could be one of the causes of the disaster.

Last Saturday, Air France had already tried to calm the fears, announcing the acceleration of the program of change of these probes, launched a few weeks before the tragedy, following several incidents. But Monday, the minority pilots Alter Union had accentuated the pressure publicly recommending flight staff no longer take orders for an Airbus A330s or A340s, "did not at least two probes Pitot" modified. Evening, branch presented to the representatives of the drivers, gathered in Inter-Union, an expedited Ulf probes modified schedule.

Since two or three days, voices were the company to claim the decision of the exploitation of unmodified devices, the principle of precaution. On some Internet forums, Air France drivers give up even their fear of a new accident, looking to play their right of withdrawal. As their trade unions, without wishing to publicly display their doubts, because of their duty of reserve and for the sake of the image of the company, they had claimed as early as last week the modification of all Airbus. Although relatively quick and simple to perform, the replacement of the impugned probes, manufactured by the French manufacturer Thales, however appeared to face a problem of supply. The decision was only made to accelerate their renewal.

33 incidents

If the causes of the disaster remain unexplained until continues the investigation of the BEA, the most likely hypothesis indeed remains a dysfunction of these probes, which could have obstructed by ice or water, in the transition from the apparatus in a cumulonimbus cloud. Alert messages sent by the A330 just before his disappearance indicated because of inconsistencies in the speed indications provided by the central navigation, on the basis of data collected by these probes, which would have caused the failure of flight control systems. This kind of failure, although rare, was known for Airbus and Air France and has happened on several occasions, fortunately without serious consequence. According to some unconfirmed accounts, Pitot tubes would be involved in at least 33 incidents on the world fleet and Air France 7, including a serious enough in May 2008 to convince the company to initiate a study with Airbus on their amendment. In 2001 already, the Directorate General of civil aviation had requested the replacement of a model of probe apparently defective, made at the time by the American Goodrich. In September 2007, Airbus had also recommended the amendment of another model of probe on aircraft of the A320 family, more exposed to the risk of icing due to their mode of operation. But not for the long haul, supposedly from the ice at their cruising altitude. More than 10,000 metres above sea level, the lack of moisture theoretically prevents the formation of frost, except to spend in a cumulonimbus cloud. According to Air France, is that in the first quarter of 2009, that tests conducted wind tunnel on versions of modified probes show a "significant improvement" to the problem of icing. On 27 April, Air France then enters the progressive modification of its long-haul Airbus. But the Rio A330 was part of the not yet modified devices. Where "real risk" invoked by Alter and other unions, for their amendment.

Other companies should do the same. This is the case of US Airways, which announced as early as Monday began its 9 aircraft modification. The French company Air Caribbean, which serves the West Indies in A330 would already have the necessary. In total, not less than 50 companies around the world and some 300 A330-340 are potentially affected. In contrast, Boeing, who use the same Pitot system, yet appear to be spared by this problem. Their different positioning could be the explanation.