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Air France pilots told not to fly Airbus jets after Brazil crash
Air France scrambled to replace pressure sensors on its A330 Airbuses yesterday after a pilots union urged crew to boycott the long-range jets because faulty airspeed readings are suspected over last weeks crash off Brazil.To prevent a repeat of this disaster we call on flight deck and cabin crew to refuse flights aboard the A330 and A340 series which have not been modified, said Alter, a union to which 10 per cent of the airlines crew belong. As salvage teams in the Atlantic recovered more of the 228 bodies from Flight 447, Air France and European aviation authorities sought to calm a scare over unreliable pitot tubes the pressure probes that assist in measuring airspeed. Several airlines flying similar aircraft rushed to reassure passengers that they used a different sensor. The first data from the doomed airliner reported a pitot failure and Air France has acknowledged that its jets had suffered several similar incidents. The Airbus went out of control as the electronic flight system failed after receiving conflicting airspeed readings via its three pitot tubes. Pitot tubes have long been prone to blocking by ice, rain and insects. A failure in airspeed indication is a big handicap for a pilot but the aircraft can still be flown by hand with power settings and attitude, the orientation of the aircraft in relation to its flight direction. Air France said that it was upgrading the probes, made by the French company Thales, on each of its 35 long-haul Airbuses but had not done so on the one that crashed on June 1. Last night the SNPL, the main pilots union, said that two out of three pitot tubes had now been replaced on all A330s. Seeking to calm fears, the European Aviation Safety Agency insisted that all A330s were airworthy and capable of flying in complete safety. Airline executives and aviation experts warned against drawing hasty conclusions since the only evidence came from a sequence of 24 messages from the aircrafts final four minutes. Unease over the A330 was strengthened by charges from the Alter pilots union that Air France had covered up problems with the airspeed instruments. It emerged this week that the airline advised pilots on November 6 last year that there had been a significant number of incidents in which false speed readings had upset the automated flight system in the manner that appears to have happened on Flight 447. These incidents, from which the crew were able to recover, occurred at cruising altitude, said the two-page circular. As a result of the false readings apparently caused by ice clogging up the pitot tubes the automatic pilot disconnected. The data from the doomed Airbus last week reported the same sequence, but the pilots were unable to regain control. A parallel is being drawn with an incident last October in which a Qantas A330 dived inexplicably under the command of its flight system, seriously injuring several passengers. James Healy Pratt, a lawyer with Stewart Law, a London firm handling the Qantas incident, said that the sequence of events was the same, with fluctuating airspeed indications apparently causing the auto-pilot to disconnect. Nearly 1,000 aircraft from the A330/340 series of long-haul airliners are in service. None had killed a passenger before. However, pilots and experts focused on what some see as a fatal chain of events that highlights flaws in the highly automated flight system on Airbus airliners. In modern aircraft, particularly the ultra-automated Airbus family, pilots have less direct control. With defective computers in the heart of a tropical storm, the crew of the stricken Air France jet may have lacked the information to keep it flying. The recovery of the aircrafts rudder has strengthened suspicions among some experts that the plane went out of control and broke up as a result of flying either too slowly or too quickly in severe turbulence. Posted by: Steve White 2009-06-10 |
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