It is over three months since Air France Flight 447 crashed into the Atlantic off Brazil. They have not found the flight recorders but the elements are falling into place. It became clear this week that Air France, the Airbus corporation and the BEA, the French state accident investigators, would like to blame the crew for the crash of the A330 Airbus, which had 228 souls aboard.Pilots are angry over what they say is an attempt to make them scapegoats for a failing in the Airbus design. Families of the victims are also accusing the authorities of obfuscation. A lot is at stake. I have been talking to Air France pilots. Gérard Arnoux, an Airbus A320 captain with the company, told me: "They are trying to blame the pilots. They do not want the truth." Arnoux is active in the Union of Air France Pilots (SPAF), a militant offshoot from the company's branch of the mainstream National Union of Airline Pilots (SNPL)
Thanks to data transmitted in the final minutes, we know the outline of what happened to AF447 as it cruised through a storm en route from Rio to Paris. The sequence began with the pitot tubes, the sensors on the outside of the plane which measure the pressure of the oncoming air, thus the plane's airspeed. The pitots failed on AF447, probably because of ice. The flawed speed data upset the electronic flight system, leaving the pilots to hand fly the plane with partially automated controls. They were unable to keep control and the plane dropped at high speed from cruising altitude, hitting the ocean in upright attitude and in one piece, according to evidence from the wreckage.
The argument centres on the question of whether the pilots should have been able to control the handicapped plane. A series of similar -- but apparently less severe -- pitot failures have hit Airbuses over the past decade, it has emerged (Since the crash, the European and US aviation authorities have ordered new pitot tubes on all long-haul Airbuses). In the previous incidents, which did not last long, the crew recovered their planes. A system failure of this type in a storm at cruising altitude would leave the crew with tiny margin to manoeuvre. In this so-called 'coffin corner', a few dozen knots too slow and the plane stalls. A few dozen knots too fast and it will overspeed and dive.
The accident investigators and Airbus say the crew should have been able to recover the plane. Paul-Louis Arslanian, chief investigator, said the pitot failure was a "factor but not the cause" of the crash. Last Monday, he suggested that Air France had not sufficiently trained its pilots in how to handle high-altitude malfunctions of this sort.
On Friday, Thomas Enders, the CEO of Airbus, told le Parisien newspaper: "The pitot probes may have been a factor in explaining the crash. They were not the principal reason." Air France is trying to finger its its pilots, according to Christophe Guillot-Noel, who heads an association of AF447 victims' families. Pierre-Henri Gourgeon, the airline boss, has told them that faulty decision-making is suspected, said Guillot-Noel, whose brother was killed in the crash.
Interestingly, Air France has just started giving special simulator training to all its Airbus crew to teach them how to handle high altitude failures in speed data. Pilots told me that they had never previously been given hands-on instruction in this field. "No appropriate safety manoeuvre exists to cope with this very dangerous situation in the coffin corner and no training was given to Air France pilots in the simulator," Captain Arnoux has just told me by e-mail. All the evidence points to the big Airbus entering a flat spin -- a pilot's absolute nightmare. The crew would have been unable to recover because the computer, having switched to so-called "alternate law", would have prevented them from deflecting the rudder enough to halt the turns, said Arnoux.
"Airbus, as well as the BEA, have obvious interests in minimizing the pitot faults as they have not demonstrated a proactive attitude since the very serious incidents which occurred on the Airbus fleet since the late 1990s," he said.
There are other points of view. James Healy-Pratt of Stewarts Law, the London firm which is representing victims' families, tells me that they have just carried out trials on a simulator and found that the pilots recovered the Airbus each time they tried. The only failure was when the pilot at the simulator controls did not realise that there was a flaw in the speed readings. Simulators cannot recreate the full violence of heavy turbulence of the kind suffered by AF447, he noted. Healy-Pratt, who is a pilot as well as lawyer, also says that questions have to be asked about the crew's failure to divert around the storm and their skills at interpreting their weather radar. Air France will face a bill of some 450 million dollars for the disaster, his firm estimates.
Without the black box recorders, no firm conclusion may ever be reached. They are about to to start a third search of the mountainous ocean floor off northeast Brazil. Airbus is contributing several million euros to the effort. Arslanian likens the task to hunting for a shoe-box at night in Switzerland using a single flash light.
One result of the disaster has been a push to replace onboard flight recorders, invented over 40 years ago, with real-time data links. Enders said Airbus is working on a system to transmit key parameters, as well as video from the cockpit, via satellite, rather than storing the data in metal boxes that can be lost at the bottom of the ocean. My Air France friend said the pilots have no objection to this "provided this data cannot be used against crew handling of the aircraft in any way and be used for disciplinary reasons."
― Elvis Telecom, Sunday, 6 September 2009 04:06 (fourteen years ago) link