Air France Flight 447′s flight recordings show the aircraft slowed to a stall after its airspeed sensors failed while the two co-pilots were at the controls, two people with knowledge of the investigation said.
According to the sources, who declined to be identified, the confidential report revealed the chief pilot, Captain Marc Dubois, was not in the cockpit when the Airbus A330′s sensors malfunctioned, causing the autopilot to disengage over the Atlantic Ocean.
A low-speed stall occurs when an aircraft slows to the point where its wings suddenly lose lift, an incident pilots are trained to overcome. Flight 447′s last automated transmissions logged faulty readings from airspeed sensors that caused the autopilot to shut down in bad weather, minutes before the June 1, 2009, accident in which all 228 passengers and crew perished.
“To get out of a stall, you stick the nose down and wait for gravity to speed up the aircraft,” said David Learmount, a former UK Royal Air Force pilot and safety editor at Flight International. Pulling out of a stall can be straightforward, “providing you realise you’re in one,” he said.
Air France spokesman Jean-Charles Trehan said the company had no comment on the investigation’s early findings. France’s BEA air-accident investigation bureau, which also declined to comment, said it plans to issue a factual statement May 27 on its preliminary findings.
The cockpit voice recorder as it was found back in early May
The cause of the crash is still unknown, but a report in German newspaper Der Spiegel suggests that a combination of human and technical errors may be to blame.
Nelson Marinho, who represents families of the Brazilian crash victims, said the group would wait for more information before commenting on the plane’s apparent stall.
“We’re rather concerned about this rush to blame the pilots,” Marinho said in an interview. “They are dead and cannot defend themselves.”
Investigators say they are making progress after maritime search and salvage experts retrieved the flight data and cockpit voice recorders this month from a depth of 3,900 metres (12,800 feet). Dubois was among the victims recovered from the sea surface in the weeks after the crash.
The failure of the Thales SA airspeed sensors, or Pitot tubes, occurred while the plane was cruising at about 35,000 feet, four hours after takeoff from Rio de Janeiro. At that stage in the Paris-bound flight, it is routine practice for the captain to take a rest break and leave the co-pilots at the controls, Air France has said.
The last minutes of Flight AF 447, based on the information that was available in February 2010
The Airbus A330 has a small sleeping compartment where pilots can recline on long-haul flights.
“All members of the flight crew have the same technical skills and qualifications,” France’s SNPL pilot union said in a statement. It criticised what it described as “deliberately selective reports that cast suspicion on the crew.”
Airbus declined to comment beyond a BEA-approved May 16 telex, in which the company told airlines that preliminary black- box analysis yielded no additional recommendations. Two months after the crash, Airbus advised A330 and A340 operators to replace the Thales sensors with a model from Goodrich.
A stall is typically preceded by shaking and vibrating of the aircraft, and modern jets are equipped with a steering-stick shaker and audio warning to alert the pilot. Stall recovery requires pilots to coordinate the aircraft’s angle and power to the engines to avoid aggravating the situation.
Geoffrey Salter
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The accident was caused by the co-pilot induced stalled glide condition and remained in that condition until impact. To recover from stall is to set engine to idle to reduce nose up side effect and try full nose down input. If no success roll the aircraft to above 60° bank angle and rudder input to lower the nose in a steep engaged turn. Pilots lack of familiarity and training along with system malfunction contributed to this terrible accident. Also the following contributed to the accident
(1)the absence of proper immediate actions to correct the stalled glide
(2) Insufficient and inappropriate situation awareness disabling the co-pilots and the captain to become aware of what was happening regarding the performance and behaviour of the aircraft
(3)lack of effective communication between the co-pilots and the captain which limited the decision making processes, the ability to choose appropriate alternatives and establish priorities in the actions to counter the stalled glide
During most of its long descent into the Atlantic Ocean, Airbus A330-203 was in a stalled glide. Far from a deep stall, this seems to have been a conventional stall in which the Airbus A330-203 displayed exemplary behavior. The aircraft responded to roll inputs, maintained the commanded pitch attitude, and neither departed nor spun. The only thing the Airbus A330-203 failed to do well was to make clear to its cockpit crew what was going on.Its pitch attitude was about 15 degrees nose up and its flight path was around 25 degrees downward, giving an angle of attack of 35 degrees or more. Its vertical speed was about 100 knots, and its true airspeed was about 250 knots. It remained in this unusual attitude not because it could not recover, but because the co-pilots did not comprehend in darkness, the actual attitude of the aircraft. The co-pilots held the nose up. If the co-pilots had pushed the stick forward, held it there, and manually retrimmed the stabilizer, the airplane would have recovered from the stall and flown normally.
Air France complained that the copilots did not have enough time to analyze the situation. Gravitational stalled glide does not allow timeouts, to thoroughly discuss the situation to find out what went wrong. The co-pilots – 37 year old David Robert and 32 year old Pierre-Cédric Bonin missed the cardinal rule that first they must fly the airplane, and after start analyzing the situation, since a falling airplane is not going to wait for them. If they did not understand the instruments, then instead of pondering on it they should have come to the quick conclusion that they did not understand those instruments, and apply the unreliable airspeed procedure clearly prescribed for that situation, which is a blind, given thrust and pitch setting for the given configuration, and let the airplane fly itself, and only after get to analyzing what went wrong, and by the time they finished, the root-cause (pitot icing) would have probably cured itself. It was the safe solution to the problem, but not applied.
The Airbus A330 performed exactly as it was designed and described when the stall warning cut out at the end of valid values, except the co-pilots did not know it. Unfortunately, it happens too often with catastrophic results that pilots are not familiar with the systems of their own airplane, such as in the case of American Airlines 587 over Queens, which was clearly the airline’s fault.
Air France also argued that the stall warning system in the A330 is too “confusing”. Every modern airplane is quite a confusing piece of machinery. It is full of buttons, levers, all kinds of red, yellow, green lights with buzzers, and a host of other indicators and controls inside, which can look very confusing indeed, but it is the pilot’s duty to reign on them, or not to be pilot.
Airbus A330-203 is a new generation, highly automated piece of equipment with drastically simplified controls, displays, and instrumentation compared to older models. Still, pilots with the same human capabilities as the ones on Air France flight 447 could very well stay in full control in those planes, and many times acted heroically saving situations much graver than where the plight of Air France flight 447 started, such as United Airlines flight UA232 at Sioux City, or Air Canada flight AC143, the Gimli Glider. If those pilots could perform well in those older, much more complicated aircraft in tougher situations, then there is no excuse for the co-pilots of AF flight 447 to be confused in a generally much simpler and easier-to-fly aircraft.
The Airbus A320 is a digital fly-by-wire aircraft as the flight control surfaces are moved by electrical and hydraulic actuators controlled by a digital computer. The computer interprets pilot commands via input from a side-stick, making adjustments on its own to keep the plane stable and on course, which is particularly useful after engine failure by allowing the pilots to concentrate on engine restart and landing planning. Some say the Airbus A330 is a “video-game” airplane due to its side-stick control, which does not match up in real hard situations. But who can say that after the successful ditching of US Airways flight 1549 on the Hudson River? It was an Airbus A320 with the same side-stick control, and it matched up with the hardest situation very well with an experienced 57 year old Captain Chesley Sullenberger at the command. The Airbus A330 is not a video-game airplane, it is the airlines that make it a video-game by cutting corners, taking advantage of its superior automated capabilities thinking that it flies by itself, and no training and no knowledge of even the basics of the principles of flying is required in them for their pilots, as was demonstrated by the co-pilots of flight 447, who seemed to be incapable to react even on a basic level to the phenomenon of the aerodynamic stall. The co-pilots had not applied the unreliable airspeed procedure. The co-pilots apparently did not notice that the plane had reached its maximum permissible altitude. The co-pilots did not read out the available data like vertical velocity, altitude, etc. The stall warning sounded continuously for 54 seconds. The absence of any training, at high altitude, in manual airplane handling and in the procedure for ”Vol avec IAS douteuse” (Flight with questionable Indicated Airspeed) caused this terrible accident. Evidently, it might not be what Airbus had on its mind designing the aircraft. They might have meant the best of the both, an airplane with superior controls, matched with seasoned pilots with superior education in the principles of flying and the handling of hard situations, best of the best, as airlines are prone to boast of their flying personnel, to represent quality improvement in flying safety by this pairing. Now, if this piece of equipment falls in the hands of the airlines who use it as a video game to save training costs, telling only their pilots that “if the red light on the right side blinks, just pull the stick back as hard as you can, and let the system do the rest”, they can get away with it as long as everything is normal, the airplane is good enough for that, but in unforeseeable situations, such as the flight 447 en-route to Paris on that night, without any independent knowledge of flying in general, the video-gaming with the aircraft may ultimately come to a fatal end.
However, beyond the reasoning and explanations there is still some eeriness about the crash, taking in consideration that Air France flight 447′s pilots just sat there in daze squeezing the control stick, barely being able to do more than commenting on how the airplane was falling out of the sky until crashing into the Atlantic Ocean, the arrival of the 58-year-old flight captain Marc Dubois in the cockpit not making much a difference either. The question might arise whether weren’t the pilots in a mentally incapacitating state of shock and disbelief? Whether do or can Air France test pilots of how well they can keep their mental stability under the duress of a catastrophic situation? None of it seems to be the fault of the Airbus A330, which needs only good, trained pilots to give superior performance for the good of the flying public. Very similarly 3 decades ago Captain Madan Kukar’s mistaken perception of the Air India Flight 855 situation resulted in causing the Boeing 747-237 to rapidly lose altitude and the airplane hit the Arabian Sea at 35 degree nose-down angle.
Practicing recovery from “Loss of Control” situations and improve flight crew training for high altitude stalls (simulator training usually has low altitude stalls which are significantly different due to energy status of the aircraft) should become the mandatory part of recurrent training.