x Abu Dhabi, UAETuesday 25 July 2017

Mystery of the lost Airbus

A flurry of automated messages from a stricken Air France flight spelt out the catastrophe that was taking place in storm clouds above the Atlantic.

Flight 447, bound for Paris Charles de Gaulle, pushed off from the gate at Rio de Janeiro's Galeão International Airport on Sunday night. Scheduled for a 7pm departure, it took off just three minutes late. On board the Airbus A330-200, settling down for their 11-hour non-stop journey, were 216 passengers and 12 crew. The majority of the passengers - 61 - were French, but altogether 32 nationalities were on the flight, including 59 Brazilians, 26 Germans, nine Chinese, five Britons, five Lebanese and two Americans.

Among them was Ana Negra Barrabeig, a 28-year-old Spanish resident of Dubai Marina, who had just spent her honeymoon in Brazil. Four days earlier, she had decided to fly home separately to visit her family in Spain, and changed her flight. She said goodbye to her new husband at the airport and Javier Alvarez, 38, flew home on a flight from Sao Paulo. Joining her on the flight were seven children, including a baby and an 11-year-old British schoolboy, on his way home to England; an American geologist and his wife; shop floor workers and captains of industry; doctors; a dancer and a party of 19 from the same French town - nine members of a company returning from the holiday in Brazil they had won in a sales contest, along with the friends and partners they had taken with them.

Forty-five minutes after take-off, the aircraft, travelling at 453 knots, reached its cruising altitude of 35,000ft and left Brazilian air force radar control. Perhaps drinks and snacks were already being served. Twelve minutes later, says Air France, Flight 447 encountered a "stormy zone with heavy turbulence". This was the Intertropical Convergence Zone, an area notorious with pilots for its turbulent conditions. Later, weather experts told Reuters that the Airbus must have flown through three thunderstorm clusters.

Aircraft bypass such storms whenever possible, but a Lufthansa source said that two of its jets had flown through the same airspace just before and just after the Air France flight, "suggesting that no one thought the weather to be exceptionally bad or dangerous". The last human contact came at about 11pm, when the pilot, Marc Dubois, sent a signal to say the Airbus was flying through "CBs" - towering thunder clouds, laced with strong winds and lightning.

Satellite data later showed the aircraft was flying directly into winds of up to 160km per hour, with equally violent updrafts. Dubois, 58, an Air France veteran of 21 years, was within months of retirement. A "highly experienced pilot, passionate about flying", according to a colleague, he had flown 11,000 hours, 1,700 of them on Airbus aircraft. With him in the cockpit were co-pilots David Robert and Pierre-Cédric Bonin. Bonin's wife, a 38-year-old physics teacher in Bordeaux, was a passenger; the couple's sons, aged four and eight, were at home in France.

Within 10 minutes, the aircraft's automated messaging system began to send an alarming series of transmissions to Air France; the autopilot had disengaged; speed and altitude sensors had failed; the main computer was offline and wing control surfaces were not functioning. At 11.14pm, the system sent its final message: cabin pressure had been lost and complete electrical failure had been suffered. No further human contact was made, and no mayday signal was sent. Either the flight crew had their hands full, or everyone was already dead or incapacitated.

At about the same time, the captain, co-pilot and a passenger on board a Spanish aircraft travelling from Lima to Lisbon, flying far to the north of the Airbus, spotted something disturbing on the horizon. "Suddenly, we saw in the distance a strong and intense flash of white light, which followed a descending and vertical trajectory and which broke up into six segments," the unnamed Air Comet pilot reported to Air France and the Spanish aviation authority.

It was, however, not until 11.40 in Paris the following morning, nearly 30 minutes after the fight failed to arrive on time, that Air France announced that one of its aircraft was missing. At a press conference later on Monday, Pierre-Henri Gourgeon, the chief executive of Air France, said: "We are without a doubt faced with an air disaster. The entire company is thinking of the families and their pain."

Until Wednesday, the Brazilian air force said it was operating on the basis that survivors might still be found. Later that day debris was spotted 685 miles off the coast of Brazil. The first piece to be picked up, however, proved to be a wooden cargo pallet that had not come from the plane. Brig Ramon Borges Cardoso, of the Brazilian air force, said yesterday that "no material from the plane has been recovered", although fuel found in the sea probably did come from it because it was not of a type used in ships.

At a press conference on Wednesday in Brasilia, Nelson Jobim, the Brazilian defence minister, was quick to dismiss speculation that a bomb might have been responsible; the presence of aircraft fuel in the water "could exclude the possibility of a fire or explosion", he said. "If we have oil stains, it means it wasn't burned." Aircrews had seen no sign of bodies, a detail that drew Mr Jobim into a moment of macabre speculation: "As well as bodies sinking, you also have problems along the coast of Pernambuco that you know about," he said. He was referring to sharks.

Later that day, Nicolas Sarkozy, the French president, joined relatives of the victims and Air France staff, many in uniform, at Notre Dame cathedral in Paris for a memorial service for the dead; some held tricolours aloft, adorned with black ribbons; others laid flowers outside the cathedral. A message of condolence from the Pope was read out and the Great Mosque of Paris held prayers in memory of the dead.

It was Wednesday afternoon before the first vessels, two Brazilian warships, reached the area of the crash. Five more ships were heading for the area and a French mini-submarine is due to arrive next week. In the absence of hard evidence, speculation about the cause of the crash mounted. On Thursday the French newspaper Le Monde quoted an anonymous "source close to the crash inquiry" as saying that the aircraft had been flying too slowly for the conditions, and claimed Airbus was about to send out an Accident Information Telex to pilots through the French aviation safety agency, BEA.

"If the BEA is making a recommendation so early, it's because they know very well what happened," Jean Serrat, a retired pilot, told AFP. "The first thing you do when you fly into turbulence is to reduce speed to counter its effects. If you reduce speed too much you stall. If the BEA is reminding pilots not to slow down too much, does that mean that the Rio-Paris slowed down too much?" The BBC said crash investigators had suggested that the plane's speed sensors could have failed or iced over, causing incorrect data to be fed to on-board computers. This might have caused the plane to fly too fast or too slowly through the storm, causing it to stall and fall out of the sky.

A stall, in which the wings lose lift and the aircraft becomes uncontrollable, would be consistent with the sequence of events from the Air France data. A stall at 35,000ft would be hard to recover from in normal conditions and nigh on impossible in the midst of a tropical storm. Some experts said the apparent loss of electrical equipment could be explained by a lightning strike, but on Thursday a British newspaper quoted an anonymous Air France pilot who said he thought a bomb was the most likely explanation for the disaster.

"It is highly likely a bomb went off," he said. "I've flown these jets 10 years. The chances of it being an electrical fault are unfeasible. There are five electricity supplies on board and they would all have to fail." The chances of a sophisticated jet crashing because of a lightning strike, he told the Daily Mirror, were "extremely rare in modern planes". This theory gained weight when it emerged that on May 27, four days before the loss of Flight 447, Air France had received a telephone call warning that there was a bomb on board one of its flights due to leave Buenos Aires that day. The threat was taken seriously; the aircraft was searched with sniffer dogs, but nothing was found and the aircraft left an hour and a half behind schedule.

If not a bomb - and in the absence of any claim of responsibility, only forensic evidence in the wreckage can rule this out - sudden decompression is another possible explanation, but loss of pressure alone should not be enough to destroy a modern aircraft. Each year there are several such incidents, often caused by faulty valves. Standard procedure is for the pilots to don their oxygen masks and descend rapidly to about 8,000ft, a height where the air is breathable and roughly equivalent to the "height" to which the cabins of most aircraft are pressurised.

Even rapid depressurisation caused by a rupture of the aircraft's body need not be fatal; on July 25, 2008, Qantas flight QF30, a Boeing 747-700, suffered just such an incident en route from Hong Kong to Melbourne, but managed to land safely in Manila, where a large hole in the fuselage was found. An exploding oxygen cylinder was blamed. The best chance of finding conclusive answers lies in the aircraft's flight data recorder and the cockpit voice recorder, the so-called "black box" carried by all aircraft. Recovering these is a race against time; the devices are equipped with "pingers", which issue homing signals once a second, but they will operate for only 30 days.

At almost 4km deep, on an ocean bed described by French accident investigators as "very mountainous", the wreckage will lie way beyond the reach of conventional submarines and recovery will be a serious challenge even to unmanned submersibles. "There is a good chance that the recorder would survive but the main problem would be finding it," Derek Clarke, joint managing director of Aberdeen-based specialists Divex, told Reuters. If the estimated location of the wreckage was correct, it lay at the same depth as the Titanic.

"If you think how long it took to find the Titanic and that the debris would be smaller, you are looking for a needle in haystack." Whatever the difficulties, there is a precedent for success. In 1987 the Helderberg, a South African Airways Boeing 747 flying from Hong Kong, crashed in the Indian Ocean after a fire broke out, killing all 159 on board. The wreckage came to rest at an even greater depth: 4.4km. It took two months to find the mass of the aircraft, and even longer to locate one of its recorders, using submersible photography and sonars towed at the end of 9km cables.

The first clues are always found in the wreckage strewn on the sea, which is why it is vital to reach the scene with surface vessels before items sink or are dispersed by winds and waves. It was just such a clue - a poignant, unexpected find - that helped searchers to find the Helderberg. In a paper about the hunt for the aircraft, the man who planned the operation - at the time, the deepest ocean recovery mission to date - reported that early in the search a purse containing three watches had been found floating on the surface. One was still running, at the correct Hong Kong time, while the other two had suffered impact damage and had stopped at the same time.

"This indicated that the aircraft had impacted some four minutes after the time of the last reported position," wrote Dr Johan P Strümpfer. "This left the aircraft speed as the only remaining major uncertainty before one could solve the location of the impact." jgornall@thenational.ae