The last minutes of Air France flight 447: what the box tells us

 

Two years after an Air France jet crashed into the Atlantic, killing everyone on board, including three Irish doctors, the ocean has begun to give up its secrets with the recovery of the aircraft’s flight recorders, writes RUADHÁN Mac CORMAIC, Paris Correspondent

PLANES DON’T just fall out of the sky. And yet, for the past two years, as search teams painstakingly trawled the icy depths of the Atlantic looking for clues that might solve one of the most baffling mysteries of modern aviation, that was the sum of our understanding of what happened to Air France flight 447.

How did a state-of-the-art aircraft manned by some of the best-trained pilots in the world suddenly crash into the ocean on June 1st, 2009, without reporting a technical problem or issuing a Mayday call, killing all 228 people on board? It’s a question that has confounded experts, but as the victims’ relatives, including the families of three Irish women who lost their lives while returning from a holiday in Brazil, marked the second anniversary of the disaster this week, they did so knowing for the first time that the mystery is beginning to unravel.

Thanks to a series of breakthroughs in the past two months, search teams in the choppy seas off the Brazilian coast were this week lifting 75 bodies nearly 4km from the seabed to the surface. Meanwhile, in a nondescript office building near Le Bourget airport, on the northern outskirts of Paris, investigators were listening to the voices of the three pilots in those final moments, poring over the aircraft’s data readings and cross-checking them against a haul of debris stored in a nearby warehouse. The ocean has begun to give up its secrets, but only after one of the most complex, extensive and frustrating search-and-salvage operations ever mounted.

After three unsuccessful searches over an 18-month period, experts considered it unlikely that the wreckage of flight 447 would be found. At a cost of €20 million and spread over an area with a radius of 80km, each successive search, involving a French nuclear submarine and two ships equipped with US navy listening devices, drew a blank.

But with Air France and Airbus, the aircraft’s manufacturer, facing possible manslaughter charges over the crash, there was a legal and financial, as well as humanitarian, impetus to keep scouring the seabed.

And so it was that the search boat Alucia, operated by specialists from the Woods Hole Oceanographic Institution in Massachusetts, set off for a fourth attempt in late March. Using three robot submarines similar to those used to find the remains of Titanicin 1985, the search team in the end needed less than two weeks to find traces of the aircraft. The discovery came as the oceanographers were looking over photographs taken by the unmanned submarines one day in early April. What they saw, to their surprise, were large parts of the fuselage and landing gear, human bodies – some still belted into their airline seats – and, later, the two bright-orange boxes containing voice recordings from the cockpit and data read-outs.

The French government initiated a €5 million recovery operation, and, as of yesterday, 77 bodies had been lifted to the surface from a depth of 3,900m. Their retrieval brings the total number found since the crash to 127, including 50 who were pulled from the sea in the days after the crash.

The body of one of the Irish victims, Jane Deasy, a 27-year-old doctor from Rathgar in Dublin, was recovered during the original search operation. Dr Aisling Butler (26) of Roscrea, Co Tipperary, and Dr Eithne Walls (28) from Ballygowan, Co Down, also died in the crash.

French police have not released information about the condition of the remains. The first two bodies recovered from the wreckage had been reasonably well preserved in the dark, cold depths of the ocean but suffered some damage as they were raised from the seabed. Investigators were working this week to identify the victims through DNA analysis.

Within a week of the main wreckage site being identified, the search team found both black boxes intact. The chips inside these boxes are designed to withstand extreme conditions, but given that recorders had never been salvaged after such a long period underwater, investigators at the Bureau d’Enquêtes et d’Analyses, France’s air-crash investigation authority, were relieved in mid-May to find that their contents had been fully preserved.

The authority says an interim report outlining early conclusions from its analysis of the recordings will be issued next month, but in its initial factual observations last week it revealed that the crew scrambled to avert disaster as the jet lost speed just a few hours into the flight, before it stalled and began a 3½-minute descent, belly-first, to the ocean surface.

The four-page report is written in spare, technical prose but sketches a chilling picture of a rapidly unfolding disaster and hints at the confusion that gripped the cockpit as the plane began its descent.

THE AIRBUS took off from Galeão airport in Rio de Janeiro just before 10.30pm on May 31st last year with a flight crew of three: captain Marc Dubois, a 58-year-old veteran pilot who had flown nearly 11,000 hours; 37-year-old David Robert, a copilot with more than 6,500 hours of flight experience; and Pierre-Cédric Bonin, the 32-year-old second copilot, who had less than 3,000 hours of experience.

According to the investigation authority, the first three-and-a-half hours of the flight passed smoothly. At 2.06am, 10 minutes after the captain had gone to the rest area for some sleep, a standard procedure for a long flight, the copilots noted they were approaching rough air. The Airbus A330 was cruising on autopilot at 10,700m and was passing over an area known as the intertropical convergence zone, close to the equator, where tall thunderstorms produce icy, windy conditions that create frequent turbulence.

One of the copilots called the cabin crew to tell them that “in two minutes we should enter an area where it’ll move about a bit more than at the moment: you should watch out”, adding: “I’ll call you back as soon as we’re out of it.” Some had speculated over the past two years that the pilots may have flown recklessly into the storm, but the black boxes show that they followed standard procedure by steering away from the worst area.

At 2.08am, the computers controlling the aircraft switched off the autothrust and autopilot and handed back to the pilots after becoming confused by conflicting speed readings. “I have the controls,” said one of the pilots as he took the control stick and pointed the nose upwards. The cause of these inconsistent readings is unclear, but it is suspected that the speed-sensing probes, or pitot tubes, that monitor the aircraft’s velocity had iced up.

Almost immediately, a stall warning sounded in the cockpit, followed by another, signalling the aerodynamics were not generating enough lift and that flight 447 was in danger of losing control, although its twin engines were working normally.

Eleven seconds after the autopilot quit, one of the pilots said, “So, we’ve lost the speeds,” meaning, presumably, the displays in front of him. They called for the captain to return.

Meanwhile, the black boxes show, the aircraft was slowing down. The pilot at the controls continued to point the aircraft’s nose up, and it ascended to 11,500m, but then a third stall warning sounded, this one lasting for about a minute.

By 2.11am, with the captain back in the cockpit, the plane was quickly losing momentum and rolling left and right. It had fallen by about 900m. Its nose was pointing upwards from the airstream at more than 40 degrees. The engines were responding to commands and continued to do so, but the crew struggled to regain lift. The plane kept falling.

Since the French air-crash investigation authority published its report last week, specialists have debated its implications and tried to draw tentative lessons for the industry. Much of the discussion has centred on why experienced pilots broke a fundamental rule of flying by continuing to raise the nose, even as the aircraft was plummeting, instead of pointing it down to gain essential speed. Raising the nose of a plane can slow it to a stall, a condition in which, as one observer noted, an aircraft acquires the aerodynamic characteristics of a brick.

Although getting out of a stall is part of standard pilot training, coping with the challenge amid bad weather, darkness and a multitude of automated alarm signals may have overwhelmed the flight crew.

“It’s easy enough in a simulator,” said Henri Marnet-Cornus, a former Air Force fighter pilot and flight captain at Air France on Airbus A330 and A340 jets. “But in reality, when you’re in the middle of a storm, shaken by turbulence, with airspeed warnings and a whole series of other alarms going off, it’s not a safe condition.”

One possibility is that the pilots simply made the wrong call. Another is that, because of the incorrect speed readings on the cockpit display, the crew believed the plane was flying too fast and was in danger of breaching the “coffin corner”: the aerodynamic window that keeps a plane flying at cruise altitude.

In setting out the chronology of events on board flight 447, the report from France’s air-crash investigation bureau offers only hints of the atmosphere in the cockpit in those final minutes. It’s not clear from the report whether the passengers were aware of the unfolding disaster, but given that the aircraft held a consistent pattern and that it was passing through a turbulent zone, experts said, the descent may not have been apparent.

At 2.12am, one of the pilots said, “I don’t have any more indications.” Then the second voice was heard: “We have no valid indications.” Just over a minute later, with the plane now rocking and falling fast, the pilot noted the speed of the descent, saying, “We’re going to arrive at level one hundred,” meaning 3,000m. At about the same time, the data recorder shows, the control sticks of both seats were being used simultaneously, suggesting the pilots were frantically trying to avert disaster.

The aircraft remained stalled throughout its three-and-a-half minute descent, with the last recorded measurement showing it falling at more than 3,300m per minute.

At 2.14am, the recordings stopped.

The Air France jet's final minutes

10.29pmAir France 447 to Paris takes off from Rio de Janeiro Galeao airport.

1.35amFlight crew makes scheduled call to Brazilian air-traffic control, advising of its location and progress. 2.06am Cockpit warns flight attendants to expect turbulence in two minutes. 2.08am Crew steers plane around stormy area.

2.10amAutopilot disengages. “I have the controls,” says one pilot, then points jet’s nose upwards. A stall warning sounds twice.

2.10amPilot calls for captain to return from his rest break. A third stall warning sounds. Pilot keeps pointing nose up and increases engine thrust.

2.11amCaptain returns. Jet falls at 3,000m a minute.

2.12am“I don’t have any more indications,” says one pilot. Thrust reduced to idle.

2.13amPilot says plane has reached 3,000m – a fall of more than 7,600m in five minutes. Both pilots try to control the aircraft.

2.20amThe time by which AF447 was supposed to reach the Brazil-Senegal airspace boundary passes with no communication from the plane. Controllers in 10 flight-information regions, including Dakar, Casablanca, Lisbon and Madrid, try to determine the aircraft’s position.

7.41amAir France and Brest air-traffic control contact France’s air-accident investigation authority.

8.15amMadrid issues an emergency alert. Then Brest launches a distress signal. Search and rescue begins.