The most persistent and worrying mystery in commercial aviation might—just might—be very near to being solved. After two years and four searches, a team has found one of two flight recorders from Air France Flight 447, which disappeared over the South Atlantic on June 1, 2009, with 228 people aboard.
Now the question is: Will the data stored in the recorder be recoverable after so long at a depth of nearly 13,000 feet on the ocean floor?
The answer will be of immense importance. For as long as this crash remains unexplained it shadows the reputation of the airplane involved, the Airbus A330-200, one of the most ubiquitous airliners in the world.
Until French experts examine the recorder in Paris, the survival of the data is debatable—there is no previous experience of a similar challenge to its survivability. It's even possible that if data are retrieved, it will not definitively explain what happened in the final minutes of Flight 447. Crucial pieces from the wreck will also need to be recovered to show exactly what made the Airbus fall out of the sky—literally, after a sudden and catastrophic failure.
Nonetheless it is a remarkable achievement to have located the wreck. Some good luck was involved. Parts of the ocean bed in the area are like a mountain range, with ravines as deep as 20,000 feet. The remains of the Airbus were found scattered over a flat and sandy area with visibility good enough for thousands of photographs to be taken.
The crash has been bedeviled not by a total lack of clues, but by the existence of just enough clues to fuel several theories of what happened.
Technology used in the search was provided by the Woods Hole Oceanographic Institute in Massachusetts. It involves two types of unmanned deep-water vehicles, a torpedo-shaped robot called the Remus 6000 with sensors and sonar scanners, used to locate and photograph the wreck, and a Remora 6000 fitted with arms that can pick up pieces—it was this machine that retrieved the recorders.
All along, the crash has been bedeviled not by a total lack of clues, but by the existence of just enough clues to fuel several theories of what happened. At the center of these clues were 24 fault messages transmitted during the last minutes of the flight via satellite to the Air France base in Paris.
These transmissions were not part of a system intended to explain a crash. They were routine reports monitoring the condition of the airplane's systems and controls. In this case, pieced together, they described a terrifying sequence in which the automated flight controls shut themselves down without any evidence of the pilots being able to intervene.
We do know that Flight 447, flying from Rio de Janeiro to Paris, had reached an area where a massive and violent storm raged at high altitude, towering above the cruise height of 36,000 feet. There were two other flights immediately behind Flight 447, the closest only 12 minutes behind, and both diverted from their assigned route to avoid the worst part of the storm.
Aviation has long ago passed the point at which a storm—any storm—should bring down an airliner. Prudent pilots avoid them when they can, not simply for safety reasons, but to give us a smoother flight. Experts have been reluctant to accept that an A330 could be fatally stricken by a storm alone. There have to be other reasons.
In this case, suspicion fell on an instrument called a pitot tube that measures the speed at which the airplane is flying. Specifically, that ice produced in the storm could cause the instrument to send false readings to the automated flight controls, which, in turn, would adjust for the assumed speed and put the jet in jeopardy before the pilots realized what was happening.
After the disappearance of Flight 447, it emerged that there had been more than 50 instances in which A330 flight crews had faced control problems related to pitot tubes, and French investigators reported 13 "significant events" involving five airlines operating A330s and A340s (the A340 has four engines, the A330 two, but otherwise the airplanes are virtually identical).
Hopefully, the scope for speculation is nearly over and a combination of data from the flight recorder and physical evidence from the wreck will conclusively explain the tragedy.
Without waiting for that evidence, the mystery of Flight 447 has already left lessons needing action. The first is that it took a long time—far too long—for the air-traffic control system between Brazil and Africa to realize that a flight was missing. That system has been tightened up.
Second, airliners that routinely cross large areas of ocean that are not covered by radar should have a new generation of flight recorders that can continually transmit a complete picture of the performance of all systems via satellite. French investigators have recommended taking this step—but it could take years to achieve, given the sclerotic nature of regulatory bodies.