The mystery of Air France Flight 447, the Airbus A330 that crashed into the Atlantic Ocean on June 1, 2009, may soon be solved. After a two-year, multi-million-dollar search, the plane's two "black boxes" have been discovered and brought to the surface. The flight data recorder, which archives measurements like altitude and airspeed from the plane's instruments, was recovered Sunday. Then, on Monday, the cockpit voice recorder was raised from the water.
The flight data recorder, in a photo provided by the BEA. Photo: Johann PESCHEL/BEA/ECPAD
NOVA reconstructed the doomed flight's final moments in Crash of Flight 447, which premiered in February. Combing weather data, radio transmissions, wreckage analysis, and flight simulations, our experts pieced together a scenario in which Flight 447 unknowingly flew into a 250-mile-wide thunderstorm. That storm may have been carrying droplets of super-cooled water that froze on contact with the plane's speed-sensing pitot tubes, producing faulty airspeed data that set off a cascade of failures and ultimately caused the plane to stall out and, when the pilots could not regain control, crash. But without the black boxes, we could never know whether this scenario was absolutely true, or very plausible historical fiction.
We went back to some of the experts who helped us reconstruct the conditions of the crash to get their views on what the discovery of the black boxes means--and whether we will finally be able to close the book on this mystery.
"I must say that the recovery of both the FDR (Flight Data Recorder) and CVR (Cockpit Voice Recorder) memories in the AF447 circumstances is a great achievement," said Tony Cable, a former investigator with the UK Air Accidents Investigation Branch. The task took a lot of tenacity and "a fair element of luck."
"Standard procedure after recovering a recorder from underwater is to store and transport it while immersed in fresh water, in order to minimize corrosion and salt crystal and mud deposition," said Cable. Once stabilized, the recorders will be transported aboard a French Navy ship to Paris for analysis. The journey will take a little over a week.
From there, an initial readout from the devices, which amounts to "replaying the flight" from takeoff to landing, should be available with 24 hours, said Captain John Cox, a veteran pilot now working as an air safety consultant. Captain Martin Alder, an Airbus training pilot, said that the recorder data can be replayed graphically, "not unlike watching Microsoft Flight Sim in the external view." Experts from Airbus, Air France, and France's investigation agency, the BEA, will work in two teams to pore through the data from each memory device. A complete analysis of the thousands of parameters archived by the flight data recorder will take several weeks.
Of course, added Alder, "It all depends on the data retrieved being usable or accessible." The flight data recorder was separated from its protective housing, causing some to question whether its data would be readable. "I'm very hopeful that there will be usable data in both recorders," said Cox, based on BEA photos which show the condition of the devices. The recorder data are stored on digital chips designed to survive immersion in deep water. "I have been pretty surprised at the impact and overheat abuse that memory chips will put up with and remain viable," said Cable.
If the data can't immediately be retrieved from the recorders, though, there is still hope: The manufacturer of the recorders may be able to remove the chips and take data from them chip by chip, explained Cox. Data might even be recoverable from corroded chips, said Cable: "If corrosion were to sever the very fine connectors within chips, it would probably be possible to make repairs; albeit a very delicate and time consuming process."
Investigators will likely be particularly interested in airspeed measurements archived on the flight data recorder. "I remain convinced that the ACARS [Aircraft Communications Addressing and Reporting System] messages clearly show that there was a loss of reliable airspeed to the crew and to aircraft systems," said Cable. "As this is arguably the most vital single parameter for both, I find the accident unsurprising, even if the exact way in which control was lost is unknown." But, our aviation safety experts emphasized, there is no single "missing piece" that will put this puzzle together. "The whole package--every bit of evidence--matters," said Cox. And as Cable pointed out, other flights have survived similar malfunctions--why not Flight 447? The recorder data may reveal the other factors that made Flight 447 different.
"As I said on the show," said Cox, "Aviation does not do well with unsolved mysteries."