Yesterday, the French agency BEA, which investigates airplane accidents, released its final report on the fall of Air France 447 in June 2009. After three years of analysis and millions of dollars to recover the plane's black boxes from the South Atlantic Ocean, which I covered for the New York Times last year, what is striking about the final report is how many questions it raises, rather than answers.
At the heart of the final report is the suggestion that pilots should have averted the crash. Though the report acknowledges mechanical failures on the plane, its emphasis falls on the decision by pilots, after the plane was already plunging toward the ocean, to point the plane's nose up and not down. To be sure, that decision is widely rejected by other pilots, who explain that pointing the nose down might have restored lift to the wings and saved Flight 447. But to focus on how pilots reacted to the falling airplane distracts from the question of why it was falling at all.
The fact remains that the crash began with a mechanical failure. In the minutes before the pilots lost control, the plane's speed sensors, which are known as pitot tubes, became covered with ice and stopped working. Those sensors are essential for pilots to stay within the narrow window of speed that is necessary to stay aloft. When the sensors fail, as they did on Flight 447, it is easy for a pilot to misjudge speed, and slip into an aerodynamic stall. This is precisely what happened on Flight 447.
What's troubling about the sensor failure is that it might easily have been avoided. The sensors on Flight 447 were a model known as the Thales AA, which were widely known to be faulty. In fact, they were subject to numerous "service bulletins" from the plane's manufacturer, Airbus, which recommended that airlines replace the Thales AA with a different model. The first of those warnings came in September 2007; over the next year and a half, other airlines followed the advice, removing the sensors from service, and at least one airline CEO, after a few close calls, filed a report with European regulators to launch an investigation.
Yet for most of that time, Air France maintained a policy to keep the Thales AA on its A330 aircraft, and to replace them "only when a failure occurred." Failure was considered most likely in the Inter-Tropical Convergence Zone, where Flight 447 eventually went down. A few weeks before the crash, Air France changed its policy, and began making efforts to replace the faulty sensors on planes like Flight 447; five days before the crash, the first batch of replacement sensors arrived at an Air France warehouse, but by the time Flight 447 took off, none of them had been installed. By then, nineteen months had passed since the first "service bulletin" to replace the faulty sensors.
Had Air France complied with the earlier bulletins, the statistical likelihood of a sensor failure on Flight 447 would be dramatically lower. Given that the airline did not follow the service bulletins, the BEA's focus on how pilots should have reacted may still be useful. Pilots should be as prepared for a crisis as possible, and perhaps the pilots of Flight 447 were not as well-prepared as they could be. But a comparison is useful: When the driver of a tractor trailer is cruising down the highway and his brakes suddenly go out, you don't begin by asking how he should have rescued the runaway truck. You begin asking questions about the brakes. Unfortunately, the question of why the faulty speed sensors on Flight 447 were never replaced is largely overlooked in the BEA report.
For years, the BEA has been viewed with some skepticism by air crash investigators in other countries. The French government owns a substantial share of both Air France and Airbus, totaling more than $4 billion, and many experts believe it is questionable for a government to investigate a company it owns. When I reported on the fall of Flight 447 for the Times last year, I spoke with Peter Goelz, a former managing director at the National Transportation Safety Board, who told me, "There's always been a sniff of politics at the BEA." Goelz recalled another Air France crash, involving a Concorde which burst into flames just after takeoff in Paris in 2000. After a four-year investigation of that incident, the BEA concluded that the explosion was not caused by any flaw in the French airplane, but by a thin strip of metal that fell onto the tarmac earlier in the day from a Continental Airlines flight. "There was never any question that somebody else was going to be pointed out as the blame," Goelz said. "And Continental became it.''
One hopes that the BEA's emphasis on pilot error does not distract from other important questions about the faulty parts on Flight 447.