Is there, at last, a smoking gun to explain what went wrong on Air France Flight 447 during the early hours of June 1 last year?
Nothing is more important to the safety of international air travel than finding the answer to a disaster that cost the lives of 228 people. There have already been two expensive efforts to scour the ocean bed of the South Atlantic since the Airbus A330 disappeared. A third operation was due to start this month but last week the French air accident investigators, the BEA, suddenly announced a delay, without explaining why.
Buried in the technical jargon of the Safety Agency’s analysis of the problem is the conclusion that the false readings “would constitute an unsafe condition.” That’s would, not could.
That announcement follows a pattern: Many things about this crash are unexplained.
First, of course, there is the question of why the Airbus fell 36,000 feet into the ocean after all its computerized flight controls failed and the crew were unable to override the systems and regain control, or even to send a distress call.
Second, why did it take seven hours for anyone to realize that the airplane was missing?
And third, there is the persistent and increasingly suspicious attention being given to the instruments that measure the air speed of both the A330 and A340. There are well over 500 A330s in service around the world and well over 300 A340s. Almost every minute, hundreds of people are boarding one or the other of these planes for long-haul flights, so their reliability is no academic matter.
Days before the BEA announced the delay in resuming the search in the South Atlantic, the European Aviation Safety Agency issued an Airworthiness Directive to all operators of the two Airbus types. An Airworthiness Directive is literally that—a directive to take action because of the discovery of a fault that could jeopardize the ability of the airplane to fly safely.
This directive suggests a far more specific flaw in the Airbus air speed gauges than has been admitted before. There are three of these gauges on each Airbus, called pitot tubes. What really gets my attention is that this new alarm came about not from reports of problems with airplanes already flying passengers. It originates from inspections carried out during the test flying of brand new airplanes.
What did the inspections reveal? That oil used in manufacturing the gauges had not been flushed out, and a residue remained. Crucially, at cruise altitude—Flight 447 was cruising at 36,000 feet when stricken—this tiny amount of oil became viscous and caused false speed readings.
In fact, buried in the technical jargon of the Safety Agency’s analysis of the problem is the conclusion that the false readings “would constitute an unsafe condition.” That’s would, not could. As a result, the agency has ordered all airlines flying A330s and A340s to check the pitot tubes by April 30.
The amazing conclusion to be drawn from this is that, all along, there has been a potentially fatal flaw in the speed gauges and many new Airbuses have been delivered while it remained undetected. (This flaw had never shown up in checks made after the crash of Flight 447.) The problem was endemic to the plant making the instruments, not unlike the case of the U.S. plant that made accelerator pedals for Toyota. Airbuses have pitot tubes made by two companies—by the U.S. company Goodrich, and by the European company Thales. It was the Thales manufactured gauges that were discovered on the assembly line with oil in them.
On Monday the BEA said the sea search was being delayed by the time needed to get vessels back into the South Atlantic.
In the absence of the flight recorders and with the bulk of the wreckage still undiscovered, the pitot tubes must now be reckoned the prime suspect. The two bulky reports on the crash so far issued by the BEA are rich in circumstantial evidence that the Airbus flight control computers crashed in an irreversible sequence because they were being fed false air speed information. For the crew, the situation was made far worse by the violent turbulence of a high-altitude storm system in their path. We have a detailed picture of the computer failure, as it happened, thanks to a series of data bursts sent automatically from the airplane, via satellite, before it disappeared.
As I reported early in the investigation of those last messages from Flight 447, this technology, at the moment aimed simply to report maintenance faults during a flight so that they can be dealt with when the airplane arrives at a gate, could easily be enhanced to provide what is so agonizingly absent in this case, a complete description of why the crash occurred that would render the old black box flight recorders redundant.
Now the lesson has been learned, apparently. The French and many other European aviation agencies want an international agreement to equip all airliners flying long distances over water to have next-generation instant-reporting of critical flight data via satellite.
So far it has cost at least $40 million for the search operations in the South Atlantic involving the navies of France, Brazil, and the United States. And there is no guarantee, given the extreme depths and mountainous terrain involved, that the definitive evidence will ever be found.