06.14.09 2:51 PM ET
Picking Up Pieces From a Midair Explosion
Piece by tiny piece, a picture emerges of what happened physically to Air France Flight 447. But not why. Debris displayed for photographers in Recife, Brazil, may appear scant, but there were two very suggestive details.
One was a curved piece of the A330’s structure about three feet long. Looked at in closeup, it reveals a row of popped rivets, with one rivet still partially stuck in place. Anyone familiar with submarine movies like The Hunt for Red October or Das Boot knows what follows when the sub sinks too deep. Outside water pressure on the hull pops bolts that fly like bullets into the crew’s air space. In an airplane suffering a sudden decompression, things work the other way round: The rivets and fasteners holding together the structure are forced outward because the air inside is at far higher pressure than at the cruising altitude of around 35,000 feet.
The angle of the rudder recovered from Flight 447 seems too acute to have been safely used at 550 miles per hour.
We know that data sent from the stricken Air France flight indicated a sudden, potentially explosive loss of cabin pressure, indicating that the airplane was breaking up.
The second detail: the torn fragments of several oxygen masks, of the kind that drop automatically from the cabin ceiling for passengers to use when cabin pressure is falling. Not put on display in Recife was the one substantial piece of the A330 yet found, its vertical stabilizer. Here, too, there was a clue that tallies with the final burst of data. The rudder was fixed at an angle indicating that the airplane was making a sharp turn to the right. There was data warning that a system to limit rudder movement had been engaged. At normal cruising speed of around 550 miles per hour, only very small rudder movements are needed. The angle of the rudder recovered from Flight 447 seems too acute to have been safely used at that speed. This might indicate that the rudder was deployed at a much lower speed, consistent with one scenario, that faulty speed-reading instruments had allowed it to slow to a dangerously unstable speed. We know from the data that the computers had given up trying to fly the airplane. We don’t know how the pilots reacted.
Perhaps of most concern, in the absence of finding the flight data recorder, or black box, is what has not been found—no other substantial section of the airframe.
The most robust part of any airplane is its center section, where the wings intersect with the fuselage and where both the landing gear and main fuel tanks are grouped. When airliners break up under extreme stress, the fuselage in front of this center section, including the flight deck, and behind it, including the tail containing the black box, sheers away. Most of the wings, including the engines, would also break up. (The engines are designed to fall away in a sharp impact and would fall like bombs.) Of these three sections of the cabin, the center remains by far the heaviest, and even though it might shed pieces on hitting water, it would sink like a stone. The two other sections could float for a brief time, but they would rapidly fill with water and sink.
Therefore the main remnants of Flight 447 were never likely to be found afloat. Finding them remains essential to explaining what all these clues—electronic and physical—are indicating, a sudden and catastrophic breakup of the A330.
Xtra Insight: Clive Irving on Flight 447’s Deadly Scenario