Did Air France Flight 447 break up midair?
Figuring out what caused the crash could shed light on the safety of composites – new materials replacing traditional metals in many aircraft.
New York — Air France Flight 447 may have broken apart in the air, new reports indicate.
A Brazilian newspaper cites unnamed investigators who say an examination of some of the retrieved bodies, which were found as far as 85 miles apart, indicates that the plane may have broken apart before it fell into the Atlantic Ocean on June 1.
The Monitor has not been able to confirm those reports. Still, that possibility adds to the urgency of finding the plane's black boxes. As each hour passes, the signals they send out lose a little strength. By the end of the month, they could fade altogether, turning a difficult search of a mountainous undersea landscape into an all-but-impossible one.
The flight data recorders and any recovered wreckage probably holds the key to the puzzle of what caused the Airbus A330-200 to suddenly drop out of the sky on a routine flight from Rio de Janeiro to Paris.
Finding out what happened is critical to safety experts and engineers, who use what they learn from each accident to prevent others, as well as to increase the safety, reliability, and flexibility of modern aircraft.
The aviation industry is currently in the midst of an historic shift in aircraft construction, from generations of using titanium and aluminum to using lighter high-tech composites – complex materials made of intricately woven fibers baked with resins. These materials are believed to be as stronger if not stronger than traditional metals.
While the A330-200 has a traditional metal fuselage, it uses more composites in components such as the wing and tail structures than older planes do. Boeing is building the first major commercial plane, the Boeing 787, with a fuselage made completely of composite materials.
"There is a very compelling need to find the wreckage," says Richard Healing, a former member of the National Transportation Safety Board and an aviation safety consultant. "We need to know, if some of the composite parts failed [on Flight 447, whether they failed at a point that any other material would have failed."
Determining what happened
The Associated Press reported Friday that three more bodies have been found, bringing the total to 44 of the 228 people aboard.
Investigators say determining their cause of death, as well as where each passenger was sitting on the plane, could help determine whether Flight 447 broke up in the air, or whether strong ocean currents are responsible for the widespread recovery zone.
A French nuclear submarine is scouring the Atlantic where debris has been found, listening for "pinger signals" from the black boxes. Special probes called "pinger locators" from the US Navy are expected to be part of the search in several days.
Some of the biggest pieces of debris found so far appear to be the plane's tail fin and vertical stabilizer. These parts are made partially of composite materials, and their failure has contributed to several crashes in the past. In the 2001 crash of American Airlines Flight 587, an Airbus 300 with a similar design to the A330, the vertical stabilizer snapped off in severe turbulence. One of the first questions investigators addressed was whether the composite materials used in the component contributed to the crash, according to Mr. Healing.
“The tail that broke off was a composite structure and was attached to the aircraft in six places. The lugs [some made of composite materials] holding it into place failed,” he says.
Healing was on hand in Germany when investigators tested the strength of one of those composite lugs, and he said it appeared to behave as it was designed to, which is called its “rated value.”
“That means that the lug was designed to be strong enough to withstand the forces it might see once in the lifetime of the aircraft,” says Healing. “That particular part failed at 192 percent of its rated value.”
That means it withstood twice as much pressure as it was designed to before it failed, and so such lugs are still being used in newer aircraft, like the A330, according to Healing. [Editor’s note: The original version used the wrong terminology for lugs in the preceding section.]
Composites less tested than metals
But some aviation analysts are less confident in the reliability of composite materials, in part because safety experts have not yet designed as many tests to determine whether this material has been compromised as they have for traditional metals like aluminum and titanium. Over the past 70 years, safety experts have designed a series of nondestructive methods of testing metals, using X-rays, dyes, and other techniques to find imperfections in the metal or cracks that could lead to a crash.
"The extent of our ability to find faults in composites is something called a tap test, believe it or not. We tap the part and if it rings true, then you say, 'Oh, it must be a good part.' But if you hear a kind of a thud, you say, 'Oh, maybe it has delaminated internally, maybe it's got a void or other problems internally."
Mr. Mann says when he saw the picture of the retrieved tail of Air France Flight 447, one of the first things he wanted to know was whether there was a parallel with AA Flight 586 and whether failure of the composite structures in any way contributed to the breakup of the plane.