Did Composites Bring Down Air France Flight AF 447?

Washington, DCWhile the black boxes of doomed Air France Flight AF 447 have yet to be found, the retrieval of bodies and debris is shedding new clues as to what might have brought down the Airbus A330 and caused the plane crash.

So far, according to a report in the Christian Science Monitor (CSM) dated yesterday, three more bodies that were found Friday brings the total body count to 44. Various pieces of debris have also been found—however the location of the debris as it relates to where the debris originated in the doomed plane, and the location of some of the bodies found have given investigators new fodder with which to speculate.

The question now being asked is…did the plane break up in mid-air?

The black boxes—the impenetrable voice and data recorders that are resting on the ocean floor—will be key to providing investigators with clues that may eventually unlock the mystery of Air France flight AF 447.

However, there are compelling reasons to speculate as to the possibility the plane may have broken up in mid-air.

The 44 bodies recovered thus far were found as much as 85 miles apart. Ocean currents may have been a factor here. However, unnamed investigators quoted in a Brazilian newspaper have suggested that such a wide debris field may also suggest that the plane broke up in mid-air, and fell to the ocean surface in pieces.

The Christian Science Monitor notes that it cannot verify those reports.

However, the location of the recovered bodies together with particular pieces of debris found are leading investigators to speculate as to whether or not the use of composite materials may have had a role to play in the downing of the plane.

According to the CSM and the Associated Press (AP), some of the largest pieces of debris found thus far appear to be the doomed plane's tail fin and vertical stabilizer that are made of composite materials.

The airline industry, in fact is undergoing a sea change in the area of aircraft construction. Historically, commercial aircraft have been built using titanium and aluminum—metals that are well understood and well tested. However, in an effort to decrease the overall weight of the aircraft (and use less fuel per flight), more recently aircraft manufacturers have been moving to high-tech and more lightweight composite materials.

These complex materials are described in the CSM report as being made from intricately woven fibers baked with resins. According to the report it is believe that these new, complex composite materials are at least as strong, if not stronger than traditional metals.

However, according to the Christian Science Monitor some aviation analysts are less confident in the reliability of composite materials, in part because safety experts have not yet designed as many tests as those brought to bear against traditional materials such as titanium and aluminum.

"We have a far less robust understanding of how composites may deteriorate," said Robert Mann, president of R.W. Mann & Co., an aviation consulting company in Port Washington, NY., in comments published in the Christian Science Monitor.

"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."

It is not known if the composite materials are tested for the effects of vibration over the long term.

While the fuselage of the Airbus A330 was built of traditional metals, the tail fin and vertical stabilizer of the plane were partially constructed from composite materials—materials that are known to have contributed to several aircraft failures in the past, according to the CSM.

The crash in 2001 of American Airlines Flight 587 occurred when the vertical stabilizer snapped off in severe turbulence. The Airbus 300 was a similar design to the A330 that was flying as Air France flight AF 447.

Engineers described the vertical stabilizer as being attached to the Airbus 300 in six places. Some, but not all of the bolts holding the stabilizer in place were made of composite materials. The tailpiece that broke off was also made of composite materials.

According to an engineer who participated in the testing of one of the composite bolts from the failed American Airlines plane, the bolt was stressed to 192 percent of its rated value before it failed. The rated value, according to Richard Healing, a former member of the National Transportation Safety Board and an aviation consultant, relates to the forces the part is designed to withstand once in a lifetime of the aircraft.

By holding up to nearly twice as much stress as it was designed for, the composite bolt passed the test and is still being used in aircraft today—including the doomed Air France flight.

"There is a very compelling need to find the wreckage," Healing said. "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."

The Airbus A330-200 uses more composite materials in the wing and tail structures, than older planes.

Recovery of the black boxes will go far in helping to determine if it was an unavoidable, catastrophic failure in severe weather that may have brought down the plane—or the failure of composite materials. Were that to be true, investigators might be then tempted to hypothesize if a plane completely constructed of more traditional materials might have survived intact, together with an expression of concern as to what that means for other planes currently in service with composite materials in key areas of the plane