Post by dgriffin on Jun 13, 2009 19:06:15 GMT -5
The Christian Science Monitor
Did Air France Flight 447 break up midair?
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 tail that broke off was a composite structure and was attached to the aircraft in six places. The bolts [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 bolts, and he said it appeared to behave as it was designed to, which is called its "rated value."
"That means that the bolt 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 bolts are still being used in newer aircraft, like the A330, according to Healing.
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.
"We have a far less robust understanding of how composites may deteriorate," says Robert Mann, president of R.W. Mann & Co., an aviation consulting company in Port Washington, N.Y.
"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."
Did Air France Flight 447 break up midair?
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 tail that broke off was a composite structure and was attached to the aircraft in six places. The bolts [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 bolts, and he said it appeared to behave as it was designed to, which is called its "rated value."
"That means that the bolt 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 bolts are still being used in newer aircraft, like the A330, according to Healing.
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.
"We have a far less robust understanding of how composites may deteriorate," says Robert Mann, president of R.W. Mann & Co., an aviation consulting company in Port Washington, N.Y.
"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."