Crash Sleuths Tackle Task of Piecing Puzzle Together

Slowly, with nearly unfathomable precision, the pieces must be fit together.

While the nation asks why Trans World Airlines Flight 800 crashed into the Atlantic Ocean 29 minutes after taking off--and may already assume that a bomb or even a missile was the cause--a cadre of scientific sleuths has begun to zero in on the definitive answer in the tiniest shreds of cloth and fragments of metal retrieved from the waters off Long Island.

The powders used in bombs leave traces on bodies and scramble the chemical structure of metallic hinges on luggage. Burn marks remain on fabric airplane seats. Bits of an aircraft’s hydraulic system can be pieced together to determine whether it could have failed. From a downed airplane’s point of impact--whether ocean or field, forest or suburb--comes the evidence that almost always tells the tale of the final moments of a plane’s flight.

“Dead men do tell tales,” said C.W. Kauffman, professor of aerospace engineering at the University of Michigan. “You look at all this pile of material, and it’s not as hopeless as you’d think.”

Are tiny bits of metal embedded in human flesh? Does a faint clicking sound, picked up by a cockpit tape recorder, signal a malfunctioning control system? Does a twist in the fuselage suggest a missile strike?

“You can totally reconstruct the time sequence in which things happened. It just takes a lot of money, a lot of time and a lot of patience,” Kauffman said. Indeed, experts said that unless investigators are lucky, it can take weeks to determine whether a crash was caused by a bomb.

In the case of the TWA crash, that work is taking place in a hangar on Long Island that once belonged to the Grumman Corp. and nearby in the morgue at Hauppauge, where the Suffolk County medical examiner works.

“What a lot of people don’t understand is that an explosion doesn’t destroy the evidence--it just makes it smaller,” said Malcolm Brady, who led a team assembled by the Bureau of Alcohol, Tobacco and Firearms to investigate the World Trade Center bombing in 1993.

But even though each crash may stem from a different combination of causes, the National Transportation Safety Board has established a standard procedure that looks at each of the potential areas of aircraft and human failure that can cause an accident as well as for the abnormalities that could show a crash was deliberate.

The board, the government agency given primary responsibility for investigating transportation crashes, maintains four “go” teams, on duty on a rotating basis. When a crash occurs, a team is activated and heads immediately to the crash scene under the supervision of a member of the board itself.

In the case of the TWA crash, the commander is Robert Francis, the board’s vice chairman. But the field chief is a senior investigator who has risen through the ranks of the board’s professional staff.

The team is broken into six groups. Members examine mechanical systems, such as hydraulics and instrumentation; structure, such as wings and fuselage; the engines; the maintenance history of the plane; air traffic control records, to determine what else may have been in the surrounding airspace, and how the plane was operating.

Another team, working in a laboratory in Washington, analyzes the information on the plane’s flight-data recorder and cockpit-voice recorder.

With speculation in this crash focusing on the possibility of a bomb, the work of the structures team, which may be staffed with mechanical engineers, metallurgists and explosives experts, could prove particularly telling.

James Kallstrom, the assistant FBI director in charge of the bureau’s New York office, said that metallurgists “will look for residue, look for streaking patterns, look for the way the metal is shaped,” as part of the effort to determine what caused the plane to erupt in a fireball.

The structures team will try to trace the progression of the plane’s breakup--from the front to the back or vice versa--to learn where an explosion might have occurred.

Did it occur in the cargo hold? If so, the panels between the hold and the passenger compartment above would likely be bent away from the blast and would reflect what is called its “seat.”

The structures team will look for traces of chemicals indicating what exploded--a bomb or fuel. The temperature of an explosion can determine what metal has melted and at what point. The relative force can be shown by the extent of distortion of the metal.

Key evidence can be as large as a turbine blade or as tiny as an instrument lightbulb.

“You can take a light filament and determine whether the light was off or on at the point of impact,” said Michael L. Barr, director of the Aviation Safety Program at the University of Southern California.

A veteran TWA pilot who has participated in NTSB investigations said that the superficial evidence available so far seems to point strongly to a bomb. “No one believes anything was wrong with that plane unless it was a catastrophic engine failure that caused damage to the fuel cells [tanks] in the wing above the engine,” he said.

“The turbine blades are at the back of the engines [under the fuel tanks] and they are very, very, hot,” he said. They offer the greatest potential for damage. But, he added, “we’ve never had a turbine burst taking out a plane.”

“So it seems more likely that it was a bomb, a well-placed bomb, that gets the fuel cell, too. Or a bomb that actually was placed in a fuel tank with a timing device to delay the detonation. It’s not that hard to get access to a fuel tank.”

The transportation board experts have been joined by ATF and FBI agents, who will take a more prominent role in the inquiry if evidence of a crime emerges.

Working in a large open space, the investigators will set the retrieved parts of the airplane as they would be positioned in flight--without actually bolting them together--to offer a picture of how an explosive concussion moved through the craft.

In the case of TWA Flight 800, there are four components to the search for wreckage:

The Coast Guard has assembled a fleet of aircraft, boats and 400 people to comb the surface, mapping 240 square miles of impact area and waters into which currents may have carried bodies and debris. The searchers repeatedly cross the area to pick up everything on the surface--bodies and airplane parts as well as luggage, personal effects, even in-flight magazines.

The precise location of the wreckage is important.

“Where the pieces came down will give you some indication of what happened and where it happened,” said R. John Hansman, professor of aeronautics and astronautics at Massachusetts Institute of Technology.

Often the most important clues are in human remains.

Not only will shards of a bomb lodge themselves in human flesh but explosives also leave chemical traces on skin--less likely, of course, after a body has been resting in sea water. The high pressure of an explosion also may collapse eardrums and lungs.

In addition, the seat positions occupied by passengers and the injuries they suffer can show where an explosion went off.

So far, said Charles V. Wetli, the chief medical examiner of Suffolk County who is responsible for the autopsies being performed on the victims, the 50 bodies examined have yielded no evidence of a bombing.

“So far, the pattern of injuries we are seeing are those from deceleration, of a high-speed impact. A great many of them died upon impact with the water,” he said.

“In most bombs, homemade bombs anyway, the human body becomes a projectile trap,” Wetli said. For that reason, he said, the bodies are X-rayed to search for bits of metal forced into them by the explosion.

Those tests, and scores of others, will be conducted by each of the investigation groups during a painstaking technical process lasting months.

Peterson reported from Washington and Gerstenzang from East Moriches. Times staff writers Eric Malnic, William Rempel and Alan Miller contributed to this story from New York.