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A Weapon Unfathomed: Jet Fuel

Engineering: The World Trade Center was built to withstand the impact of a jet, but a key component was overlooked.


NEW YORK — During planning for the World Trade Center in the 1960s, structural engineers designed the twin towers to withstand the worst storm in 150 years. As an afterthought, the project engineer said, they calculated that the skyscrapers could sustain a direct hit from a 124-ton Boeing 707.

But the engineer concedes that they did not take into account a critically important ingredient in an airplane crash: volatile jet fuel.

That oversight bred false confidence among the trade center's managers, the New York City Fire Department and other emergency agencies. Had officials been aware that the towers were not designed to remain standing in the face of jet fuel burning at 2,000 degrees, a series of miscalculations might have been avoided:

* The Fire Department's emergency command post was set up directly beneath the twin towers, which collapsed and killed the department's chief, chaplain and other firefighters.

* Workers on some lower floors of both towers were not told to evacuate immediately, and instead remained inside during the crucial minutes before each tower fell.

* The Fire Department's top structural expert rushed into the trade center in a desperate--and ultimately fatal--effort to assess the skyscrapers' structural viability as the flames spread.

* And firefighters raced into the towers unaware that they had a short window of time--less than an hour in one building and less than two hours in the other--in which to evacuate thousands of workers and get themselves, police and other rescuers to safety.

The center's south tower toppled 52 minutes after it was struck by United Flight 175 on Sept. 11. The north tower, which was struck first, went down an hour and 43 minutes after American Airlines Flight 11 sliced into the building.

The sight of those towers crumbling so quickly was never anticipated by generations of trade center officials and Fire Department commanders, who were assured for years by engineers that the towers could stand up to a crashing Boeing 707.

"Our guys stayed in there so long because they didn't think the building would come down," said Fire Lt. Andrew Graf of Engine No. 4 and Ladder No. 5, from which 14 firefighters are missing and feared dead.

It was not until the south tower began collapsing that his men were ordered to turn around and get out of the north tower, Graf said. That tower came tumbling down with firefighters inside just 28 minutes after the first collapse.

"I'm sure it was realized after the building burned for a while that the steel was going to get weak," said Lt. Chris Piazza of Engine No. 24 on Sixth Avenue, which lost 11 firefighters. "The chiefs on the scene had called for evacuation before the collapse, but a building of that size takes a long time."

Firefighters say they were never trained to fight a building fire caused by an airplane crash. Their drills never included training on how to handle burning jet fuel inside a skyscraper, they said.

"Everyone's fears were focused on a chemical attack or a bomb," Piazza said.

A former top city official familiar with emergency procedures said there was "some talk" among contingency planners about a small private plane accidentally striking the towers, but that possibility never was translated into the Fire Department's training.

Hyman M. Brown, the project engineer for the twin towers, said that in designing the trade center in the 1960s, "we thought of the structural impact of a plane hitting, but not the burning fuel." The towers withstood the tremendous structural impact of the two hijacked airliners as they slammed into the buildings on the morning of Sept. 11, Brown said.

The towers' supporting columns were made of steel, which melts at 1,500 degrees, Brown said, or about 500 degrees lower than the heat of the burning fuel. The searing heat caused the columns to buckle and sag, triggering the collapses.

At least 35 firefighters have been confirmed dead as a result of the attack, and more than 300 are among the missing.

A Fire Department spokesman did not respond to questions faxed to department headquarters Wednesday. A spokesman for the firefighters' union referred all questions to the department.

Officials have said they would not have set up their emergency command post at the foot of the towers had they realized that a jet fuel fire was capable of bringing down the skyscrapers so swiftly. They were accustomed to high-rise fires, which, no matter how extensive, normally leave the buildings standing.

Richard Sheirer, director of the mayor's Office of Emergency Management, said officials decided to move the command post across the street to the World Financial Center after the second tower was struck at 9:08 a.m.

Ray Downey, chief of the special operations command and the Fire Department's top expert on building collapses, ran into the World Trade Center complex after the first plane struck. As he attempted to determine the stability of the structures, the south tower collapsed.

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