By Don Phillips and Michael Powell 

Washington Post Staff Writers Thursday,November 15, 2001; Page A18

NEW YORK, Nov. 14 -- The vertical tail section of American Airlines Flight

587 cracked off when its modern reinforced plastic "composite" fittings

failed, investigators said today, and the National Transportation Safety

Board announced that American will inspect the tail section of all its

similar Airbus A300-600 widebody planes. The Federal Aviation Administration

said it was dispatching its chief scientist to examine the composite

materials as well.

The investigators' conclusion is significant because composites are used on

virtually all civilian and military aircraft introduced since the mid-1980s.

But it does not answer the vital question of why they failed in this

instance -- whether they were overwhelmed by some outside force beyond their

design limits or were somehow faulty or incorrectly attached.

Safety Board Chairman Marion Blakey said there was no evidence of physical

damage to the vertical tail fin, which was recovered from Jamaica Bay soon

after the Airbus crashed into a Queens neighborhood Monday.

But she presented radar data indicating that wake turbulence from a Japan

Airlines 747 that took off just before Flight 587 could have hit the

American widebody. The 747's path was to the west and about 800 feet higher

than the A300's, she said, with the wind blowing from the northwest at about

12 mph. Because the swirling winds that flow from an aircraft's wingtips

tend to move down slightly and drift with the wind, the aircrafts' paths

"would be consistent with a wake vortex encounter," Blakey said.

But board member George Black said he was unaware that any civilian aircraft

had ever lost a vertical tail fin to wake turbulence.

Investigators could not explain what outside force, combination of forces,

human error or aerodynamic forces could have produced enough force to rip

the vertical tail fin and rudder off the plane and rip both engines from the

wing.

The board last night released some preliminary data from the recovered

flight data recorder indicating that the vertical tail fin came off first.

Both engines continued to operate normally for a short period after the crew

said on the cockpit voice recorder that they had lost control. Further

information from the sophisticated recorder should provide a wealth of other

evidence.

The pilots immediately lost control after the vertical fin came off, and the

plane spiraled and tumbled into a neighborhood of neatly kept houses in the

Rockaways section of Queens, destroying four houses and badly damaging three

others.

Investigators at first believed the plane landed nose-down -- because of the

lack of wider destruction that would have resulted had it hit the ground at

a shallower angle. That did not explain, however, why they found so many

intact or nearly intact bodies so quickly.

Several sources now believe the explanation may be the speed of descent. The

plane, they believe, having lost its heavy engines and vertical tail, made a

relatively slow belly flop, nose tilted down and turning sideways. Its

engines were found about 800 feet away -- with the left and right engines

exactly opposite to where they would have been attached to the plane,

indicating the plane might have been upside down or flopping around.

The composite material used in the doomed aircraft was a carbon-fiber-

reinforced plastic -- which, like most composites, is much lighter and

stronger than a like amount of aluminum. The Airbus A300 pioneered the use

of composites in the early 1980s, and both Airbus and Boeing have used them

increasingly since then. The new Boeing 777, the most modern passenger

aircraft flying, is significantly made up of composites.

Blakey announced American's planned inspection of all 24 of the tail fins on

its Airbus A300-600 fleet. She also said the FAA was sending its chief

scientist to the Flight 587 scene to study the possible relevance of

composite materials. FAA spokeswoman Laura Brown said that if the scientist

and other FAA officials find that more inspections or corrective actions are

needed in other parts of the aircraft industry, "the FAA will mandate that

immediately."

Hans Weber, an airline engineering expert in San Diego, said most airliners

still have metal tails. He also said that although the composite tails on

Airbus planes are made with carbon fiber, the composition of that fiber has

been constantly evolving as the plane maker tries to keep costs down.

Composite tail structures are five times more expensive than aluminum -- $1,

500 a pound compared with $240 a pound.

Weber also noted that the composite tails can be repaired, but that in most

cases when damage involves a primary structure, they are not readily

repairable and are often discarded. The layering, bonding and curing of the

materials, he said, have to be just right -- and they have to be inspected

more often than aluminum tails.

Officials continued today to describe the crash as more likely an accident

than an act of terror. But Attorney General John D. Ashcroft said

investigators had ruled out nothing.

"We're actively investigating all possibilities, including terrorism,"

Ashcroft said.

Although the NTSB is the lead investigating agency, the FBI is conducting

its own probe, with 130 agents assigned to it. An explosives residue team is

combing the wreckage for traces of explosives -- they have found nothing

suggestive, sources say.

If terror was the cause, sabotage appears more likely than a bomb, sources

said. FBI agents have interviewed more than 70 airline employees, including

mechanics who may have worked on the plane while it was parked at John F.

Kennedy International Airport overnight before taking off Monday morning.

But spokesmen for American Airlines and the Port Authority of New York and

New Jersey -- which manages JFK -- declined to say where at the airport the

plane was parked, or how many workers might have worked on or around it.

The Port Authority's management of the airport has attracted much criticism

over the years, and authority directors have periodically announced new

security plans. The Port Authority, airline companies, cargo companies,

private security firms and the FAA claim a security role at the airport.

The conclusion of the NTSB investigation hangs like a dagger over the

airline industry. If the federal government concludes that mechanical

failure caused the crash, analysts expect that American and the industry

will recover.

Should sabotage or terror have played a role, however, the consequences

could be dire.

"For the most part, people are fairly forgiving. If management gets out

front, they are okay," said Darryl Jenkins of George Washington University's

Airline Institute. "But terrorism would about put us all under. It's much

worse than anything else."

Staff writers Cheryl W. Thompson and Frank Swoboda in Washington contributed

to this report.

© 2001 The Washington Post Company