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Posted on 11/13/2001 11:48:01 PM PST by kattracks

A rattle heard on cockpit tapes could mean that the stabiliser's bolts were coming out

Investigators looking for the cause of the latest disaster to hit New York City, the plane crash that killed at least 262 people, have switched their focus to the aircraft's tail, aviation sources said early today.

Evidence from the first of American Airlines flight 587's black-box recorders turned attention away from earlier speculation about mechanical failure in one or more engines, or the notion that birds might have been sucked into the machinery.

Instead, it is thought now that the pilots' mentions of rattles, caught on the cockpit voice tape, might have been unwitting references to a loosening of the bolts fixing the vertical stabiliser to the tail.

The two engines and the bulk of the fuselage landed on the peninsula suburb of Rockaway, five miles from the aircraft's takeoff at JFK airport; the vertical stabiliser and part of a wing were found in the water west of the impact zone.

The airbus would have been uncontrollable without the stabiliser. The first rattle is noted 107 seconds into the flight tape and the next, 14 seconds later; the recording becomes silent after a total of 144 seconds. Investigators are looking at whether the bolts came loose through overload or stress fatigue. They have not ruled out sabotage, the sources said.

A preliminary inspection of the engines showed "no evidence of any sort of internal failure", investigators reported yesterday.

"They all appear to be in one piece," George Black of the national transportation safety board told a news conference.

The possibility of a bird strike - one or more birds being sucked into one or both engines causing them to fail -was one of the elements the inquiry team was considering at that point.

There have been documented failures involving the family of CF6 General Electric engines, the type installed on the plane, though none has involved fatalities.

The Airbus A300 dropped from the sky minutes after taking off bound for Santo Domingo in the Dominican Republic on Monday morning.

Mr Black mentioned the rattling noises heard in the cockpit, but gave no indication at the press briefing of what his experts thought had caused the noise.

From takeoff to the end the tape lasted less than two minutes 24 seconds, Mr Black said.

The first part of the flight, with the co-pilot at the controls, seemed to be normal. Then the rattles became audible, he said, and the pilots made several comments suggesting loss of control before the cockpit voice recording ended. There was nothing on the voice recorder to suggest an intrusion by hijackers into the cockpit - a possibility already ruled out by the fact that the plane broke into pieces before it hit the ground.

At first the crash of flight 587 raised the spectre of another terrorist attack, after hijacked planes crashed into buildings in New York and Washington on September 11.

Mr Black said mechanical sabotage before takeoff had not been eliminated from the inquiry.

"We're not going to exclude that possibility until the investigation goes much further than this," he said.

The black box retrieved from the rubble caused by the plane as it ploughed into the seaside community of Rockaway in Queens showed that the pilots had little warning before the plane began to nosedive.

Yesterday, divers recovered the flight data recorder, which will help the investigators to work out more. They will also consider the structural integrity of the plane, because both engines fell off as it nosedived to the ground.

The joints with the wings will be closely examined, as will the state of the fuselage.

The maintenance records of the plane, which was 13 years old, and those involved in servicing it, will also be studied.

Mr Black said it was "way too early" to connect the crash with other failures involving this type of engine. But he added: "We will be looking at that."

Investigators had earlier told the Wall Street Journal that the discovery of debris in one engine suggested that the engine did not suffer a catastrophic failure from some mechanical breakdown but from sucking in sucking in birds.

A bird strike would not fully account for the apparent mid-air break-up of the plane, but investigators said it could set off a chain of events in which the burning engine damaged other parts of the plane.

Birds have been a problem at JFK in the past. The airport lies near a seashore wildlife preserve where various migrating species stop over at this time of year.

If birds are to blame, ornithologists say the most likely suspects would be white egrets, which fly close together in large numbers.

Birds are estimated to cause an estimated $500m-worth of damage to US civilian and military aircraft each year.

A group formed to raise awareness of the problem, Bird Strike Committee USA, says that more than 400 air deaths in the US can be linked to bird strikes.

"This is a worldwide problem," said Martin Lenhardt, a biomedical professor at the Medical College of Virginia and inventor of a microwave device to scare birds away.

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