Image: US Airways plane
With Jersey City in the background, a crippled US Airway jet rests on a barge on the Hudson River on Sunday in New York. The aircraft will be moved to an undisclosed location for inspection by National Transportation Safety Board investigators.
updated 1/18/2009 6:06:58 PM ET 2009-01-18T23:06:58

Safety investigators are going back over radar data to see if there were any readings that might have been birds around the time US Airways Flight 1549 took off from LaGuardia Airport in New York.

National Transportation Safety Board spokesman Peter Knudson said Sunday that preliminary indications from investigators' playback of the departure controller's radar screen "did not show any targets" that might be birds.

"There are other ways to get that information, however," Knudson said. "We are going to go and get all the electronic data necessary to get a complete picture of what was on his screen. It's possible there was more being displayed than we initially understood. We just don't know definitively at this point — we don't know exactly what was shown on that radar screen."

Barrett Byrnes, who spent 35 years as an air traffic controller and worked at John F. Kennedy International Airport before retiring a few months ago, said controllers at LaGuardia and New York Terminal Radar Approach Control in Westbury, N.Y. told him that there was a radar "return" at some point during takeoff of Flight 1549. He said the "return" was not passed along to the pilots of Flight 1549 because it was unidentified, as are many radar returns or blips.

"I was told there was raw data that came back with associated stuff, but they couldn't differentiate whether it was birds or not," said Byrnes, who added that he last spoke to some of the controllers on Saturday.

He said the radar returns, unless they are planes with transponders, are difficult to identify and sometimes are nothing at all. He said controllers wouldn't necessarily pass along information about a radar return unless there was something specific that they could identify.

"If you have pilot reports that say a flock of birds is north of a bridge, you pass that along to everybody, but if you don't have those pilot reports and are just getting unreliable information as far as radar returns, then you could be using information that nothing exists there," Byrnes said.

Moments after takeoff from LaGuardia on Thursday, US Airways Capt. Chesley B. "Sully" Sullenberger reported a double bird strike — that the Airbus 320 had ingested birds in both engines — and had lost all power. Unable to return to LaGuardia or make a landing at nearby Teterboro Airport in New Jersey, Sullenberger glided the airliner to a landing in the Hudson River.

Aviation safety experts said the radar used by air traffic controllers is designed to pinpoint and track airplanes made of metal and equipped with transponders that report altitude and identification of the aircraft. They said the flesh and feathers of small birds rarely registers on radar, while a large bird or a group of birds flying closely together may show up as a small blip that to the controller looks the same as any number of possible "targets."

"There have been many attempts to get a good radar to read birds, but we have not been successful at getting one that can read birds reliably," said former NTSB board member John Goglia. "It's just like trying to read a human being. The right range of frequencies is needed — you don't always have it."

Even if a controller sees a blip that might be a bird and passes that information along to a flight crew, there's not much a pilot who has just taken off can do about it, Goglia said. With the aircraft's nose is tilted up for a climb, horizontal visibility is limited and the pilot would probably be unable to see if he was headed toward a large bird or group of birds, he said.

"Even if he looks out the window he may look in the wrong direction, and if even if he looks in right direction he might not see (the birds)," Goglia said. "There are a million variables here and none of them good."

Byrnes noted that even if a controller had a rough idea of what an object on the radar display was, if it doesn't have a transponder you wouldn't know its altitude or how fast it was traveling.

"Basically, radar is unreliable as far as birds to begin with," Byrnes said.

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.


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