Wind Shear Suspected in 25-Death Colorado Air Crash : Aviation: The tower broadcast a warning of treacherous air currents. But federal official says it’s too early to determine cause of accident.

Attention focused on a weather phenomenon known as wind shear on Monday as federal investigators began searching for clues in the crash of a United Airlines jetliner that killed all 25 aboard.

Initial reports indicated that Colorado Springs Municipal Airport had been broadcasting a wind-shear advisory moments before the Boeing 737 plunged into a neighborhood park when on final approach for a landing Sunday morning.

Wind shear is a sudden, violent shift in wind direction near the surface of the Earth, creating powerful downdrafts that can hurl a low-flying jetliner to the ground.

That’s exactly what happened on Aug. 2, 1985, when a Delta Air Lines L-1011 jumbo jet crashed short of the runway at Dallas-Ft. Worth Airport, killing 137.

John Lauber, the National Transportation Safety Board member heading up the investigation here, said Monday that it is still far too early to tell what caused Sunday’s crash of Flight 585.

“This is very much a wide open investigation at this point,” he said. “We haven’t ruled out anything.”

But, in addition to the recording broadcast by the airport tower--which warned of winds out of the northwest at 20 knots gusting occasionally to 30 knots, with a possibility of wind shear--several pilots radioed in reports of treacherous winds.

Colorado Springs policeman Mike Spitzmiller, who was monitoring control tower chatter on his scanner radio, said that, about a minute before the crash, he heard a pilot--apparently in the cockpit of Flight 585--comment: “It looks like this is going to be an interesting landing.”

“That whole area just east of the Rockies is notorious for wind shear,” said John Galipault, who heads up the Aviation Safety Institute, a nonprofit consulting firm in Worthington, Ohio.

“When you blow air across a barrier like the Rockies, you get turbulence on the lee side,” he said. “You get downdrafts, you get updrafts, you get strong winds from the side.”

Because wind shear is a relatively common occurrence along the eastern slope of the Rockies, a lot of research on the phenomenon has been done in this area. Denver’s Stapleton Airport, about 80 miles to the north, was one of the first airfields in the nation to be outfitted with special Doppler radar for detecting wind shear.

The airport at Colorado Springs is equipped with a complex system of anemometers for detecting fluctuating winds, but the field does not have Doppler radar.

Lauber said this system issued a number of wind shear alerts up to about 10 minutes before the accident, but there were no alerts while the plane was making its final approach.

Although sources close to the investigation were talking primarily about wind shear on Monday, they said there were reports that a single piece of engine debris had been found some distance from the main body of wreckage.

This, they said, might indicate some sort of engine trouble before the crash.

However, Lauber said Monday night a preliminary inspection of the engine debris showed no evidence of fire or “distress” prior to impact, and both engines apparently were running when the plane hit the ground.

Galipault, however, noted that some kind of failure in one of the plane’s two engines could have caused a wing to drop, “and if a wing is down, (wind shear) can make a plane rotate on its axis.”

Witnesses said the big plane had rolled to the right, almost on its back as it plunged nose first into the park about four miles short of the runway.

“We saw a shadow go past the window and heard this loud swooshing noise,” said Margaret Fine, 38, who lives in an apartment complex about 100 yards from the crash site.

“We ran outside, just in time to see it coming out of the sky, pointing straight down,” she said. “Then there was a terrible explosion and a large ball of fire.”

Fine said that she, her 17-year-old son, Tom, and a couple who live next door, Russell and Silvia Babcock, ran down the gently sloping hillside to the shallow gully where the plane had hit.

“We tried to help, but there was nothing there, just fire,” Fine said.

“We found a leg, and part of an arm,” Mrs. Babcock said. “That was the only way you could tell there had ever been people there.”

“Tom was crying,” Fine remembered later. “ ‘They’re all dead,’ he said.”

The NTSB’s Lauber said Monday that, because of the steepness of the angle at which the plane hit, virtually all the wreckage was buried on impact--much of it, along with most of the victims, within a circle not much larger than the diameter of the fuselage.

Crews with hand tools and a large crane were brought in Monday to begin digging up the wreckage and remains. The NTSB said it would be several days before the excavation process is completed.

Among the debris recovered by Monday afternoon were the plane’s two “black boxes.”

One of these records the last few minutes of cockpit conversation. The other provides a record of the plane’s altitude and control settings during the final minutes of flight.

Lauber said the recordings, if intelligible, should provide valuable clues as to the cause of the crash.

Both boxes were battered in the crash, he said, and it may be several days before NTSB specialists in Washington know whether the recordings can be deciphered.

Another important source of information on the crash will be recordings made at the control tower of conversations between the cockpit crew and air traffic controllers.

The content of these recordings has not been made public, but there are unconfirmed reports that the cockpit crew gave no indication that it was in trouble in the moments before the crash.

Lauber said some small feathers were found on the wreckage of the leading edge of one wing, but he said there were no birds reported flying in the approach pattern at the time of the crash, and investigators placed no special significance in the find.