Jet plunged into sea upside down, tape shows

OXNARD, Calif. - The pilots of Alaska Airlines Flight 261 battled stabilizer problems for more than 30 minutes before their airplane suddenly tumbled from the sky. Accounts of the pilots' comments

Friday, February 4th 2000, 12:00 am

By: News On 6

OXNARD, Calif. - The pilots of Alaska Airlines Flight 261 battled stabilizer problems for more than 30 minutes before their airplane suddenly tumbled from the sky. Accounts of the pilots' comments on the cockpit voice recorder indicate that, in the seconds before the airplane crashed into the Pacific Ocean, it had flipped upside down.

"The crew made references to being inverted," Jim Hall, chairman of the National Transportation Safety Board, said shortly after officials reviewed the recording Thursday in Washington.

The McDonnell Douglas MD-83, which was flying from Puerto Vallarta, Mexico, to San Francisco and Seattle, plunged into the ocean about 10 miles off the California coast north of Los Angeles on Monday afternoon, killing all 88 aboard.

Witnesses reported seeing the jet spinning and rolling upside down as it fell from about 17,000 feet. Although the recording contained the voices and sounds in the cockpit as the crew worked on the problem until the end, it shed little light on what led to the plane's sudden dive.

Sources familiar with the investigation said that the pilots had gone through the airplane's emergency checklist for a jammed stabilizer and had tried several control settings without losing control of the airplane. Information contained on the airplane's flight data recorder may solve the mystery of what caused the plane to abruptly begin its dive.

U.S. Navy crews retrieved Flight 261's data recorder with a remote-control submersible shortly before noon Thursday. The recorder was rushed to Los Angeles International Airport and was expected to arrive at the safety board's Washington laboratory late in the evening.

Mr. Hall said that the crew's conversations in the cockpit indicated that they were fighting an airplane that wanted to dive. They spent a portion of that time on the radio with airline mechanics on the ground.

Such a condition would result if the stabilizer - essentially a 40-foot adjustable wing atop the tail - were jammed in such a way that it forced the airplane's nose down.

Engineers and pilots say that it is possible to fly the airplane at such a setting but that during certain phases of flight, such as when the airplane is slowing, the control forces might be so heavy that it would take the strength of both pilots to keep the nose up.

Jammed stabilizers are rare. Pilots are trained to eliminate the problem by turning off the motors that drive the stabilizer.

Officials said Thursday evening that the pilots had reported to investigators that their attempts to follow emergency procedures for a jammed stabilizer had failed. They asked the mechanic if there were any "hidden circuit breakers," but the mechanic said he knew of none.

The mechanic said he closed his conversation with the crew by saying something to the effect of, "We'll see you on the ground," said safety board member John Hammerschmidt.
After reviewing the new information from the voice recorder, some pilots and others familiar with the aerodynamics of the twin-engine MD-83 suggested that the tail of the aircraft may have stalled.

A stall occurs when the angle of any aerodynamic surface, such as a wing, becomes so great that the air flowing over it is disrupted. When this occurs, the surface stops providing lift.

Most airliners, including the MD-83, are designed so the main wings will stall first, giving the crew the ability to use elevator pressure from the tail to change the wings' position and restore lift.

If the tail stalls, it could potentially flip the airplane upside down because of the sudden loss of all pitch control.

Aviation consultant C.O. Miller, a former senior safety board official, said that modern aircraft become unpredictable after a stall, which is why manufacturers go to extraordinary lengths to design automatic systems that prevent an airplane from ever coming close to a full stall.

"You cannot predict what will happen other than it is going to go through some wild gyrations, and you are not going to be able to get it out," he said. "These gyrations are so violent that the pilot is along for the ride for the most part, if not entirely."

Investigators said Thursday that it is far too early to know exactly what happened. They said they cannot rule out a mechanical failure other than the stabilizer, such as the loss of a flight control, as a possible factor.

Officials said Thursday that they are continuing to investigate a reportedly jammed stabilizer aboard an American Airlines MD-83 that was en route from Phoenix to Dallas/Fort Worth International Airport on Wednesday.

Mr. Hammerschmidt said that mechanics determined that an electrical problem in the co-pilot's stabilizer trim switch had resulted in an inability to bring the nose of the plane up and intermittently failing to trim the nose down. A secondary trim switch also did not work properly. The safety board quarantined the parts pending investigation.

The American pilots told investigators that they were able to control the aircraft at all times. Mr. Hammerschmidt said the pilots told investigators that they were aware of the Alaska Airlines crash "and decided not to troubleshoot the problem any further."

Mr. Hall said the cockpit voice recording from the Alaska Airlines flight added further details to information that was already gleaned from conversations that the crew had with air traffic controllers and maintenance experts.

Officials also said Thursday that the plane had reported no mechanical problems on its two previous flights before the accident.

Investigators now know that the stabilizer problem had been nagging the crew well before the final 11 minutes of the flight. Mr. Hall said the problem apparently became worse as the crew tried to diagnose and fix it.

The plane's final dive apparently began within a minute after the crew told a controller that they needed to change the airplane's configuration for descent.

Navy officials said late Thursday that they had identified pieces of the tail assembly, including the horizontal stabilizer, on the ocean floor. Navy officials said video of a 100-foot swath of wreckage showed that the largest piece of the outside fuselage was about 5 to 6 feet long, but most were less than 3 feet.

Navy officials said they were bringing additional vessels to the area to map the debris field. One will have ability to recover human remains and significant components of the aircraft, but officials sidestepped specific questions about when removal of human remains would begin.