Pilots May Have Put Off Flight 261 Landing Plan

A mechanical problem aboard Alaska Airlines Flight 261 apparently festered for most of its two-hour and 43-minute journey, but the pilots may have thought the problem was more of an irritant than a threat and they postponed a decision to attempt an emergency landing, new data released Tuesday indicate.

In the most comprehensive account yet of the ill-fated flight on Jan. 31, National Transportation Safety Board Chairman Jim Hall said the pilots turned off the autopilot soon after departure from Puerto Vallarta, Mexico. They then flew manually for an hour and 53 minutes.

A veteran pilot said the decision to fly manually was unusual and suggests that the crew ran into a problem but decided it was manageable.

“This is significant,” said Lou Aaronson, a retired pilot who flew jets of the same type for Continental. “One does not normally disengage the autopilot at that point. In hindsight, you can draw the conclusion that this is where the problem began. There might have been a structural failure that was getting worse and worse as the flight continued, something that had worn out and was beginning to give way.”

In radio conversations with the ground, the pilots indicated that their problem was with the plane’s horizontal stabilizer, the winglike portion of the tail that controls the up-and-down pitch of the aircraft’s nose. Aaronson said the pilots probably chose to fly manually because that would make it easier to control the pitch.

However, the problem worsened, and after almost two hours the cockpit crew requested clearance for an emergency landing in Los Angeles. They never made it.

The twin-engine MD-83 jetliner crashed into the sea near Anacapa Island, killing all 88 people aboard.

Whether an earlier attempt to land the plane might have prevented a crash is a matter of speculation. Experts point out that the strain of reconfiguring the MD-83 for a landing, even early in the fight, might have exacerbated the problem.

On Tuesday, Hall provided details of the plane’s final plunge from 17,900 feet, which lasted little more than a minute. In the initial moments of the dive, occupants were thrust toward the cabin roof by forces three times the pull of gravity. The aircraft then rolled to the left and turned upside down as it fell.

The plane’s cockpit voice recorder picked up a loud noise just before the dive began. Radar suggests that a piece of the plane broke away about the time of the noise, falling into the sea about four miles from the main debris field. Navy ships have begun a search for that piece.

Hall said the Navy has recovered two fragments of wreckage from the main debris field--both of them sections of the stabilizer. Experts have suggested that the stabilizer may have slowly broken apart in flight and that the piece that apparently separated in flight may have been another part of the stabilizer.

Using information from the flight data recorder and the cockpit voice recorder recovered from the ocean floor, along with radar data and interviews with ground support staff, investigators are piecing together a clearer picture of what caused the crash of Flight 261.

Experts have suggested that mechanical failures and human decisions both played a role, but the NTSB said it could be months before any official conclusions are drawn.

Boeing on Monday issued an advisory to pilots of similar aircraft, recommending an emergency landing if a standard check list fails to resolve a stabilizer problem.

“It seems like the prudent thing to do at this point,” a company spokesman said.

In-flight glitches with the stabilizer system are relatively common and may not be perceived as immediate threats by pilots, according to investigators and pilots.

During a normal flight, many small adjustments in the stabilizer are required to keep an aircraft in level flight. The movements are generated by two electrical motors, which back each other up. Usually, adjustments are handled by the autopilot system.

Hall reported that the pilots had turned on the autopilot as the plane was climbing through 7,500 feet, but turned it off 13 minutes later as the aircraft climbed through 29,000 feet.

“They might disconnect the autopilot thinking they can manually keep the plane in trim,” explained Aaronson, the retired pilot. The crew could use other control surfaces to counteract a problem.

Why wouldn’t the pilots make an emergency landing, especially on a long flight such as this one, to check out the problem on the ground?

“They apparently didn’t think it was serious enough,” said Aaronson.

As the cockpit voice recorder tape began, about 31 minutes before the crash, the pilots were discussing their problem with the stabilizer.

About 20 minutes later, with the plane still cruising at 31,000 feet, the pilots turned on the autopilot again.

“They probably did it just to see if it would work,” said Aaronson. “Sometimes systems stop working for an hour and then start working again.”

Then--virtually simultaneously--the autopilot was turned off again and the stabilizer moved into the full nose-down position, Hall said. At that point, the crew was no longer dealing with anything that could be termed a routine stabilizer problem.

The plane began to dive at a rate of 7,000 feet per minute, more than three times the normal descent rate from cruising altitude. On the voice recorder, the crew could be heard trying to arrest the dive. The plane’s speed brakes--flaps on the wings--were deployed, and after about a minute Flight 261 leveled off at 24,300 feet.

For the next nine minutes or so, the plane apparently was under control. The stabilizer was jammed in the nose-down position, but the crew was able to compensate by pulling back hard on the control yoke, tipping up the plane’s elevator, which consists of hinged panels on the trailing edge of the stabilizer. Crew members announced their intention to make an emergency landing in Los Angeles.

“Then things began to happen very quickly,” Hall said.

The pilots had extended the flaps and slats--hinged panels in the back and front of the wings--in their continuing efforts to gain the upper hand. That slowed the airplane and may have added to the nose-down pressure.

“What they are trying to do is slow the airplane down more to get better control,” said Aaronson. “I agree with what they did.”

Suddenly, at about the same time the loud noise was heard, the plane pitched down, ultimately reaching a nose-down angle of 70 degrees..

“At this point, they had no pitch control at all,” said Aaronson. “They are turning left, right, pulling, pushing, trying every combination to find something that will give them control. But it’s too late--at this point, there is nothing they can do.”

Rolling slowly left until it was inverted, the plane slammed into the Pacific.

Hall said the plane that crashed had two previous stabilizer trim maintenance write-ups, both last fall. In October, no problem was found. In November, a switch was replaced.

Barry Schiff, a retired TWA captain and air safety consultant, said he does not believe that the investigation will point to a widespread problem with the MD-83 or other aircraft in the same family, including the widely used DC-9.

“I don’t think this is a problem endemic to this aircraft,” he said. “I think it’s an aberration.”

Remains of four victims have been identified and the recovery staff is close to identifying five to 10 more, a spokesman said.

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The Last 13 Minutes

The final minutes of Flight 261 alternated between controlled flight and extreme drops in altitude. Nine minutes after pilots stabilized the plane, the nose dropped again and the MD-83 rolled to its left and descended the final 17,900 feet in less than a minute. Here, according to investigators, are the flight’s last minutes:

Sources: National Transportation Safety Board; National Oceanographic and Atmospheric Administration.

Researched by RICHARD O’REILLY and LYNN MEERSMAN / Los Angeles Times

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Crash Debris Field

The Navy has completed the video mapping of the Alaska Air crash site and recovered an 8-foot section of the plane’s left horizontal stabilizer and some portions of the central stabilizer, according to the National Transportation Safety Board. Here is the primary undersea wreckage field:

Source: MAPTECH, Talbot Pratt and Ted Shanstrom

Researched by LESLIE CARLSON/Los Angeles Times

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Times staff writer Anna Gorman and Times Community News reporters Gina Piccalo and Katie Cooper contributed to this story.