Crash investigation focuses on jet's stabilizer

COVERAGE Top story Feb. 1 Crash investigation focuses on jet's stabilizer Experts say no common thread in in-flight crashes Alaska employees choke back tears as they deal with loss At airports, grief and relief follow news of crash Jan. 31 Alaska Airlines jet crashes off California In rising swells and spreading oil, boats search for plane, people  REALVIDEO Feb. 1 Recording of final minutes of Flight 261 is released NTSB briefs press on crash Tragedy strikes Alaska Airlines Search and rescue mission continues off Calif. coast Officials address public regarding crash Jan. 31 Alaska Airlines Flight 261 crash This video clip is viewed using RealPlayer. Get RealPlayer | Help  THE VICTIMS List of passengers and crew aboard Flight 261 Biographical sketches of several passengers  ABOUT THE PLANE A look at McDonnell Douglas's MD-80 series More from the Boeing Web site  ABOUT ALASKA AIRLINES Alaska Airlines Web site Has its roots in a three-seat shuttle service begun in 1932 between Anchorage and Bristol Bay, Alaska. The service merged with Star Air Service in 1934 and, after several more mergers, adopted the name Alaska Airlines. With deregulation in 1979, Alaska began expanding throughout the West Coast and within a decade had tripled in size. Alaska now carries more than 12 million customers per year, and its route system serves more than 40 cities in Alaska, Canada, Mexico and five Western states. Alaska says its fleet of 88 Boeing jets is the youngest among all major airlines. Alaska planes are distinctive for the image of an Eskimo painted on their tails. Source: Associated Press  CRASH TIMELINE Reconstruction of the crash of Flight 261 Following is summary of the last radio exchanges of Alaska Airlines Flight 261, as described by John Hammerschmidt of the National Transportation Safety Board. These are not direct quotes from pilots and controllers, but are based on what the NTSB called a  rough transcript.  Times are Pacific Standard. 3:55 p.m. Last routine transmission before problems are reported. Los Angeles ATC (air traffic control center located in Palmdale, Calif.) clears Flight 261 to head for San Francisco at 31,000 feet. 4:10 p.m. Flight 261 advises it is having control difficulties and descends to 26,000 feet. Seconds later Flight 261 reports it is at 23,700 feet. Discussion about pilots having trouble controlling the plane. 10 second later ATC asks Flight 261 what altitude it wants to maintain. 4:11 p.m. ATC asks Flight 261 its condition. Flight 261 advises it is "kind of stabilized," in Hammerschmidt's words, and is going to do some troubleshooting. Flight 261 asks for clearance to fly between 20,000 and 25,000 feet. ATC gives clearance. 4:14 p.m. ATC asks if Flight 261 needs anything. Flight 261 responds that pilots are still working on the problem. Seconds later Discussion between air traffic controllers about handing off control of plane from one sector to the next. 4:15 p.m. ATC traffic control hands off to a new controller who was aware of its problems. Seconds later Flight 261 advises it has a jammed stabilizer and difficulty maintaining altitude. Pilots think they can maintain altitude and land at Los Angeles International Airport. 4:16 p.m. Flight 261 cleared to land at LAX. ATC asks if flight needs a lower altitude. Flight 261 says it needs to get to 10,000 feet and change configuration -- set the wing flaps to slow the plane down -- while over water. ATC issues clearance to 17,000 feet. Flight 261 says OK and advises it needs a block of altitudes. Last known transmission of Flight 261. 4:17 p.m. ATC advises Flight 261 to contact another sector on a different frequency. Transmission not acknowledged. 4:21 p.m. Flight 261 is lost off radar. Source: Associated Press

LOS ANGELES -- Early theories on the Alaska Airlines crash focus on the horizontal stabilizer, a tail-mounted wing that helps point the jet's nose up or down. But experts said other, still-unexplained factors probably played a major role, too.

Shortly before the airliner went down, a crew member reported that the horizontal stabilizer had jammed. Minutes later, the MD-83 jetliner, with 88 people aboard, slammed into the Pacific as it was flying to Los Angeles for an emergency landing.

Problems with the device are rare and can usually be resolved by switching its motors off, said Barry Schiff, an aviation consultant and former TWA pilot. The system has not been tied to any other crashes involving the MD-80 series of jets.

"This could be precedent-setting," he said. "That's a pretty rugged hunk of machinery back there, and it's designed not to fail."

The 40-foot-wide horizontal stabilizer is used to balance the plane's up-and-down motion in a process called trimming. A plane can fly without such a system, but the crew would have to push extremely hard on the yoke to maintain level flight.

Pilots routinely train for an unusual scenario called runaway trim, in which an electrical short or some other glitch causes a loss of control of the stabilizer, said Dugan Blechschmidt, an Alaska Airlines pilot who checks the qualifications of the airline's flight crews.

"All of a sudden the airplane wants to pitch up without any input from the pilot," he said. "We have procedures to deal with that."

In the 11 minutes between the first call of trouble and the time the plane disappeared from radar, the crew should have had time to deal with the problem, including using other controls or even cutting power to the system altogether without losing control, experts said.

Other factors, however, could have complicated the situation.

"What if something catastrophically occurred back in the tail that rendered of these controls inoperative? Then you could have a real problem on your hands," Schiff said. "Or what if a piece of the tail actually came off and then jammed the stabilizer?"

In May, the Federal Aviation Administration ordered operators of MD-80s and related jets to undergo inspection for signs that hinges connecting parts of the plane's tail were corroded.

Alaska Airlines was in the process of inspecting its fleet and had not checked out the plane that crashed Monday.

Airline spokesman David Marriott said 10 planes that were inspected showed "nothing of any significance." He said the aircraft involved in the crash had been scheduled to be checked in June.

A horizontal stabilizer has the same effect as the feathers on an arrow or the fins of a dart. It counteracts the aerodynamic effects that cause bobbing during flight. Another stabilizer controls left-right motion.

"If you fired an arrow and there were no feathers back there, the arrow would wobble through the air," Schiff said. "So we put tail feathers on an airplane for the very same reason -- to stabilize the airplane so it doesn't wobble."

The system is controlled by flight-deck switches on the pilot's and first officer's steering columns. Electrical motors controlled by the switches can move the stabilizer up or down by 14 degrees, said John Thom, a spokesman for the Boeing Co., which in 1997 bought McDonnell Douglas, maker of the MD-80s.

"Trimming" the stabilizer is an action a pilot uses to bring it into balance.

If the crew lost control of the horizontal stabilizer, it would have no way to keep the nose pointed at the proper angle up or down, though it is unlikely there would be a sudden change in the plane's pitch. Aerodynamic forces would cause the plane to gradually point toward the ground.

"The fact that they had at least a few minutes to deal with the situation, whatever started was probably subtle," said William Waldock, associate director of the Center for Aerospace Safety Education at Embry-Riddle Aeronautical University in Arizona.

"It sounds like something happened relatively quickly at the end," he said. "Whatever it was, it was obviously beyond the capability of the crew to overcome."

It will probably be weeks or months before any conclusions can be made. Flight recorders will shed light on the condition of the instruments, and radar tracking data might reveal how quickly the plane dropped.

"What we're doing is interpolating between that comment and the crash itself to try to create some scenario that would all of this to happen," he said. "If you have a catastrophic failure in some way, that could lead us to the accident site."