With retrieval of the second "black box," investigators will study whether emergency procedures influenced the crash.
For more than seven minutes, the crew of Alaska Airlines Flight 261 had regained some semblance of control over their disabled plane. Then something happened that plunged them into an upside-down death spiral.
This sequence of events is prompting investigators to ask whether the emergency procedures the crew was following during the seven-minute span somehow triggered the fall that killed 88 people Monday.
It's too soon to tell, but the aircraft's second and more sophisticated "black box," containing 48 flight data parameters, may answer that question soon. It was found Thursday in the Pacific Ocean northwest of Los Angeles and whisked to the National Transportation Safety Board's lab in Washington, D.C.
Searchers also found the intact tail of the plane on the ocean floor. A submersible sent up video images of a piece of the fuselage with four windows, several large pieces up to six feet wide and numerous smaller pieces. It was not released whether searchers had found any bodies, some of which are believed trapped under the debris.
A quick analysis of the first "black box," which contained the last 30 minutes of cockpit conversations, revealed a crew coping with a jammed stabilizer the entire time, NTSB chairman Jim Hall told reporters Thursday in Washington. They were having difficulty "controlling the airplane's tendency to pitch nose-down," he said.
But something worked _ almost. The plane leveled off. The crew, while still struggling with the horizontal stabilizer controls, started preparing for an emergency landing at Los Angeles International Airport. "Then control was suddenly lost," Hall said.
"We'll look at emergency procedures for dealing with jammed stabilizers," NTSB aviation safety director Bernard Loeb said Thursday.
Regaining some control is much like walking a tightrope, said Bob Sweginnis, an aviation safety professor at Embry-Riddle Aeronautical University in Prescott, Ariz.
"You're on the tightrope and you're in trouble and the tightrope breaks," said Sweginnis, a friend of the plane's pilot, Ted Thompson. "Was it because you bounced a little too hard? Or the stress of the situation? Or someone jiggling the tightrope?"
The timing of the emergency landing procedures may be key, experts and NTSB officials said.
"I would be looking at the emergency procedures," said Embry-Riddle professor Mike Polay, a former military crash investigator. "No. 1: Were they adequate? No. 2: Were they followed?"
Sweginnis added: "It was something that no one had anticipated happening. I looked at the procedures (for dealing with a semi-jammed stabilizer). It was kind of, come on, there's more than this, isn't there?"
Sweginnis said he was looking at a manual from a different airline for a sister-type ship, a DC-9, to Alaska Airline's MD-83, but most manuals are very similar.
There are several ways that following emergency procedures can make matters worse.
One involves preparations for landing. When a plane prepares to land, flaps are lowered and landing gear drops. Those small acts change the aerodynamic properties around the plane. That could have been enough to throw off the wounded jet's precarious balance, said Bill Waldock, associate director of the Center for Aerospace Safety Education at Embry-Riddle.
Sometimes, emergency procedures don't really fit the situation. Waldock sited a 1979 American Airlines DC-10 crash near Chicago, when most of a jet's engine fell off. For that, there were no emergency procedures, so the crew followed the plan for a flaming engine, hastening the crash, he said, which killed 273 people.
Alaska Airlines spokesman Greg Witter declined to comment on Flight 261's problems, citing NTSB gag rules. He said the airline had scored well in top-to-bottom inspections _ including emergency procedures _ in September 1998 from the Department of Defense and in 1995 from the Federal Aviation Administration.
Emergency procedures, while a suspect, may not be the culprit. An internal weight shift might have taken the plane out of trim. Or something mechanical _ such as a bent bolt _ could have eased for a few minutes, allowing the crew to get control, then broken catastrophically.
But the list of suspects is narrowing, as the only problem mentioned on the cockpit voice tape is the jammed stabilizer, Loeb said. Further, the pilots had been fighting the stabilizer problem for at least 30 minutes _ the length of the tape _ Hall said.
Although these stabilizer problems have occurred before on the MD-80 series of jets, and forced an emergency landing Wednesday in Phoenix, they are rare, according to Loeb.
He said his agency is "nowhere near" calling for grounding the fleet.
_ Information from the Associated Press was used in this report.