DENVER — Aviation experts say it could take up to a year to figure out what caused a Continental Airlines plane to veer off a runway and slide into a snowy field at Denver International Airport on Saturday, injuring 38 people.
So far, National Transportation Safety Board investigators said they haven't found any problems with the Boeing 737-500's engines, brakes or wheels, but they haven't ruled anything out.
They also haven't released any information about the landing gear under the plane's nose. That gear ended up under the plane, which landed on its belly in a frozen field about 2,000 feet from the runway.
Former NTSB chairman Jim Hall said the complex investigation will look at the condition of the plane's undercarriage, possible wind shifts as the plane sped down the runway and the position of the controls. Hall said investigators are advantaged by having a relatively intact plane and a crew that's able to answer questions.
"The good news is, they appear to have all the information to come up with a cause for this tragedy," he said.
Authorities are trying to determine why an odd bumping and rattling noise was heard on the flight's recorders in the seconds before Saturday's crash.
The noise was detected 41 seconds after the jet, bound for Houston, started speeding down the runway. Four seconds later, one of the crew members called for the takeoff to be aborted, said Robert Sumwalt, a NTSB spokesman.
The recording ends six seconds after that, probably because the plane slammed to the ground after hurtling off an embankment, he said.
The first officer has also told investigators that the plane was pulling away from the center line as it reached about 103 mph before taking a sudden left turn off the runway.
Tire marks and debris show the plane slid across a grassy strip and a taxiway before going off the embankment, hitting the ground at its base. It then went up a slight hill, over an access road and then down another small hill before stopping.
All passengers and crew members escaped the plane, which caught fire on the right side. Thirty-eight people were injured, including the plane's captain. Four people remained hospitalized Tuesday.
It was the first major crash of a commercial airliner in the United States since August 2006, according to the FAA. In that crash, 49 people were killed after a Comair jetliner mistakenly took off in pre-dawn darkness from Blue Grass Airport in Lexington, Ky., on a runway that was too short.
Former NTSB board member John Goglia said the rattling sound heard on the plane's voice recorder could have been caused by a problem with the plane's nose gear, which would have been easy to hear in the cockpit. He said the subsequent attempt to stop takeoff would also have put a lot of stress on the gear, exacerbating any existing damage.
"It's going to put an additional load on the nose gear, which may have caused it to fail," he said.
However, Goglia said a plane with damaged nose gear should still be able to continue down the runway rather than veer off. He said the chances of a very strong wind hitting at that exact moment and pushing it off seemed slim.
Former NTSB managing director Peter Goelz said he would expect investigators to focus on how far the plane was from the center of the runway when the sound was heard and how the controls, including the rudder, were positioned at the time.
The crew didn't talk on the recording about any problem with wind, which former Department of Transportation inspector general Mary Schiavo said she would expect if a strong crosswind was a factor. Still, she expected investigators to get more detailed information about wind conditions for that particular runway to check out that possibility.
Schiavo pointed out that some things did go right Saturday night since all passengers and crew members walked away alive. She said there was little for the plane to crash into in Denver's sprawling airport on the plains east of the city. Had the accident happened at a denser airport, including the city's former Stapleton airport, she thinks there likely would have been deaths.
On the Net:
Denver Airport: http://www.flydenver.com
National Transportation Safety Board: http://www.ntsb.gov