The Spanish airliner that crashed at Madrid airport last month killing 154 people did not have its wing flaps set for take off, investigators said today.
The pilots were unaware that the vital devices, which provide extra lifting power, had not been deployed because a cockpit warning alert did not go off.
The findings are based on information from the MD-82's flight and cockpit voice recorders and contained in a preliminary report on the August 20 crash of the Spanair flight.
The report said further study was needed of a malfunction of an air temperature gauge outside the cockpit, which forced the pilot to abandon a first take off attempt. Spanair called it a minor glitch resolved by turning off the gauge because it was not an absolutely essential piece of equipment.
But the Spanish investigators said that this might have had something to do with the failure of the cockpit alarm that is supposed to sound when a plane trying to take off is not properly configured.
The data recorder showed no evidence of problems with the plane's two engines, it added.
But the flight recorder did reveal that from the time the plane's engines started on the runway until the crash itself, sensors measuring the position of the flaps gave a reading of "zero degrees," which means they did not extend as they were supposed to.
A loud alarm should have gone off in the cockpit, but "the cockpit voice recorder registered no sound from the take off warning system," the report said.
Some of the 18 survivors have said the plane struggled to gain speed and altitude during takeoff. The report said the plane only got 40 feet off the ground.
Investigators say the aircraft crashed tail-first, bounced three times as it skidded through a grassy area near the runway, then largely disintegrated and burned after coming to a halt at the edge of a stream.
The report said makers McDonnell Douglas recommended after a fatal MD-82 crash in 1987 in Detroit, Michigan, that airlines check the take-off warning system before each flight.
But Spanair's policy is to check the system before a plane's first flight of the day and during stopovers, but in the latter case only if an entirely new cockpit crew takes over for the continuing leg.
If one member of the cockpit crew stays on for the next leg, Spanair does not carry out such checks and this was the case of the plane that crashed, the investigators said.
The flight originated in Barcelona, stopped off in Madrid and was to go on to Las Palmas in the Canary Islands, and the pilot and co-pilot were not changed.
Spanair official declined to comment.