During the examination by the judge, both mechanics have admitted that they did not consult the official Boeing manual when they removed the fuse that seems to have deactivated the fatal alarm, instead they were guided by the minimum equipment list, which requires a less stringent test of the equipment and is designed to just check the plane is ready for flight.
The same plane had been revised the day before for a similar incident in El Prat airport in Barcelona. In comparing the mechanics reports from the previous incident, the judge has noted that the Catalan mechanics followed the official Boeing checklist; the Madrilenos didn’t.
The official Boeing checklist would have required that the plane be taken back to the hanger for an exhaustive test. It appears that after consultation with the pilot of the plane, it was decided that this was not necessary.
It was also confirmed that the supervisor who checked the mechanics work was not the official Spanir head of maintainence; instead it appears it was the duty head from Barajas. This is perfectly OK under current rules, but the question is why did the investigation believe the Spainair head was involved when he wasn’t?
The current hypothesis is that a non essential alarm that is designed to check the outside air temperature was malfunctioning. It seems the mechanics removed the fuse for this alarm, as was permitted under flight regulations, in order to prevent a long delay to the flight. However, it appears that a vital alarm that measures the flaps angle for takeoff was also either disconnected or touched, which meant that upon takeoff the alarm did not sound and the pilots did not realise that flaps were not locked for takeoff – which caused the crash. The investigation is now concentrating on whether the fault lies with the mechanics, or with the pilots who may have ignored an alarm before takeoff.