The captain of the AirAsia jet that crashed into the sea in December was out of his seat conducting an unorthodox procedure when his co-pilot apparently lost control, and by the time he returned it was too late to save the plane, two people familiar with the investigation said.
Details emerging of the final moments of Flight QZ8501 are likely to focus attention partly on maintenance, procedures and training, though Indonesian officials have stressed publicly that it is too early to draw any firm conclusions.
The Airbus A320 jet plunged into the Java Sea while en route from Surabaya, Indonesia, toSingapore on Dec. 28, killing all 162 people on board.
It had been suffering maintenance faults with a key flight control computer for over a week, and one person familiar with the matter said the captain had flown on the same plane with the intermittently faulty device just days before the crash.
Reuters reported this week that maintenance problems on the Flight Augmentation Computer (FAC), and the way the pilots reacted to them, were at the heart of the investigation.
People familiar with the matter told Reuters it was the Indonesian captain Iriyanto who took this step, rather than his less experienced French co-pilot Remy Plesel, who was flying the plane.
The decision to cut off the FAC has surprised people following the investigation because the usual procedure for resetting it is to press a button on the overhead panel.
It is also significant because to pull the circuit breaker the captain had to rise from his seat.
Shortly afterwards the junior pilot pulled the plane into a sharp climb from which investigators have said it stalled or lost lift.
The captain eventually resumed control, but a person familiar with the matter said he was not in a position to intervene immediately to recover the aircraft from its upset.
Data already published on the plane's trajectory suggest it may have been difficult for someone to move around the cockpit in an upward-tilting and by then possibly unstable aircraft, but there is so far no confirmation of the cockpit movements.
"The co-pilot pulled the plane up, and by the time the captain regained the controls it was too late," one of the people familiar with the investigation said.
Tatang Kurniadi, chief of Indonesia's NTSC, told Reuters there had been no delay in the captain resuming control but declined further comment.
Airbus declined to comment.
Lawyers for the family of the French co-pilot say they have filed a lawsuit against AirAsia in Parisfor "endangering the lives of others" by flying the route without official authorisation on that day.
Investigators have said the accident was not related to the permit issue.
AirAsia did not immediately respond to requests for comment on the lawsuit.
Although more is becoming known about the chain of events, people familiar with the investigation warned against making assumptions on the accident's cause, which needed more analysis.
Safety experts say air crashes are most often caused by a chain of events, each of which is necessary but not sufficient to explain the underlying causes of the accident.
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