Details emerging of the final moments of Flight QZ8501 are likely to focus attention partly on maintenance, procedures and training, though Indonesian officials have not ruled out any cause and stress it is too early to draw firm conclusions.
The Airbus A320 jet plunged into the Java Sea while en route from Surabaya, Indonesia, to Singapore on Dec. 28, killing all 162 people on board.
People familiar with the matter said earlier this week that investigators were examining maintenance records of one of the automated systems, the Flight Augmentation Computer (FAC), and the way the pilots reacted to any outage.
One person familiar with the matter said the captain had flown on the same plane with the intermittently faulty device days earlier. There was no independent confirmation of this.
After trying to reset this device, pilots pulled a circuit-breaker to cut its power, Bloomberg News reported on Friday.
People familiar with the matter said 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.
AirAsia said it would not comment while the matter was under investigation by the National Transportation Safety Committee (NTSC) of Indonesia. The NTSC has said it is too early to say what role either human factors or equipment may have played in the crash, which is still being investigated.
Experts say the loss of the FAC would not directly alter the trajectory of the aircraft but would remove flight envelope protection, which prevents a pilot from taking a plane beyond its safety limits, and require the crew to fly it manually.

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