The final report from Indonesia’s national transport safety agency said an existing fault in the system that controlled the Airbus A320-200’s rudder had set off a chain of events that caused the crash.
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Although the investigators do not have evidence to prove their theory about how the airplane crashed, they strongly speculate that one of the pilots in the cockpit had reset the computer’s circuit breaker, in a report made by The New York Times. This turned off the autopilot, and the plane then started to roll, the report found.
An official from the National Transportation Safety Committee said that analysis of the flight data recorder showed that warning signs had popped up four times due to disturbances in the rudder control system after the plane departed for the two-hour flight.
“Subsequent flight crew action resulted in inability to control the aircraft”, the report said.
The report also revealed that QZ8501’s RTL had suffered 23 reported malfunctions over the previous year, according to aircraft maintenance records. On the fourth warning, the plane disengaged from autopilot, causing the crew to lose control of the aircraft.
Accident investigator Nurcahyo Utomo said the “pull down” order was confusing as when one pulls down [the gear controls] the plane goes up.
Investigators said the flight crew’s actions while flying manually led to the stall.
In other words, “it’s a series of technical failures but it’s the pilot response that leads to the plane crashing”, CNN’s aviation correspondent Richard Quest said. The plane eventually stalled before diving downward at 20,000 feet per minute into the water. He had apparently watched a technician fixing the system by changing the circuit breaker.
Among safety recommendations, the committee called on Airbus to develop a means for pilots “to effectively manage multiple and repetitive master caution alarms to reduce distraction”.
Air Asia has since required upset recovery training for its pilots, Utomo said.
AirAsia chief executive Tony Fernandes has vowed to support the investigation and said in August that the group had already ordered a review of its systems following the crash.
All 162 people on board the flight died when the flight went down past year.
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“We are now carefully studying its content”, the statement said.
