Faulty part of the plane was a “major factor” in the AirAsia plane crash last December that killed all 162 people on board, Indonesian officials say.
The plane’s rudder control system malfunctioned four times during the flight – a fault that occurred 23 times in the preceding year, officials said.
Their report added that the crew’s response contributed to the disaster.
The Airbus A320-200, travelling from Surabaya to Singapore, crashed into the Java Sea on 28 December 2014.
Investigators had initially indicated that stormy weather was a major factor in the crash – however, they now say that this was not a cause.
The new report from the National Transport Safety Committee, released after a year-long investigation, found that the soldering on a tiny electronic part in the system that controlled the rudder was cracked, causing it to send four warning signals to the pilots.
The crew tried to fix the problem by resetting the computer system, but this disabled the autopilot. They then lost control of the plane.
The plane then entered “a prolonged stall condition that was beyond the capability of the flight crew to recover”, the report said.
Maintenance crews were aware of the problem as it had occurred 23 times in the past year, and resetting the system was one of several methods used previously to address it, the report added.