Jakarta (AFP) - A faulty component and the crew's inadequate response caused an AirAsia A320 to crash into the Java Sea last year, killing all 162 people on board, an Indonesian report said Tuesday.
Flight QZ8501 plunged into the ocean in stormy weather on December 28, during what was supposed to be a routine flight from the Indonesian city of Surabaya to Singapore.
The crash of the Airbus A320-200 triggered a huge international search, with ships and aircraft from several nations involved in a lengthy hunt that was hampered by strong currents and bad weather.
The bodies of 56 of those who died have never been found.
In their final report into the accident released Tuesday, Indonesia's official National Transportation Safety Committee said poor maintenance and a fault with the system that helps control the rudder's movement was a major contributing factor to the crash.
Cracked soldering in the component caused it to malfunction and send repeated warning messages to the pilots, it said.
In response, they tried to reset a computer system but in the process turned off the plane's autopilot, sending it into a sharp roll from which they were unable to recover.
"Subsequent flight crew action resulted in inability to control the aircraft," said the report. The plane went into a "prolonged stall condition that was beyond the capability of the crew to recover", it said.
Investigators said there was miscommunication between the pilots as the plane plunged towards the sea, with the men at one point pushing their control sticks in opposite directions.
- 'Find those responsible' -
Investigator Nurcahyo Utomo said that AirAsia pilots flying Airbus aircraft had not received adequate training for when their planes became severely destabilised, as it was not recommended by the manufacturer.
The report said the faulty component, the Rudder Travel Limiter, had suffered 23 problems in the past 12 months, citing maintenance records.
"The investigation found some inadequacy in the maintenance system, leading to the unresolved, repeated problem" with the rudder system, said Utomo.
Before crashing, the plane climbed fast and went into an aerodynamic stall, losing lift. The French co-pilot, Remi Plesel, was at the controls in the moments before the crash, rather than the more experienced pilot.
Family members of those killed in the accident had been waiting anxiously for the report, and Eka Santoso -- whose brother, sister-in-law and their two children died in the crash -- urged AirAsia to take action following its recommendations.
"AirAsia must find the people who were responsible for this problem," he told AFP, referring to the faulty competent, and adding those who failed to fix it should be prosecuted. "It has been proven there was a weakness."
The crash was the first major setback for Malaysia-based AirAsia, which has enjoyed a spectacular 13-year run of success, and the group's flamboyant boss Tony Fernandes thanked the transport committee for their work.
"These are scars that are left on me forever but I remain committed to make AirAsia the very best," he said.
An Airbus spokesman said the company was studying the report.
Rescuers faced difficulties in the choppy waters of the Java Sea, but the main body of the plane was eventually located on the seabed by a Singapore navy ship and both black box data recorders were recovered.
Search efforts were finally called off in March after almost three months.
The crash was one of several aviation disasters in the sprawling archipelago in the past year.
In August, a turbo-prop plane operated by Indonesian domestic carrier Trigana crashed in the remote eastern region of Papua during a short flight in bad weather, killing all 54 people on board.
And in June an Indonesian military plane went down into a residential neighbourhood in the city of Medan, exploding in a fireball and killing 142 people.
Indonesian airlines are expanding rapidly after years of strong economic growth and the emergence of a new middle class, but carriers are struggling to find enough well-trained personnel to keep up with the boom, experts say.