JAKARTA (Reuters) - The French first officer of an AirAsia (AIRA.KL) passenger jet that crashed into the sea last month was at the controls just before the accident, Indonesia's lead investigator said on Thursday.
The Airbus (AIR.PA) A320 vanished from radar screens in bad weather on Dec. 28, less than half way into a two-hour flight from Indonesia's second-biggest city of Surabaya to Singapore. All 162 people on board were killed.
"The second-in-command, popularly known as the co-pilot, who usually sits to the right of the cockpit, at the time, he was flying the plane," said National Transport Safety Committee (NTSC) investigator Mardjono Siswosuwarno, referring to first officer Remi Plesel.
"The captain, sitting to the left, was the pilot monitoring."
Data from the black box flight data recorder has provided the accident probe with a "pretty clear picture" of what happened in the last moments of AirAsia flight QZ8501, Siswosuwarno said, although few details have been made public.
Indonesia has previously said the aircraft climbed abruptly from its cruising height and then stalled, or lost lift, before plunging out of control into the sea.
Using a hand-held model of an A320 officials demonstrated to reporters how the aircraft veered left and climbed steeply to more then 37,000 ft (11,300 metres), before rapidly losing altitude in the moments before the crash.
Captain Iriyanto, 53, an Indonesia air force veteran with about 20,000 flying hours logged, was believed to have taken over control of the aircraft from the less experienced Plesel when it started to ascend and then descend, officials said.
The stall warning - an automated voice that repeats the words "stall, stall" - had sounded in the cockpit. The aircraft was still in a stall when the black box recordings ended seconds before impact, Siswosuwarno said.
Indonesia's meteorological bureau said soon after the crash that seasonal tropical storms were likely a factor, prompting speculation that there might be parallels with the loss of Air France flight AF447 over the Atlantic in 2009.
Icing on the airframe of AF447 caused the pilots to lose air speed readings, and the crew's reaction put the plane into a stall from which it never recovered.
Investigators were still studying if there was any icing on the AirAsia plane's air speed indicators, and any other similarities to AF447, Mardjono said.
Last week, the head of the NTSC said there were "no similarities" with AF447, and sources familiar with the investigation have told Reuters icing on the air speed indicators does not seem to have been an issue with QZ8501.
Investigators said the cockpit voice and flight data recorders showed that the plane had been cruising at a stable altitude before the accident. The aircraft was in sound condition when it took off, and all crew members were properly certified, they said.
"The plane was flying before the incident within the limits of its weight and balance envelope," Mardjono said. "While the flight crew had valid licences and medical certificates."
NTSC chief Tatang Kurniadi told the same Jakarta news conference that Indonesia submitted its preliminary report on the crash to the International Civil Aviation Organization (ICAO) on Wednesday, as required under global aviation rules.
The report, which has not been made public, was purely factual and contained no analysis, he said, adding that the full, final report would take at least six to seven months to complete.
On Wednesday, Indonesia said the search for dozens of victims still unaccounted for could end within days if no more bodies were found.
A multinational search and recovery operation has found 70 bodies in the Java Sea and had hoped to find more after finding the fuselage of the plane. But days of rough weather and poor underwater visibility hampered navy divers' efforts.
Additional reporting by Fransiska Nangoy in Jakarta and Siva Govindasamy in Singapore; Writing by Randy Fabi; Editing by Alex Richardson