Investigator: AirAsia plane wobbled, climbed and triggered stall warning

Story highlights

  • Pilot monitored flight as co-pilot flew AirAsia Flight 8501
  • Stall warning blared as plane climbed suddenly and until it crashed
  • Plane wobbled and veered left

Jakarta, Indonesia (CNN)Before AirAsia Flight 8501 crashed, the co-pilot was flying the plane as the more experienced pilot monitored the flight. And things may have gone wrong in a span of just three minutes and 20 seconds, triggering a stall warning that sounded until it crashed into the Java Sea.

Those are the new details released by the Indonesia's National Transportation Safety Committee in a news conference Thursday.
    Though it's common for the co-pilot to be in control of the aircraft, significant questions still linger over the crash of the AirAsia jet. Why did the plane start a sudden, steep ascent? Was bad weather a factor?
    QZ8501 crashed December 28 as it flew from the Indonesian city of Surabaya toward Singapore. There were 162 people on board.

    Stall warning sounded

    The plane was in good condition and entire crew were all certified, said Mardjono Siswosuwarno, the chief investigator for the transportation committee.
    The flight took off and cruised at 32,000 feet amid stormy weather. About 11:12 p.m. UTC (coordinated universal time), the pilot asked the control tower whether it could ascend to 38,000 feet, according to the committee.
    The plane was veering left and wobbling, said Ertata Lanang Galih, a senior pilot and investigator with the committee.
    QZ8501 then ascended from its cruising altitude to 37,400 feet in about 30 seconds in a steep ascent, said Mardjono.
    Commercial planes are not designed to ascend so quickly, analysts have said. It may have been climbing at a rate twice as fast as it could and should, one analyst told CNN.
    The stall warnings -- which blare the words "Stall, Stall" -- went on as the plane started the steep climb and continued until it crashed, according to information on the flight data recorder.
    The voice warning doesn't always mean the aircraft has stalled, said Mardjono. The warning can be triggered when the angle of attack, which is the angle at which the wing tackles the oncoming wind, hits 8 degrees.
    The plane dropped quickly, falling to 24,000 feet, out of radar detection.
    Air traffic control permitted the plane to ascend to 34,000 feet about four minutes after the pilot's initial request.
    Officials have said that the aircraft climbed rapidly before it fell into the water. Last week, Indonesian transportation minister Ignasius Jonan said the AirAsia jet stalled after its sudden ascent.
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    Investigators have submitted their preliminary report into the crash, officials said. But Tatang Kurniadi, the chief of the National Transportation Safety Committee, said they would not release the preliminary report during a Thursday news briefing.
    It's unclear whether or when the initial report will be released fully to the public. While the preliminary report presents facts, officials indicated there isn't enough verification yet.

    Pilots' experience

    The French co-pilot, Remi Emmanuel Plesel, had less experience than the captain.
    Plesel, 46, had 2,275 hours with AirAsia Indonesia, compared with the captain, known only as Irianto (as many Indonesians go by one name), who had 6,100 hours on AirAsia on the Airbus 320.
    Irianto had more than 20,000 flying hours under his belt, having worked for another airline in Indonesia for 13 years before that, and had been a Indonesian Air Force pilot for a decade prior.
    But it's common for the co-pilot to be in control of the aircraft.
    "They usually rotate back and forth," said David Soucie, a CNN aviation expert. "And that's a matter of maintaining experience. You wouldn't want one pilot to get all the flight time and the others not to be current on what's going on."
    Indonesian aviation investigators are trying to establish why Flight 8501 went down in an area of heavy thunderstorms last month while other planes nearby completed their journeys safely.
    Authorities have recovered 72 bodies from the sea, with 90 still unaccounted for, according to AirAsia.