Bloomberg reports that pilots had shut down power to a flight protection system after trying to deal with a string of alerts from it.

The pilots of the AirAsia flight which plunged into the Java sea last month had cut power to a critical computer system as they struggled to deal with the unfolding crisis, a report suggested on Friday.

All 162 people on board were killed when flight 8501 crashed on 28 December, en route from Surabaya in Indonesia to Singapore, in stormy weather.

On Thursday, Indonesian investigators said that the less experienced co-pilot was flying the plane as stall warnings began to sound, while the captain was monitoring him and communicating air traffic control.

The Airbus A320-200 climbed so rapidly - probably to avoid the bad weather in the area - that it lost lift and began falling.

The new report from Bloomberg, which cites two unnamed sources “with knowledge of the investigation”, said that pilots had shut down power to a flight protection system after trying to deal with a string of alerts from it.

The separate computers, which serve as back-up to each other, control the plane’s rudder - preventing it from making turns that are too sharp - and prevent the aircraft from going too slowly. If they lose power or go wrong they will shut down.

But it is not clear why the crew should have turned them off, nor why the plane then went into a steep climb, as the pilots should still have been able to fly the plane manually.

Investigators did not comment publicly on whether the flight augmentation computers were turned off in their Thursday briefing. They said their final report would not be ready for at least six to seven months.

The flight and cockpit data recorders showed that the jet was cruising at a stable altitude of 32,000 feet when the plane made a sharp left and the crew contacted ground control requesting permission to climb to 38,000 feet.

Controllers in Jakarta asked them to stand by.

The chief investigator of Indonesia’s National Transportation Safety Committee, Marjono Siswosuwarno, said satellite images from the time of the crash showed storm clouds in the area reaching up to 44,000 feet.

He added that the jet had been in a dangerously fast climb and stalled before falling to 24,000 feet, the last position recorded on radar.
“In many cases, the engine is not strong enough to fly in this high angle,” Siswosuwarno said.

He said investigators were examining whether turbulence or updrafts were a factor in the steep climb.

Indonesia Minister of Transportation Ignasius Jonan said previously that the Airbus A320 was climbing at around 6,000 feet a minute.

Ertata Lananggalih, another investigator with the National Transportation Safety Committee, said the pilots were conscious during the three minute descent and trying to control the plane.

The Wall Street Journal reported that unnamed sources indicated that it was the first officer’s control stick which pulled the plane’s nose up.

Reuters meanwhile reported that officials believed Captain Iriyanto, 53, an Indonesia air force veteran with about 20,000 flying hours logged, had taken over control of the aircraft from his less experienced French co-pilot Remi-Emmanuel Plesel when it started to climb and then descend.

The investigation team told reporters that the aircraft was in sound condition when it took off and all crew members properly certified.

Asked about the status of the flight augmentation computers prior to the crash, a spokesperson for Air Asia said: “We are unable to comment at this time as we would like to avoid adding to speculations while the investigation by The National Transportation Safety Commission is still ongoing.”

Indonesian rescuers have so far retrieved 72 bodies. Unconfirmed reports said another body may have been found on Thursday, drifting around 1000km from the crash site.