The captain of Indonesia AirAsia flight QZ8501 that crashed into the Java Sea on December 28 killing all 162 aboard was out of his seat, preoccupied with computer problems, when his plane was swept up by a massive thunderstorm related updraft before stalling and plummeting out of control.
According to sources privy to the investigation Captain Iriyanto was trying to disconnect the plane’s critical dual Flight Augmentation Computers through the circuit breakers which are located behind and above the pilots requiring the non-flying pilot to exit his seat.
Disconnecting the FAC removed a host of features including the critical the cockpit speed warnings and protections. It also makes the A320 “harder to fly” according to an A320 Check and Training Captain.
“It is highly likely that the French co-pilot, Remi Plesel, who was flying the A320 was preoccupied with the computer problems and not paying attention to the radar and missed the severity of the weather ahead,” said the A320 pilot.
Indonesia AirAsia had apparently been having problems with the FAC. According to a report in the Singapore Straits Times there were 9 writes ups in the plane’s technical log for issues with the FAC in 2014 alone.
The co-pilot had 2247 hours of experience, while the captain was a 20,537 hour veteran.
These types of crashes are termed in the industry “light bulb crashes” referring to the fact a simple malfunction that distracts all the crew can lead to the loss of the entire plane.
More details have also emerged of the terrifying ride that the passengers and crew on the flight from Surabaya to Singapore endured before impacting the sea.
When the A320 flew into the thunderstorm related updraft it initially soared at up to 6000ft per minute before stalling and then turning to the left and spiralling down at up to 24,000ft a minute.
While initially it was thought the G Forces would have render passengers unconscious pilot experts say they “would have been conscious through the ordeal until impact.”
Ertata Lananggalih, an investigator with Indonesia’s National Transportation Safety Committee, told media that the “pilots were conscious when the manoeuvres happened.”
Indonesia is not publically releasing the preliminary report into the crash although all countries involved have received the document.
Authorities have now recovered 72 bodies but have been unable to lift the A320s main cabin off the sea bed.