The report into last December’s AirAsia crash suggests significant parallels with the Air France disaster of 2009.
In both incidents, a technical issue helped trigger a chain of events in the cockpit where the pilots’ commands took the plane out of control. And on both occasions, a possibly disoriented co-pilot pulled back on his stick, pointing the nose of the plane up and putting it into a disastrous stall.
Questions will be asked about AirAsia’s maintenance after an unresolved problem with the wires leading to the rudder of the Airbus A320 had triggered repeated warnings in the weeks before the plane took off from Surabaya to Singapore on 28 December. On this flight, on three occasions, an alert flashed in the cockpit telling pilots of a problem with the rudder controls. Three times, the pilots responded with a series of commands to restore it as instructed.
When the warning flashed for a fourth time in the space of 15 minutes, one of the pilots – possibly having seen a fix employed by an engineer on the ground – cut the circuits to reset the system, and disabled the autopilot.
With the rudder now not being immediately controlled, the plane banked quickly, to an angle of 54 degrees. In correcting this severe roll, the co-pilot appears to have pulled back on his controls. But he then continued to pull back even as the captain attempted to do the opposite, until the plane’s “angle of attack” was too near the vertical and it stalled, out of control, and plummeted.
Although the cockpit voice recorder does not give the same picture as from the AirFrance disaster, where 228 people died when the plane crashed in the southern Atlantic, there appears to have been the same contradiction between the pilot’s commands and the unwitting actions taken by the second-in-command.
In the AirFrance disaster, the instruments supplying the speed readings to the cockpit had iced over and the autopilot was disabled, although investigators have never fully established what led the pilot to get the controls so disastrously wrong and ignore the stall warnings on the Airbus A330. The immediate situation facing the AirAsia pilots, once the plane started to roll, must have been far more disorientating. The report issued by the Indonesian safety board does not apportion blame. But the incident suggests again that pilots have become decreasingly able to cope when computer systems go wrong.
David Learmount, of FlightGlobal, said: “These guys had more excuse than the AirFrance crew. This was a repetitive fault and they did the correct thing three times, before trying something else. And the aircraft was in an upset condition before the autopilot was switched off. But the pilot should have been aware of the fault. Had they used traditional pilot skills the aircraft [would have been] controllable, but once it was in a rapid dive it was difficult. They didn’t pick up the full import of what was happening to them.”
Learmount said the incidence of pilots losing control had increased as planes had become more and more automated, as a US Federal Aviation Administration report had shown. He said: “Most of the time computers are brilliant and accurate and we learn to trust them, but when they do go wrong it’s very unsettling. Very rarely does anything serious go wrong with the plane or its computers but if it does, the pilots often don’t cope.”
