On December 28, 2014 AirAsia Flight 8501, flown by an Airbus A320, took off from Surabaya, Indonesia bound for Singapore. Shortly after reaching its cruising altitude of 32,000 feet it plunged into the Java Sea, killing all 162 on board. The accident report released by Indonesia’s National Transportation Safety Committee concludes that the crew stalled the aircraft and failed to recover after inadvertently disabling the autopilot and flight control system while attempting to resolve a problem.
Based on analysis of flight data recorder and cockpit voice recorder data, the report determined that there were four warnings of a malfunction of the rudder control system while the crew maneuvered around cloud buildups. Each time the crew responded by resetting the flight control computers, as prompted by the on board electronic monitoring system. However, when the fault warning occurred again, the crew reset the computers’ circuit breakers, rather than the computers themselves. This action interrupted the power supply, disconnected the autopilot and auto throttle systems, and caused the flight control to revert to “alternate law,” which provided a degraded level of protection. The airplane rolled sharply to the left, and the co-pilot reacted by moving the sidestick controller to the right and pulling it fully back, putting the plane into a steep climb.
The captain pushed his sidestick forward, but did not tell the co-pilot that he was taking control. Instead, he said “pull down” several times, and the co-pilot pulled fully back on his stick. Because the Airbus sidesticks operate independently, the co-pilot’s inputs overrode the captain’s, and the aircraft pitched up until it stalled. After the stall warning sounded the co-pilot continued pulling back on his stick, and the aircraft plummeted into the sea at more than 12,000 feet per minute.
The AirAsia accident was similar to Air France Flight 447, where an Airbus A330 stalled and crashed into the South Atlantic in May, 2009. Ice crystals blocked the intake ports for the air speed sensors, causing the autopilot to disengage and the automated flight control system to revert to alternate law. The co-pilot pulled his sidestick back, and held it there while the aircraft stalled and fell from the sky.
The parallels are striking. In each case the autopilot disconnected and the flight control system unexpectedly reverted to alternate law. In each case the co-pilot pulled back on his control stick, stalled the aircraft, and held the stick back after the stall warning began. In each case, there was ample time and altitude available to recover simply by pushing the stick forward. Yet in each case the captain failed to intervene and regain control of the aircraft.
In a 2014 article on Air France 447 author and pilot William Langewiesche blamed automation, saying, “It seems that we are locked into a spiral in which poor human performance begets automation, which begets increasing automation.” And he predicted, “Next time it will be some other airline, some other culture and some other failure—but it will almost certainly involve automation and perplex us when it does.” His prediction came true for AirAsia 8501.
Is Langewiesche right? Has automation made pilots unable to fly when unexpectedly deprived of sophisticated flight control systems? The regulations state the historic rule: “The pilot in command is directly responsible for, and is the final authority as to, the operation of that aircraft.” A pilot’s most important responsibility is always to maintain control. The pilot in command must be ready and able to fly the airplane at all times. That is no less true today than it was in the earliest days of flight.