What happened
On 28 December 2014, an Airbus A3/20-216, registration PK-AXC, operated by Indonesia AirAsia, crashed into the Karimata Strait. During the flight, the aircraft experienced an uncommanded roll. This maneuver was accompanied by electrical interruptions and a series of system messages regarding the Rudder Travel Limiter Unit (RTLU). As the aircraft's attitude became extreme, the crew encountered aural stall warnings. Despite attempts to manage the situation, the aircraft entered a stall state, leading to the loss of the aircraft.
The investigation
The investigation focused on the sequence of events leading to the uncommanded roll and the subsequent stall. Investigators examined the aircraft's flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the flight path and the crew's actions. A significant portion of the inquiry was dedicated to the functionality of the Flight Augmentation Computer (FAC) and the Rudder Travel Limiter Unit (RTLU). The investigation also scrutinized maintenance records, specifically looking at how previous defects related to the RTLU were handled by line maintenance. Furthermore, the investigators analyzed the crew's response to the unusual attitude, considering the physiological effects of the 'startle reflex' and the 'fight or flight' response on pilot cognition and decision-making during high-stress, ambiguous flight deck scenarios.