What happened
On 1 January 2007, an AdamAir Boeing 737-4Q8, registration PK-KKW, crashed into the Makassar Strait, Sulawesi, during a scheduled flight. While navigating the airspace, the crew encountered issues with the aircraft's Inertial Reference System (IRS). As the crew attempted to manage the navigation system discrepancy, the aircraft entered a state of uncontrolled descent. The impact resulted in all occupants being killed.
The investigation
The investigation focused on the sequence of events leading to the loss of control, specifically examining the flight recorders and the crew's interaction with the aircraft's instruments. Investigators analyzed the behavior of the Inertial Reference System and the Mode Selector Unit. The inquiry also scrutinized the cockpit environment, looking at the communication between the pilot in command and the copilot. Evidence from the cockpit voice recorder suggested that the crew was dealing with a technical defect regarding the IRS alignment, which led to significant distractions during a critical phase of flight.
Findings
- The primary cause of the accident was spatial disorientation caused by complex vestibular illusions.
- The crew experienced a cycle of turns and recoveries where the loss of visual cues led to the sensation of flying level while the aircraft was actually in a spiral turn.
- A lack of effective Crew Resource Management (CRM) was evident; the crew failed to appropriately allocate tasks or communicate clearly regarding the selection of navigation modes.
- The crew's focus was diverted by the unresolved IRS defect, preventing them from properly monitoring the aircraft's flight instruments.
- The pilot in command and the copilot exhibited a lack of assertiveness, which hindered the detection and correction of the developing flight path error.