Incident Description
On 1 January 2007, a Boeing 737-4Q8 aircraft, registered PK-KKW, operated by Adam SkyConnection Airlines (AdamAir) as flight number DHI574, was on a scheduled passenger flight from Surabaya (SUB), East Java to Manado (MDC), Sulawesi. The aircraft departed from Djuanda Airport, Surabaya at 05:59 Coordinated Universal Time (UTC) under instrument flight rules (IFR), with an estimated time of arrival at Sam Ratulangi Airport, Manado of 08:14. The crew had flight planned for an alternate of Gorontalo (GTO). The aircraft was cruising at flight level 350 (approximately 35,000 feet) when it disappeared from radar. The pilot in command (PIC) was designated as the pilot flying for the sector, while the copilot served as the monitoring and support pilot. There were 102 people on board: two pilots, four cabin crew, and 96 passengers consisting of 85 adults, 7 children, and 4 infants.
Investigation Findings
The official investigation identified several findings regarding the accident. Flight crew coordination was described as less than effective; the PIC did not manage task sharing effectively, and crew resource management practices were not followed. The crew focused their attention on troubleshooting an Inertial Reference System (IRS) failure, and as a result, neither pilot was actively flying the aircraft. After the autopilot disengaged and the aircraft exceeded a 30-degree right bank, the pilots appeared to have become spatially disoriented. The investigation also found that the AdamAir syllabus of pilot training did not cover complete or partial IRS failure, and the pilots had not received training in aircraft upset recovery, including spatial disorientation.
Additionally, other causal factors were identified. At the time of the accident, AdamAir had not resolved airworthiness problems with the IRS that had been recurring on their Boeing 737 fleet for more than three months. Furthermore, AdamAir's maintenance engineering supervision and oversight was not effective and did not ensure that repetitive defects were rectified.
Probable Cause
The probable cause, as stated in the official findings, encompasses the identified findings and causal factors.