What happened
On 9 January 2021, a Boeing 737-500, registration PK-CLC, departed from Soekarno-Hatta International Airport in Jakarta, bound for Pontianak. The aircraft, operated by PT. Sriwijaya Air, was carrying 56 passengers and 6 crew members. Shortly after takeoff, the flight crew received instructions to climb to 29,000 feet via a standard instrument departure.
During the initial climb, the flight crew requested a heading change to 075 degrees to navigate around weather. While the aircraft was climbing, flight data recorder information indicates that the thrust lever for the left engine began to decrease, while the right engine remained stable. As the aircraft reached approximately 10,600 feet, it was observed to be turning left. Following a final instruction to climb to 13,000 feet, the aircraft's altitude peaked at roughly 10,900 feet.
At this point, the autopilot disengaged, and the aircraft entered a significant left roll of more than 45 degrees. The pitch angle subsequently dropped to more than 10 degrees nose down, and the left engine thrust continued to decrease. Shortly after these maneuvers, the flight data recorder stopped transmitting data. Air traffic controllers attempted to contact the pilot multiple times on both standard and emergency frequencies, but received no response. The aircraft disappeared from radar screens at approximately 14:40:48 LT. The flight resulted in 62 fatalities.
Findings
Flight data indicates that a continuous reduction in left engine thrust occurred during the climb phase, coinciding with the aircraft's loss of stability and subsequent descent.