What happened
On 20 December 2011, a Boeing 737-300, registration PK-CKM, operated by PT. Sriwijaya Air, was performing a scheduled passenger flight from Jakarta to Yogyakarta. After an initial diversion to Surabaya due to deteriorating weather, the flight resumed toward Yogyakarta with 137 people on board.
During the final approach to Adisutjipto International Airport, the aircraft failed to maintain a stabilized approach. The pilot flying disengaged the autopilot and autothrollle at approximately 1,200 feet to manually correct the flight path after realizing the aircraft was not aligned with the runway. This maneuver resulted in a steep descent rate of up to 2,040 feet per minute, triggering multiple Ground Proximity Warning System (GPWS) 'sink rate' and 'pull up' alerts. The aircraft touched down at 156 knots, significantly exceeding the target landing speed of 138 knots. Due to the high speed, the aircraft could not stop within the runway limits, forcing the pilot to steer left. The aircraft eventually came to a halt 75 meters beyond the runway end. While most passengers evacuated safely, 6 passengers sustained minor injuries, and the aircraft suffered major damage to the nose and right main landing gear.
The investigation
The investigation examined flight data from the FDR and cockpit audio from the CVR, alongside aircraft maintenance and crew performance records. Investigators looked into the crew's adherence to standard operating procedures, the availability of approach charts, and the impact of external stressors, including a passenger's verbal confrontation with the captain during the previous leg in Surabaya. The inquiry also assessed the crew's fatigue levels, noting the pilot in command had flown over 100 hours per month in the preceding six months.
Findings
- The flight crew failed to conduct an approach briefing or utilize checklists during the final segment.
- The pilot flying lacked immediate access to the necessary instrument approach procedures.
- The approach was highly unstable, characterized by inaccurate course settings and excessive descent rates.
- The crew failed to respond to critical GPWS warnings.
- Crew Resource Management (CRM) was poorly implemented, with the pilot monitoring failing to perform standard callouts or identify speed and flap limitations.
- Factors of fixation and complacency, potentially exacerbated by fatigue, prevented the crew from recognizing the unsafe approach criteria.
Safety action
Following the accident, the operator initiated internal reviews of CRM, standard callouts, and stabilized approach procedures. The NTSC issued recommendations to the Directorate General of Civil Aviation to improve oversight of pilot training and duty monitoring to prevent fatigue. Additionally, recommendations were made to the operator to ensure systematic compliance with safety audits and more rigorous monitoring of pilot fatigue levels.