What happened
On 12 April 2017, a Cessna 208 aircraft, registration PK-FSO, was conducting an unscheduled cargo flight from Tanah Merah to Oksibil in the Republic of Indonesia. The flight was being operated by PT. Spirit Avia Sentosa (FlyingSAS) and was carrying 1,225 kg of general cargo.
During the flight, the aircraft was observed by another pilot flying in the opposite direction, maintaining an altitude of 7,000 feet. However, later that day, the operator's flight following system triggered an SOS signal indicating the aircraft was approximately 6 nautical miles north of Oksibil. The aircraft was subsequently located on a ridge of Anem Mountain. The impact destroyed the aircraft and resulted in one fatality.
The investigation
Investigators from the KNKT examined the aircraft's flight profile, the pilot's medical history, and the oversight provided by both the operator and the Aviation Medical Center. The investigation confirmed that the aircraft's mechanical serviceability was not a factor in the crash.
Review of medical records revealed that the pilot's recent examinations had not included a required electrocardiogram (ECG) despite the pilot being over 40 years of age. Furthermore, the investigation looked into the pilot's physiological state, noting high cholesterol and an elevated Body Mass Index (BMI). The investigation also scrutinized the operational environment, including the pilot's habits and the functionality of the aircraft's terrain warning systems.
Findings
- The primary cause of the accident was the pilot inadvertently falling asleep due to fatigue, physical condition, and environmental factors.
- The pilot had engaged the Terrain Inhibit switch, which disabled the aircraft's GA-EGPWS aural alerts, preventing the system from warning the pilot of the approaching terrain.
- The pilot's medical examination was incomplete, as the required ECG testing had not been performed in accordance with regulations for pilots over 40.
- The pilot's physical health, characterized by obesity and difficulty breathing deeply, likely contributed to increased sleepiness during flight.
- The operator's hazard reporting system failed to identify operational safety issues, such as the pilot smoking in the cockpit or disabling safety systems.
Safety action
Following the investigation, the KNKT issued several recommendations to improve safety standards. The Aviation Medical Center was advised to ensure all required ECG examinations are performed according to regulations and to analyze examiner workloads to ensure thoroughness. The DGCA was recommended to establish clear methods for reporting decreases in medical fitness and to review the implementation of Safety Management Systems regarding hazard reporting.