What happened
On 11 October 2015, a Eurocopter EC130 B4 helicopter, registration PK-BKA, was performing an unscheduled charter flight from Siparmahan to Kualanamu in North Sumatra, Indonesia. The flight, operated by PT. Penerbangan Angkasa Semesta, carried five people: a pilot, an engineer, and three passengers.
Shortly after departing Siparmahan, the aircraft encountered a sudden change in weather. While the flight initially proceeded under clear conditions, the aircraft subsequently entered an area of dense cloud and smoke, which significantly reduced visibility. During this period of low visibility, the helicopter descended to approximately 500 feet above the water surface, likely in an attempt to find visual references. The aircraft ultimately impacted the surface of Toba Lake.
Following the impact, the wreckage could not be recovered. Of the five occupants, four fatalities occurred. One passenger survived the crash and remained in the water for approximately 50 hours before being rescued.
The investigation
The investigation conducted by the KNKT focused on the environmental conditions and the aircraft's safety equipment. Investigators examined satellite imagery from the National Agency of Meteorology, Climatology and Geophysics (BMKG), which confirmed the presence of haze and cloud formations over the flight path.
Evidence from the surviving passenger indicated that no safety briefing was conducted prior to departure. Furthermore, while the flight plan suggested the presence of survival gear, the investigation found that individual life jackets were unavailable to the passengers. The investigation also looked into the search and rescue response, noting that the lack of instrument flight ratings for certain rescue pilots and the use of high-speed fixed-wing aircraft limited the effectiveness of the initial search.
Findings
- The pilot likely suffered from spatial disorientation due to the sudden loss of visual references in dense smoke and clouds, leading to an inability to maintain the aircraft's proper attitude.
- The lack of individual flotation devices and the failure to activate the aircraft's onboard flotation device significantly reduced the chances of survival for the occupants.
- The pilot was not certified for instrument flight rules (IFR), which contributed to the difficulty in navigating the degraded weather conditions.