NTSC Investigates 2011 Bell 412 Sling Load Accident in Sumbawa (PK-OCV)

Accident Overview and Flight History On 25 September 2011, a Bell 412 helicopter operated by PT. Airfast Indonesia crashed in the Lemurung area of Sumbawa, Nusa Tenggara Barat, Indonesia. The aircraft, registered PK-OCV, was chartered by PT. Newmont Nusa Tenggara to transport supplies between the Lemurung and Dodo camps, a distance of approximately 17 kilometers. The flight crew consisted of one pilot and one load master. The helicopter had been conducting external load operations using a 50-foot cable since 5 August 2011. On the day of the accident, the aircraft departed Benete at 0035 UTC and completed 16 flight cycles between Dodo and Lemurung before a lunch break. At 0539 UTC, the helicopter took off from Lemurung to drop a load at Dodo and was returning to Lemurung with an empty long-line hook. ## Emergency Response and Wreckage Location Approximately two minutes after departing Dodo, a ground radio operator received a MAYDAY call on the company frequency, but no reply was obtained. At 0915 UTC, the helicopter's Emergency Locator Transmitter (ELT) signal was received at coordinates 08º54’S 117º24’E. The following day, 26 September 2011, at 0113 UTC, the helicopter was found at coordinates 08º54’00”S 117º23’10”E at an elevation of approximately 850 meters. A land search group from Dodo reached the site at 0234 UTC. Both occupants were fatally injured. ## Investigation Findings The tail rotor and tail rotor gearbox were not immediately located but were recovered several weeks later about 300 meters from the accident site, amidst vegetation in a rainforest. Examination of the cable and tail rotor blade provided evidence consistent with the tail rotor blade striking the cable. This strike caused the tail rotor system to enter an extreme out-of-balance condition, resulting in loads that fractured the mounting bulkhead of the 90° gearbox. The incident also caused a significant shift in the center of gravity, leading to uncontrollable flight. The investigation noted that flying with an empty long-line was not in accordance with PT. Airfast Indonesia's standard operating procedures. The National Transportation Safety Committee issued safety recommendations to the Directorate General of Civil Aviation and PT. Airfast Indonesia.