NTSB Identification: ANC13FA017
14 CFR Part 133: Rotorcraft Ext. Load
Accident occurred Saturday, December 15, 2012 in Beluga, AK
Probable Cause Approval Date: 05/08/2014
Aircraft: EUROCOPTER AS350 B3, registration: C-GYPH
Injuries: 1 Serious.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The commercial helicopter pilot was transporting a 1,000-pound external sling load attached to a lightweight, synthetic 100-foot long-line when the load began to spin and swing underneath the helicopter. As the helicopter neared its destination, it suddenly yawed, and then started to spin uncontrollably, and the pilot immediately jettisoned the external load. As the helicopter continued to spin uncontrollably, it descended into an area of tall trees and then came to rest on its left side.
A postaccident inspection of the helicopter revealed that portions of the severed lightweight synthetic long-line had become entangled in the tail rotor gearbox output shaft and that the tail rotor gearbox assembly was torn free of the tail boom. Examination of the long-line revealed that its entire length was tightly wrapped, knotted, and kinked. The pilot reported that he had not received training in procedures to adequately stabilize external sling loads. Given the postaccident condition of the lightweight synthetic long-line, the pilot's statements, and the lack of a rotating swivel, it is likely that, once the external load began to spin, the long-line continued to tangle and tightly knot and ultimately reached its breaking point. Once the synthetic long-line separated, the portion still attached to the belly of the helicopter recoiled upward and eventually became entangled with the tail rotor gearbox output shaft. In addition, it is likely the pilot did not adequately monitor the condition of the external sling load while en route, and he failed to recognize the need to stabilize the load.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to stabilize the external load, which led to the synthetic long-line separating about midspan and the remaining line becoming entangled in the tail rotor gearbox output shaft and resulted in the separation of the tail rotor gearbox and subsequent loss of control. Contributing to the accident was the pilot's inadequate training. Full narrative available
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