NTSB Identification: LAX01LA009.
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Accident occurred Tuesday, October 03, 2000 in EL CAJON, CA
Probable Cause Approval Date: 11/06/2001
Aircraft: Aerospatiale AS350BA, registration: N189ND
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

While positioning the helicopter from the ground to a storage cart, the pilot lost directional, made a hard landing, and the tail boom struck the ground. Prior to the loss of directional control, the pilot saw something depart the tail section. He attributed the loss of directional control to a tail rotor failure. He initiated an autorotation over the landing cart. He maneuvered away from the cart in order to land on the ground and prevent a partial landing on the cart. The on-scene investigation revealed the aft drive shaft coupling was detached from the tail rotor drive shaft. Three bolts retain the coupling. One bolt was found attached to the coupling, another bolt was found on the ground, and the third bolt, and two of the retaining nuts, were not located. Neither bolt exhibited stripped threads or deformation. The last maintenance performed on the helicopter was by the previous owner. A track and balance of the tail rotor system was performed about 48 flight hours prior to the accident. According to the manufacturer's maintenance instructions, the balancing is accomplished by placement of washers under the nuts that are used to secure the bolts that attach to the aft drive shaft coupling. These are the same nuts that were not located at the accident site. Maintenance instructions also specify that the bolts in this area should be checked for proper torque and safety after an inspection.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Improper torquing procedure of the aft tail rotor drive shaft coupling by maintenance personnel after tracking the tail rotor.

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