NTSB Identification: LAX99LA319.
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Accident occurred Saturday, September 18, 1999 in SALINAS, CA
Probable Cause Approval Date: 05/09/2001
Aircraft: Bell OH58A, registration: N5800K
Injuries: 1 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.

The pilot was performing low level aerial application work. Wires ran perpendicular to his flight path at the end of a crop row and a berm was located just in front of the wires. The pilot planned to fly under the wires. As he flew under the wires he heard a loud noise to his rear and the helicopter began to rotate clockwise. He increased pitch on the collective and climbed to approximately 100 feet. He could not control the rotation and completed an autorotation to a hard landing. A ground witness saw the helicopter's tail contact the berm. The tail rotor blades were fractured and separated, and, the tail rotor drive shaft was fractured midway between the aft short shaft and the tail rotor gearbox. The fracture exhibited torsional overload signatures angled aft along a 45-degree plane from the bottom to the top of the shaft. The torsional twist was in a clockwise direction as viewed from the rear. The tail rotor drive shaft normally rotates clockwise as viewed from the rear. No preimpact malfunctions were identified with the tail rotor gearbox or pitch control.

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

The pilot's failure to maintain an adequate clearance from all ground obstacles during a low altitude aerial application flight.

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