NTSB Identification: LAX01LA098.
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Accident occurred Friday, February 09, 2001 in Winterhaven, CA
Probable Cause Approval Date: 07/15/2002
Aircraft: Bell 47-G3B1, registration: N3084G
Injuries: 1 Uninjured.

NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot was applying chemicals at night to a field of lettuce and had just taken off from his truck platform with 60 gallons of chemicals. He was about 20 feet above ground level and had a forward air speed of approximately 30 miles per hour when he heard a loud screeching sound, followed by a yaw to the left, a rapid decay of rotor rpm, and an increase/overspeed in engine rpm. The helicopter landed hard, collapsing the skids. Post accident examination of the transmission was conducted, revealing that the outer surface of the free wheeling unit of the inner gear assembly was worn below allowable limits at the roller/gear operating surface. The worn freewheeling inner ring gear allowed a mechanical disconnect between the engine output and the main rotor transmission, and resulted in a loss of main rotor speed and the subsequent hard landing.

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

A failure of the transmission free wheeling unit due to improper maintenance. A factor was the dark night visual condition.

Full narrative available

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