On May 24, 1983, an Enstrom 280C (registration N51763) operated by Norman L. Clark was involved in an aviation accident near Goshen, CA. Investigators recorded the probable cause as: Failure of the tail rotor aft drive coupling due to inadequate lubrication. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced sudden tail rotor power loss about five minutes after takeoff. During an autorotative landing, insufficient collective pitch prevented a proper flare, and the main rotor blades severed the tail boom. Investigation found the tail rotor aft drive coupling had failed with stripped internal gear teeth and evidence of inadequate lubrication.
Accident
Approximately five minutes after departure, the pilot noticed a sudden loss of power to the tail rotor. He executed an emergency landing in an alfalfa field. During the autorotative landing, the pilot reported having insufficient collective pitch to flare properly. Consequently, the main rotor blades severed the tail boom.
Findings
A post-accident examination revealed that the tail rotor aft drive coupling, part number 28-13609, had failed. All internal gear teeth on the female portion of the coupling were stripped. There was evidence of inadequate lubrication on the coupling.
Probable cause
Failure of the tail rotor aft drive coupling due to inadequate lubrication.