On August 7, 1987, a Bell 47J-2A (registration N8523F) was involved in an aviation accident near Orlando, FL. Investigators recorded the probable cause as: Torsional failure of the forward short shaft due to a lack of lubrication. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During approach to land, the tail rotor drive assembly failed due to a lack of lubrication, causing a momentary loss of control. The pilot autorotated and landed on the company helipad, sustaining substantial damage.
Incident Sequence
During the approach to land, the tail rotor drive assembly failed, leading to a momentary loss of control. The pilot promptly initiated an autorotation and landed on the company helipad. The helicopter sustained substantial damage in the landing.
Examination Findings
Examination of the tail rotor drive assembly revealed that the forward short shaft had failed torsionally. The fracture was located approximately two inches aft of the transmission drive coupling. The torsional failure was caused by a lack of lubrication in the shaft. The failure occurred at an altitude of about 40 feet above ground level.
Component Failure
The forward short shaft, a component of the tail rotor drive assembly, failed due to inadequate lubrication. This failure resulted in the momentary loss of control. The shaft separated torsionally at a point two inches aft of the coupling. The incident occurred during the approach at 40 feet AGL.
Probable cause
Torsional failure of the forward short shaft due to a lack of lubrication.