On October 20, 1986, a Bell 206B III (registration N2204Z) was involved in an aviation accident near Nashville, TN. Investigators recorded the probable cause as: The oil delivery tube for the forward spline lubrication did not meet requirements established by the engine manufacturer. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced a hard landing during an autorotation after the pilot reported a hard jerk and left yaw at 1700 ft AGL. Post-accident inspection found a fractured spur adapter gearshaft and an oil delivery tube that did not meet manufacturer specifications.
Accident Summary
A pilot was descending toward a building in a downtown area to take aerial photographs. At approximately 1,700 ft AGL, the pilot reported that the helicopter jerked hard and yawed to the left. The pilot initiated an autorotation. During the descent to a selected landing site, the pilot had to bleed off rotor RPM to clear wires across the approach path. The helicopter made a hard landing in a street intersection.
Investigation Findings
Post-accident inspection revealed that the spur adapter gearshaft forward splines were severely worn. The forward end of the gearshaft was fractured, with the fracture having originated from the shaft spline teeth. Additionally, the oil delivery tube for the forward spline lubrication did not meet requirements established by the engine manufacturer.
Probable cause
The oil delivery tube for the forward spline lubrication did not meet requirements established by the engine manufacturer.
Frequently asked questions
What happened in the 20 Oct 1986 Bell 206B III accident near Nashville, TN?
A helicopter experienced a hard landing during an autorotation after the pilot reported a hard jerk and left yaw at 1700 ft AGL. Post-accident inspection found a fractured spur adapter gearshaft and an oil delivery tube that did not meet manufacturer specifications.
What aircraft was involved and where did it happen?
The accident on 20 Oct 1986 involved a Bell 206B III, registration N2204Z, at Nashville, TN.
What was the probable cause of the accident?
The oil delivery tube for the forward spline lubrication did not meet requirements established by the engine manufacturer.
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