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Tail Rotor Drive Failure Causes Loss of Yaw Control and Accident (N2837B)

Grove, OK, US

On July 27, 1984, a Bell 47J (registration N2837B) was involved in an aviation accident near Grove, OK. Investigators recorded the probable cause as: Both pins in the tail rotor drive universal joint sheared due to insufficient torque on the acorn nuts. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

During a local flight with two passengers, the pilot lost yaw control when the aircraft began a right rotation and anti-torque pedals proved ineffective. The aircraft held a minimum descent over buildings before impacting the ground, rolling onto its right side and catching fire.

Sequence of Events

The pilot reported that yaw control was lost during the climb out for a local flight with two passengers on board. The aircraft began to rotate to the right, and the anti-torque pedals were ineffective. Because the aircraft was over buildings at the time, the pilot maintained a minimum descent until clear of the buildings. The aircraft continued to rotate until ground impact.

Accident Details

After ground impact, the aircraft rolled onto its right side and caught fire. Post-accident inspection of the aircraft revealed the cause of the loss of yaw control.

Investigation Findings

Inspection of the aircraft revealed that both pins in the tail rotor drive universal joint had sheared. The shearing was due to insufficient torque on the acorn nuts.

Probable cause

Both pins in the tail rotor drive universal joint sheared due to insufficient torque on the acorn nuts.
Structural failure

Frequently asked questions

What happened in the 27 Jul 1984 Bell 47J accident near Grove, OK?

During a local flight with two passengers, the pilot lost yaw control when the aircraft began a right rotation and anti-torque pedals proved ineffective. The aircraft held a minimum descent over buildings before impacting the ground, rolling onto its right side and catching fire.

What aircraft was involved and where did it happen?

The accident on 27 Jul 1984 involved a Bell 47J, registration N2837B, at Grove, OK.

What was the probable cause of the accident?

Both pins in the tail rotor drive universal joint sheared due to insufficient torque on the acorn nuts.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X40334. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.