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Casualties unknown

Helicopter Tail Rotor Drive System Malfunction During Offshore Takeoff (N5753D)

South Marsh, US

On July 21, 1985, a Bell 206L-1 (registration N5753D) was involved in an aviation accident near South Marsh. Investigators recorded the probable cause as: The aircraft experienced a malfunction in the tail rotor drive system. 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 takeoff from an offshore oil rig, a helicopter's pilot heard a loud noise from the tailboom, and the aircraft began rotating right. The pilot autorotated into the water, where the main rotor severed the tailboom. The tail rotor drive system is believed to have malfunctioned.

Accident Details

The pilot was initiating a takeoff from a hover off an offshore oil rig. As the nose was lowered for takeoff, a loud noise was heard emanating from the tailboom area, and the aircraft began to rotate to the right. The pilot continued to apply power and then performed an autorotation, landing the aircraft on the water.

Impact and Damage

Upon impact with the water, the main rotor struck the tailboom and severed it. The aft section of the tailboom and the tail rotor gearbox were not recovered. Indications from the investigation suggest that the aircraft experienced a malfunction in the tail rotor drive system.

Investigation

No further details about the aircraft type, registration, operator, or occupants have been released. The exact cause of the tail rotor drive system malfunction remains under investigation.

Probable cause

The aircraft experienced a malfunction in the tail rotor drive system.

Frequently asked questions

What happened in the 21 Jul 1985 Bell 206L-1 accident near South Marsh?

During takeoff from an offshore oil rig, a helicopter's pilot heard a loud noise from the tailboom, and the aircraft began rotating right. The pilot autorotated into the water, where the main rotor severed the tailboom. The tail rotor drive system is believed to have malfunctioned.

What aircraft was involved and where did it happen?

The accident on 21 Jul 1985 involved a Bell 206L-1, registration N5753D, at South Marsh.

What was the probable cause of the accident?

The aircraft experienced a malfunction in the tail rotor drive system.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X37146. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.