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Helicopter Tail Rotor Shaft Failure During Snow Rescue Mission (N16733)

Park City, UT, US

On January 8, 1989, a Bell 206B III (registration N16733) operated by Avman Inc was involved in an aviation accident near Park City, UT. No fatalities were reported. Investigators recorded the probable cause as: The tail rotor blades entered loose snow, causing rapid deceleration and shearing of the tail rotor shaft under applied torque. 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

While unloading a rescue team in an avalanche area, a helicopter settled into loose snow. Attempting to hover, an uncommanded right spin led to a hovering autorotation. The tail boom entered deep snow, and the tail rotor shaft was found broken after the accident.

Incident Details

A commercial pilot transported a rescue team to a mountainous avalanche area. After the team deplaned, the helicopter settled backwards into loose snow during the unloading procedure. The pilot added collective pitch and attempted to hover. As the helicopter left the ground, an uncommanded right spin developed. The pilot performed a hovering autorotation, landing approximately 30 feet away from ground personnel. At touchdown, the tail boom entered deep snow, and the aircraft came to rest in a nose-high attitude.

Investigation Findings

A post-accident investigation revealed that the tail rotor shaft had broken forward of the tail rotor gearbox. Evidence indicated that the tail rotor blades entered loose snow, subjecting them to rapid deceleration. The shaft sheared under the applied torque.

Probable cause

The tail rotor blades entered loose snow, causing rapid deceleration and shearing of the tail rotor shaft under applied torque.
Structural failure

Frequently asked questions

What happened in the 8 Jan 1989 Bell 206B III accident near Park City, UT?

While unloading a rescue team in an avalanche area, a helicopter settled into loose snow. Attempting to hover, an uncommanded right spin led to a hovering autorotation. The tail boom entered deep snow, and the tail rotor shaft was found broken after the accident.

Were there any fatalities in the 8 Jan 1989 Bell 206B III accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 8 Jan 1989 involved a Bell 206B III, registration N16733, operated by Avman Inc, at Park City, UT.

What was the probable cause of the accident?

The tail rotor blades entered loose snow, causing rapid deceleration and shearing of the tail rotor shaft under applied torque.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001213X27572. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.