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Helicopter Tail Boom Severed After Autorotation Touchdown During Biennial Flight Review (N500CD)

Plymouth, IN, US

On October 29, 1989, a Bell 47G-2A-1 (registration N500CD) was involved in an aviation accident near Plymouth, IN. No fatalities were reported. Investigators recorded the probable cause as: THE STUDENT'S IMPROPER USE OF THE CYCLIC CONTROL AND THE INSTRUCTOR'S (CFI'S) INADEQUATE SUPERVISION. 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 biennial flight review, a helicopter touched down on a sod taxiway after the final practice autorotation. The CFI reported a soft touchdown, but aft cyclic application led to the main rotor blades severing the tail boom.

Accident Details

A biennial flight review (BFR) was in progress for the pilot occupying the left seat. The flight instructor (CFI), seated in the right seat, reported that several practice autorotations were performed during the review. The BFR was progressing very well until the final autorotation, when the helicopter touched down on a sod taxiway.

The CFI described the touchdown as soft. However, immediately after touchdown, aft cyclic was applied. Subsequently, the main rotor blades came into contact with the tail boom, severing it. The CFI noted that the accident was unexpected and occurred so quickly that he was unable to intervene.

Pilot Experience

The pilot undergoing the BFR had a total flight time of 344 hours, with 310 hours in the same make and model of helicopter as the accident aircraft.

Weather Conditions

The CFI stated that the weather was clear with calm winds at the time of the event.

Frequently asked questions

What happened in the 29 Oct 1989 Bell 47G-2A-1 accident near Plymouth, IN?

During a biennial flight review, a helicopter touched down on a sod taxiway after the final practice autorotation. The CFI reported a soft touchdown, but aft cyclic application led to the main rotor blades severing the tail boom.

Were there any fatalities in the 29 Oct 1989 Bell 47G-2A-1 accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 29 Oct 1989 involved a Bell 47G-2A-1, registration N500CD, at Plymouth, IN.

What was the probable cause of the accident?

THE STUDENT'S IMPROPER USE OF THE CYCLIC CONTROL AND THE INSTRUCTOR'S (CFI'S) INADEQUATE SUPERVISION.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001213X29572. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.