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Tailboom Wrinkling Noted After Autorotation Demonstration (N6197N)

Thermal, CA, US

On April 26, 1995, a Bell 206-L4 (registration N6197N) was involved in an aviation accident near Thermal, CA. No fatalities were reported. Investigators recorded the probable cause as: The CFI's failure to follow the flight manual procedures by using full up collective during an autorotation landing. 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 hovering autorotation demonstration, a helicopter experienced an abrupt stop upon touchdown. The CFI later noticed wrinkled tailboom skin. The manufacturer had previously issued an operational safety notice regarding tailboom wrinkling.

Incident Details

A certified flight instructor (CFI) was demonstrating a hovering autorotation to touchdown in a helicopter equipped with full skid shoes. The wind conditions included a quartering headwind of 15 knots, gusting to 30 knots. To cushion the landing, the CFI applied full up collective. The touchdown itself was smooth, but the helicopter came to an abrupt stop. Upon returning to the pad, the CFI observed that the tailboom skin was wrinkled.

Manufacturer's Safety Notice

The helicopter manufacturer had previously addressed tailboom wrinkling in an Operational Safety Notice (OSN), which was incorporated into the helicopter flight manual. The OSN specifies that main rotor blade RPM should not be less than 70 percent, and that the collective should be immediately lowered on touchdown. The incident occurred despite the existence of this guidance.

Frequently asked questions

What happened in the 26 Apr 1995 Bell 206-L4 accident near Thermal, CA?

During a hovering autorotation demonstration, a helicopter experienced an abrupt stop upon touchdown. The CFI later noticed wrinkled tailboom skin. The manufacturer had previously issued an operational safety notice regarding tailboom wrinkling.

Were there any fatalities in the 26 Apr 1995 Bell 206-L4 accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 26 Apr 1995 involved a Bell 206-L4, registration N6197N, at Thermal, CA.

What was the probable cause of the accident?

The CFI's failure to follow the flight manual procedures by using full up collective during an autorotation landing.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001207X03330. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.