In-Flight Abnormal Bell 206L Vertical Vibrations

Notice Number: NOTC4399

The FAA has received reports of severe vertical vibrations occurring during flight on Bell 206L series (L, L-1, L-3, L-4) helicopters and is investigating the concern. The FAA is aware of at least one event where continued vibration resulted in substantial damage to the helicopter’s tail boom, but the aircraft was able to land safely. To assist in the FAA’s investigation, the FAA is interested in receiving any information from operators on occurrences of abnormal in-flight vertical vibrations on the Bell 206L series helicopters, including the conditions/configurations of the helicopter at the time of the event.

To read the Airworthiness Concern Sheet select this link:

https://www.faasafety.gov/files/notices/2025/May/FAA_ACS_-_206L_Series_Vertical_Vibration.pdf

For questions or to provide feedback please contact:

James Guo, Aviation Safety EngineerAIR-7723960 Paramount Blvd, Suite 100Lakewood, CA 90712562-627-5357 james.guo@faa.gov