On August 12, 1987, a Bell 206L-1 (registration N2764F) operated by Petroleum Helicopters,inc. was involved in an aviation accident near New Iberia, LA. Investigators recorded the probable cause as: Tailboom separation due to resonance. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 2 related events involving the same aircraft type or operator are linked below.
During a training flight, a helicopter performing practice touchdown autorotations skidded 75 feet on wet soft grass after landing with excess ground speed. When power was applied, a grinding sound and vibration occurred, and the tailboom separated due to resonance.
Accident Summary
A training flight involved a helicopter practicing touchdown autorotations. On the fourth autorotation, the helicopter touched down with excessive ground speed and skidded for approximately 75 feet on wet, soft grass. When the crew applied power to return to flight rotor RPM, they heard a grinding sound and felt a vibration. A visual inspection revealed that the tailboom had separated aft of its attachments due to resonance.
Resonance Condition
The source states that this aircraft is subject to resonance if rotor RPM is allowed to decay below 70% during touchdown autorotations or during lengthy ground runs.
What happened in the 12 Aug 1987 Bell 206L-1 accident near New Iberia, LA?
During a training flight, a helicopter performing practice touchdown autorotations skidded 75 feet on wet soft grass after landing with excess ground speed. When power was applied, a grinding sound and vibration occurred, and the tailboom separated due to resonance.
What aircraft was involved and where did it happen?
The accident on 12 Aug 1987 involved a Bell 206L-1, registration N2764F, operated by Petroleum Helicopters,inc., at New Iberia, LA.
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