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Tail Rotor Drive Shaft Failure Leads to Water Impact During External Load Operation (N7929J)

Oak Grove, LA, US

On August 23, 1997, a Bell 206B (registration N7929J) was involved in an aviation accident near Oak Grove, LA. Investigators recorded the probable cause as: Separation of the #5 tail rotor drive shaft segment at the bonded joint due to plastic blast media impingement, which compromised the moisture barrier and allowed moist chloride environment to degrade the adhesive, leading to loss of tail rotor authority. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 8 related events involving the same aircraft type or operator are linked below.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

During an external load operation, a helicopter's main rotor blades struck a boat after the aircraft began spinning and the pilot reduced throttle. The helicopter then settled into water and sank. Investigation found that the #5 tail rotor drive shaft segment had separated due to plastic blast media impingement degrading the adhesive bond.

Event Description

During an external load operation, the pilot was hovering the helicopter at about 60 feet above a boat when the helicopter began to spin to the right. The pilot rolled off the throttle, and the spin stopped. He then maneuvered the helicopter to the right as it descended in an effort to clear the boat; however, the main rotor blades struck the front of the boat. Subsequently, the helicopter settled into the water and sank.

Examination Findings

Examination of the tail rotor drive system revealed that the #5 tail rotor drive shaft segment, part number 206-040-931-9, had separated at the bonded joint between the shaft tube and the flange fitting. Further examination by a metallurgist showed that the separated joint exhibited evidence of pitting indicative of plastic blast media impingement. The remaining adhesive had the consistency of powder or talc with no apparent structural integrity. According to the metallurgist, the blast media impingement may effectively compromise the moisture barrier at the joint and allow the moist chloride environment to invade the joint and chemically degrade the adhesive. Blast media impingement is not approved by Bell Helicopter.

Probable cause

Separation of the #5 tail rotor drive shaft segment at the bonded joint due to plastic blast media impingement, which compromised the moisture barrier and allowed moist chloride environment to degrade the adhesive, leading to loss of tail rotor authority.

Related events

Same aircraft family

All Bell 206 accidents →

Frequently asked questions

What happened in the 23 Aug 1997 Bell 206B accident near Oak Grove, LA?

During an external load operation, a helicopter's main rotor blades struck a boat after the aircraft began spinning and the pilot reduced throttle. The helicopter then settled into water and sank. Investigation found that the #5 tail rotor drive shaft segment had separated due to plastic blast media impingement…

What aircraft was involved and where did it happen?

The accident on 23 Aug 1997 involved a Bell 206B, registration N7929J, at Oak Grove, LA.

What was the probable cause of the accident?

Separation of the #5 tail rotor drive shaft segment at the bonded joint due to plastic blast media impingement, which compromised the moisture barrier and allowed moist chloride environment to degrade the adhesive, leading to loss of tail rotor authority.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001208X08637. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.