ASN Wikibase Occurrence # 355357
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| Date: | Saturday 23 August 1997 |
| Time: | 09:00 LT |
| Type: |  Bell 206B |
| Owner/operator: | Evergreen Helicopter Int., Inc |
| Registration: | N7929J |
| MSN: | 663 |
| Year of manufacture: | 1971 |
| Total airframe hrs: | 12857 hours |
| Engine model: | Allison 250-C20B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Oak Grove, LA -
 United States of America
|
| Phase: | Unknown |
| Nature: | Unknown |
| Departure airport: | Cameron, LA |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During an external load operation, the pilot was hovering the helicopter at about 60 feet above the boat, when the helicopter began to 'spin' to the right. He '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 of the tail rotor drive system revealed that the #5 tail rotor drive shaft segment P/N 206-040-931-9 had separated at the bonded joint between the shaft tube and the flange fitting. Examination of this tail rotor drive segment by a metallurgist revealed that the separated joint revealed evidence of pitting which was indicative of plastic blast media impingement and the remaining adhesive had the consistency of powder/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: The disconnect of the #5 tail rotor drive segment due to the debonding of the joint between the shaft tube and the flange fitting. Factors were the improper bead blasting of the tail rotor drive segment by an unknown maintenance personnel, and the lack of altitude and suitable terrain for the forced landing.
Accident investigation:
 |
|
Sources:
NTSB FTW97LA326
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 12-Mar-2024 11:05 | ASN Update Bot | Added |
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