ASN Wikibase Occurrence # 354544
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| Date: | Monday 27 April 1998 |
| Time: | 16:00 LT |
| Type: |  Robinson R22 BETA |
| Owner/operator: | W.w. Helicopter |
| Registration: | N8331F |
| MSN: | 2578 |
| Year of manufacture: | 1996 |
| Total airframe hrs: | 889 hours |
| Engine model: | Lycoming O-360 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Minor |
| Category: | Serious incident |
| Location: | Franklin, WI -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Milwaukee, WI (KMKE) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot said he felt an abnormal vibration in his helicopter during cruise flight. He said he reduced power and made a partial power auto-rotation to a normal landing in an open field. The on-scene investigation revealed that the tail rotor's hub bolt had fractured completely. The hub bolt attaches the tail rotor assembly to its drive shaft. Examination of the bolt revealed it had failed due to fatigue. Maintenance records showed the bolt had 168.3-hours on it since had been examined. It had been removed from the hub assembly so that new teeter bearings could be installed in the hub. The mechanic said he visually examined the bolt and believed it could be returned to service. The mechanic said he did not use the required teeter bearing alignment tool to reinstall the new bearings because the fit was not tight. He said he did not re-balance the tail rotor assembly afer the work had been done. Re-balancing is a required process according to the manufacturer's maintenance procedures. The mechanic said he told the customer to have it checked if he felt any vibration.
Probable Cause: The mechanic's failure to follow the manufacturer's maintenance rebuilding instructions.
Accident investigation:
 |
|
Sources:
NTSB CHI98IA136
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 11-Mar-2024 15:39 | ASN Update Bot | Added |
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