ASN Wikibase Occurrence # 176161
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| Date: | Saturday 3 April 2004 |
| Time: | 07:45 |
| Type: |  Bell 47G-4A |
| Owner/operator: | Inland Crop Dusters Inc. |
| Registration: | N7NB |
| MSN: | 7732 |
| Year of manufacture: | 1970 |
| Total airframe hrs: | 9916 hours |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Bakersfield, CA -
 United States of America
|
| Phase: | Landing |
| Nature: | Agricultural |
| Departure airport: | Shafter, CA (KMIT) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The helicopter experienced a loss of tail rotor control and collided with terrain. During an aerial application flight, the pilot heard a rattling noise from the aft end of the helicopter. He then lost tail rotor authority and entered a flat spin. The pilot attempted to make a run-on landing, but the helicopter continued to spin until it impacted terrain. A Federal Aviation Administration inspector examined the helicopter after the accident. He noted that the cross-over support tube near the aft end of the tail boom was missing. A crack was found on the tail boom left side frame tubes. Deposits of rust in the area suggests that the crack was a pre-existing crack. The inspector thought that this would have added excessive stress to the structure during turning maneuvers and caused the last spline coupling shaft to disconnect from the tail rotor gear box as the tail boom flexed. A 50-hour maintenance inspection was completed the day before the accident.
Probable Cause: a loss of tail rotor drive due to a disconnection of the drive shaft's splined coupling at the tail rotor gear box. The splined coupling to tail rotor gear box disconnection occurred as a result of tail boom flexing due to the combined effects of an uninstalled structural support tube and a crack in left side frame tubes. Inadequate maintenance inspection was a factor.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20040409X00442&key=1
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 16-May-2015 19:23 | Noro | Added |
| 07-Dec-2017 18:50 | ASN Update Bot | Updated [Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
Corrections or additions? ... Edit this accident description
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