ASN Wikibase Occurrence # 44381
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| Date: | Wednesday 10 August 2005 |
| Time: | 06:00 |
| Type: |  Bell OH-58A |
| Owner/operator: | San Joaquin Helicopters |
| Registration: | N177SJ |
| MSN: | 42097 |
| Year of manufacture: | 1972 |
| Total airframe hrs: | 5211 hours |
| Engine model: | Allison T63A720/250-C |
| Fatalities: | Fatalities: 1 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Lancaster, CA -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Agricultural |
| Departure airport: | Lancaster, CA |
| Lancaster, CA | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Following a loss of engine power, the helicopter impacted the ground during the application of chemicals to an agricultural field. Post accident examination of the engine showed that the power turbine to pinion gear coupling had fractured. Metallurgical examination of the affected components showed that the coupling failed in fatigue, which effectively separated the engine from the main rotor gearbox. The fatigue was the result of a misaligned power turbine outer shaft, where the axis of the turbine shaft was angled slightly relative to the coupling and pinion axes. The turbine section had been removed from another engine due to metal contamination. The turbine section was repaired and subsequently installed on the accident helicopter on August 11, 2004, where it operated for 770.3 hours prior to the accident. Weight and balance calculations showed that the helicopter was in excess of its certificated maximum gross weight by 174 pounds.
Probable Cause: The pinion to turbine shaft coupling failed in fatigue due to a misaligned turbine shaft, which resulted in a loss of engine power.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20050817X01264&key=1
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 28-Oct-2008 00:45 | ASN archive | Added |
| 21-Dec-2016 19:24 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 06-Dec-2017 10:53 | ASN Update Bot | Updated [Aircraft type, Source, Narrative] |
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