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ASN Wikibase Occurrence # 72252
Last updated: 26 May 2021
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Type:Silhouette image of generic B06 model; specific model in this crash may look slightly different
Bell OH-58A Kiowa
Registration: N9286U
MSN: 69-16198
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Location:Escalon, California -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Departure airport:Escalon, CA
Destination airport:Modesto, CA
Investigating agency: NTSB
The pilot had reported to his mechanic prior to the accident flight that the helicopter was not producing full power, was vibrating heavily, and that the DC generator caution light had illuminated. He also reported that his work load was heavy, and that he would continue onwards to return the helicopter to its home base. Shortly after takeoff the engine lost power, the pilot performed a forced landing, and the helicopter collided with terrain. Examination of the engine revealed that a stainless steel pneumatic fuel-to-governor control line had failed at its fitting. Witness marks on the line revealed that it had been rubbing against an adjacent oil line. Additionally, the pneumatic line had been bent during installation such that its surface was in contact with the connector ferrule. Analysis of the line's fracture surface revealed indications of high cycle fatigue. The fuel controller was replaced about 26 flight hours prior to the accident; replacement of the controller would have required the removal and installation of the failed line. The engine manufacturer provided installation guidance in multiple publications, and specifically cautioned against improper installations of engine lines. Examination of the DC starter-generator revealed that it had experienced a partial mechanical failure, which was likely the reason the pilot felt a vibration and observed a dc generator caution light. During the investigation the failed line was replaced, and the engine was successfully run in a test cell throughout its power range.
Probable Cause: A loss of engine power during cruise flight due to the fatigue failure of the pneumatic fuel-to-governor control line. Also causal was the inadequate installation of the pneumatic line by maintenance personnel, and the pilotís decision to continue flight with a known discrepancy.





Photo: NTSB

Revision history:

02-Feb-2010 20:48 slowkid Added
03-Feb-2010 10:04 Alpine Flight Updated [Aircraft type]
20-Jul-2010 11:04 harro Updated [Time, Nature, Departure airport, Source, Narrative]
21-Dec-2016 19:25 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
26-Nov-2017 15:24 ASN Update Bot Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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