NTSB Identification: CHI08CA210.
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Accident occurred Thursday, July 24, 2008 in Lafetyette, IN
Probable Cause Approval Date: 09/26/2008
Aircraft: Bell 47G-3B-2, registration: N4029G
Injuries: 1 Uninjured.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

The helicopter began losing engine power during an aerial application run while maneuvering. The pilot attempted a landing in the field and the helicopter impacted terrain about 80 yards from an access road at the north edge of the field. The helicopter sustained substantial damage. The pilot was uninjured. Examination of the helicopter revealed that the carburetor heat control spring that keeps the carburetor closed was broken and its support rod had worn into the housing. The heat valve could only be opened about 1/3 and while corresponding cockpit control remained in the closed position. The fracture surface of the spring was consistent with fatigue. The spring had accumulated a total time in service of 832 hours. The pilot was a certificated aircraft mechanic who also performed maintenance on the helicopter. A National Transportation Safety Board Pilot/Operator Aircraft Accident/Incident Report was not received from the pilot.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The loss of engine power during an aerial application flight due to a fatigue fracture of the carburetor heat control valve spring and the inadequate maintenance inspection by the pilot/mechanic. An additional cause was the low altitude of the operation.

Full narrative available

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