NTSB Identification: SEA07LA204.
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Accident occurred Saturday, June 30, 2007 in Chowchilla, CA
Probable Cause Approval Date: 07/30/2008
Aircraft: Air Tractor AT-502A, registration: N6176L
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The engine lost power about 20 to 30 feet above ground level in the takeoff initial climb. The pilot landed in a pasture, with the airplane coming to rest upright after colliding with several fences. A post accident examination of the engine revealed that the engine failure was the result of the fatigue fracture and separation of two compressor turbine blades. Once liberated, the two blades impacted the other compressor turbine blades, which resulted in the airfoil portions of those remaining blades to fracture in overstress. The fatigue crack in one blade occupied about 40 percent of the fracture surface, while the fatigue crack in the second blade occupied about 60 percent of the fracture surface.

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

The loss of engine power as the result of the fatigue fracture and separation of two compressor turbine blades, which induced a catastrophic failure of the compressor turbine section.

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