NTSB Identification: WPR11LA288
14 CFR Part 137: Agricultural
Accident occurred Friday, June 24, 2011 in Lewistown, MT
Probable Cause Approval Date: 12/05/2012
Aircraft: AIR TRACTOR INC AT-502, registration: N1022N
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 pilot reported that while in cruise flight about 800 feet above ground level, the engine lost power, and he initiated a forced landing to an area of open, uneven terrain. During the landing roll, the left wing struck the ground and the airplane ground looped. Postaccident examination revealed that the fuel bypass line was fractured and had separated from the fuel control unit.
Metallurgical analysis revealed that the fuel bypass line fractured near a ferrule at the edge of the braze filler metal fillet. Striations on the fracture surface were consistent with a fatigue crack originating on the outside surface of the tube and propagating toward the inside surface and circumferentially around the tube wall. No maintenance records for the airplane were recovered during the course of the investigation, and, therefore, the amount of time and maintenance history on the line was undetermined.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The fatigue fracture and separation of the fuel bypass line, which resulted in a total loss of engine power. Full narrative available
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