NTSB Identification: CHI02LA293.
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Accident occurred Tuesday, September 24, 2002 in Council Bluffs, IA
Probable Cause Approval Date: 09/30/2003
Aircraft: Hughes 269A, registration: N1040S
Injuries: 2 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 helicopter landed hard despite cyclic being applied during an instructional flight in which a certified flight instructor (CFI) and a dual student, seeking a CFI certificate, were performing autorotations. Inspection of the wreckage revealed a fractured cyclic/mixture support attachment bracket. A major portion of the fracture surface contained a very dark discoloration. The discoloration was heavier on the forward side of the fracture, and there were portions of the fracture without discoloration on the aft side of the fracture. Prolonged ultrasonic cleaning in an acetone failed to remove significant amount of this discoloration. The discoloration covered more than 85 percent of the fracture surface. Examination of the fracture surface with a scanning electron microscope after cleaning revealed that the discolored areas had a rounded globular appearance, typical of casting porosity. Features typical of overstress separation were noted in areas without discoloration. The broken arm also contained a secondary crack that extended aft from near the forward edge.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The premature fracture of the cyclic/mixture bracket resulting in the inability to conduct a landing flare. Full narrative available
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