REDWOOD, MS, USA
N8511S
AIR TRACTOR AT-301
THE ACFT MADE A FORCED LANDING IN A SOYBEAN FIELD AFTER SEVERE VIBRATION DEVELOPED DURING A SPRAYING OPERATION. THE PILOT STATED THAT THE POWERPLANT AND FLT CONTROLS WERE FUNCTIONING NORMALLY AT THE TIME OF THE ACCIDENT. AN ON-SCENE INVESTIGATION REVEALED THAT THE COUNTERWEIGHT BEARING SHAFT (P/N 63546) BROKE ALLOWING THE PROPELLER BLADE TO GO TO HIGHER PITCH WHILE THE OTHER BLADE REMAINED AT CRUISE PITCH SETTING. EXAMINATION OF BOTH PROPELLER BLADE COUNTERWEIGHTS REVEALED THAT THE INTERNAL PARTS HAD MINIMUM AMOUNT OF LUBRICATION. THE SHAFT THAT BROKE WAS ALSO RUSTY AND THE INNER BEARING RACE WAS BROKEN WITH 5 BALL BEARING MISSING. THERE WERE OTHER MAINTENANCE DICREPANCIES ON THIS SHAFT ASSEMBLY. THE TOTAL TIME OF THIS HAMILTON STANDARD 12D40 PROPELLER IS UNKNOWN. THE TIME SINCE THE ACFT WAS INSPECTED IS 194 HOURS.
Source: NTSB Aviation Accident Database
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