NTSB Identification: ATL83FKQ03.
The docket is stored on NTSB microfiche number 21071.
Accident occurred Thursday, August 25, 1983 in REDWOOD, MS
Aircraft: AIR TRACTOR AT-301, registration: N8511S
Injuries: 1 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

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.

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

PROPELLER SYSTEM/ACCESSORIES,COUNTERWEIGHT..FAILURE,TOTAL

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

MAINTENANCE,INSPECTION..POOR..OTHER MAINTENANCE PERSONNEL

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

MAINTENANCE,LUBRICATION..POOR..OTHER MAINTENANCE PERSONNEL

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