On August 25, 1983, an Air Tractor AT-301 (registration N8511S) operated by Martin L. Hallman was involved in an aviation accident near Redwood, MS. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An agricultural aircraft made a forced landing in a soybean field after severe vibration developed during spraying. Investigation revealed a broken counterweight bearing shaft and other propeller maintenance discrepancies.
Accident Details
During a spraying operation, the aircraft experienced severe vibration, prompting the pilot to perform a forced landing in a soybean field. The pilot reported that the powerplant and flight controls were functioning normally at the time of the accident.
Investigation Findings
An on-scene investigation found that the counterweight bearing shaft (part number 63546) had broken. This failure allowed one propeller blade to move to a higher pitch setting while the other blade remained at the cruise pitch setting. Examination of both propeller blade counterweights revealed that the internal parts had a minimum amount of lubrication. The broken shaft was also rusty, and the inner bearing race was fractured, with five ball bearings missing. Additional maintenance discrepancies were noted on the shaft assembly.
The total operating time of the Hamilton Standard 12D40 propeller was unknown. The time since the aircraft's last inspection was 194 hours.