On October 5, 1994, at 1200 eastern daylight time, an Aero Commander S2R, N8971Q, was substantially damaged during a forced landing near Ashburn, Georgia. The commercial pilot was not injured. The aircraft was operated under the provisions of 14 CFR Part 137 by Coney Ag Service, of Cordele, Georgia. Visual meteorological conditions prevailed at the time, and no flight plan was filed for the local, aerial application flight. The flight originated in Ashburn at 1115. The pilot reported that he was spraying defoliant chemicals on a cotton field. When he was exiting the field, he heard a loud "bang" or "ping", audible above the engine noise. The aircraft started to vibrate, and would not maintain altitude. The only landing site available was a cotton field. During the forced landing, the aircraft bogged down in the cotton plants, and began to nose over. The left wing contacted the ground, pulling the tail back down, and the aircraft came to a stop. An airworthiness inspector from the Federal Aviation Administration visited the accident site, and inspected the aircraft. His inspection of the propeller revealed that a counterweight bearing shaft failed, allowing one blade to go to high pitch during flight. The propeller logbook could not be located, therefore propeller service and overhaul information could not be determined.