On September 12, 1996, at 0923 central daylight time, a Hiller UH12E, N156HA, registered to and operated by Summit Helicopters Inc., as a Title 14 CFR Part 137 aerial application flight, was substantially damaged during a forced landing, following a loss of tail rotor control near Hamburg, Arkansas. Visual meteorological conditions prevailed, and a flight plan was not filed. The commercial pilot received minor injuries. The helicopter departed Hamburg about daybreak, and had completed spraying several tracts of land prior to the accident. The pilot reported to the investigator-in-charge that he had refueled and loaded chemicals at a field location. About 1 minute after takeoff, he heard a "loud bang," followed by a vibration. A forced landing was initiated towards a dirt road. However, prior to landing, the helicopter began to "spin." Subsequently, the helicopter impacted trees in a "slight nose low attitude." An examination of the helicopter at the accident site by the FAA inspector revealed that one tail rotor blade was separated approximately 10 inches from the hub. Both main rotor blades were damaged, and the main transmission was partially separated from its mounts. Further examination of the helicopter revealed that the tailboom ballast weight was partially disconnected. It was secured to the tailboom only by its forward retaining pin. The ground crew reported that the day prior to the accident, they had observed the tailboom ballast weight disconnected at its aft attaching point. They informed the pilot, and observed him reinstalling the ballast weight and securing it with the retaining pin. One of the ground crew also reported that "the pin seemed to lock in place."