On September 13, 1994, at 1015 central daylight time, a Weatherly 620TP, N4607C, was substantially damaged following a loss of control during approach near Montrose, Arkansas. The airplane was flown by a commercial pilot for this aerial application flight. Visual meteorological conditions prevailed for the flight and there were no injuries. According to the pilot, while on final approach he throttled back in preparation for landing, the aircraft's nose then "whipped abruptly 30 degrees left, then back to the right." He lowered the nose and added left aileron at approximately 30 feet AGL. The airplane then impacted in a ditch, slid across a road and came to rest in another ditch. An examination of the aircraft by a Federal Aviation Administration inspector revealed no anomalies were present and the pilot reported he experienced no mechanical difficulties.