On May 7, 1994, at 0715 Pacific daylight time an Aero Commander S2R, N5646X, experienced a loss of engine power during an aerial application flight near Dayton, Washington. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane was substantially damaged and the commercial pilot was not injured. The pilot reported that during a spray operation, the engine began to run rough and the chip detector light illuminated. While en route back to the airstrip, the engine began to smoke and a backfire was heard. The engine lost power and the airplane was unable to make it to the airstrip. The pilot initiated a forced landing to an open field, short of the airstrip, where the airplane collided with the terrain during the landing roll. During the inspection of the engine, it was found that the number five connecting rod broke.