On July 22, 1999, at 1415 central daylight time, a Ryan Navion A, N4902K, piloted by a private pilot, sustained substantial damage during a forced landing near Keokuk Municipal Airport, Keokuk, Iowa. The 14 CFR Part 91 flight was not on a flight plan. The pilot and passenger received minor injuries. Visual meteorological conditions prevailed at the time of the accident. The flight originated from West Kentucky Airpark Airport, Paducah, Kentucky at 1200. In a written statement, the pilot stated that he had topped off the accident airplane's fuel before departing West Kentucky Airpark Airport. He said that during the downwind segment of the approach to runway 26 at Keokuk Municipal Airport, he reduced engine power, he lowered the gear, and lowered 1/2 flaps. He said that he applied power to stabilize the decent and found that the engine did not respond to the throttle. He stated that he had chosen a soybean field and made a forced landed in that field. The pilot reported that both main landing gears were sheared off, damage occurred to both wings, and that the engine compartment was torn loose from the fuselage during the forced landing. A FAA inspection, conducted on July 27, 1999, revealed engine continuity. No pre-existing engine anomalies were found. Three and three quarter gallons of fuel were recovered from the airplane. An area soaked with fuel was present on the ground under the firewall area and the glass gascolator bowl was found broken. The fuel selector was found selecting the main tank and was selected to the off position by the first person to arrive.