On May 18, 2013, about 1230 central daylight time, a Piper PA-28-161 airplane, N47539, experienced a loss of engine power and the pilot performed a forced landing near Oskaloosa, Iowa. The commercial rated pilot and the two passengers received minor injuries. The airplane was substantially damaged. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight that operated without a flight plan. The flight originated from Washington Municipal Airport (KAWG), Washington, Iowa about 1200. According to the pilot, during cruise flight he felt a slight “bump” in the engine. He switched fuel tanks and turned on the fuel boost pump. He noted that the engine was down to about 1,500 rpm. He checked the magnetos, applied carburetor heat, and switched back to the first fuel tank; the engine did not respond to the changes. He added that when the engine was down to 1,000 rpm, he knew they wouldn’t make an airport, so he selected a field for the forced landing. During the landing the airplane impacted a berm and came to rest on its belly. The responding Federal Aviation Administration (FAA) inspector examined the airplane on site and noted that the airplane’s landing gear had collapsed and there was substantial damage to the fuselage. A subsequent examination of the engine was conducted by an A&P mechanic under the supervision of the FAA inspector. The engine’s compression, fuel and ignition systems were checked. The engine’s electric driven pump appeared to operate when turned on, the carburetor bowl was empty of fuel, and minor debris was found in the inlet screen. The engine’s spark plugs were worn, but would fire on the left magneto, when the engine was rotated by hand. The intake box was crushed in the accident; however, the heat cables were in operational condition. No anomalies were noted during the examination that would have precluded normal engine operation. The carburetor icing probability chart included in the Federal Aviation Administration Special Airworthiness Information Bulletin No. CE-09-35, Carburetor Icing Prevention, indicated that the airplane was operating in an area that was associated with a serious risk of carburetor ice at glide power settings. A reason for the loss of engine power was not determined.