On February 5, 2011, at 1500 central standard time, a Piper model PA-16 airplane, N5945H, was substantially damaged when it nosed-over during a forced landing on Lake Koshkonong, Wisconsin. The pilot was not injured. The passenger sustained minor injuries. The airplane was registered to and operated by a private pilot under the provisions of 14 Code of Federal Regulations Part 91. Day visual meteorological conditions prevailed for the flight, which was operated without a flight plan. The flight departed Palmyra Municipal Airport (88C), Palmyra, Wisconsin, at approximately 1330 for the local flight. According to the pilot, during the local flight he decided to overfly Lake Koshkonong at a low altitude. He reduced engine power to idle and the airplane descended from 1,200 feet mean sea level to about 10 feet above the lake. The pilot attempted to arrest the airplane's descent with an increase of engine power; however, advancing the engine throttle did not result in an increase in engine power. A forced landing was immediately performed on the frozen lake. The pilot reported that he was not concerned about landing on the frozen lake because he believed there was bare ice beneath the airplane; however, during touchdown the airplane encountered an area of deep snow and subsequently nosed-over. The pilot and passenger were able to exit the airplane through the cabin doors. The airplane sustained substantial damage to the vertical stabilizer, rudder, right wing, fuselage structure, and the engine firewall. The pilot reported that at departure the airplane had 28 gallons of automobile gas on board and following the accident he had repositioned the airplane's fuel valve to the OFF position. Local law enforcement reported that upon reaching the accident site there was the smell of fuel and the airplane's fuel tanks contained ample fuel. In a postaccident interview, the pilot confirmed that he had not applied carburetor heat during the descent at idle power to the lake. He noted that after identifying the engine was unresponsive to throttle inputs, he did not have enough time to apply carburetor heat before the airplane touched down on the frozen lake. A review of a carburetor-icing probability chart and weather conditions at the time of the accident did not support the accretion of carburetor ice. Further examination of the engine did not reveal any preimpact anomalies or failures that would have prevented normal operation. A postaccident engine run was not performed due to observed airframe and propeller damage.