On December 30, 2003, about 1415 Alaska standard time, a tundra tire-equipped Piper PA-12 airplane, N3624M, sustained substantial damage when the right main landing gear collapsed during a forced landing following a loss of engine power, about 20 miles northeast of Togiak, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country personal flight under Title 14, CFR Part 91, when the accident occurred. The commercial certificated pilot, and the sole passenger aboard sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated about 1310, from the Togiak Airport, Togiak, and was returning to Togiak when the accident occurred. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on January 1, 2004, the pilot related that the purpose of the flight was to view some Alaskan scenery. He said that on the return flight to Togiak, while over tree-covered terrain, he noted a rough running engine and a slight reduction in engine rpm. He said that engine emergency procedures did not remedy the engine roughness, which was followed by a rapid loss of engine power, and subsequent loss of altitude. The pilot said that he was unable to restore adequate engine power to maintain level flight, and he selected a snow and tree-covered area as a forced landing site. During touch down on the soft, snow-covered terrain, the right main landing gear collapsed, the airplane pivoted to the left, and the left wing struck a stand of trees. The airplane sustained structural damage to the left wing and fuselage. The pilot reported that weather conditions at the time of the accident were, in part: Visibility, 25 statute miles; clouds and sky condition, 8,000 feet overcast; temperature, 24 degrees F. During a follow-up telephone conversation with the NTSB IIC on June 30, the pilot reported that after the airplane was retrieved from the accident site and transported to Togiak, maintenance personnel inspected the engine, but were unable to determine the reason for the loss of engine power.