On July 26, 1999, at 0930, eastern daylight time, a Maule M-5-200, N5643T, collided with the ground and flipped inverted during a forced landing near St. Simons Island, Georgia. The personal flight operated was by the pilot under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane sustained substantial damage, and the private pilot was not injured. The flight departed from the Malcolm McKinnon Airport, St. Simons Island, Georgia, at 0928. According to the pilot, shortly after liftoff from runway 34, at Malcolm McKinnon Airport, the engine lost power. Attempts by the pilot to restore full engine power failed. The pilot selected a marshy area for a forced landing. The airplane flipped inverted during the attempted forced landing two miles northwest of the airport. The post-examination of the airplane disclosed that the dual magneto had separated from the engine assembly. The examination also showed that the magneto retention nuts and washers were not attached to the magneto. After the magneto was reinstalled on the engine, a satisfactory engine run was conducted. A review of the engine and airframe maintenance log books disclosed that the airplane was approximately 30 hours out of the last annual inspection. There was no record of magneto assembly removal during the last inspection.