On October 18, 1998, at 1400 Alaska daylight time, a tundra tire equipped DeHavilland DHC-2 airplane, N94DC, sustained substantial damage when it nosed over during a forced landing after takeoff from a remote lodge airstrip about 70 miles east of Chitina, Alaska. The commercial pilot and the five passengers on board were not injured. The airplane was operated by Ultima Thule Outfitters, Inc., doing business as Ultima Thule Lodge, of Chitina. The flight was conducted as a personal flight under 14 CFR Part 91, returning local friends to Chitina. Visual meteorological conditions prevailed at the time of the accident, and a company VFR flight plan was filed. The pilot, and a pilot-rated passenger, told the NTSB investigator-in-charge during telephone interviews on October 18, that immediately after takeoff the engine vibrated, then quit. They both stated that an attempt was made to land straight ahead on a river bar located off the end of the lodge landing strip. The airplane hit a rut, ran off the end of the short gravel bar into the three feet deep river, and nosed over onto its back. The occupants exited through the main doors and left pilot door. The pilot indicated in his NTSB Pilot / Operator report, and the pilot-rated passenger confirmed, that the front fuel tank was full, and there was five gallons of fuel in the center tank. The fuel selector was set to the front tank for takeoff. The most recent maintenance indicated in the engine logbook was a 100 hour inspection on September 15, 85 hours prior to the accident. The engine was inspected by an FAA inspector on November 11, and revealed no mechanical anomalies with the fuel system or magnetos. The engine and propeller were mechanically intact and rotated freely. All screens and filters were free of debris. Propeller blades were bent rearward with no indication of rotation at impact. The fuel lines were intact, and no fuel was found in the fuel hose between the firewall and the fuel pump. The residual fuel in the carburetor bowl was mixed with water. The airplane came to rest in the river with the carburetor above the water.