On July 11, 1999, about 1430 Alaska daylight time, a wheel equipped Cessna 337B airplane, N5499S, sustained substantial damage during takeoff from the Seldovia Airport, Seldovia, 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 certificated commercial pilot, and the one passenger aboard, received serious injuries. Visual meteorological conditions prevailed, and a VFR flight plan was filed. During a conversation with the National Transportation Safety Board investigator-in-charge on August 13, the pilot reported that three days before the accident, he parked the airplane with the main fuel tanks about one-half full. He said that on the day of the accident, during his preflight inspection, he noted that the cockpit fuel quantity indicators indicated that both main tanks were about one-quarter full. The pilot stated that he did not climb up on the wings and verify the remaining fuel quantity in the main fuel tanks, but planned to make the short flight to Homer, Alaska, to purchase fuel. He said that just after departure from runway 34, about 500 feet msl, both engines began to run rough, followed by a total loss of engine power. He indicated that he turned the airplane 180 degrees, but did not have sufficient altitude to return to the runway, and made a gear-up, forced landing on a tidal beach. During the forced landing, the left wing struck a stand of trees, and the airplane landed hard on the beach. The pilot added that the flight was accomplished with the fuel selector valve on the main fuel tanks, and that both auxiliary fuel tanks were empty, and not in use. An Alaska State Trooper who responded to the accident site, arrived on scene about one hour after the accident. He reported that upon his arrival, both the left and right main fuel tanks were "dry." He added that the left auxiliary fuel tank appeared to have a "minimal amount of fuel left, and the right auxiliary fuel tank was empty." The airplane sustained substantial damage to the wings, fuselage, and empennage.