On November 27, 1996, about 1713 eastern standard time, a Lake LA-4-200, N1109L, collided with a tree and the ground during a visual approach to the Albert Whitted Airport, St. Petersburg, Florida. The airplane was operated by the private pilot under the provisions of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed. A flight plan was not filed for the personal flight. The pilot was seriously injured, and the airplane was substantially damaged. Origination of the flight was Berry Hill Airport in Stockbridge, Georgia, at 1425 the same day. When the airplane was about four miles north of the airport, the pilot declared a "MAYDAY" report to the airport tower that he was "going down in the water." The airplane subsequently crashed into a church yard near the airport. The airplane came to rest inverted. The FAA inspector who visited the site reported that there was no fuel, or the odor of fuel, at the impact site. The were no mechanical problems reported by the pilot. According to the pilot, the gas cap on the left wing was not a Lake Aircraft gas cap. Therefore, he believed that fuel siphoned out of the overflow vent. According to Lake Aircraft personnel, fuel could not siphon out of the airplane unless the gas cap was removed and the fuel door was open. The pilot stated that he had calculated his time enroute, along with the amount of fuel the flight would require. He planned for a distance, between Stockbridge and Albert Whitted, of 328 nautical miles (nm), an average ground speed of 129 knots (kts or nm/hr), a time enroute of 2.8 hr., and a fuel flow of 12 gallons per hour (gph). He stated that his calculations left him with a half hour reserve. The pilot believed his airplane to have a fuel capacity of 42 gallons. According to the Lake Aircraft Manual and FAA Type Certificate Data Sheets, the LA-4-200 has a fuel capacity of 40 gallons, all of which is considered to be usable fuel. Given: 0.3 gallon for startup, taxi and runup. 0.1 gallon for combustion heater operation. 4.0 gallons for 20 minutes of climb power (averaging 450 feet per minute to climb from 770 feet msl departure point to 7,500 feet cruise altitude, at 16 gallons per hour) Subtracting the above fuel burn from a full tank leaves 35.5 gallons available. The pilot stated that he had used 24" of manifold pressure and 2400 rpm for the flight, which is approximately 70 percent of maximum power, according to Lycoming power charts available to the pilot for a normally aspirated IO-360 engine. Using the best-economy mixture setting at 70 percent power, approximately 3.67 hours of endurance would remain at top of climb, for a total endurance, including climb, of 4 hours. At best-power mixture settings at a cruise power of 70 percent, approximately 3.16 hours of endurance would remain, for a total endurance, including climb, of 3.49 hours. At 12 gallons per hour, the observed fuel consumption rate cited by the pilot for previous flights, 2.96 hours of endurance would remain, for a total flight endurance, including climb, of 3.29 hours. Total flight time was reported by the pilot as being 2.8 hours. No performance data or fuel consumption data for the on-demand manual-wastegate turbocharger was provided by the manufacturer. The petitioner reported that he had based his flight planning upon a distance of 328 nautical miles between his departure point and destination, as obtained from his GPS receiver. He stated that he flew a direct flight between the two locations of between 328 and 330 miles. According to the DUATS flight planning program, the flight distance using Victor airways is 359.0 nautical miles; the great circle distance (the shortest distance between two points) between the point of departure and destination is 355.4 nautical miles. The pilot stated that he encountered winds aloft of 20 to 25 knots from 020 degrees at 7,500 feet (his cruising altitude for the flight). Both forecast and observed winds aloft reports for the period of this flight are attached to this report. According to those reports, tailwinds existed along the flightpath during the time period of this flight.