On September 19, 2005, at 1315 Pacific daylight time, a North American Navion A, N91597, sustained substantial damage during a forced landing on a road approximately 3 miles east of Chowchilla, California. The forced landing was precipitated by a loss of engine power during cruise. The private pilot, who was also the registered owner of the airplane, was operating it under the provisions of 14 CFR Part 91. The pilot sustained minor injuries. The pilot departed from Calaveras County-Maury Rasmussen Field Airport, San Andreas, California, at 1220, and was destined for Ramona Airport, Ramona, California. Visual meteorological conditions prevailed for the flight, and the pilot had filed and activated a visual flight rules (VFR) flight plan. In a written statement, the pilot reported that he fueled the airplane's main tanks and tip tanks prior to his departure, and that the auxiliary fuel tank had been previously filled. Normally, the pilot would fill up either the auxiliary fuel tank or the tip tanks, but not both. He would use the auxiliary tank for 3 to 4 months, then switch to using only the wing tip tanks for the next 3 to 4 months. Because he had been using the auxiliary fuel tank for the last several months, he decided to use the wing tip tanks for this flight. The pilot estimated that he had over 30 gallons of 100 low lead (LL) in the main fuel tanks and a total of approximately 60 gallons of 100 LL in his auxiliary and tip tanks. He visually checked the fuel prior to his departure and did not note any sediment or contamination. The pilot reported that for takeoff and climb out the fuel selector was placed to the main fuel tank and he did not run the engine from each of the fuel tanks prior to takeoff. Once the airplane reached a cruise altitude of 7,500 feet mean sea level he leaned the fuel mixture. At 1300, he turned on the auxiliary fuel pump and switched to the right tip tank. As had happened in the past when he had not used the wing tip tanks for several months, he expected the engine to sputter and then restart. However, on this occasion, after the engine sputtered, it did not restart although the propeller continued to windmill. The pilot then switched the fuel selector back to the main tank and verified that he was getting fuel pressure after advancing the throttle and mixture controls to their full forward positions. The pilot activated the starter once during the descent while advising an air traffic controller of his emergency and transitioning to the nearest airport. When it became evident to the pilot that he would be unable to make the nearest airport, he chose to land on a dirt road. Prior to reaching the road that he had chosen to make the emergency landing, he saw a closer road. The pilot realigned the airplane on the nearer road, and set up for landing. During touchdown, the outer section of the left wing was sheared off and the airplane spun 90 degrees while skidding about 100 feet. The pilot had not reported the sputtering problem to his aviation maintenance technician (AMT). The Federal Aviation Administration accident coordinator responded to the accident scene. The airplane came to rest on a road, next to a vineyard. During the landing sequence, the left tip tank was torn from the wing and located about 20 feet from the main wreckage. The left tip tank contained an undetermined amount of fuel with a substantial amount in the soil near the tank. The main fuel tank had less than 5 gallons with a leak evident underneath the airplane. The auxiliary fuel tank was measured with a calibrated stick found in the airplane and contained about 30 gallons. The right wing had a crush line parallel to the longitudinal axis of the airplane approximately mid-wing. The outboard section from this crush line appeared to be pulled aft. The lower cowling was crumpled and the propeller spinner was resting on a portion of a vineyard post. The right tip tank was breached after it was torn from the airplane and no fuel remained in the tank; there was no fuel located on the ground underneath the tank. No mechanical malfunctions were evident during the on-scene portion of the investigation. A technical advisor for the American Navion Society described the fuel system for the airplane. The fuel system was modified with a supplemental type certificate for the tip tanks. With a four-tank fuel system utilizing an under seat auxiliary tank, the common method was to install a five position valve with the following tanks labeled: left tip, main, right tip, auxiliary, and off. All fuel at the valve feeds directly from the selected tank to the engine through the installed plumbing. In addition, he reported that if the possibility for air in the fuel lines exists, during run-up prior to takeoff, the pilot should switch to each tank and the engine allowed to run long enough on each to be certain fuel flow is not interrupted. An AMT examined the airplane. Low-pressure air was blown through the fuel lines from the right tip tank with no obvious obstructions. The AMT also noted that the right tip tank was damaged from the accident sequence. Low-pressure air was induced into the fuel line from the engine and airflow was noted in the main tank and the auxiliary tank. The fuel tanks were inspected using a flashlight and mirror and no contaminants were observed. The fuel selector rotated with no resistance and the detents were noted in the appropriate positions. The spark plugs were removed from the Teledyne Continental E-225 engine and the spark plug electrodes were gray in color, which corresponded to normal operation according to the Champion Aviation Check-A-Plug AV-27 Chart.