On July 26, 1993, about 1545 hours mountain standard time, a homebuilt Ferdon Thorp S-18, N119FF, crashed during a precautionary landing, about 1 mile east of Ash Fork, Arizona. The airplane was being operated as a visual flight rules (VFR) cross country personal flight to Flagstaff, Arizona, when the accident occurred. The airplane, registered to and operated by the pilot, received substantial damage. The certificated private pilot and a passenger, received minor injuries. Visual meteorological conditions prevailed. The flight originated from General William J. Fox Airfield, Lancaster, California, about 1350 hours. The pilot reported that while flying in an easterly direction enroute to Flagstaff, he encountered severe turbulence and strong cross winds from the south. The airplane's Loran navigational receiver indicated that the wind velocity was 51 knots. The pilot reported that..."Engine began to cut out from strong turbulence". The pilot decided to make a precautionary landing on a secondary road, adjacent to Interstate Highway 40, that is oriented in an east and west direction. During the landing with a quartering tail wind condition, the airplane veered of the roadway and the left main landing gear dug into soft terrain. The airplane struck a fence adjacent to the road and the airplane nosed over. The pilot holds a private pilot certificate with an airplane single engine land rating. The most recent third class medical certificate was issued to the pilot on November 6, 1992, and contained the limitation that the pilot shall wear lenses that correct for distant vision and possess glasses that correct for near vision while exercising the privileges of his airman certificate. According to the pilot/operator report submitted by the pilot, his total aeronautical experience consists of about 588 hours, of which 356 were accrued in the accident airplane make and model. In the preceding 90 and 30 days prior to the accident, the report lists a total of 6 and 4 hours respectively flown. The airplane had accumulated a total time in service of 304 flight hours. In the recommendation section of the pilot/operator report, the pilot indicated that... "Put baffles in main fuel tank to prevent surging during severe turbulence to prevent momentary fuel starvation". Fueling records at Fox Field established that the aircraft was last fueled on July 25, 1993, with the addition of 7.1 gallons of 100LL octane aviation fuel. The pilot reported that the airplane departed with 29 gallons of fuel, which are full tanks. He indicated that the airplane has a maximum endurance of 3.2 hours, and a maximum range of 515 miles. The accident flight was about 2 hours long and the airplane burns about 9 gallons per hour at 160 miles per hour. The closest official weather observation station is Prescott, Arizona, which is located about 35 nautical miles south of the accident site. At 1550 hours, a surface observation was reporting in part: Sky condition and ceiling, clear; visibility, 65 miles; temperature, 88 degrees F; dew point, 21 degrees F; wind, 220 degrees at 12 knots, gust to 18 knots; altimeter, 30.12 inHg. Flagstaff, Arizona, is located about 40 nautical miles east of the accident site. At 1549 hours, an automated meteorological observation station was reporting in part: Sky condition and ceiling, clear; visibility, 20 miles; temperature, 80 degrees F; dew point, 34 degrees F; wind, 210 degrees at 6 knots; altimeter, 30.26 inHg; peak wind in the last hourly report, 17 knots.