On October 10, 1998, at 1020 central daylight time, a Hiller FH-1100, N580RH, collided with a log, while attempting an emergency landing near Fayette, Mississippi. The aerial application flight was operated by Ward Aviation Incorporated under the provisions of Title 14 CFR Part 137 with visual flight rules. Visual weather conditions prevailed at the time of the accident, with no flight plan filed. The commercial rated pilot was not injured, and the helicopter was substantially damaged. The flight departed Fayette, Mississippi, at 1007 of the same day. According to the pilot, while making a 180 degree turn, the boost pump fail light came on. Shortly afterwards the engine shutdown at about 150 feet AGL. He selected a field for an emergency landing and entered an autorotation. During the touchdown phase of the autorotation, the helicopter collided with a log and rolled over. The pilot also stated that there was insufficient RPM to stop roll over (see attached pilot statement). The examination of the engine and the fuel supply vacuum system disclosed that there was an air leak between the fuel tank and the engine driven fuel pump. Also both the airframe and engine fuel filters were clogged with an unidentifiable brownish, jelly-like substance. A review of the maintenance log revealed that the last 100 hour inspection was 98 hours before the accident. There were no further indications of any other maintenance done on the fuel system. (see attached inspector's report).