On July 30, 1994, at 1030 hours mountain standard time, a Bell 47G-2A, N6749D, sustained substantial damage during a hard landing on the Salt River Indian Reservation, Scottsdale, Arizona. The aircraft was operated by San Tan Dusters, Inc., and was conducting agricultural operations under 14 CFR Part 137 of Federal Aviation Regulations. Visual meteorological conditions were prevalent at the time and no flight plan was filed for the operation. The certificated commercial pilot was not injured. The flight originated from an improvised loading site on the Salt River Indian Reservation at 0500 on the day of the accident. The pilot stated that he had flown the aircraft the day before and during one flight had heard the engine sputter. As a precaution, he landed, checked the fuel, and verified that he still had approximately 5 or 6 gallons of fuel on board. The pilot stated that he had just finished an application run and was in the process of pulling up and turning right when the engine sputtered briefly and quit. While at an altitude of approximately 40 feet and an airspeed of 40 knots, the pilot initiated an autorotation to the ground. The pilot stated that the aircraft touched down hard, at which time the main rotor blade flexed downward striking the tail boom. The pilot exited the aircraft unassisted. According to the to height/velocity diagram obtained from Bell Helicopter for the 47G-2A model, the engine stoppage occurred at an airspeed and altitude unsafe for autorotative landings. According to a company mechanic who performed a postaccident inspection of the aircraft, there was approximately 1 quart of fuel remaining in the tank. After the aircraft was recovered, the engine was refueled. The engine started and ran normally on the first attempt.