On June 5, 1994, about 1120 eastern daylight time, an Aerospatiale SA318C, N4682, in cruise flight lost total engine power and collided with trees during the emergency descent. The pilot was seriously injured. The helicopter sustained substantial damage. Visual meteorological conditions prevailed at the time of the accident. The aerial application flight was conducted under 14 CFR 137. The pilot reported that the purpose of the flight was to spray chemicals over a specific land area. He stated he completed numerous flights throughout the morning and had refueled the helicopter three times prior to the accident. He also stated that after the last refueling, prior to the accident, the helicopter had about 75 gallons on board. The pilot reported that since the last refueling the helicopter had been airborne about a total of 65 minutes when its low fuel pressure light illuminated. He stated that the light did go out however, he decided to return to the fuel landing area anyway. He stated shortly after the light went off, a compressor stall occurred. He stated he located a clearing and initiated a descent when "...the aircraft shuttered and very violently tucked its nose." The helicopter fell through the trees until it contacted the ground. The helicopter and accident site were examined on June 6, 1994. Examination of the helicopter's fuel tank and fuel system revealed the tank was empty and no fuel was present in the fuel lines. No leaks were found throughout the fuel system. The pilot stated that the on board fuel quantity gauge was not operational and he had been using a calibrated "dip stick" to measure the quantity of fuel in the fuel tank after each refueling. He stated that the owner of the helicopter had told him that the engine consumed about 35 gallons of fuel an hour and that he used a fuel rate burn of 40 gallons an hour for his fuel calculations. According to the engine manufacturer's fuel consumption data, the engine could consume up to 36 gallons of fuel per hour. A fuel pump meter reading was not recorded after each time the helicopter was fueled. The helicopter's maintenance records were not available for review. *THIS NARRATIVE WAS MODIFIED ON NOVEMBER 30, 2006.*