On December 4, 1998, at 0100 hours Pacific standard time, a Bell 47G-3B-1 helicopter, N3084G, lost rotor rpm on takeoff and impacted the ground near Winterhaven, California. The aircraft sustained substantial damage, and the commercial pilot, the sole occupant, was not injured. The aerial application flight was conducted under the provisions of 14 CFR Part 137, and the aircraft was being operated by Sundown Helicopters, Yuma, Arizona. The local flight originated about 2200. Night visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that he had been spraying a field with fertilizer for 3 hours. He stopped for approximately 5 minutes to add "30 to 40 gallons of fuel and about 50 gallons of [spray] material." He reported that the takeoff seemed normal and the helicopter accelerated through translational lift. The pilot stated that the rotor rpm began to decay and he was unable to regain it. The aircraft was positioned perpendicular to the furrowed rows in the field, and when the pilot attempted to land, the left skid dug into the mud. The helicopter bounced forward and the main rotor blades flexed downward and cut through the tailboom. The pilot reported that he had not experienced any mechanical discrepancies with the aircraft prior to the accident. He further stated that he had not experienced any problems with the engine during the accident. According to the Bell Pilot Operator Handbook, the maximum gross weight for the Bell 47G-3B-1 is 2,950 pounds. The pilot supplied the weight and balance he had worked out for the accident flight, which listed a takeoff weight of 2,930.13 pounds. He calculated 35 gallons of 100 low lead aviation fuel at 6 pounds per gallon, totaling 210 pounds. Aviation fuel weighs 6.7 pounds; 35 gallons of fuel at 6.7 pounds per gallon equals 234.5 pounds. This calculation of fuel weight adds 24.5 gallons to the pilot's calculation of 2,930.13, bringing the takeoff weight to 2,954.63 pounds.