On June 16, 1999, about 1530 eastern daylight time, a Hiller UH-12C helicopter, N57CR, was substantially damaged during a forced landing to a field near Delphos, Ohio. The certificated commercial pilot was not injured. Visual meteorological conditions prevailed. No flight plan was filed for the ferry flight conducted under 14 CFR Part 91, that departed Sidney, Ohio, destined for Defiance, Ohio. According to the pilot, the helicopter had under gone maintenance for an engine change in Sidney. The pilot arrived at the maintenance facility about 1415, to conduct a test flight, and then ferry the helicopter home. He added that the replacement engine was manufactured from new parts by an individual in Texas. After conducting a preflight, the pilot started the helicopter's engine on the first attempt. He allowed the engine to warm-up, then brought the helicopter to a hover. The pilot hovered the helicopter for approximately 15 minutes then executed a takeoff. He climbed to 500 feet agl, and entered an autorotation to check rotor rpm. After recovering from the autorotation at 200 feet agl, the pilot preformed a "normal" approach, terminating at a 5 foot hover. While at hover, the pilot performed a left pedal turn to verify tailrotor rigging, and hovering characteristics with a tailwind. The flight lasted about 30 minutes, and the pilot noticed no anomalies. After a 2 minute cool down, the pilot secured the engine, and paid the bill for the installation of the replacement engine. The helicopter was then fueled for the non-stop flight back to Defiance. The pilot, with the assistance of the mechanic, conducted another preflight flight, and no engine oil leaks, or discrepancies were identified. The pilot boarded the helicopter, and once again, the engine started on the first attempt. He checked the magnetos, and observed a drop of 75 to 100 rpm for both sides. The pilot departed to the northeast to avoid some structures, and powerlines. Once clear of the powerlines, he established the helicopter on a northwest course, and climbed to a cruise altitude of 500 feet agl. About 30 minutes into the flight, the pilot felt the helicopter shutter, and noticed a partial loss of power, accompanied by engine surges. With the only open area to the helicopter's 6 o'clock position, the pilot executed a left turn. When the helicopter completed the turn, it was about 100 feet agl, and indicating 30 knots of airspeed. With rotor rpm decaying, and the helicopter yawing left and right, the pilot lowered the collective, and entered an autorotation, leaving the throttle open. The pilot said the engine was behaving like the, "key was being turned on and off." About 25 feet agl, the helicopter experienced a total loss off power. The pilot felt rotor rpm was slower then "normal" when he initiated the flare. When the helicopter was about 8 to 10 feet agl, the collective was full up, and the helicopter was traveling forward about 10 knots. When the helicopter touched down the main rotor flexed, and severed the tailboom. The helicopter slid about 15 feet, and rotated about 30 degrees to the left before coming to a stop. The pilot secured the magnetos, electrical master, and unplugged the battery before walking to a house. According to a Federal Aviation Administration Inspector, on June 21, 1999, he examined the helicopter at a recovery facility in Ohio. He removed both magnetos, rotated their drive shafts by hand, and observed spark on all magneto leads. He removed the carburetor bowl, and observed approximately one teaspoon of fuel. While still connected to the helicopter's fuel and electrical systems, power was applied to the auxiliary fuel pump. The pump rotated, but no fuel was expelled. The Inspector then rotated the engine drive fuel pump's drive shaft by hand, and detected no anomalies. In addition the engine driven fuel pump, and auxiliary fuel pump share a common fuel filter, and plumbing. The Inspector estimated the helicopter had 25 gallons of fuel onboard during the examination.