On August 30, 1997, about 1020 Eastern Daylight Time, a Hiller UH-12B, N5303V, a helicopter, was substantially damaged when it impacted the ground during an uncontrolled descent from a hover at the Slatington Airport, Slatington, Pennsylvania. The certificated commercial pilot received minor injuries. Visual meteorological conditions prevailed for the local flight. No flight plan was filed for the personal flight conducted under 14 CFR Part 91. According to the owner of the helicopter, it was not airworthy. The helicopter was for sale, and had not flown for approximately 6 months due to required maintenance. The rotor tachometer was inaccurate and needed to be repaired or replaced. One week prior to the accident, the pilot expressed interest in purchasing the helicopter. The owner allowed the pilot to examine it. As they operated the engine on the ground, the pilot insisted they conduct a test flight. The owner repeatedly told the pilot that he could not fly the helicopter due to the erroneous rotor tachometer. On the day of the accident, the pilot flew the helicopter without permission, and without the owner present. On the third attempt at liftoff, the pilot lost control, and the helicopter impacted the ground. Witnesses reported that the helicopter did not appear to be stable at any time in the repeated attempts at takeoff. On the third attempted lift off, the helicopter became airborne, moved forward, and climbed to an altitude of approximately 5 to 10 feet above the ground. Then the helicopter move aft, followed by a decrease in power. The tailboom impacted the ground, the helicopter rolled right, and the main rotor blades struck the ground. After the accident, the pilot attempted to conceal the wreckage in a hanger, but a Federal Aviation Administration (FAA) Inspector was at the airport during the accident. The FAA Inspector reported the accident to the Flight Standards District Office. According to a Federal Aviation Administration Inspector, there was no evidence of pre-impact mechanical malfunctions with the helicopter. Flight control continuity was confirmed and approximately 12 gallons of fuel remained in the tanks. Witnesses told him the engine sounded "normal." During a period of 18 months, repeated attempts to have the pilot provide a statement, or complete and return the required National Transportation Safety Board Pilot/Operator Aircraft Accident Report form 6120.1/2, were unsuccessful.