On February 16, 1996, at 1015 central standard time, a Hiller UH-12D helicopter, N67065, registered to, and operated by T.M. Davis Construction Inc., as a Title 14 CFR Part 91 aerial observation flight, was substantially damaged following a loss of control while maneuvering near Carrizo Springs, Texas. The private pilot and his passenger were not injured. Visual meteorological conditions prevailed for the personal flight for which a flight plan was not filed. The flight originated at the ranch office at approximately 0830. The pilot reported that the helicopter departed the Windship Ranch for a local flight to spot deer. "While cruising at about 50 feet and about 40 knots indicated airspeed and after making a 360 degree turn, the engine either lost power or for some other reason would not maintain adequate rotor RPM." The pilot further reported that he lowered the collective in an attempt to increase rotor RPM, "but, the RPM would not reach the minimum required to fly." Subsequently, he landed the helicopter hard, and "the main rotor blade struck the tailboom, severing the boom and 3 feet of blade." The helicopter came to rest on its side. Examination of the airframe and engine by the FAA inspector did not reveal any pre-mishap discrepancies. The reason for the loss of engine power and rotor RPM could not be determined.