On December 24, 1993, at 1330 central standard time, a Brantly B-2 helicopter, N2111U, was substantially damaged following a forced landing due to a loss of engine power, near Giddings, Texas. The pilot/owner and passenger were not injured. Visual meteorological conditions prevailed for the personal flight. No flight plan was filed. The pilot reported, during an interview conducted by the investigator-in-charge, that while in cruise flight he noticed that the engine started to run rough and the carburetor temperature gauge was indicating that the temperature had reached the cautionary zone. He further reported that he applied carburetor heat; however, the engine lost complete power and he entered an autorotation into the wind. During the autorotative descent, he observed electrical power lines in front of him; he turned to the right to avoid the power lines. The right turn resulted in the helicopter landing with a left quartering tail wind. Additionally, the pilot stated he applied initial pitch for cushioning at ten feet; however, the main rotor rpm had decayed to a point insufficient to sustain the landing and the helicopter impacted the ground hard and bounced. During the landing, the skids collapsed and the main rotor flexed downward resulting in a strike by a blade to the tailboom. The pilot further stated he believed he had carburetor icing. Temperature and dewpoint 51 and 30 degrees respectively