On May 11, 2000, at 1715 central daylight time, a Robinson R22 Beta, N8321K, operated by a private pilot, lost power just after takeoff from the roof of a public building in Ham Lake, Minnesota. The helicopter was subsequently destroyed when it impacted the terrain and rolled over. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under 14 CFR part 91, and was not operating on a flight plan. The pilot and passenger on board reported no injuries. The local flight was originating at the time of the accident. In his written statement, the pilot said that he took off from the roof of a building and turned into the wind. He said that as he started forward, "the rpms start to drop." The pilot checked his manifold pressure and saw it was 24 inches. He continued forward, manipulating the collective and throttle, so that he could clear a nearby 2-story building. "When I cleared the roof line, I dropped the collective, rolled the throttle and aft cyclic, but [I] didn't have enough altitude to recover, and into the ground we went." A Federal Aviation Administration (FAA)inspector examined the helicopter at the accident site. The cockpit and fuselage were crushed inward and aft. The windscreen was broken out. The main rotor blades were bent and twisted. The left skid was bent inward. The tail boom was severed midway between the fuselage and the tail rotor system. Control continuity was confirmed. The engine, engine controls, and other helicopter systems revealed no anomalies. At 1655 cdt, the Aviation Routine Weather Report (METAR) for Anoka County Airport, Anoka, Minnesota, 10 miles south-southeast of the accident site, was 800 overcast, 2 miles visibility with fog, temperature 60 degrees F, dew point 58 degrees F, and altimeter 29.39 inches of Mercury (Hg). Department of Transportation/FAA Publication CT-82/44, Light Aircraft Piston Engine Carburetor Ice Detector/Warning Device Sensitivity/Effectiveness, June 1982, Carburetor Icing Probability Chart, shows for a temperature of 60 degrees F, and a dew point of 58 degrees F, "serious icing conditions at cruise power" exists.