On December 18, 2005, about 1220 eastern standard time, a Robinson R44 helicopter, N44EK, was substantially damaged during a forced landing after takeoff from Linden Airport (LDJ), Linden, New Jersey. The certificated flight instructor (CFI) and a student pilot were not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the local instructional flight conducted under 14 CFR Part 91. The CFI reported that as the helicopter climbed after takeoff, it began to vibrate and experience a loss of engine power. The CFI conducted an autorotation to a nearby construction site that was located about 1/4 mile from the approach end of runway 27. During the autorotation, the helicopter's skids dug into the muddy ground, and the main rotor blades contacted the tail boom. Review of maintenance records revealed that the helicopter had been operated for about 20 hours since its most recent annual inspection, which was performed on November 10, 2005. Subsequent examination of the helicopter by a Federal Aviation Administration (FAA) airworthiness inspector, and other maintenance personnel did not reveal any preimpact mechanical malfunctions. The CFI reported 1,920 hours of total flight experience, which included about 300 hours in the accident helicopter make and model. The reported temperature and dew point at an airport about 5 miles northeast of the accident site, about the time of the accident, was 37 and 21 degrees F; respectively. Review of a carburetor icing probability chart placed the reported temperature and dew point in the "serious icing - glide power" range of the chart.