On July 21, 2001, at 1155 hours Pacific daylight time, a Hughes 269C, N5015V, was substantially damaged when it landed hard and rolled over during an autorotation for training purposes, at the New Jerusalem Airport, Tracy, California. The flight instructor and dual student were not injured. Visual meteorological conditions prevailed for the instructional flight conducted under 14 CFR Part 91 by Advanced Aviation, Stockton, California. The helicopter departed Stockton Metropolitan Airport approximately 1045, and no flight plan was filed. The flight instructor stated that he was demonstrating an autorotation to his student when the accident occurred. He said that he initiated a straight in autorotation to runway 30 at the New Jerusalem airport at 600 feet above ground level (agl). The descent rate was stabilized until 200 feet agl, when he felt a sudden increase in the rate of descent. He began the flare at 50 feet agl. He stated that the vertical speed did not decrease at the rate he was accustomed to, causing the helicopter to land hard. He stated that the tail boom hit the ground first in a right yawing moment. The helicopter then rolled to the right, crushing the right skid, severing the tail boom, and allowing the rotor blades to contact the ground. He noted that no mechanical problems existed with the helicopter during the flight. He did not notice any mechanical anomalies during the autorotation demonstration. He stated that the engine was running normally during the autorotation and the landing flare. The pilot stated that wind shear may have been a factor. He had observed the winds to be from the northwest at 8 knots, and gusts to 12 knots with light turbulence. According to the pilot, he had a total flight time of 2,100 hours, of which 650 hours were in helicopters. He had 300 hours of flight experience in this make and model prior to the accident, 6 of which were in the last 30 days. The student had a total of 1,750 hours, of which 1,210 were in helicopters. He had 50 hours in this make and model.