On August 5, 1999, about 1745 eastern daylight time, a Robinson R-22A, N8561K, was substantially damaged while landing at the Brookhaven Airport, Shirley, New York. The certificated flight instructor (CFI) sustained minor injuries, and the student pilot (SP) was not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the local instructional flight conducted under 14 CFR Part 91. In a written statement, the CFI said he was demonstrating a 180 degree autorotation to the SP. He further stated: "...As I turned final I was at 40 knots and 90 percent RPM. I then lowered the collective to flat pitch before pushing forward on the cyclic to gain airspeed. At approximately 50 feet I started to flare. Loss of RPM occurred immediately after initiation of flare. Helicopter fell rapidly to [the] ground, bouncing once before coming to rest upside down." The helicopter impacted the ground, approximately 50 feet south of the approach end of runway 6. Examination of the helicopter by a Federal Aviation Administration Inspector did not reveal any pre-impact malfunctions of the airframe or engine. The pilot reported 518 total hours of flight experience in rotorcraft. He also reported 505 total flight hours in the make and model of the accident helicopter; of which, 207 flight hours were as a CFI.