On July 25, 1998, approximately 1330 central daylight time, a Robinson R22 helicopter, N789HP, owned and operated by High Plains Helicopters, was substantially damaged during an autorotational landing near Lubbock, Texas. The commercial flight instructor and his passenger sustained minor injuries. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations (CFR) Part 91 business flight. The flight originated from the Lubbock International Airport about 1320. According to the flight instructor, he was demonstrating autorotations with power recovery to a prospective student pilot. The instructor had executed a go-around during the first autorotation (180 degree turn) and was demonstrating a second autorotation when the accident occurred. The flight instructor reported that he initiated the autorotation from a heading of approximately 040 degrees at 600 feet agl, with an airspeed of 60 knots and a rotor RPM of 100 percent. The pilot stated he normally performs autorotations with 180 degree turns at 700 feet agl, therefore he determined he would only turn 100 degrees. During the 100 degree right turn toward the south (about a 140 degree heading), the airspeed decreased to 54 knots. The instructor further reported that he lowered the aircraft's nose to regain airspeed and the rotor RPM decreased to 96 percent, activating the low rotor RPM warning system. He then lowered the collective and rotor RPM was regained (100 percent). At 60 feet, he looked up and observed the ground coming up "very fast." At 40 feet he initiated a flare, and noticed that "instead of the flare dragging out, we just kept dropping towards the ground." The instructor also reported that at this time "I decided that we were past the point of no-return and I prepared for impact." At 25 feet he aligned the aircraft for landing, and "just prior to touchdown I applied full collective pitch. I can't remember if I rolled throttle on or not." The helicopter struck the ground with the tailboom first, then the skids, and came to rest on its left side. The pilot reported in the Pilot/Operator Accident Report, NTSB Form 6120.1/2 that the winds at the time of the accident were from 190 degrees at 10 knots gusting to 21 knots. At 1356, 26 minutes after the accident, the reported winds at the Lubbock International Airport, located about 3.5 nautical miles south, were from 180 degrees at 12 knots. The density altitude calculated by the NTSB investigator-in-charge was 6,359 feet. Examination of the helicopter by the FAA inspector revealed that the tailboom and skids were separated from the fuselage, and the main rotor blades were damaged.