On August 20, 2002, approximately 1120 mountain daylight time, a Schweizer 269C, N7508L, operated by Rotors of the Rockies, was substantially damaged when the left rear landing skid collapsed during a practice autorotation at Jefferson County Airport, Broomfield, Colorado. The commercial pilot receiving instruction and the commercial flight instructor were not injured. Day visual meteorological conditions prevailed at the time, and no flight plan had been filed for the instructional flight being conducted under Title 14 CFR Part 91. The flight originated at Broomfield at an undetermined time. According to the flight instructor's accident report, the student was practicing autorotations in preparation for taking his rotorcraft-helicopter practical flight test the following day. They had successfully performed two "full down" autorotations. As the student completed the third autorotation, they heard a loud noise and the helicopter settled toward the left rear, enough that the tail rotor struck the asphalt taxiway. Postaccident inspection disclosed that the bolt that attaches the left rear oleo strut to the crossbeam was missing. The tail rotor blades were damaged, the tail rotor driveshaft was twisted, and the splined end was separated from the main transmission. The skids and fuselage bottom were not damaged. According to maintenance records, the helicopter had accrued 5.1 hours since the last 50-hour inspection, at which time the landing gear struts had been overhauled and the skid shoes replaced.