On September 16, 1995, approximately 1830 hours Pacific daylight time, a Hiller UH-12A, N8180H, being flown by a commercial flight instructor, was substantially damaged during a hard landing following an auto-rotation approximately six miles north northwest of Bonners Ferry, Idaho. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was instructional, was to have been operated under 14CFR91, and originated from the Boundary County Airport, Bonners Ferry, Idaho. The instructor pilot reported that he was demonstrating a practice auto-rotation to the owner/student pilot when the aircraft impacted the ground and the left skid collapsed. He reported that during the maneuver he "began to raise collective pitch to cushion the landing, (and) it was at this point in the autorotation that I made contact with the ground. I misjudged my elevation by approximately 5 to 10 feet." The main rotor blade severed the tail boom during the ground impact. The instructor pilot reported that there was no mechanical malfunction with the aircraft at the time of the accident.