On September 30, 1996, about 1300 hours Pacific daylight time, a Bell 206B, N59576 rolled over while practicing hovering autorotations near Fillmore, California. The aircraft sustained substantial damage; however, neither the instructor nor his student was injured. The aircraft was operated as an instructional flight by the owner/student when the accident occurred. The flight originated from Whiteman airport, Los Angeles, California, on the morning of the accident. Visual meteorological conditions prevailed at the time and no flight plan had been filed. The flight instructor stated he directed his student to perform a hovering autorotation with an entry from a 3-foot hover. As the aircraft descended to about 1 foot above the ground, it began to drift to the left. He took the controls and applied right cyclic as the rotor rpm continued to decay. His control input did not stop the helicopter's accelerating leftward movement. As the left skid touched down, the helicopter abruptly pivoted about the skid and rolled onto its left side. During the rollover, the main rotor blade(s) severed the tailboom. He reported to an FAA inspector that he estimated surface winds at the accident site to have been westerly at approximately 10 knots.