On July 8, 1993, at 1520 hours Pacific daylight time, a Schweizer 269C helicopter, N9588F, sustained a tail boom separation during a hard landing while practicing auto rotations at Rialto, California. The aircraft was operated by CARI Aviation, Inc., of Rialto, California, and was engaged in a dual student instructional flight. Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation. The helicopter incurred substantial damage. Neither the certificated commercial pilot flight instructor nor the dual student were injured. The flight originated at the Rialto airport at about 1500 hours on the day of the mishap as a local area dual instructional flight. According to the flight instructor's verbal statement, the student was practicing auto rotations to a power recovery. On the last practice auto rotation, the engine quit when the student rolled the throttle to idle. The instructor took over control of the helicopter and executed a complete auto rotation to touch down. During the landing flare, the tail boom contacted the ground and the helicopter landed hard. The helicopter was examined by an FAA airworthiness inspector from the Riverside, California, Flight Standards District Office. He reported that no discrepancies were found with the helicopter.