On October 30, 1993, at 1931 Pacific daylight time, a Robinson R-22A helicopter, N8452Z, sustained substantial damage during a hard landing from an autorotation in Santa Rosa, California. The autorotation was precipitated by a loss of the tail rotor following an inflight contact with a mylar balloon. The helicopter was owned and operated by Peregrine Helicopters, Inc., of Santa Rosa, California, and was rented by the pilot for a local area personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation. The helicopter sustained substantial damage. Neither the certificated private pilot nor his one passenger were injured. The flight originated at the Santa Rosa airport on the day of the mishap at about 1900 hours. According to statements from the pilot, his passenger, and ground witnesses, the pilot was providing helicopter rides to fellow employees at a company halloween party. While overflying the party location, a large mylar party balloon broke free and drifted up in the path of the helicopter. The tail rotor blades struck the balloon and then separated from the helicopter. The pilot initiated an autorotation to a parking lot and touched down hard. Responding sheriff's department officers found fragments of a mylar balloon about 100 feet south east of the helicopter.