On September 6, 1995, at 0906 hours Pacific daylight time, a Hiller UH-12C helicopter, N1348Z, sustained a hard landing at Porterville Municipal Airport, Porterville, California. The pilots were conducting a local visual flight rules instructional flight. The helicopter, operated by Whirlybirds, Inc., Concord, California, sustained substantial damage. The certificated commercial pilot/flight instructor (CFI), and the certificated private pilot/dual student received minor injuries. Visual meteorological conditions prevailed. The flight originated at Porterville Municipal Airport, at 0830 hours. The CFI reported in a telephone interview conducted on September 7, 1995, that before the accident the dual student was practicing some maneuvers and had landed. During the lift-off, the helicopter began to drift backwards. The dual student immediately applied "full up collective," the helicopter continued to go backwards, and rapidly raised about 15 to 18 feet above the ground. The CFI immediately assumed the flight controls and applied full throttle. This action did not arrest the decaying main rotor rpm. The CFI simultaneously attempted to regain the main rotor rpm by trying to "milk down the collective," but was unsuccessful. During this process, the helicopter descended to 10 feet above the ground. Due to the decaying main rotor rpm, the helicopter experienced a loss of tail rotor effectiveness. The CFI then elected to execute a hovering autorotation. He was unable to cushion the landing due to the low main rotor rpm and the helicopter sustained a hard landing. The CFI reiterated this telephone statement in the Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1/2. He indicated in the form that the helicopter did not experience any preimpact malfunctions or failures.