On November 28, 1994, approximately 1440 hours Pacific standard time (PST), a Hiller UH-12C helicopter, N54594, registered to and being flown by Ross C. Darling, a student pilot, was substantially damaged during a hard landing following a loss of power at the Twisp Municipal Airport, Twisp, Washington. The pilot was uninjured. Visual meteorological conditions existed and no flight plan had been filed. The flight, which was an instructional solo flight, was to have been operated under 14CFR91, and originated from the Twisp airport approximately 15 minutes before the accident. The student pilot reported that he was conducting a practice autorotation from approximately 1000 feet above ground commencing with a 300 RPM split between the engine/rotor tachometers. He reported applying carburetor heat and then reducing power to yield a 500-600 RPM split between the engine/rotor tachometers. Approaching 150 feet above ground, he began applying power with no effect. He transitioned into a full autorotation and between 50-75 feet above ground began his flare. He stated that he "began to apply collective but was (a) second slow fully levelling (the) helicopter." During the touchdown the tail boom was severed when it was struck by one of the rotor blades. FAA Inspector Doug Vaubel inspected the helicopter's Franklin engine subsequent to the accident and found no significant mechanical malfunctions.