On October 13, 2000, at 0845 hours Hawaiian standard time, an Aerospatiale AS350-BH, N532BH, was substantially damaged when the tail boom was bent downward during landing following a practice hovering autorotation at Hilo International Airport, Hilo, Hawaii. The commercial certificated flight instructor and the airline transport certificated pilot being instructed were not injured. Visual meteorological conditions prevailed for the local area training flight, operated by Blue Hawaiian Helicopters under 14 CFR Part 91. The flight departed from Hilo at 0825, and no flight plan was filed. The pilot reported that the accident occurred following their third hovering autorotation landing. The pilot reported that the touchdown was acceptable and would have met check ride criteria. About 2 seconds after touchdown there was "an obvious component failure" felt throughout the airframe, accompanied by severe vibrations and "audible and physical indications" of failure. After exiting the aircraft, the pilot expected to find a problem in the main rotor head and was surprised to find the tail boom bent downward at the midpoint. A postaccident examination of the helicopter revealed that the tail boom was fabricated from skins of thickness 0.025 inches, as opposed to a skin thickness of 0.032 inches identified in the structural repair manual. The helicopter records showed that the tail boom was originally installed on the (new) helicopter at the factory and had acquired 14,053 hours in service.