On March 16, 2001, about 0930 eastern standard time, a Robinson R22 helicopter, N666BH, registered to a private owner, operating as a Title 14 CFR Part 91 instructional flight, had an in-flight collision with the ground and separation of the tailboom during a simulated engine failure/autorotation near Okeechobee, Florida. Visual meteorological conditions prevailed. No flight plan was filed. The helicopter sustained substantial damage. The commercial rated-pilot/certified flight instructor (CFI), and student pilot, reported no injuries. The flight had departed from Stuart, Florida, at 0815. The CFI was demonstrating a low-level simulated engine failure to the student. According to the CFI's statement, "…on our first approach the student entered on a very steep approach angle and low airspeed, we aborted and made right traffic pattern to reenter on a normal to shallow approach angle, at about 250ft I took the controls and entered an autorotation to demonstrate the importance of maintaining sufficient airspeed incase of an engine failure. I started the power recovery too late allowing the rotor rpm to decay and the heel of the skids to contact the ground hard rocking the helicopter forward followed by a loud bang as the main rotor struck and severed the tailboom. The landing site was grass level ground. According to the FAA inspector's statement, "the flight instructor was flying the aircraft..…interviews with the flight instructor and student pilot [revealed]..…the rotor rpm decreased to a critically low valve. The flight instructor attempted a power recovery, but was not able to prevent the helicopter from striking the ground. After ground contact, one main rotor blade flexed downward and completely severed the tailboom…."