On April 18, 2006, approximately 1030 central daylight time, a Schweizer 269C single-engine helicopter, N209LH, was substantially damaged during a hard landing following a simulated loss of engine power about three miles west of the Denton Municipal Airport (DTO), near Denton, Texas. The flight instructor and pilot receiving instruction sustained serious injuries. The helicopter was registered to and operated by Longhorn Helicopters, Inc., of Trophy Club, Texas. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 instructional flight. The local flight originated from DTO about 1000. The 4,000-hour helicopter flight instructor reported that he was demonstrating a simulated forced landing to an open field. The flight instructor initiated an autorotation and, after descending in autorotation to about 200 feet above ground level (agl), he applied engine power to initiate an engine recovery; however, the rotor RPM had decayed “below limits.” Subsequently the helicopter developed a high sink rate. Despite the flight instructor's attempt to regain rotor RPM, the helicopter landed hard on its skid landing gear before rolling over on its side. According to a Federal Aviation Administration (FAA) inspector who responded to the accident site, the helicopter's main rotor, tail boom, and fuselage sustained structural damage. The inspector further reported that an examination of the helicopter's flight controls and engine revealed no preimpact anomalies.