On December 4, 2000, about 1330 hours Pacific standard time, a Hughes 269C, N1097N, operated by Civic Helicopters, Inc., Carlsbad, California, landed hard at the McClellan-Palomar Airport, in Carlsbad. The tail boom was severed, and the helicopter was substantially damaged. Neither the airline transport certificated pilot, who held a flight instructor certificate, nor the pilot who was receiving a checkout were injured. The training flight was performed under 14 CFR Part 91. Visual meteorological conditions prevailed. The flight originated from Carlsbad about 1300. According to the flight instructor (CFI), the purpose of the flight was to observe the skill level of the second pilot, and to provide any needed instruction. The CFI assigned the second pilot the task of performing an autorotation to a landing on an airport helipad. During the approach the second pilot, who was handling the flight controls, was a "little short" of the desired touchdown mark. Main rotor rpm decreased, and upon touchdown a rotor blade chopped off the tail boom. The helicopter remained in an upright attitude.