On January 28, 2005, about 1630 mountain standard time, a Robinson R22, N7535Z, collided with terrain during a practice landing near Chandler Municipal Airport, Chandler, Arizona. Quantum Helicopters was operating the helicopter under the provisions of 14 CFR Part 91. The certified flight instructor (CFI) and pilot undergoing instruction (PUI) were not injured; the helicopter sustained substantial damage. The local instructional flight originated from Chandler about 1525. Visual meteorological conditions prevailed, and a flight plan had not been filed. In a telephone conversation with a National Transportation Safety Board investigator, the CFI stated that the PUI was performing practice slope landings. On the third or fourth practice landing, the helicopter touched down on uneven terrain. The helicopter's skids were positioned so that the rear portions angled downwards toward lower terrain. As the student pilot configured the flight controls to remove the load off the rotor blades, the tail of the helicopter began to tip backwards. The CFI took control of the helicopter and added power to prevent the tail rotor from striking terrain. The helicopter responded by rotating to the right about the vertical axis. The pilot attempted to maintain level flight and counteract the spin by applying antitorque pedal input, but was unable to maintain control of the helicopter. After four or five revolutions to the right, the helicopter's right front section impacted terrain. The helicopter sustained damage to the tail cone assembly and both rotor blades. The pilot was unable to verify the orientation of the cyclic during the accident. The CFI reported no preimpact mechanical malfunctions or failures with the helicopter.