The flight instructor uneventfully demonstrated a rapid deceleration maneuver to the fixed-wing pilot-rated passenger into the wind, performed a left pedal turn, and performed another rapid deceleration maneuver (with a tailwind). The flight instructor then initiated another left pedal turn; however, the helicopter failed to turn, and the low-rotor RPM light came on. The flight instructor said that he attempted to recover by lowering the collective and adding full throttle, but the throttle was already fully open. The low-rotor RPM light remained illuminated and engine RPM started to drop. The helicopter landed and slid down a slope adjacent to the runway and came to rest on its left side. This resulted in substantial damage to the main rotor blades and tail cone. The pilot rated passenger provided a similar account of the events and said that after he exited the helicopter, the instructor told him that they had just “settled with power.” The flight instructor reported there were no mechanical deficiencies that contributed to the accident.