The flight instructor and student pilot reported that the purpose of the flight was to practice off-airport landings. On the fourth and final landing, they set up a steep approach with the student pilot on the flight controls. The helicopter was above the effective translational lift (ETL) airspeed as they descended through 100 ft above ground level (agl) in a stabilized descent. The helicopter then started to yaw left and the flight instructor took the controls. As the spin rate increased, the flight instructor’s efforts to regain control were not successful. He then realized the helicopter was spinning out of control. He lowered the collective and the spin rate slowed as the helicopter contacted the ground. The flight instructor shut down the engine and both pilots exited the helicopter. The helicopter’s fuselage sustained substantial damage. The flight instructor reported that there were no preaccident failures or malfunctions with the helicopter that would have precluded normal operations.