During the accident flight, the certified flight instructor (CFI) was providing dual instruction to his student. The CFI was showing the student how to make a landing approach over 2,500-foot mean sea level hilly terrain. The student had about 13 hours of total flying experience, and the CFI was handling the controls. According to the CFI, the first approach to the landing site was uneventful. During the second approach the low rotor rpm warning horn activated. In the CFI's original statement to the Federal Aviation Administration and National Transportation Safety Board, the CFI reported that he tried to "milk collective and get it back," but he was not successful. The CFI opined that the wind direction may have changed, and he attempted to redirect the helicopter's course into the wind. The CFI was unable to regain rpm and stop the descent. The helicopter impacted the field and rolled over. The CFI reported that when the accident occurred, the helicopter was operating near its maximum certificated gross weight. The out of ground effect hover ceiling was about 3,000 feet, and the density altitude was about 3,200 feet.