According to the certificated flight instructor (CFI), during the helicopter instructional flight, a simulated engine failure maneuver was being performed. During the descent, the engine rpm began to decrease. The anticipated approach path to the landing area required the helicopter to overfly trees. As the helicopter approached the intended landing area, the student pilot raised the collective, which further decreased the rotor rpm. The CFI lowered the collective and increased the throttle; the helicopter landed hard, bounced, landed a second time, and rolled onto its left side, which resulted in substantial damage to the tailboom. A postaccident investigation revealed no preexisting mechanical anomalies that would have precluded normal operation. Additionally, neither pilot reported any mechanical malfunctions with the helicopter.