Incident Overview
During an instructional flight, a student pilot was practicing landings with the hydraulic system off. The Certified Flight Instructor (CFI) reported that the student experienced a loss of control over the helicopter's yaw and pitch, prompting the CFI to take control of the aircraft.
Instructor's Actions
Despite the CFI's intervention, the helicopter began to rotate uncontrollably. The CFI was unable to arrest the rotation or prevent the helicopter from striking the ground.
Damage
As a result of the ground contact, the helicopter sustained substantial damage to the tail boom and main rotor blades. No other damage was reported.
Mechanical Status
The CFI reported that there were no preexisting mechanical malfunctions or failures with the helicopter that would have precluded normal operation.