NTSB Factual Report

The flight instructor reported that during their fifth practice autorotation, the student let the rotor rpm decay to the point that the CFI attempted to intercede and perform a run on landing. The student and CFI both struggled with each other on the controls until the helicopter hit the ground hard. During the impact sequence, the helicopter spun around, and ultimately came to rest on the left side.

NTSB Probable Cause

The student pilot's failure to maintain rotor rpm resulting in an excessive descent rate and a hard landing. Factors in the accident were the student's failure to relinquish the controls, and the CFI's inadequate supervision.