What happened
A flight instructor was conducting training for a new-hire pilot to prepare for a 14 CFR Part 135 check ride. An additional new-hire pilot was present in the rear seat as an observer. The training session involved performing a hydraulics-off, run-on landing.
As the trainee approached the touchdown point, the instructor advised the pilot to maintain sufficient airspeed. Just before touchdown, the pilot reported that the aircraft controls became extremely stiff. In response, the instructor directed the trainee to re-engage the hydraulics isolation switch located on the collective control. Although the student re-engaged the hydraulics, the controls remained stiff, and the pilot experienced difficulty applying forward cyclic.
When the instructor took control of the aircraft, the helicopter began a slow turn to the left. As the instructor attempted to correct this movement, the rate of the turn increased. The helicopter subsequently impacted the ground while in a left turn with rear lateral movement, resulting in the collapse of the landing gear skids. There were no injuries reported in the accident.