Incident Overview
The helicopter was engaged in high altitude flight tests aimed at obtaining two Supplemental Type Certificates. The pilot initiated an intentional autorotation from an altitude of 200 feet at a gross weight of 8,000 pounds. The autorotation was performed at 42 knots with a one-second delay before lowering the collective control. As the helicopter approached the runway at 40 knots, the pilot reported being unable to arrest the descent rate. The helicopter subsequently impacted the runway and was destroyed.
Video Evidence
A video camera recorded the flight tests. Review of the footage revealed that on at least two previous autorotations, the tail boom stinger struck the ground first. This observation was noted by an FAA helicopter operations inspector.
Inspector's Assessment
According to the FAA inspector, the tail boom strikes indicated that the pilot was operating outside the low end of the height-velocity curve. The inspector stated that "either there was insufficient airspeed for the altitude used, or there was insufficient altitude for the airspeed used."