N2024Z

The purpose of the instructional flight was to practice pinnacle approaches. Approaching a ridgeline to be used for the pinnacle approach, the flight instructor observed the airspeed drop below 41 knots (translational lift), resulting in a loss of altitude and the inability to clear the ridgeline. The flight instructor took control of the helicopter, initiated a left turn to avoid the ridgeline, and lowered collective in an attempt to gain airspeed. The helicopter subsequently impacted terrain in a level attitude after failing to gain sufficient altitude to clear a ravine, sliding about 30 to 40 feet after impact. The instructor said there were no preimpact anomalies with the airframe or engine during the flight.