Incident Overview
A training flight focused on practicing pinnacle approaches resulted in a terrain impact when the helicopter failed to clear a ridgeline. The incident occurred as the helicopter approached a ridgeline intended for the pinnacle approach maneuver.
Sequence of Events
During the approach, the flight instructor noted that the airspeed dropped below 41 knots, a condition associated with the loss of translational lift. This resulted in a loss of altitude, preventing the helicopter from clearing the ridgeline. The instructor took control of the helicopter, initiating a left turn to avoid the ridgeline and lowering the collective in an effort to gain airspeed.
Despite these actions, the helicopter did not gain sufficient altitude to clear a ravine. The aircraft subsequently impacted terrain in a level attitude and slid approximately 30 to 40 feet after the initial impact.
Aircraft Condition
The instructor reported that there were no preimpact anomalies with the airframe or engine throughout the flight. The helicopter was operating normally until the loss of airspeed occurred.