N1510A

In a written statement, the instructor pilot reported that he and the private pilot under instruction performed a normal takeoff and departure. After a short flight they arrived at Rocky Point (9 miles north of Ogden-Hinckly Airport), where they were to practice pinnacle approaches and landings. They reconnoitered the area at 300 feet above ground level (agl) in preparation for landing. They performed a power check at 500 feet agl, and concluded that engine power was sufficient to maintain an out of ground effect (OGE) hover. The student began the approach at 350 feet agl. The approach became slightly steep and went past the point of the intended landing. The pilot under instruction reported that the rate of descent was 500 feet per minute (fpm) at 25 knots. At 30 feet agl, the helicopter's descent rate increased, the pilot under instruction aborted the approach, and began a go-around. The instructor realized that rotor revolutions-per-minute (rpm) had degraded below the normal range, so he took the controls from the student. Because the go-around had been initiated, the helicopter was moving forward slowly over a descending hill slope and the instructor was not able to land the helicopter. He attempted to gain power by lowering and raising collective; however, the helicopter's skid contacted the ground and the helicopter rolled over.

FAA-H-8083-21, Rotorcraft Flying Handbook, states that vortex ring state (settling with power) is likely when the rate of descent exceeds 300 fpm, and the horizontal velocity is slower than effective translational lift.