Incident Summary
A helicopter pilot reported that while flying at a low altitude and low airspeed over tree-covered terrain, he executed a steep left turn downwind. During the maneuver, the low rotor rpm horn sounded. The pilot stated that he lowered the collective slightly and rolled on the throttle, but the helicopter descended and impacted trees and terrain.
Pilot Actions and Flight Outcome
After the impact, the pilot completed a damage assessment and then flew the helicopter to his home airport without further incident. The helicopter sustained substantial damage to the left aft fuselage frame assembly. The pilot reported that there were no mechanical malfunctions or anomalies prior to or during the flight that would have prevented normal helicopter operation.
Additional Information
The source provided information on vortex ring state, commonly known as settling with power. According to FAA-H-8023-21A, a vortex ring state may be entered during any maneuver that places the main rotor in a condition of descending in a column of disturbed air and low forward airspeed. Airspeeds below translational lift airspeeds are within this region of susceptibility. Situations conducive to settling with power include any hover above ground effect altitude, attempting to hover out of ground effect without precise altitude control, pinnacle or rooftop helipads when the wind is not aligned with the landing direction, and downwind and steep power approaches where airspeed drops below 10 knots depending on the helicopter type.