Accident Details
The pilot of the helicopter was engaged in relocating Christmas trees to a nearby drop site. Over a duration of about 15 minutes, he had completed several loads. While maneuvering to the drop site with another load, the helicopter began to settle with power, according to the pilot. In response, he applied more collective pitch in an attempt to arrest the descent, but the helicopter continued to descend. He then attempted to reduce collective and maneuver forward. The helicopter touched down hard on the heels of the skids, and its nose came to rest in a pile of Christmas trees. The tailboom was bent as a result of the hard landing.
Mechanical Condition
The pilot stated that there were no preimpact mechanical malfunctions or failures with the airframe or engine.
Background on Settling with Power
The Rotorcraft Flying Handbook, FAA-H-8083-21, Chapter 11, discusses vortex ring state, also known as settling with power. It notes that a combination of conditions is likely to cause this phenomenon: a vertical or nearly vertical descent of at least 300 feet per minute, the rotor system using 20 to 100 percent of available engine power, and horizontal velocity slower than effective translational lift. The handbook warns that when recovering from settling with power, a pilot's tendency to first try to stop the descent by increasing collective pitch only results in increasing the stalled area of the rotor, thus increasing the rate of descent. Since inboard portions of the blades are stalled, cyclic control is limited. Recovery is accomplished by increasing forward speed and/or partially lowering collective pitch. In a fully developed vortex ring state, the only recovery may be to enter autorotation to break the vortex ring state, after which cyclic authority is regained and forward airspeed can be increased.