Accident Overview
On June 28, 2013, at about 1308 mountain daylight time, a Bell 206L-3 helicopter, registration N868H, was substantially damaged following an impact with terrain while maneuvering near Missoula, Montana. The commercial pilot was seriously injured. The helicopter was registered to and operated by Hillcrest Aircraft Company under 14 Code of Federal Regulations Part 133 as a proficiency check flight. Visual meteorological conditions prevailed, and no flight plan was filed. The helicopter had departed Missoula International Airport (MSO) around 1200.
Pilot Account
According to a statement from the pilot to the National Transportation Safety Board investigator-in-charge, he was undergoing an evaluation by a United States Forest Service (USFS) evaluator. After demonstrating basic flying techniques with the evaluator on board, the pilot landed on a sandbar to let the evaluator deplane. He then took off and made three water drops. On the planned fourth water drop, he made a shallow approach to the water. The pilot stated that while looking down at the bucket and just as it entered the water, "things did not feel right." He opined that he immediately knew he was "settling [with power]." Believing that with 150 feet of line he could descend enough to get into good air without dropping the bucket, he reduced collective slightly, moved the cyclic right and forward, and descended. He reported being in good air and moving forward. When he pulled aft cyclic as the line became tight, the nose went very low and he felt the main rotor strike the tail, creating a severe vibration. As he moved closer to the shoreline, the vibration stopped, but the aircraft began to spin to the right. After two or three turns, realizing he could not control the helicopter sufficiently to reach the shoreline, he rolled the throttle off, the spin stopped, and the aircraft descended and made hard contact with the water. The pilot concluded that he had not accounted for the river moving the bucket downstream.
Helicopter Damage and Conditions
The helicopter sustained damage to the tail boom, vertical stabilizers, tail rotor drive shaft, belly/tub, and skid gear tubes. The pilot reported no anomalies with the helicopter that would have precluded normal operation.
At 1253, the Missoula International Airport weather reporting facility, located about 1 nautical mile northeast of the accident site, reported calm winds, clear skies, temperature 28°C, dew point 11°C, and an altimeter setting of 30.26 inches of mercury.
Relevant Background Information
The Federal Aviation Administration Helicopter Flying Handbook (FAA-H-8083-21, Chapter 11, p. 11-13) describes vortex ring state as an aerodynamic condition in which a helicopter in a vertical descent with 20 percent to maximum power applied has little or no climb performance. Settling with power occurs when the helicopter continues to descend despite full engine power. Main rotor tip vortices generate drag and degrade airfoil efficiency; when the helicopter descends vertically into its own downwash, the vortices enlarge, wasting engine power in circulating air around the rotor. Conditions conducive to settling with power include hovering above ground effect altitude, attempting to hover out of ground effect above the hovering ceiling, downwind and steep power approaches with airspeed below 10 knots, and others.