On May 14, 1997, about 1159 hours Pacific daylight time, a Hiller UH-12E, N7082D, crashed during an emergency landing 7 miles northeast of Truckee, California. The helicopter was substantially damaged, and the commercial instrument rated pilot was seriously injured. Visual meteorological conditions existed for the 14 CFR Part 133 external load operation, and no flight plan was filed. The flight was originating from a private dirt helipad in Truckee at the time for the purpose of moving a 200-foot long line to a work site. The pilot stated that after physically "hooking up the long line to the belly hook, I climbed back in and started the aircraft." He stated that the primary mission for this flight was to drop off the long line at a new site and pick up the woodcutters. The pilot reported that the preflight and engine start appeared normal. After lifting to a hover, he repositioned the aircraft over the long line. He said that "As I transitioned to forward flight, I experienced a left yaw and decreasing aircraft noises." The pilot then picked out a place to make an emergency landing and then moved his attention back inside the aircraft, trying to switch his radio from FM to VHF to transmit on the Truckee Unicom. Prior to trying to switch the radio frequency ". . .the RPM rapidly increased causing the aircraft to yaw to the right and increase in forward speed." The pilot reported that corrective action was taken and he then attempted to release the long line; however, it became entangled around a tree and the helicopter impacted the ground. FAA inspectors from the Reno, Nevada, Flight Standards District Office responded to the accident site and examined both the long line and the helicopter. According to their report, they could not make a determination of when the long line became entangled in the tree; during takeoff or upon returning to land. The wreckage was removed to the operator's home base in White City, Oregon, where an engine inspection was accomplished. An FAA inspector from the Hillsboro, Oregon, Flight Standards District Office was present at the engine inspection. Engine continuity was established and no preexisting malfunctions were noted. See attached report.