On November 7, 2009, about 0830 Pacific standard time (PST), an experimental Piasecki/Pike PV-18, N183YP, collided with high tension wires and then terrain near Adelanto, California. The owner/pilot was operating the helicopter under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The two commercial pilots and one passenger were fatally injured. The helicopter was substantially damaged by impact forces and post crash fire. The local personal flight departed Adelanto Airport (52CL) about 0825, with a planned destination of Riverside, California. Visual meteorological conditions prevailed, and no flight plan had been filed. A witness pilot, who was flying about .5 miles behind and slightly above the accident helicopter, stated that he had established radio contact with the two pilots during their takeoff. Just prior to the accident, the witness pilot made multiple unanswered radio calls to the pilots to warn them about the approaching wires. The witness pilot further stated that he felt the helicopter was "laboring" at about 300 feet; however, he did not observe any smoke or other visible malfunction. The main rotor blade struck the power lines and the helicopter subsequently descended into the desert terrain below and was consumed by fire. On scene examination of the wreckage revealed evidence of engine rotation. No anomalies were noted.