On September 9, 1999, at 1015 hours Pacific daylight time, a Bell B212 helicopter, N212AR, was destroyed when it struck high tension power transmission wires and fell to the ground and burned, 6 miles east of Bakersfield, California. The airline transport certificated pilot received minor injuries. The helicopter was owned by Aviation International Rotors, Inc., and was operated under contract to the U.S. Forest Service as a public-use aircraft under the provisions of 14 CFR Part 133. Visual meteorological conditions prevailed and no flight plan was filed for the local area fire-fighting mission, which originated near the accident site at 1000. An on-scene investigation was conducted by the USDA Forest Service Aviation and Fire Management Office. According to their report, the helicopter was engaged in dropping water on a brush fire in an area identified as the Richbar Complex, using a fixed tank water dropping system, which employs a snorkel for refilling. The pilot and helicopter were reassigned from another nearby base on the morning of the accident and, at the time of the wire strike, the pilot was engaged in his first operational sortie in the Richbar area. Prior to takeoff, the pilot had been formally briefed by the Forest Service helibase manager about wire hazards in the area, the location of the fires, potential water dip sites, other aircraft expected to be in the area, and communications. A topographical map that was used in the briefing showed high power transmission wires, including the set the pilot later impacted, as red lines. After takeoff, the pilot proceeded to the fire area and located the area of the fire he was to drop water on. He then proceeded to the dip site, filled with water, and made his initial drop on the fire. It was while returning to the dip site to refill that the wire strike occurred. The pilot reported that as he approached the dip site at 250 - 300 feet agl, he was aware of a power transmission tower high on the mountain to his right, well above him. He was also aware of another tower to his left on the valley floor below, and an electrical powerhouse on the valley floor nearly in front of him. He thought that the wires from both the tower on his right and the tower on his left went to the powerhouse and were beneath him. The investigation disclosed that the wires were strung directly from the tower above him, on the right, to the lower tower, on his left, and crossed his flight path at the helicopter's altitude. When the pilot saw the wires, he attempted to bank the helicopter steeply to the left; however, the rotors contacted and severed the lowest pair of wires. The helicopter shook violently and became only marginally controllable. The helicopter then fell to the ground under partial control and impacted on its right side after severing a second set of (lower) electrical power distribution wires. The lower wires arced and a grass fire ignited, which spread to fuel leaking from the helicopter. The pilot, seated in the left-hand seat, was able to extricate himself before the fire engulfed the helicopter. Flights flown after the accident, in the same model helicopter, in like conditions of daylight and visibility, and knowing the wires were present, showed the wires could not be visually detected until the helicopter was "extremely close to the wires." Smoke was not present in the area of the accident site at the time of the wire strike