On September 23, 2005, about 1415 Hawaiian standard time, an Aerospatiale AS350BA helicopter, N355NT, registered to Jan Leasing, LLC, and operated by Heli-USA Airways, Inc., of Las Vegas, Nevada, encountered adverse weather and crashed into the Pacific Ocean several hundred feet off the coast of Kailiu Point, near Haena, Hawaii, on the island of Kauai. The sightseeing air tour flight was operated under the provisions of 14 Code of Federal Regulations Part 135 and visual flight rules with a company flight plan in effect. Localized instrument meteorological conditions prevailed in the vicinity of the accident site. Three passengers were killed, and the commercial pilot and two other passengers received minor injuries. The flight departed from Lihue Airport (LIH), Lihue, Hawaii, on the island of Kauai, at 1354 for the intended 45-minute tour. The flight was operated under Special Federal Aviation Regulation 71, "Special Operating Rules for Air Tour Operators in the State of Hawaii," and in accordance with a certificate of waiver or authorization approved for Heli-USA by the Federal Aviation Administration Honolulu Flight Standards District Office in Honolulu, Hawaii. The flight proceeded westbound from LIH, which is on the southeastern part of the island, on the operator's standard clockwise tour route around the island. The pilot reported that the weather and visibility were good during the initial part of the tour. The pilot stated that he flew the helicopter over the Na Pali Coast on the northern part of the island at 2,000 feet above ground level and that the weather along the coastline was clear and without rain. The pilot stated that he saw rain showers offshore as the flight approached Kee Beach and Kailiu Point on the northern part of the island. The pilot reported that, as the flight came around Kailiu Point, he "suddenly saw [an MD?500 helicopter] coming straight for [his helicopter]" and that he made a left turn to avoid it. He stated that, when he leveled his helicopter out of the turn, it was "already inside the storm," and it encountered heavy rain. Two passengers reported that they saw another helicopter flying in the opposite direction but that it was far below them, and one passenger stated that it was far enough below them that she thought it was a bird. Both of these passengers said that their helicopter made no evasive maneuver, or any maneuver, before entering what they described as "a wall of pure rain and thick clouds." The pilot stated that, while the helicopter was in the heavy rain, he could still see down and to the right to the coastline and that he reduced the helicopter's airspeed and initiated a descent to maintain visual reference to the beach. One passenger reported that he could not see anything in the heavy rain and that he was about to say something about this to the pilot when the pilot announced that they were turning back. The pilot said that he started a right turn over the beach and that, during the turn, the helicopter's airspeed dropped to zero and the helicopter started to rapidly descend. The pilot said that his control inputs were not effective and that he realized that the helicopter was going to hit the beach at a high rate of descent. The pilot stated that he applied full power and that the helicopter's rate of descent suddenly stopped. He stated that the helicopter went back up in the air momentarily and entered an immediate hard spin to the left, which took the flight over the water. The pilot stated that he instructed the passengers to open the doors to get ready for the water impact and that the helicopter hit the water, bounced back into the air, and continued to spin. The pilot said that he transmitted a mayday call on the radio and that the helicopter impacted the water again and remained on the surface spinning. The pilot stated that the helicopter was submerged to the belly panel when it stopped spinning, then it rolled to the right and immediately began to sink. A pilot flying a tour for another operator said that he heard the mayday call over the common traffic advisory frequency (CTAF) and twice attempted to fly his helicopter in the Kee Beach area to try to locate the downed helicopter but was unable to do so because of poor visibility. While returning to the airport to alert rescue authorities, he saw another Heli-USA helicopter in flight and used the CTAF to inform that pilot of the mayday call. That Heli-USA pilot then conducted a brief search and spotted an oil slick on the water extending toward the area of poor weather. He made an unscheduled landing on a beach to let out his passengers then searched the area near the oil slick. He said that the visibility was low but usable and that he saw debris and people in the water. He used his radio to direct U.S. Navy aircraft into the area. [ The Safety Board's full brief is available at http://ntsb.gov/Publictn/publictn.htm. The Aviation Accident Brief number is NTSB/AAB-07/01. ]