"THIS CASE WAS MODIFIED JUNE 4, 2008." On June 24, 2004, about 2110 mountain standard time, a Bell 206B, N97AZ, experienced a dynamic rollover and impacted terrain during an attempted takeoff from a trailer parked at the Falcon Field Airport, Mesa, Arizona. The pilot was operating the helicopter under the provisions of 14 CFR Part 91. The certified flight instructor pilot, the sole occupant, was fatally injured and the helicopter was substantially damaged. Visual meteorological conditions prevailed, and a flight plan had not been filed. The personal local flight originated from Falcon Field Airport about 2105. In a written statement, a friend of the pilot reported that upon arriving at the airport, he observed the pilot land the helicopter adjacent to a trailer. After the helicopter was shutdown, he engaged in conversation with the pilot, who informed him that he was intending to practice landings on his recently purchased transport trailer that night. The pilot stated that his earlier attempts to land the helicopter on the trailer were unsuccessful, which he attributed to the helicopter's weight distribution. Specifically, he thought that the center of gravity was too far aft due to the low fuel level, which was making it difficult to maintain the appropriate hover configurations. The pilot added that he intended to obtain fuel, and make another attempt to land the helicopter on the trailer. During a telephone interview with a National Transportation Safety Board investigator, the friend of the pilot further added that the pilot had recently purchased the trailer, and was not experienced at maneuvering the helicopter onto it. He described the trailer as a modified boat trailer, with an open and trough-shaped platform, which he did not think was suitable for safe takeoff and landing operations. He opined that during the accident sequence the helicopter's left skid caught on one of the numerous "D" shaped rings affixed to the platform surface. He added that at the time of the accident sky conditions were dark. In a written statement, an air traffic control specialist reported that he observed the pilot make three or four unsuccessful attempts at landing the helicopter on the transport trailer about 45 minutes prior to the accident. In statements collected by the Mesa Police Department, witnesses reported observing the helicopter land on the trailer. As the helicopter began to liftoff the trailer surface, the left skid caught on the trailer, resulting in a dynamic rollover and collision with the ground.