On June 18, 1994, at 1604 hours Pacific daylight time, a homebuilt experimental Discovery S-12 Airaile, N999, collided with a standpipe during an off-airport forced landing near Salinas, California. The airplane was being operated by the noncertificated owner/pilot when it inadvertently became airborne during high-speed taxi tests at the Salinas Municipal Airport, Salinas, California. The airplane was destroyed. The pilot received serious injuries. Visual meteorological conditions prevailed. Witnesses reported the propeller, muffler, and reduction gearbox separated before the airplane struck the standpipe. Examination of the three-bladed propeller by the Federal Aviation Administration (FAA) revealed one of the propeller blades had separated several inches outboard of the hub. The airplane then glided into a lettuce field. During the force landing flare, the right wing struck a 6-inch-diameter standpipe separating the right wing tip. The muffler and dampener plate from the reduction gearbox was sent to the Safety Board's Material Laboratory for examination. The muffler was fractured in the area of a factory weld. The weld area was oxidized. Numerous fractures were found in the dampener. Microscopic examination of the fractures disclosed no evidence of progressive separation. A copy of the Safety Board's Materials Laboratory Report is attached.