On July 9, 2010, about 1740 mountain standard time, a Ronald V White CH701, N3784A, collided with a tree during an off airport forced landing following a loss of engine power near Pima, Arizona. The pilot/owner was operating the experimental airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The private pilot was not injured; one passenger sustained serious injuries. The airplane sustained substantial damage to the wing by impact forces. The pilot departed Pima at 1700 on a local personal flight. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that he climbed to 2,000 feet above ground level (agl) after departure. The engine was running smoothly, and making full power. He performed several maneuvers, and experienced no anomalies with the airframe or engine. He descended to 1,000 feet agl under cruise power. Shortly after completing a turn, the engine exhibited an immediate loss of power, and began to vibrate significantly. The airplane could not maintain altitude, so the pilot picked a landing spot, and made a 180-degree turn to final approach for landing on a road. He pulled the throttle back, and the engine abruptly stopped. The airplane touched down at 45 miles per hour; the left wing immediately struck a tree and uneven terrain. The airplane spun sideways, and the right main landing gear collapsed. After exiting the airplane, the pilot noted that fuel was leaking from the vent cap on the right wing, which was bent downward. The leak stopped after he raised the wing to a level attitude. A Federal Aviation Administration inspector examined the airplane at the accident site. He observed that the spark plug in the right rear cylinder was fractured and separated in the porcelain area of the plug. The spark plug base remained screwed into the cylinder, and it was more than finger tight. The remainder of the plug remained in the ignition harness’s rubber boot. There was no indication that the spark plug fractured during impact; the plug was partly protected by the exhaust stack, which showed no sign of impact damage. The pilot replaced the spark plug, and the engine ran successfully with no problems encountered. The inspector noted that the pilot had experienced numerous engine problems during the 40 hours of phase 1 flights required in the operations specifications of the airplane. Upon completing phase 1, the engine was overhauled by the shop that had built up the engine originally. It had 4 hours since being reinstalled on the airplane. The pilot stated that the engine was totally assembled when he received it, and that he did not install or remove the spark plugs. According to the pilot, the Volkswagen, VE-2276, 100-horsepower engine in his airplane only has one spark plug in each cylinder. The spark plug, Champion part number RA6HC, was installed by the engine’s manufacturer.