On July 5, 2003, approximately 1400 mountain daylight time, a Conn Vans RV-4, N78DR, owned and operated by the pilot, was substantially damaged when it impacted terrain during a forced landing about 30 miles south of Durango, Colorado. The airline transport pilot, the sole occupant of the aircraft, was seriously injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the cross-country flight being conducted under Title 14 CFR Part 91. The flight originated at Durango approximately 1330, and was en route to Los Lunas, New Mexico. According to the pilot, he was climbing through 8,500 feet when the engine began to shake violently. He reduced power to idle and eventually shut the engine down. When the propeller stopped, he noticed the trailing edge of the wood blade had separated. He saw a dirt road next to a clearing and decided it was suitable for landing. He made a 360-degree turn and dropped full flaps but overshot the road. The airplane struck two trees and came to rest next to an oil field road on County Road 311. The propeller was sent to the Sensenich Wood Propeller Company in Plant City, Florida, for examination. According to Sensenich's report, one blade was broken off near the hub and the other blade had "a massive split extending from the tip trailing edge to just outside the hub." The report noted that whereas the hub face was discolored somewhat, "the bolt holes and counterbores appear normal." The report concluded, "There are no signs of defects or other damage to the propeller which provides any clues for why the propeller is in its present state."