On November 6, 2007, at 1253 eastern standard time, a Piper PA-18-135, N3257B, was substantially damaged during a forced landing in Durbin, West Virginia. The certificated commercial pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the flight that originated at the Allegheny County Airport (AGC), Pittsburgh, Pennsylvania, destined for the Richmond International Airport (RIC), Richmond, Virginia. The positioning flight was conducted under 14 Code of Federal Regulations Part 91. According to the pilot, the day before the accident he noticed a slow oil leak, and oil covering part of the windshield and firewall. He informed his company, and was told if the leak was not too serious, he should fly the airplane to RIC where a company mechanic could examine the engine. Prior to departure on the morning of the accident, a local mechanic examined the engine and did not observe a significant oil leak, so the pilot decided to depart for RIC. As the airplane approached 'Cheat Mountain' in West Virginia, at an altitude of 5,000 feet, the pilot began to smell oil and observed smoke emanating from the engine. Shortly after, he heard an "explosion" and observed a "chunk of oil" blow out of the engine and cover the windshield. The oil pressure gauge continually decreased and the pilot looked for a place to perform a forced landing. He landed on a dirt road, during which the right wing struck a tree. The airplane turned 90 degrees and came to rest upright. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed substantial damage to the right wing and fuselage. Examination of the engine revealed the engine crankshaft oil seal was partially dislodged, and protruding from the front of the engine case. The most recent annual inspection was completed on August 30, 2007, and the most recent condition inspection was completed on September 27, 2007, with no anomalies noted. The engine had accumulated 660 hours of operation since overhaul, at the time of the most recent condition inspection. The airplane flew 43 hours since the condition inspection.