On September 29, 1999, at 1445 central daylight time, a Stinson L-5 vintage airplane, N68591, registered to the American Airpower Heritage Flying Museum and operated by the pilot, was substantially damaged during a precautionary landing near Woodward, Oklahoma. The private pilot, sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The cross-country flight originated from Hutchinson, Kansas, at 1305, with a destination of Midland, Texas. The pilot reported that during cruise flight, the airplane developed an "extreme" vibration. During the ensuing precautionary landing to a dirt road, the airplane encountered soft dirt and veered to the right, impacting a ditch. Examination of the airplane by the FAA inspector revealed that the right wing was structurally damaged. Further examination revealed that one of the blades of the wooden propeller was missing its metal tip, and the wood beneath the missing metal tip was discolored. The propeller was a Fahlin model 44K15005, S/N 49779.