On April 16, 1994, about 0815 eastern daylight time, a Piper PA-24-260, N8572P, registered to Roger L. Millheim, was substantially damaged during a forced landing near the Pilot Country Airport, Spring Hill, Florida, while on a 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The commercial-rated pilot, the sole occupant, was not injured. The flight originated from the Pilot Country Airport, Spring Hill, Florida, about 7 minutes earlier. The pilot stated that during cruise flight he felt a severe vibration through the airframe which he attributed to be from the propeller. He attempted a forced landing on a road but during the descent, the airplane collided with the top of a 40-foot-tall dirt embankment. The airplane slid over the top down the other side coming to rest upright. The propeller was removed for examination which revealed that a pitch change knob on one of the propeller blades was failed. The failed knob and butt end of the propeller blade was sent to the NTSB Metallurgy Laboratory in Washington, DC, for examination. Metallurgical examination of the failed pitch change knob revealed that it failed due to fatigue. Review of the aircraft logbooks revealed that the propeller was overhauled on June 28, 1989. At the time of the accident the propeller had accumulated about 397 hours since overhaul.