19980117000419A

The pilot reported that, while cruising at 1200 feet and about thirty minutes into the flight, the engine began to speed. When the pilot reduced the throttle, he noticed that the propeller assembly had seperated from the engine. The pilot selected an emergency landing area on the nearby interstate highway. The right wing of the airplane collided with an overpass bridge as the pilot attempted to fly under the bridge during the forced landing. An examination of the airframe, at the accident site, confirmed that the propeller assembly had seperated from the engine assembly. During the examination of the airframe, it was also noted that six propeller retention bolts were not present with the engine. The propeller assembly and the six propeller retention bolts were not recovered for examination. According to the pilot, he assembled the airplane in accordance with the kit instruction. The propeller assembly was installed on the engine and secured with six 5/16 inch coarse threaded bolts provided. (-23) while in cruise flight the propeller separated from N132BC, the right wing and nose gear were substantially damaged. Inspection of the propeller attachment assembly revealed that non-aviation hardware was used, and not required for this type of aircraft.