The cause of a small airplane crash that killed one person near Bolivar, in Polk County, is under investigation. A preliminary report released by the highway patrol says the single-engine 2007 Zenith-601 went down, Tuesday morning, in a wooded area along the Silo Ridge Golf Course less than a mile south of Bolivar Municipal Airport. The pilot, identified as 87-year-old James Donald Baker of Bolivar, was taken to a nearby hospital where he died a short time later. Investigators from the FAA responded to the scene to try and determine the cause of the crash.