On December 4, 1997, about 1430 mountain standard time, N89DD, a homebuilt Blue Denney Kitfox Model 3 airplane, impacted terrain and was substantially damaged while approaching to land at an airport in Caldwell, Idaho. The private pilot, who was the sole occupant, was seriously injured. Visual meteorological conditions prevailed and no flight plan had been filed. The local flight was conducted under 14 CFR 91. In a written statement, the pilot reported that after takeoff, he made a climbing left turn to downwind to practice a touch-and-go landing. The pilot stated that he was unclear as to what happened, but thought that he let the aircraft get too slow and the wing stalled. According to a Federal Aviation Administration (FAA) aviation safety inspector from Boise, Idaho, witnesses observed the airplane in a "sharp left turn" while turning onto final approach to runway 30 at the Caldwell Airport. The airplane was then observed to nose down and descend into terrain about 1/4-mile east of the runway centerline. No pre-impact mechanical malfunctions were reported.