On February 25, 2005, about 0945 central standard time, a Piper PA-28-140, N4468T, piloted by a commercial pilot, was substantially damaged when it struck trees and a house during an attempted landing at the Macon-Fower Memorial Airport (K89), Macon, Missouri. The pilot reported that he experienced engine problems and was diverting to K89 when the accident occurred. The airplane was operating in visual meteorological conditions under 14 CFR Part 91 and was not on a flight plan. The pilot and one passenger received minor injuries. A second passenger received serious injuries. The flight originated from the North Central Missouri Regional Airport, Brookfield, Missouri, at 0915, and was bound for the Creve Coeur Airport, St. Louis, Missouri. The pilot reported that while climbing through 4,200 feet, he heard a loud noise from the engine. He stated that the tachometer read 2,500 rpm during the climb and 1,200 rpm after hearing the noise. He stated that he applied throttle and the engine achieved between 1,500 and 1,900 rpm. He stated that there was heavy vibration and "banging" noises coming from the engine. The pilot said that he diverted to K89 and while landing he realized that he would not be able to stop the airplane before the trees at the end of the runway. The pilot then attempted to clear the trees at the end of the runway and land in a clearing on the opposite side. He stated that after clearing the trees, the airspeed started to fall rapidly and the airplane struck trees and came to rest on the roof of a house that he had not seen. Subsequent to the accident, the exhaust valve for the number four engine cylinder was found to be fractured. Pieces of the exhaust valve were found embedded in the top of the piston. The top of the piston and the cylinder head combustion chamber were found to have numerous dents.