On August 11, 1997, at 1245 central daylight time, a Piper PA-28-140, N7294F, executed a forced landing after a partial power failure on climbout from Gibson County Airport, Milan, Tennessee. The airplane was operated by the pilot under the provisions of Title 14 CFR Part 91 and visual flight rules. Visual meteorological conditions prevailed at the time of the accident. No flight plan was filed for this instructional flight. The airplane incurred substantial damage. The certified flight instructor (CFI) pilot in command was not injured, while the student pilot received minor injuries. The flight was originating at the time of the accident. According to the CFI, the airplane had recently been inspected after a major overhaul, so he elected to test fly the airplane alone. After finding it ran satisfactory, he and his student took off for an instructional flight. At an altitude of 100 feet, there was a "noticeable change in the airplane's ability to climb". The engine RPM had "dropped to 2,100". The CFI stated he intended to reach a safe altitude and then return to the departure airport. But, the RPM was steadily decreasing, and the airplane was unable to maintain altitude. The CFI took control of the airplane and landed the airplane straight ahead, in the trees, approximately 1000 feet from the end of the runway. Both occupants evacuated the airplane. After waiting a short time, the CFI returned to the airplane and called the airport for assistance. The pilot reported no mechanical difficulties with the airplane. The atmospheric conditions were favorable for the formation of carburetor ice.