On November 20, 2009, about 1130 eastern standard time, a Piper PA-28-151, N41765, registered to Universel Technologies/Unitec, Inc., experienced partial loss of engine power and was substantially damaged during a forced landing in a wooded area near Port Charlotte, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 91 personal, local flight, from Charlotte County Airport (PGD), Punta Gorda, Florida. The certificated commercial pilot and two passengers were not injured. The flight originated from PGD about 1100. The pilot stated that after takeoff, while flying over the Port Charlotte area, he heard a loud "pop" sound, followed by a substantial loss of engine power. Attempts to restore engine power were unsuccessful and the engine was not producing enough power to sustain flight. He announced on the PGD common traffic advisory frequency that he intended on performing a forced landing and also activated the emergency locater transmitter. While descending for the forced landing, the airplane collided with small trees short of a clearing and the right wing then contacted elevated terrain, causing the airplane to yaw 180 degrees to the right. The airplane came to rest upright and all occupants exited it. Postaccident inspection of the engine by a Federal Aviation Administration airworthiness inspector revealed the bottom spark plug from the No. 3 cylinder was not secured to the cylinder, and had only remained secured to the engine by the ignition lead. A helicoil threaded insert remained attached to the threaded portion of the spark plug, but the insert was unwound. Review of the maintenance records revealed the engine was overhauled in 1992. The entry pertaining to the overhaul indicates that two repaired cylinders were installed and the other two cylinders, which were reconditioned, were installed. A review of the serviceable tags for the two cylinders that were repaired revealed no indication that a helicoil was installed. No determination was made as to when the helicoil was installed in the bottom spark plug position of the No. 3 cylinder. The engine had accumulated approximately 2,142 hours since major overhaul.