On September 29, 2003, about 1109 eastern daylight time, a Mooney M20K single-engine airplane, N231PG, registered to and operated by Coral Bay Company, Inc., sustained substantial damage during a forced landing following a loss of engine power during cruise flight near Chesterfield, Virginia. The commercial pilot, sole occupant of the airplane, was not injured. An instrument flight rules flight plan was filed for the flight that originated at Easton/Newnam (ESN), Easton, Maryland, about 0945, and destined for Blue Ridge Airport (MTV), Martinsville, Virginia. Visual meteorological conditions prevailed for the personal flight conducted under 14 Code of Federal Regulations Part 91. In a written statement, the 692-hour pilot said that he was flying at an altitude of 6,000 feet, with engine operating parameters set at 2,500 rpm, and 28 inches of manifold pressure (MP). At 1105, the pilot reported an unusual and sudden vibration, followed by a sudden, and total loss of cylinder head temperature (CHT) and exhaust gas temperature (EGT) readings on the JPI Fuel Scan instrument for the #2 cylinder. The pilot advised air traffic control (ATC) that he had "lost a cylinder" and requested to land at the nearest airport. Approximately 1-minute later, while being vectored to the nearest airport, engine rpm dropped "dramatically", and would not develop power even though it was still turning. The pilot added that he slowed the airplane to best glide speed, and attempted to make a forced landing to a 4-lane highway. During the landing roll on the highway, the airplane struck a vehicle with its left wing. A Federal Aviation Administration (FAA) inspector examined the airplane and reported that the left wing tip and wing spar were damaged. In addition, the #2 cylinder head was found partially separated from the engine. The 215-horsepower Continental TSIO-360-GB engine had accrued a total of 326 hours since top overhaul, and 887 hours since major overhaul. Several of the cylinders, including the #2 cylinder, had a Cerminil finish. The #2 cylinder was retained for further examination at the NTSB Materials Laboratory in Washington, D.C. According to a Senior Materials Engineer at the laboratory, a detailed examination of the #2 cylinder head revealed that the cylinder head was fractured circumferentially between that fourth and fifth fins from the engine end of the head. As a result, the head was in two pieces: the engine side and the dome side. The engine side of the head remained attached to the barrel and the injector line was fractured at one of the brazed joint for one of the ferrules. The piston, push rods, and lifters appeared undamaged, and the oil filter was not examined. Weather at the time of the accident included wind from 270 degrees at 5 knots, visibility 5 statute miles, mist, and the sky condition was clear. The temperature was 75 degrees Fahrenheit, the dew point was 71 degrees Fahrenheit, and the barometric pressure setting was 29.74 inches of Mercury.