On March 9, 2006, at 1730 eastern standard time, a Cessna 210, N6540X, registered to CVL Enterprise LLC. and operated by a private owner, as a 14 CFR Part 91 personal flight, from St. Simon Island, Georgia, to Chamblee, Georgia, collided with trees during a forced landing following loss of engine power near Jesup, Georgia. Visual meteorological conditions prevailed, and instrument flight rules flight plan was filed. The airplane sustained substantial damage, and the airline transport rated pilot reported minor injuries. The flight originated from Malcolm Mc Kinnon Airport, St. Simon Island, Georgia, on March 9, 2006 at 1536. The pilot stated he departed on an instrument cross-country flight to Peachtree DeKalb Airport, Chamblee, Georgia. After climb out he leveled off at 6,000 feet, and noticed that the engine analyzer No. 2 cylinder light began to flicker, and the low voltage light illuminated. The pilot contacted air traffic control personnel and requested to return to St. Simon Island. The pilot stated that then the engine began to shake violently while making a loud "banging" noise, and the propeller stopped rotating abruptly. The pilot declared an emergency and requested to be diverted to the nearest airport. The air traffic controller reported that the nearest airport was the Jesup-Wayne County Airport, Jesup, Georgia. The pilot stated that he doubted that he would be able to make it to airport and that he would have to make an emergency landing in a field. During the emergency landing, the airplane collided with a stand of trees two miles south east of Jesup-Wayne County Airport. Examination of the engine, revealed it remained partially attached to the airframe via the engine mount assemblies, miscellaneous hoses, cables, and wires. There was a counter balance weight protruding up through the a hole in the crankcase above the number one cylinder deck area, approximately eight inches by six inches. The No. 1 cylinder was dislodged from the cylinder deck and was in a lower orientation than the number three and five cylinders. The crankcase area surrounding the No. 1 cylinder deck area was fractured in multiple pieces. With the induction air box removed, the alternator belt was found off of both the alternator pulley and starter adapter pulley. The exhaust system was intact and had damage to the number one, three, five exhaust riser assembly. Examination of the two bladed McCauley constant speed propeller revealed one blade had minor scoring and the second blade was bent aft approximately mid-span. Examination of the number one main bearing support-mating surfaces revealed rough surfaces from fretting. The number one main bearing support diameter exhibited displaced material and damage from bearing displacement. The number one main bearing support lock-slot was elongated. Examination of the number two main bearing support-mating surfaces revealed rough surfaces from fretting. The number two main bearing support diameter revealed displaced material and mechanical damage. The number two main bearing support lock-slot was elongated. The lower portion of the number two main bearing support on the number 2,4,6 cylinder side revealed a crack approximately one inch from the mating surface. Examination of the number one connecting rod revealed thermal and mechanical damage around the thrust surfaces. The connecting rod cap revealed thermal and mechanical damage on both sides of the thrust surfaces. Pieces of connecting rod bolts and nuts were fractured through and revealed mechanical damage. The crankshaft fractured along the number two long cheeks. The damage to the crankshaft was concentrated to the number one connecting rod journal, number two long cheek and corresponding counter weights, and the aft portion of the number one main bearing journal. The forward set of counterweight assemblies were undamaged and had free and unrestricted movement on the hanger blades. The rear set of counterweight assemblies were damaged and did not have free and unrestricted movement on the hanger blades. All of the counter weight pins, plates and snap-rings were intact. The oil transfer passages were blown through with compressed air and were found open and unrestricted. The oil transfer collar was intact and undamaged. Review of the airplane logbooks revealed that the last annual inspection was conducted on June 15, 2005. The tachometer time was 4,118.0 hours and the airframe time at annual inspection was 4,118.0 hours. On November 20, 1989 a gear up landing occurred. The propeller was removed and the crankshaft was run-out and found to be .0006 out of round. The crankshaft was returned to service. According to the Service Bulletin M84-16, which was in place at the time of the mishap, if any damage greater than "minor dressing of the propeller tips to correct the problem" occurs, a complete disassembly inspection of the engine must be performed. A disassembly inspection was not performed and a serviceable propeller was reinstalled and the aircraft returned to service. In addition, the logbooks revealed there were approximately 750 flight hours on the crankshaft before it failed. Review of FAA Form 337 revealed that an ALCOR Alternator kit Model No. 1255A was installed on May 24, 1989. A primer painted bracket was found to be installed to the aft side of the number 2,4,6 crankcase halve just inboard of the new STC mounting bar. The primer colored bracket was not a factory installed component, and required the installer to remove the nuts and break the torque from the aft set of crankcase thru bolts in order to install the bracket. The logbooks did not reflect the compliance of Service Bulletin 96-7C with the re-torquing of the crankcase thru bolts after reinstalling the bracket. The IO-470 Overhaul Manual states that if the torque on a thru bolt is broken that both nuts on a thru bolt must be re-torqued. The fractured crankshaft was sent to the National Transportation Safety Board, Office of Research and Engineering, Materials Laboratory Division, for further examination. Examination of the fractured crankshaft revealed it was broken through the crank cheek between the number 1 and number 2 connecting rod journals. The fracture intersected the centerline hole of the crankshaft. The forging number from the crankshaft, "539664", was noted on the 6th crank cheek from the aft end of the shaft. A representative of Teledyne Continental Motors indicated that this forging number was superseded in April of 1975. The representative also indicated that based on their records, engine S/N 77813 was originally shipped from the factory in 1961. Examination with a bench binocular microscope revealed that the fracture on both sides of the centerline hole was largely flat and contained faint crack arrest positions, features indicative of fatigue cracking. The fracture faces on the forward portion of the crankshaft contained much less post-fracture damage than the fracture faces on the aft portion of the fracture, and these faces were arbitrarily label "1" and "2" for identification. In fracture area "1", the fatigue features emanated from a subsurface origin below the corner between the centerline hole and the aft side of the crankshaft. In fracture area "2", the fatigue features emanated from a subsurface origin below the corner between the centerline hole and the forward side of the crankshaft. Corresponding areas on the fracture faces on the aft portion of the crankshaft were totally obliterated by post fracture damage. Therefore, the remainder of the examination was conducted on the forward portion of the crankshaft. On both fractures "1" and "2", the fatigue cracking progressed nearly all of the way through the cross sections of the crank cheek before final fracture. Both of the origin areas contained nearly circular features, 0.09 inch to 0.1 inch in diameter, indicative of fatigue initiation from subsurface locations. Although the overall features suggested that fatigue initiation was somewhere within the circular feature, the exact location of the origin area was not determined.