On March 7, 2009, about 1750 Pacific standard time, a Cessna 172R, N2478B, made an off airport forced landing following a loss of engine power near Oceanside, California. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The private pilot and one passenger sustained serious injuries; another passenger sustained minor injuries. The airplane sustained substantial damage to the fuselage, wings, and empennage from impact forces. The cross-country personal flight departed Orange County Airport, Santa Ana, California, at an undetermined time, with a planned destination of Montgomery Field, San Diego, California. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot made a forced landing near a portable landing strip on the Camp Pendleton Marine Corps Base. The airplane touched down on flat ground, and then collided with the upslope side of a ditch. The engine and propeller separated as a unit. The airframe fractured and separated circumferentially aft of the cabin with just electrical wires, flight control cables, and a 1-foot piece of sheet metal remaining attached. There were oil stains along the bottom of the fuselage, on the struts, and horizontal stabilizers. A follow-up examination of the airframe revealed no anomalies. The propeller spinner exhibited aft crush damage. The left side of the engine had more oil staining than the right side, and the oil staining began between the number two and number four cylinders. The number four cylinder (left rear) fractured and separated circumferentially in the area where the head joins the barrel. A specialist from the Safety Board’s Materials Laboratory examined the cylinder, and the report is part of the public docket for this accident report. Pertinent parts of the report follow. Engine Components, Inc. (ECi), manufactured the cylinder. On assembly, the aluminum alloy cylinder head is screwed onto the alloy steel barrel while at an elevated temperature. It is firmly seated on the upper barrel flange. The cylinder head cools and shrinks onto the barrel threads and the plain diameter above them. The specialist identified three zones on the fracture faces; two zones displayed relatively smooth surfaces, and the other was a rough grainy surface. The major smooth zone was primarily on the exhaust side of the cylinder head; a smaller smooth zone was on the intake valve side of the cylinder head. The major smooth zone was perpendicular to the axis of the barrel. Its inner edge abutted the crest of the first thread on the barrel, and displayed multiple ratchet marks initiating at the interface. The examination determined that the materials met the material specifications. ECi issued Mandatory Service Bulletin (MSB) No.08-1, Revision 3, dated August 19, 2008. It stated that the purpose of the MSB was to alert their customers about possible fatigue cracking and head separations on a specified group of replacement cylinders for Lycoming parallel valve engines. They noted that the failure history indicated that there are two groups of manufactured cylinders with two different remedial actions to address the situation. The first and largest group (Group “A”) would require a periodic inspection/pressure test to insure continued airworthiness. They produced Group “A” cylinders between August, 2002, and December 2005. The second group (Group ‘B’) would require a one time inspection, and then removal of the cylinder assembly from service when meeting the criteria specified in the MSB. They produced Group “B” cylinders between December 2005 and February 2006. They indicated that cylinders that are removed may be replaced with ECi cylinders Part Number AEL65102 and serial numbers 37017 and higher. On October 20, 2008, Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2008-19-05 became effective. The AD applied to Lycoming Engines with certain ECi cylinders installed. It required initial and repetitive visual inspections and compression tests to detect cracks at the head-to-barrel interface. It required replacement of cylinder assemblies that were cracked, and required replacement of certain cylinder assemblies at new reduced times-in-service. The AD resulted from reports of 45 failures with head separations of ECi cylinder assemblies. The AD stated that the intent was to prevent loss of engine power due to cracks at the head-to-barrel interface in the cylinder assemblies and possible engine failure caused by separation of a cylinder head. The cylinder assembly from the accident airplane was part number AEL65102. The cylinder head was part number AEL85099, and the serial number was 42129-16. The AD applied to ECi cylinder assemblies part number AEL65102 series “Titan” with a cylinder head part number of AEL85099. It applied to serial numbers SN 1138-02 through SN 35171-22, and referred to them as Group “A” cylinder assemblies. It applied to serial numbers SN 35239-01-02 through SN 37016-28, and referred to them as Group “B” cylinder assemblies. Cylinder assemblies with serial numbers that fell outside the range of the AD required no further action. The FAA has issued AD 2009-26-12, which supersedes AD 2008-19-05. It becomes effective February 4, 2010; it requires the same actions for the superseded AD, but applies to an expanded population of cylinders assemblies. ECi has made a design change to the cylinder assemblies that is pending FAA approval.