Accident Details
On March 7, 2009, at about 1750 Pacific standard time, a Cessna 172R, registration N2478B, experienced a loss of engine power and made an off-airport forced landing near Oceanside, California. The pilot, who was also the owner, was operating the airplane under 14 Code of Federal Regulations Part 91 for a cross-country personal flight. The flight had departed Orange County Airport in Santa Ana, California, at an undetermined time, with a planned destination of Montgomery Field in San Diego, California. Visual meteorological conditions prevailed, and no flight plan was filed.
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 forced landing took place near a portable landing strip on 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 only electrical wires, flight control cables, and a 1-foot piece of sheet metal remaining attached. Oil stains were present along the bottom of the fuselage, on the struts, and horizontal stabilizers.
Aircraft and Engine Examination
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, with staining beginning 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. The cylinder was manufactured by Engine Components, Inc. (ECi). During assembly, the aluminum alloy cylinder head is screwed onto the alloy steel barrel at elevated temperature and then cools, shrinking onto the barrel threads and plain diameter. The fracture faces displayed three zones: two relatively smooth surfaces and one rough grainy surface. The major smooth zone was on the exhaust side of the cylinder head, perpendicular to the barrel axis, with its inner edge abutting the first thread crest and displaying multiple ratchet marks. A smaller smooth zone was on the intake valve side. Materials met specifications.
Service Bulletins and Airworthiness Directives
ECi issued Mandatory Service Bulletin (MSB) No.08-1, Revision 3, dated August 19, 2008, alerting customers about possible fatigue cracking and head separations on certain replacement cylinders for Lycoming parallel valve engines. Two groups were identified: Group “A” cylinders (produced between August 2002 and December 2005) required periodic inspection/pressure tests; Group “B” cylinders (produced between December 2005 and February 2006) required a one-time inspection and removal if criteria were met. Removed cylinders could be replaced with ECi cylinders part number AEL65102 with serial numbers 37017 and higher.
On October 20, 2008, FAA Airworthiness Directive (AD) 2008-19-05 became effective, applying to Lycoming Engines with certain ECi cylinders. It required initial and repetitive visual inspections and compression tests to detect cracks at the head-to-barrel interface, and replacement of cracked assemblies or those at reduced times-in-service. The AD resulted from 45 failures with head separations. The cylinder assembly from the accident airplane was part number AEL65102, cylinder head part number AEL85099, serial number 42129-16. The AD applied to ECi cylinder assemblies part number AEL65102 series “Titan” with head part number AEL85099: Group “A” serial numbers SN 1138-02 through SN 35171-22, and Group “B” serial numbers SN 35239-01-02 through SN 37016-28. Serial numbers outside the range required no further action.
FAA AD 2009-26-12, effective February 4, 2010, superseded AD 2008-19-05, requiring the same actions but applying to an expanded population of cylinders. ECi has made a design change pending FAA approval.