HISTORY OF FLIGHT On October 12, 2003, at 1205 Pacific daylight time, a Cessna 172RG, N6543V, sustained a collapse of the left main landing gear strut on landing at Camarillo, California, airport. Channel Islands Aviation operated the airplane under the provisions of 14 CFR Part 91. The private pilot and single passenger were not injured, and the airplane was substantially damaged. Visual meteorological conditions prevailed, and a flight plan was not filed. The flight originated at Camarillo about 1100. The pilot told the National Transportation Safety Board investigator that he was flying to Santa Barbara, California, from Camarillo. When over Ventura, he heard a clank sound from under the airplane's floor decking and thought that it was unusual. When he lowered the landing gear for landing at Santa Barbara, he observed an unsafe indication for the left main landing gear strut. The pilot decided to return to Camarillo, where he discussed the situation with Channel Islands Aviation over the radio. He then decided to make the landing with the landing gear down. Upon the landing touchdown the left landing gear collapsed. The left horizontal stabilizer and elevator contacted the runway; the airplane then departed the runway to the left. A Federal Aviation Administration (FAA) Investigator examined the airplane and maintenance logbooks. He reported that the left main landing gear actuator had fractures in its housing and appeared to have failed. The actuator was removed from the airplane and sent to the Safety Board Materials Laboratory for examination. TESTS & RESERCH Materials Laboratory Examination The entire Materials Laboratory Factual Report is available in the docket for this accident. The landing gear actuator, part number 9882015-2, serial number 7660, with an assembly date of 4Q80, was examined. The gear housing portion of the actuator had fractured in two locations; diagonally from the small diameter end and at a upper interior mounting hole. The actuator was sectioned at the upper interior mounting hole to facilitate fracture surface examination. The fractures along the small diameter of the actuator revealed a rough grainy surface with substantial shear lips, consistent with an overload event. The fracture at the upper interior mounting hole revealed a rough grainy surface with a woody appearance and parallel lines that were perpendicular to the inner edge of the large gear diameter of the housing, also consistent with an overload event. Examination of the flat side of the rack opposite to the teeth revealed a polished surface that had obliterated the original machining marks. The surface, consistent with contact with the rack support roller during retract and extend operations, was uniformly polished with the exception of a distinctly deeper arced impression where the rack support roller would contact the surface in the fully retracted position (landing gear down). Cessna Service Bulletin SEB01-2 Cessna Service Bulletin SEB01-2, originally issued on September 17, 2001, is applicable to part number 9882015-2. SEB01-2 directed initial inspection and rework for actuator/bodies exceeding 3,000 hours of total time in service and subsequent inspections every 500 hours thereafter. The inspection was to detect cracks in the location of the failures on the accident actuator. The Service Bulletin advised that failure to comply could result in failure of the actuator. Airplane Maintenance Records An FAA Inspector examined the airplane's maintenance logbooks. He reported that the logbooks have no entry of SEB01-2 compliance. The operator reported that the actuator was original equipment with 7,171 hours of total time in service.