FOLSOM, CA, USA
N52185
Cessna 177RG
The aircraft was in cruise flight when the pilot noticed the oil pressure rapidly decrease, followed shortly thereafter by engine roughness. With a loud knock, the engine lost power and oil began to spray on the windshield. The aircraft collided with ground obstructions during a forced landing attempt on a road. Disassembly of the engine revealed only trace amounts of oil in the case, with a typical oil starvation heat distress failure of the numbers 3 and 4 connecting rods. During removal of the propeller governor only a MS9144-01 screen gasket was installed between the governor and the mounting pad. An oil path was observed running between the gasket and the pad from the high pressure oil port to the outside edge of the pad. Review of Lycoming publications (published in 1987) revealed that this particular engine requires a unique gasket and plate stack to prevent oil leakage between the governor and it's mounting pad. The maintenance records disclosed that 1.4 hours prior to the accident, the propeller governor was removed for repair then reinstalled on the engine. Both the mechanic who performed the work and the IA who inspected the job stated that the current Cessna 177 maintenance and parts manuals were used for procedural guidance. Both said they were unaware of a special gasket stack requirement for this particular engine, and they would not routinely refer to engine manuals for a governor installation since the governor is an airframe component. The Cessna service manual only speaks to the installation of the MS screen gasket, and uses the term 'gasket' in the singular form. The special Lycoming gasket and plate are not mentioned in either Cessna manual. Cessna Aircraft stated that they were aware of the Lycoming requirement for a special gasket stack for the Cessna 177RG aircraft application and are in the process of revising the Service and Parts manuals accordingly.
On July 13, 1996, at 1152 hours Pacific daylight time, a Cessna 177RG, N52185, collided with ground obstructions during a forced landing near Folsom, California. The forced landing was precipitated by a catastrophic engine failure while in cruise flight. The aircraft was operated by California Airways of Hayward, California, and was rented by the pilot for a personal cross-country flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft incurred substantial damage. The certificated private pilot and his one passenger were not injured. The flight originated at Hayward on the morning of the accident at 1109 with a destination of Georgetown, California. The pilot reported in a telephone interview that the aircraft was in cruise flight when he noticed the oil pressure began to decrease, followed shortly thereafter by engine roughness. With a loud knock, the engine lost power and oil began to spray on the windshield. The aircraft collided with ground obstructions during a forced landing attempt on a road. Following retrieval of the aircraft from the accident site, the engine was removed and shipped to an examination facility in Livermore, California. The Lycoming IO-360-A1B6D engine, serial number L-18006-51A, was disassembled and examined by a Safety Board investigator on August 6, 1996, with technical assistance provided by Textron Lycoming. A report of the engine disassembly is appended to this report. Continuity was found throughout the engine's valve train, camshaft and accessory gear case. Only trace amounts of oil were noted in the engine. A large quantity of ferris and non-ferris metal fragments were found in the oil sump along with extruded and heat distressed bearing fragments. A large hole was evident in the crankcase above the number 4 cylinder flange, with the number 4 connecting rod protruding through the hole. Both the number 3 and 4 connecting rods were found separated from the crankshaft; ductile and necking separation signatures were observed on the rod end cap bolts. Heat distress was noted to all rod bearings. The severity of the heat distress followed the oil path through the engine, with the most severe signatures noted to the number 4 rod bearing and the least amount observed on the number 1. The rod bearings for the numbers 1 and 2 rods exhibited plastic deformation and extrusion. The oil pump was disassembled, with minor scoring observed on the impellers and internal housing walls. No abnormalities were noted to the valves, pistons, or combustion chambers. The propeller governor was examined on its rear accessory case mounting pad, then removed with careful attention to not disturbing the gasket. Only a MS9144-01 screen gasket was installed between the governor and the mounting pad. An oil path was observed running between the gasket and the pad from the high pressure oil port to the outside edge of the pad. A review of the Lycoming Overhaul and Parts manuals in addition to Service Instruction SI1438 (first published in 1987), revealed that the A1B6D and A3B6D Lycoming 360 series engines require a unique gasket and plate stack to prevent oil leakage between the governor and it's mounting pad. According to the referenced Lycoming publications, a Lycoming 72053 gasket must be installed first, followed by a LW-12347 plate, before the MS9144-01 screen gasket and the governor are installed. The airframe and engine maintenance records were reviewed and they disclosed that on July 12, 1996, 1.4 hours prior to the accident, the propeller governor was removed for repair then reinstalled on the engine. Both the mechanic who performed the work and the IA who inspected the job were interviewed on the day of the engine examination. The mechanic stated that the current Cessna 177RG maintenance and parts manuals were used for procedural guidance during the removal and reinstallation of the governor. Both interviewees stated that following the installation of the governor, the engine was test run with no leaks observed. Both of the individuals reported that they were unaware of a special gasket stack requirement for this particular engine. According to both individuals statements, the shop has the engine service and parts manuals available, but they would not routinely refer to them for a governor installation since the governor is an airframe component. Review of the FAA approved type certificate data sheets for the airframe and engine revealed that the governor is considered an airframe component and not part of the engine. The Cessna 177RG Service and Parts Manuals used by the mechanic for the job were examined. The service manual only speaks to the installation of the MS screen gasket, and uses the term "gasket" in the singular form. The special Lycoming gasket and plate are not mentioned in either manual. Cessna Aircraft was contacted and they reported that the manual used by the mechanic is the most current published version. The company representative further stated that they were aware of the Lycoming requirement for a special gasket stack for the Cessna 177RG aircraft application and are in the process of revising the Service and Parts manuals accordingly.
An oil starvation failure of the engine due to a mechanic's failure to put the proper gasket stack on when the propeller governor was replaced. The mechanic's omission was due to the airframe manufacturer's failure to ensure that the service and parts manuals for the aircraft contained the most recent information concerning the unique gasket requirement for this airplane.
Source: NTSB Aviation Accident Database
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