NTSB Identification: LAX96LA270.
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Accident occurred Saturday, July 13, 1996 in FOLSOM, CA
Probable Cause Approval Date: 12/16/1996
Aircraft: Cessna 177RG, registration: N52185
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

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.

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