On April 29, 1986, a Cessna 177RG (registration N34020) operated by Puc Flight Service was involved in an aviation accident near Placerville, CA. Investigators recorded the probable cause as: Failure to secure the governor oil pressure line with clamps per the Avco Lycoming maintenance manual, leading to chafing and fracture, which resulted in oil pressure loss and engine overspeed. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An engine overspeed and oil pressure loss forced a pilot to land in Ice House Reservoir. Investigation revealed a fractured governor oil pressure line that was not secured with required clamps, following a 100-hour inspection the day before.
Incident Overview
During an en route flight to San Francisco, California, the engine began to overspeed. The propeller governor control was ineffective in arresting or controlling the overspeed condition. Shortly thereafter, engine oil pressure depleted to zero. The pilot elected to land in the Ice House Reservoir. The pilot and passenger were rescued by local boaters.
Examination Findings
Post-incident examination of the engine disclosed that the governor oil pressure line had been chafing against the engine crankcase and had fractured. The line was not secured with clamps as required by the Avco Lycoming maintenance manual. A 100-hour inspection had been performed on the aircraft the day before the accident.
Probable Cause
The failure to secure the governor oil pressure line with clamps per the maintenance manual, leading to chafing and fracture, resulting in oil pressure loss and engine overspeed.