What happened
While operating in cruise flight, the pilot of the Lycoming engine aircraft noticed a burning smell. Shortly thereafter, the pilot observed a low oil pressure indication, followed by a vibration and a brief engine overspeed to 3,000 rpm. The engine subsequently lost all power. The pilot performed a forced landing in a field, during which the aircraft collided with multiple ground obstacles. There were no fatalities reported.
The investigation
Post-accident examination of the engine at the accident site revealed that the No. 6 connecting rod had penetrated the engine crankcase. An excess of engine oil was found on the bottom of the airplane. Further inspection determined that an oil filter gasket, Lycoming part number LW-13388, had been extruded at the base of the filter assembly. This extrusion allowed virtually all engine oil to escape the system.
Findings
- The engine suffered a catastrophic failure after losing nearly all oil due to a failed gasket.
- A Lycoming Mandatory Service Bulletin (MSB-543) and an emergency Airworthiness Directive (AD 2000-18-53, later superseded by AD 2002-12-17) were applicable to this specific issue.
- These directives required repetitive inspections and either the replacement of the gasket or the installation of a different part number for the gasket adapter plate.
- The investigation found no evidence of compliance with the applicable Airworthiness Directives.