Accident Overview
An aircraft experienced an engine seizure during its first flight following an engine overhaul. The forced landing resulted in a collision with obstructions. Post-accident examination revealed the engine failure was caused by oil exhaustion due to an incorrect gasket setup on the prop governor pad.
Overhaul and Ground Run
The engine was overhauled at an engine facility and then installed in the aircraft by a maintenance shop. According to Lycoming specifications, the ground run should have lasted 2 hours and 25 minutes, but the engine was only run for 40 minutes. During the ground run, an oil leak was detected at the prop governor oil pressure line fitting. The fitting was tightened, and the aircraft was subsequently placed in the owner’s hangar.
Accident Sequence
On the first flight after the overhaul, the engine seized after 15 minutes. The aircraft was forced to land and collided with obstructions. After the accident, a large smear of oil was found on the fuselage belly and left side.
Investigation Findings
Disassembly of the engine revealed damage consistent with a lack of lubrication due to oil exhaustion. The dipstick was in place, and all oil lines and fittings were tight and not leaking. When the prop governor was removed, only an MS9144-01 screen gasket was found installed. A raised channel and oil trail were observed from a pressure port in the governor pad under the gasket to the pad edge.
Lycoming’s parts manual and service instructions specify that this engine requires an additional special gasket and plate to be installed together with the MS9144-01 gasket to prevent oil leakage. The overhaul shop was unaware of this special gasket stack requirement and delivered the engine to the maintenance shop without any gaskets on the governor pad. The maintenance shop used only the Mooney maintenance manual for the engine installation, which does not mention the special gaskets, and installed the prop governor with only the MS9144 gasket.
Probable Cause
The overhaul shop’s lack of awareness of the special gasket requirement and the maintenance shop’s reliance on a manual that did not include the necessary gasket details resulted in improper installation of the prop governor gasket, leading to oil leakage and subsequent engine seizure.