What happened
On May 19, 2017, while operating a Cessna 172 under Visual Flight Rules (VFR) within the Warsaw FIR, the pilot-in-command noticed a decrease in oil pressure. Although the pressure remained within a safe operating range, the pilot elected to terminate the flight immediately. Following the landing, maintenance personnel conducted an inspection of the oil system and discovered a small number of metal particles on the oil filter.
The investigation
Due to the nature of the particles, the engine was removed from the aircraft and sent to the maintenance organization responsible for its previous overhaul, as the engine was still under warranty. The investigation focused on identifying the source of the metallic debris. The analysis revealed unusual wear patterns on the main and connecting rod bearings of the crankshaft. While the exact cause of the metal contamination could not be definitively established, the investigation considered that the wear might have resulted from improper initial engine startup following a period of extended storage or inactivity.
Findings
- The presence of metal particles was confirmed on the oil filter.
- Unusual wear patterns were identified on the crankshaft's main and connecting rod bearings.
- The investigation could not definitively determine the precise cause of the metal shavings, though improper startup after long-term storage was noted as a potential contributing factor.
- Following the inspection and reinstallation, the engine was returned to service and has since operated without further issues.