What happened
On November 3, 2018, a Cessna A-188B, registration LV-MYH, was conducting aerial application operations in Mesón de Fierro, Chaco. After approximately 20 minutes of flight, the pilot noticed a sudden drop in oil pressure followed immediately by a loss of engine power. At the time of the failure, the aircraft was flying at an altitude of approximately 25 meters. The pilot was able to level the aircraft and execute an emergency landing in a field, coming to a stop after traveling 10/0 meters. The pilot exited the aircraft without injury, and the aircraft sustained no damage.
The investigation
The investigation was initiated after the JIAAC became aware of the incident through an anonymous report, as the event had not been reported through official channels in a timely manner. Upon the investigators' arrival, the aircraft had already been moved from the site.
Technical examination of the engine at a repair workshop revealed significant internal damage. Investigators found metallic particles and fine shavings within the oil filter and oil residue. Specifically, the crankshaft showed evidence of overheating and friction on the second main bearing. Additionally, the second and third connecting rod bearings exhibited damage caused by a lack of lubrication. The investigation also noted abrasive wear on the bearing surfaces and engine semi-block contact areas.
Maintenance records indicated that the aircraft was properly certified and maintained according to regulations. The engine had completed 232.3 hours since its last overhaul and 27 hours since its last inspection.
Findings
- The engine failure was caused by the partial rotation of the number 2 main bearing.
- This movement caused the obstruction of internal engine lubrication orifices.
- The resulting obstruction led to excessive temperatures and a subsequent loss of engine power.
- The presence of metallic particles in the lubrication system likely caused collateral damage to other bearings.
- The investigation could not determine the specific pre-existing condition that caused the bearing to shift out of position.