What happened
On April 11, 2015, during a training flight within the EPRZ control zone, the crew of a PZL M-20 Mewa experienced uneven performance from the aircraft's left engine. The pilot requested an approach using the ILS "Z" procedure, performing a left pattern for landing on runway 27. The landing was completed without incident.
Following the arrival, the crew conducted ground engine checks while taxiing on the apron. These inspections did not reveal any identifiable malfunctions. However, during a subsequent flight, the same uneven engine performance recurred. The aircraft landed safely, and the plane was subsequently handed over to technical personnel for inspection.
The investigation
The investigation focused on identifying the source of the intermittent power imbalance in the left engine. Technical examinations of the engine components were conducted to determine why the irregularity appeared during flight but remained undetected during ground testing.
Findings
- The investigation established that the uneven engine operation was caused by carbon buildup on the electrodes of one of the spark plugs.