What happened
On June 29, 2020, an instructor and a student pilot were conducting flight training for a Private Pilot License (PPL(A)) at the Babice airport (EPBC). The flight involved performing circuit patterns using runway 28R. After completing two full circuits, the crew noticed irregular engine performance immediately following the takeoff for the third circuit.
The crew notified the AFIS controller on the Babice Information frequency of their intention to perform a precautionary landing. They opted to land with a wind component on the grass runway 10L. The landing was completed without further incident. Once on the ground, the instructor performed an engine ground run, during which the engine experienced a drop in RPM of more than 150 rpm accompanied by noticeable vibrations. The technical malfunction was documented in the aircraft's technical log.
The investigation
The investigation focused on identifying the source of the engine instability and the drop in engine speed observed during the ground test.
Findings
- The primary cause of the engine malfunction was the fracture of the porcelain insulator on the lower part of the spark plug in the second cylinder.