Incident Overview
On August 25, 2014, an AN-2 aircraft was climbing from Bielsko-Biała-Aleksandrowice airfield (EPBA) with parachutists on board. During the second minute of flight, at an altitude of 200 meters above the airfield, a loud bang was heard emanating from under the engine cowling, accompanied by a small cloud of smoke appearing at the top of the cowling and uneven engine operation.
Pilot Response
The pilot checked engine parameters, which were within normal ranges except for the cylinder head temperature of cylinder no. 1. A decision was made to land at the departure airfield. The landing was completed safely, and the aircraft sustained no damage.
Post-Flight Inspection
After landing, an inspection revealed that a spark plug had been forcibly ejected from the second row of spark plugs on cylinder no. 1. Further examination determined that the cause of the spark plug ejection was fatigue damage to the cylinder head.
Follow-Up Actions
Following the identification of the cause, the operator decided to inspect the cylinder heads of the remaining cylinders, with particular attention to the spark plug seats. No additional damage was found.
Conclusion
The incident was attributed to fatigue damage of the cylinder head, which led to the spark plug being dislodged.