What happened
On August 25, 2014, an An-2 aircraft was performing a climb-out from the Bielsko-Biała-Aleksandrowice (EPBA) aerodrome. The aircraft was carrying several skydivers at the time of the incident. Approximately two minutes into the flight, at an altitude of 200 meters above the airfield, a loud bang was heard originating from beneath the engine cowlings. This was accompanied by a small cloud of smoke appearing near the upper part of the cowlings and an uneven engine rhythm.
The pilot monitored the engine parameters and noted that while most readings remained within normal limits, the temperature of the cylinder number 1 head was abnormal. Following this observation, the decision was made to return to the departure airfield. The aircraft landed safely at EPBA without any damage to the airframe or injuries to the occupants.
The investigation
Following the landing, a physical inspection of the engine was conducted. During this inspection, investigators discovered that a spark plug from the second row of plugs in cylinder number 1 had been dislodged.
Findings
- The investigation established that the fatigue failure of the cylinder head was the direct cause of the spark plug being ejected.
- No injuries were reported among the passengers or the crew.
Safety action
Upon identifying the cause, the operator performed a thorough inspection of the cylinder heads on the remaining cylinders, specifically focusing on the spark plug seats. No further damage or defects were found during this inspection.