Incident Overview
On June 29, 2023, a Cessna 152 (registration SP-FZY) experienced a significant engine power loss during climb after takeoff from Rudniki airfield (EPRU). The aircraft was at an altitude of approximately 70 meters above ground level when the power loss occurred. The pilot executed a straight-ahead landing on the usable portion of concrete runway 26. During the final roll, the aircraft exited the runway. No crew injuries were reported, and the aircraft was not damaged.
Investigation Findings
Post-incident engine inspection revealed a lack of seal on the second cylinder. After removing the valve covers, it was found that the lock nut on the exhaust valve adjusting screw was loose. The adjusting screw had positioned itself such that the exhaust valve did not open.
Probable Cause
The probable cause of the incident was the loosening of the lock nut on the exhaust valve adjusting screw, which resulted in the exhaust valve not opening.
Contributing Factors
The investigation identified two contributing factors: (1) the lock nut was likely tightened with insufficient force, and (2) the lock nut had been machined, which may have affected its locking capability.
Preventive Actions
The entity conducting the investigation replaced the lock nuts on the valve adjusting screws with new ones as a preventive measure. No further safety recommendations were issued.