Incident Overview
On August 6, 2020, at approximately 10:00 local time, a Cessna 152 (registration SP-WLA) departed from the Świdnik airstrip near Lublin (EPSL) for a solo cross-country flight. The student pilot was under the supervision of an instructor as per the PPL(A) training syllabus. About one minute after reaching level flight at an altitude of approximately 2000 feet, the student reported a drop in engine RPM and rough engine operation over the radio. The engine RPM, which was around 2100 in level flight, decreased to 1500. When the pilot moved the throttle to the takeoff position, the RPM increased to about 2000, but not to maximum. The outside air temperature was 23°C with a dew point of 11°C, and carburetor heat was off. The pilot declared an intention to perform a precautionary landing and activated carburetor heat during the approach. The landing on runway 06 at approximately 10:13 local time was uneventful, with no further consequences.
Investigation Findings
After the flight, a visual inspection of the aircraft was conducted, along with a fuel quality check and an engine test. All engine parameters were found to be within the limits specified in the aircraft's flight manual. A subsequent test flight on August 9, 2020, also showed normal engine performance, and the aircraft was returned to service. Analysis of the meteorological conditions at the time of the incident indicated that the ambient temperature and dew point were conducive to the formation of carburetor ice at cruise power settings. The symptoms observed—RPM drop and rough engine operation—are characteristic of carburetor icing. According to the report, the pilot did not associate the symptoms with possible icing and failed to activate carburetor heat in response.
Probable Cause
The probable cause of the incident was carburetor icing.