What happened
On August 6, 2020, at approximately 10:00 LMT, a student pilot departed from the Świdnik airfield (EPSL) in a Cessna 152, registration SP-WLA, for a solo flight as part of a PPL(A) training program. Approximately one minute after completing the climb and entering level flight, the pilot reported via radio a drop in engine RPM and irregular engine performance, subsequently declaring an intention to perform a precautionary landing.
At the time of the incident, the aircraft was at an altitude of approximately 2,000 feet. Engine RPM had dropped from 2,100 to 1,500; moving the throttle to the takeoff position only restored power to approximately 2,000 RPM, failing to reach maximum rated power. Ground conditions included an ambient temperature of 23°C and a dew point of 11°C, with the carburetor heat being in the off position. The pilot engaged the carburetor heat during the approach. The precautionary landing on runway 06 was completed at approximately 10:13 LMT without further incident.
Following the flight, inspections of the fuel cleanliness and engine tests showed parameters were within normal operating limits. A subsequent test flight on August 9, 2020, also confirmed normal engine performance, and the aircraft was returned to service.
The investigation
The investigation examined the meteorological conditions present during the flight and the pilot's response to the engine symptoms. Analysis of the ambient temperature and dew point indicated that the atmospheric conditions were conducive to the formation of carburetor ice during level flight.
Findings
- The probable cause of the engine power loss was carburetor icing.
- Meteorological conditions, specifically the relationship between the ambient temperature and the dew point, favored the formation of ice within the carburetor.
- The pilot did not immediately associate the engine's irregular operation and power loss with the possibility of icing, and therefore did not initially apply the carburetor heat.