Incident Sequence
On March 10, 2020, at 14:14 UTC, a student pilot under the supervision of an instructor conducted a takeoff from runway 28 at Warsaw Babice Airport (EPBC) in a Cessna 152, registration SP-KOG, for a training flight. During the first turn, the instructor observed a decrease in engine rpm to 1700–1800 rpm, accompanied by uneven engine operation and noticeable vibrations. The instructor took control, informed Babice air traffic services of the engine issue, and requested landing on runway 10. After receiving clearance, he performed a landing without further incident.
Weather Conditions
Meteorological reports for the time of the flight were: METAR EPWA 101400Z 17011KT 9999 BKN040 10/04 Q1009 NOSIG and METAR EPWA 101430Z 18010KT 9999 SCT042 11/04 Q1009 NOSIG. Analysis indicated that the ambient temperature and dew point were conducive to severe carburetor icing at any engine power setting.
Investigation Findings
Post-flight inspection and an engine run-up by maintenance personnel revealed no abnormalities. A subsequent test flight with another instructor showed normal engine parameters and operation. The investigation concluded that the symptoms – rpm drop, vibrations, and uneven engine operation – were characteristic of carburetor icing, which reduces the cross-section of the fuel-air mixture duct and decreases engine power. The instructor did not associate these symptoms with possible icing and believed an engine malfunction had occurred. He had reviewed the weather forecast before the flight but did not analyze it for the risk of icing.
Recommendations
The investigating entity recommended discussing the event with flight crew and specifically informing the instructor about the need for more thorough pre-flight weather analysis to assess icing risks. No additional safety recommendations were formulated.
Probable Cause
The probable cause of the incident was carburetor icing.