What happened
On February 20, 2016, a private sightseeing flight was conducted using a Cessna 150M, registration SP-KCG, operated by Salt Aviation Sp. z o.o. The aircraft departed from Warsaw/Modlin (EPMO) with a pilot and one passenger aboard. During the pre-flight sequence at the ramp, the pilot attempted to start the engine but encountered difficulties. He later described pushing the carburetor heat lever fully forward to engage the heater due to the humid conditions, assuming this position activated it.
After taxiing to the holding point, the pilot performed a magneto check at 1700 RPM. During this test, he pulled the carburetor heat lever toward himself, observing a slight increase in engine RPM. He interpreted this as the heater being turned off and subsequently pushed the lever forward again to "normalize" its operation before applying full power for takeoff at approximately 13:28 local time. The aircraft took off and flew toward the Zegrze Reservoir area.
Approximately 25 minutes into the return flight, while cruising at around 1,400 feet, the pilot noticed a gradual loss of engine power. Initially considering a return to Warsaw/Modlin, he decided to divert to a previously identified field near Michałów Grabina as his altitude decreased to 1,100 feet. The landing site was muddy and soft. Upon touchdown, the nose gear collapsed, causing the aircraft to capsize. Both the pilot and the passenger exited the wreckage under their own power without sustaining injuries.
The investigation
The PKBWL examined the sequence of events, weather conditions, and pilot actions. Meteorological data from Warsaw/Modlin indicated visibility of 4,500–5,000 meters in mist, with cloud bases between 1,100 and 2,300 feet. The temperature was 3°C and the dew point was 1°C, creating conditions favorable for structural icing at lower altitudes. A GAMET forecast also indicated moderate icing potential east of longitude 0219.
The investigation focused on the pilot's interaction with the carburetor heat control. Evidence suggested that a previous user had left the carburetor heat lever in the "on" (pulled out) position after landing. The current pilot, unfamiliar with the specific lever configuration or its effect on RPM changes during a magneto check, misinterpreted the engine's response. When he pulled the lever during the check, the heater was actually turned off, removing existing ice and causing a slight RPM rise. He then pushed it forward, inadvertently turning the heater off completely (or leaving it in a neutral/disengaged state relative to his expectation), allowing ice to accumulate rapidly.
Findings
The primary cause of the accident was the pilot's error in operating the carburetor heat control. He confused the direction of movement required to engage and disengage the heater. This mistake resulted in the engine ingesting cold, moist air, leading to significant carburetor icing and subsequent power loss.
Contributing factors included:
- Weather Conditions: The flight was conducted in conditions with a high risk of structural and carburetor icing, characterized by low cloud bases and temperatures near freezing.
- Pre-flight Inspection: The pilot failed to verify the position of the carburetor heat lever before starting the engine. It is likely that the lever had been left in the "on" position by a previous user, which misled the pilot's understanding of the control's function during his subsequent checks.
- Misinterpretation of Engine Response: The pilot incorrectly interpreted the RPM increase during the magneto check as the heater being turned off, when it was actually the removal of ice. He then proceeded to take off with the heater effectively disabled or in an incorrect state for the conditions.
Safety action
The PKBWL noted that pilots should regularly refresh their knowledge of cockpit equipment operation to prevent confusion regarding control directions and effects. No formal safety recommendations were issued by the commission for this specific incident, but the report highlights the critical importance of verifying control positions during pre-flight checks, especially when renting aircraft from different operators.