What happened
On October 13, 2018, a pilot departed from EPSY airport with the intention of repositioning a PZL101 Wilga 35A to Mielec (EPML). The flight was planned for a duration of 2 hours and 55 minutes, and the aircraft was fueled to its full capacity of 195 liters. After climbing to 1,500 feet, the pilot established flight parameters at 680 mmHg manifold pressure and 1,750 RPM.
While en route, the aircraft passed Wyszogród (EPMO) and later established contact with FIS Kraków near Łagów. As the aircraft began a slow descent, GPS indications suggested approximately 25 minutes remained until arrival at EPML, with fuel gauges showing roughly 40 liters remaining. During communications with the Mielec tower regarding landing on runway 09, the engine began to run unevenly before eventually failing. The pilot subsequently performed an emergency landing in a meadow near Ossala. The pilot sustained no injuries, and the aircraft remained undamaged.
The investigation
The investigation examined the fuel consumption and engine performance during the flight. A follow-up test flight was conducted on October 29, 2018, to determine the average fuel consumption under comparable conditions. During this one-hour test flight, the engine consumed 93 liters of fuel.
Data analysis revealed that the fuel consumption rate during the accident flight was significantly higher than previous averages. While the average consumption for the current year was 56 l/h, the rate during the October 13 flight was 69 l/h. The test flight showed a rate of 76 l/h. Furthermore, the investigation noted that cylinder head temperatures remained at the lower end of the range (130°C) and the engine failed to respond to adjustments of the mixture control lever. These findings indicated that the engine was operating on an excessively rich mixture.
Findings
- The engine failure was caused by fuel exhaustion.
- The depletion of fuel was a direct result of a significantly increased fuel consumption rate compared to standard operating norms.
- The increased consumption was caused by a malfunctioning carburetor, which resulted in an overly rich fuel mixture that also caused excessive cooling of the cylinder heads.