What happened
On August 3, 2021, an instructor and a student pilot were conducting a training flight in a BushCat CH-162B, registration SP-SZKY. The flight originated from Łososiny Dolna, and after performing several landings at that airfield, the crew intended to return to their starting point.
While descending toward the Tarnów airfield at approximately 1,800 ft AGL, the engine stopped functioning. The instructor attempted to restart the engine several times; however, the engine would only run for a few seconds before failing again. Due to the decreasing altitude, the instructor decided to perform an emergency landing in a nearby meadow near Tarnowiec.
During the landing roll, the aircraft encountered a soft, ungrassed, and wet area of the field. The sudden deceleration caused the nose gear strut to break away from its mounting bolts. This led to the aircraft tilting forward, resulting in a broken propeller and damage to the wing skin near the cockpit. The crew sustained no injuries and exited the aircraft safely.
The investigation
The PKBWL examined the aircraft's fuel system to determine the cause of the engine failure. Investigators inspected the carburetors, fuel lines, and pumps, finding them to be clean and functional. The mechanical and electric fuel pumps were also found to be in working order.
Upon inspecting the fuel strainer, investigators discovered a light gray, greasy, paraffin-like substance coating the filter. While the fuel in the tanks appeared relatively clear, the presence of this substance in the strainer was identified as the primary issue. Following the replacement of the fuel filters and various fuel lines, the engine was successfully tested on the ground.
Findings
- The engine failure was caused by blockage in the fuel system due to an oily, paraffin-like substance accumulated on the fuel strainer filter.
- The emergency landing was a necessary consequence of the engine failure.
- The damage to the aircraft's landing gear and propeller was caused by the aircraft hitting soft, uneven ground during the landing roll.
- It is suspected that the oily residue precipitated from automotive gasoline used in the aircraft's fuel system.