What happened
On August 18, 2015, during the landing phase of a flight at the Polska Nowa Wieś airport (EPOP), the pilot of an Mi-2 helicopter observed the "Filter contaminated" (Filtr zanieczyszczony) warning light illuminate on the instrument panel. This indicator signals that the fuel filters are clogged, resulting in a drop in pressure. Following the conclusion of the flight, the pilot reported the occurrence to the maintenance mechanic.
In the Mi-2 engine configuration, fuel is supplied to the engines through a filter block. This system includes a pressure drop indicator that activates when the pressure falls below a specific limit due to filter contamination. To maintain engine operation during such an event, fuel is diverted to the engine via a bypass line.
The investigation
Following the report, a technical inspection of the aircraft was conducted. The investigation focused on the fuel filter block and the functionality of the pressure signaling system. The examination of the aircraft's mechanical components did not reveal any underlying mechanical failures or defects.
Findings
- The investigation confirmed that the maintenance performed on the filter block prior to the flight was carried out correctly.
- Post-event inspections showed no mechanical malfunctions.
- As a corrective measure, the fuel filters for both engines were replaced.
- A subsequent technical test flight was performed, which confirmed that all aircraft parameters were operating within standard technical specifications.
- The primary cause of the incident was the illumination of the fuel filter contamination warning light.