Incident Description
On 18 August 2015, a Mi-2 helicopter was conducting a landing at Polska Nowa Wieś airfield (EPOP) near Opole, Poland. During the landing, the pilot observed the illumination of the "Filter contaminated" indicator on the instrument panel, which signals contamination of the fuel filters. After the flight, the pilot reported the observation to the mechanic.
In the Mi-2 helicopter, fuel flows to the engines through a fuel filter block. The block includes a pressure drop sensor that triggers the "Filter contaminated" indicator when filter contamination causes pressure to fall below a specified threshold. If the indicator activates, fuel continues to be supplied to the engine via a bypass line, maintaining engine operation.
Investigation
A post-incident inspection found no mechanical faults. The fuel filters of both engines were replaced. A technical test flight was then conducted, which confirmed that all parameters met technical requirements. The maintenance performed on the filter block prior to the incident was determined to have been correct.
Cause
The cause of the incident was determined to be the illumination of the "Filter contaminated" indicator. No safety recommendations were issued by the commission.