Event Description
On 12 March 2017, a Piper PA44 180T aircraft, registration SP-MIS, was conducting an instrument rating and multi-engine (IR/ME) training flight from Modlin Airport (EPMO). During the flight, the crew detected vibrations from the left engine and observed smoke emerging from the trailing edge of the left wing. As a precaution, the left engine was shut down. The crew reported technical issues without declaring an emergency and requested to return to EPMO. After stabilizing the flight pattern, about 7 nautical miles from the airport, they requested landing priority. Air traffic control was informed of the planned single-engine landing. The flight lasted 54 minutes total. The crew landed on Runway 08 and taxied to the parking position without further incident.
Findings
Post-flight inspection revealed damage to the left engine's turbine and exhaust valve. The damaged valve components had also destroyed the piston, necessitating replacement of those parts. The aircraft had two occupants, both of whom were uninjured.
Probable Cause
The cause of the incident was not conclusively determined. One probable cause identified was the operation of the aircraft on an excessively lean fuel-air mixture during several flights preceding the incident.
Safety Actions
The operator communicated the incident circumstances and corrective actions internally and externally via a safety bulletin (KRONIKA SMS No. 03/2017). Additionally, the event and its probable causes were reviewed and discussed during a BL Salt Working Group meeting in December 2017. No safety recommendations were formulated by the investigation commission.