What happened
On July 29, 2022, at approximately 09:20 local time, a Pilatus PC-12/47E, registration HB-FWA, departed from Bern Airport (LSZB) bound for Saarbrücken. The flight was being conducted under Instrument Flight Rules (IFR) for private purposes. During the initial takeoff roll on runway 14, the crew noted that the engine was operating with an elevated interstage turbine temperature. As the aircraft entered the initial climb, the engine failed to produce its standard performance levels. Due to this loss of power, the crew elected to perform a precautionary landing back at Bern.
During the final approach to runway 14, the engine's available power decreased further. The crew observed sparks emitting from the engine exhaust nozzles during this phase of the flight. The aircraft landed at Bern with light damage to the airframe, and there were no injuries to the two crew members or the two passengers on board.
The investigation
The investigation into this occurrence was delegated to the German Federal Bureau of Aircraft Accident Investigation (BFU) by the Swiss Transportation Safety Investigation Board (SUST) to avoid any potential conflict of interest. The investigation focused on the engine's thermal irregularities and the subsequent loss of thrust during the departure and approach phases.