What happened
During preparations for takeoff at the Red Lake, Ontario, Airport, a Pilatus PC-12/45 experienced a sudden engine flame-out. The aircraft, operated by BLS, was positioned on Runway 26 with two pilots and three passengers on board. After the engine had reached ground idle, the flight crew advanced the condition lever to flight idle. During this transition, the battery ammeter recorded a significant electrical draw of +300 A, and the engine simultaneously lost all power.
The crew attempted to restart the engine, but the effort failed as battery voltage dropped to 19 V. The aircraft was subsequently towed off the runway. At the time of the incident, weather conditions were clear with calm winds and a temperature of 33°C.
The investigation
Investigators examined the engine, the electrical system, and the fuel components. While maintenance staff could not replicate the engine power loss using a ground power unit, an inspection of the oil filter revealed particles consisting of wood, synthetic, and mineral fibers, along with black carbon-like particles.
Further analysis of the engine's reduction gearbox (RGB) revealed evidence of fretting on the second-stage mating splines and the ring gear. A previous oil analysis had shown a magnesium count of 39.9 ppm, which exceeded the manufacturer's internal guideline of 35 ppm. This elevated magnesium level was linked to the wear found in the gearbox. Additionally, investigators found carbonaceous soot on the thermal blanket, power turbine shaft housing, and bearing covers.
Testing of the fuel control unit, fuel pump, and flow divider showed no anomalies, and the electrical system showed no faults that would have caused the engine to fail. The high electrical load observed during the incident was attributed to the simultaneous operation of the air conditioning, navigation lights, beacon, and vent blowers alongside the battery charging process.
Findings
- The engine power loss most likely resulted from an interruption in fuel supply, though the exact cause could not be definitively determined.
- Fretting between the second-stage ring gear teeth and the magnesium reduction gearbox case produced magnesium dust, which entered the engine oil.
- The 300-A electrical draw was likely coincidental to the engine failure and did not contribute to the power loss.
- Carbon particles found in the oil filter originated from the #2 bearing area from a period prior to recent service bulletin modifications.