What happened
Shortly after takeoff, once the landing gear had been retracted, the pilot observed an over-temperature indication on the right engine. In response, power was reduced, which was followed by symptoms indicating a compressor stall. The pilot subsequently shut down the right engine and executed a 180-degree turn to return to the airport.
During this turn, smoke filled the cockpit with flames visible coming from the right engine area. The pilot discharged the right fire bottle, but the fire continued. When the landing gear was lowered, the fire extinguished itself.
The investigation
Examination of the aircraft revealed that the snap ring for the right engine oil temperature relief valve was missing. The relief valve itself was located on the floor of the engine nacelle. Records indicated that the right engine had been replaced approximately 1.8 hours prior to the flight due to foreign object damage (FOD).
Findings
The separation of the relief valve allowed engine oil to escape and accumulate in the wheel well, wing, and engine nacelle. This accumulated oil was ignited, feeding the inflight fire. The incident highlights the critical importance of proper installation of retaining hardware during engine maintenance.