What happened
Before the flight, observers noted the pilot adding oil to the right engine in an unorganized manner. Following this, the engines were operated at medium power for roughly 20 minutes before the aircraft taxied from the ramp and began its departure. Shortly after rotation, flames were seen coming from the right engine. The aircraft maintained a shallow climb while flying at a low altitude with the engine fire active. The pilot attempted a right bank to return to the airfield, but the aircraft descended into a residential neighborhood.
Findings
Post-accident investigations of the right engine identified an exhaust leak at the No. 4 cylinder exhaust riser flange. The investigation also noted that a flange bolthole had become elongated, likely due to vibrations caused by the leak. While the fuel nozzle and B-nut remained attached to the No. 4 cylinder, the associated fuel line had detached approximately 8 inches from the nozzle. It was impossible to determine if this separation occurred during flight or during the impact due to the extent of the fire and crash damage.
Further inspection of the right engine turbocharger showed that the compressor wheel contained uniform aluminum alloy deposits. These deposits were consistent with the ingestion of material from the melting of the aluminum fresh air duct. Additionally, the right propeller was positioned near the low pitch setting. This configuration was inconsistent with the emergency procedures outlined in the owner's manual, which require the propeller to be feathered to secure the engine during an engine fire.