What happened
Shortly after initiating the start sequence for the left engine, the pilot reported hearing a loud explosion. He immediately observed flames spreading from the accessory section of the left engine toward the tip of the left wing and into the cabin. Acting quickly, the pilot shut down the engine by turning off the magnetos. He and his passenger exited the aircraft before the fire intensified. The left wing and cabin were subsequently completely engulfed in flame.
The investigation
Examination of the wreckage revealed extensive fire damage concentrated in the accessory area of the left engine. Fuel and hydraulic lines in this section had been burned to almost complete destruction. Investigators also noted that the fuel caps on both wings had been wrapped with rags, a modification the pilot stated was intended to prevent leaks.
Findings
The pilot reported that the aircraft logbooks were inside the cabin and were destroyed by the fire. He could not recall who performed the last inspection of the aircraft. The presence of rags on the fuel caps suggests an attempt to manage a leak, which may have contributed to the ignition source or fuel availability near the hot engine components.