What happened
The pilot reported that the aircraft was lightly loaded at the time of departure; however, following takeoff, the aircraft exhibited sluggish flight and climbing characteristics. In an attempt to increase airspeed, the pilot maintained flight within ground effect, but the aircraft failed to respond as expected.
To attempt a recovery, the pilot began dumping the chemical load. Despite this effort, the aircraft continued to settle, eventually touching down in a field and colliding with a tree. The pilot was not injured during the event.
The investigation
The engine was inspected by an FAA airworthiness inspector, who found no evidence of internal engine failure. During the examination, all spark plugs were found to have excessive black soot deposits on the electrodes. Additionally, investigators discovered an unidentified contaminant present throughout the fuel system.