What happened
The incident occurred while the aircraft was returning from a fire patrol flight. During this phase of the operation, the engine lost power unexpectedly. In response to the mechanical failure, the pilot initiated a forced landing in an adjacent field. Upon touchdown, the aircraft encountered soft dirt conditions which caused it to run forward and nose over.
The pilot reported that he had departed with full fuel tanks, a status he had visually confirmed prior to takeoff. The flight profile involved initial operation on the left tank for 1.5 hours, followed by a switch to the right tank for 2.1 hours. When the right tank became empty, the pilot switched back to the left tank in an attempt to restore engine power, but this action was unsuccessful.
The pilot noted that previous patrol flights lasting approximately 3.5 hours typically resulted in 5 to 6 gallons of fuel remaining. He estimated fuel quantity based on the known average consumption rate and elapsed time rather than relying on the aircraft's fuel gauge indications, which he considered inaccurate.
The investigation
A post-crash examination of the aircraft revealed critical findings regarding the fuel system. Investigators found no evidence of any fuel remaining in the fuel system at the time of the crash. Additionally, the inspection identified that the gasket for the left tank fuel cap was missing. A large fuel stain was observed in the area surrounding the left tank filler opening, suggesting a potential leak or spillage point.
Findings
The primary factor leading to the accident was fuel exhaustion. The investigation highlighted that the pilot's reliance on time-based fuel estimation rather than direct gauge readings contributed to the outcome. The missing gasket on the left tank fuel cap may have allowed fuel to escape, further reducing the available supply during the extended patrol mission.