Accident Overview
On June 5, 2024, at approximately 0630 eastern daylight time, a Piper PA-25-235 airplane, registration N8715L, was substantially damaged during a forced landing near Colquitt, Georgia. The commercial pilot, who was the sole occupant, sustained minor injuries. The aircraft was being operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight.
Flight Sequence
The flight originated from a private airstrip. The pilot reported that preflight operations were normal. He noted that the engine contained 10 quarts of oil and that no water was detected in the fuel samples. The engine run-up and takeoff were performed without incident; however, as the airplane climbed to an altitude of about 200-300 ft mean sea level, the engine began to "miss" and its speed dropped by approximately 50 rpm. The pilot confirmed that the engine controls were fully forward, but then the engine lost all power. He executed a forced landing into a wooded swamp area. The airplane came to rest upright in shallow water. The pilot exited the aircraft and was met by first responders. Both wings and the fuselage were substantially damaged during the accident sequence.
Wreckage Examination
The wreckage was recovered to a salvage facility for examination. The engine remained partially attached to the firewall through the tubular engine mount. The firewall was cut away, and the engine was placed on a hoist. Rotation of the propeller confirmed continuity of the crankshaft to the rear gears and valvetrain. Compression and suction were present on all six cylinders. A lighted borescope inspection of the cylinder interiors revealed no anomalies. The carburetor was partially disassembled, and approximately two ounces of liquid were found in the bowl; the liquid tested positive for water using water-finding paste. The carburetor floats and other internal components were undamaged. The magnetos were removed and produced spark on all towers when rotated with an electric drill.
Fuel System Analysis
The airplane was equipped with a single, fuselage-mounted fuel tank. The fuel filler cap was secure and in place, with no signs of fuel leakage. The tank vent was unobstructed. The gascolator bowl and screen were removed, revealing residue resembling sand, grit, unknown organic matter, and water. Notably, the lower fuselage in the area of the gascolator had been submerged in swamp water at the accident site.
The fuel shutoff valve from the fuel tank to the gascolator was removed. Its pre-accident position could not be determined due to impact damage to the forward fuselage and engine mount. When manually manipulated, the through-port was not totally obstructed in the "closed" position. The valve arm moved with minimal resistance. Disassembly revealed that the connection to the interior plastic gate was broken, and the gate did not move when the valve stem was actuated. The valve was sent to the NTSB Materials Laboratory for further examination.
Valve Failure Determination
The laboratory examination determined that the valve failed due to two fractured rivets that joined the stem flange to the adjacent internal component. The lower rivet failed from intergranular corrosion attack, while the upper rivet showed signs of overstress bending and shear. This failure allowed the valve stem to move without manual input, obstructing the port and compromising fuel flow to the engine.
Findings
The investigation documented water contamination in the carburetor and gascolator, as well as a failed fuel shutoff valve that could obstruct fuel flow. No other mechanical anomalies were found in the engine or ignition system.