What happened
On September 29, 2018, an Air Tractor AT-502B, registration N268TW, was conducting aerial spraying operations over a banana plantation at Finca Palo Blanco, located in the municipality of La Gomera, Escuintla, Guatemala. During the final spray pass of the mission, the aircraft's engine suddenly ceased operation. The pilot was forced to execute emergency landing procedures to bring the aircraft down within the plantation.
The impact resulted in significant damage to the engine, the propeller blades, and the main landing gear. There were no fatalities and no injuries were reported following the event. The surrounding vegetation sustained only minor damage.
The investigation
The DGAC/UIA investigation examined the aircraft's maintenance records, the engine's history, and the physical wreckage. Investigators noted that the engine had been replaced on September 21, 2018, and had accumulated 97.2 flight hours since its repair. Maintenance logs indicated that all scheduled services and inspections had been performed according to the manufacturer's manual and that the aircraft's airworthiness certificate was valid.
Physical examination of the fuel system revealed critical contamination. Investigators found evidence of solid particles and biological growth within the fuel system. Specifically, the primary fuel filter contained solid debris and fuel fungus, while the fuel drained from the primary filter was heavily contaminated. Additionally, residue from tank sealant was identified within the system.
Findings
- The primary cause of the engine failure was a sudden loss of fuel flow to the engine.
- The fuel flow was interrupted by heavy contamination within the primary fuel filter, which included the presence of fuel fungus and solid residues from tank adhesive/glue.
- The aircraft was in a condition of airworthiness regarding its maintenance program and engine components prior to the failure.
- Weather conditions at the time of the accident were calm with no significant cloud cover.