What happened
On January 17, 1990, a Piper PA-25-260, registration PT-DOF, operated by Aeroagrícola Caiçara LTDA, was performing its first crop spraying mission of the day in Eldorado, São Paulo. Shortly after takeoff, while the pilot was positioning the aircraft for the first spray pass, an audible noise was heard followed by engine oil coating the windshield.
A fire erupted in the engine and quickly spread into the cockpit. Due to the intensity of the flames, the pilot was unable to activate the chemical payload jettison system. The pilot performed an emergency landing into a banana plantation. The aircraft was completely destroyed by the fire, and the pilot sustained severe injuries (burns ranging from 1st to 3rd degree). The impact occurred with the wings level and the aircraft in a zero-degree pitch.
The investigation
CENIPA investigators examined the wreckage of the Lycoming 0540-B2B5 engine. The investigation found that several components, including parts of the cylinder, piston, piston pin, and oil/compression rings, were missing. Analysis of the engine remnants revealed a completely deformed connecting rod and a piston that had split longitudinally.
The investigation also noted that the aircraft had been stationary for a significant period following the harvest season, having flown only 34 hours since its last 100-hour inspection. Investigators also observed that the pilot was not wearing any personal protective equipment, such as fire-resistant flight suits, gloves, or helmets, at the time of the accident.
Findings
- The primary cause of the fire was an engine oil leak that ignited upon contact with the highly heated exhaust manifolds.
- The engine failure was likely caused by internal mechanical failure; the longitudinal split of the piston and the deformation of the connecting rod increased internal friction and heat, leading to the piston seizing against the cylinder wall.
- The pilot was unable to jettison the agricultural chemicals because the flames prevented access to the control lever.
- The pilot's severe burns were exacerbated by the lack of fire-resistant personal protective equipment (PPE).
- The investigation could not definitively determine if the failure was due to material fatigue or improper maintenance, though the possibility of inadequate maintenance during the aircraft's storage period was considered.