Incident Overview
On 9 February 2021, a Piper PA-25-235 aircraft, registration LV-LXD, operated by Aviagro S.R.L., was returning to its base in Zaira, Córdoba, after completing an agricultural application flight. While cruising at an altitude of 500 feet, the engine experienced a partial loss of power, accompanied by a drop in the RPM indicator. The pilot's attempts to restore power were unsuccessful, and when the RPM reached approximately 2000, he decided to perform an emergency landing in a soybean field. During the landing, the aircraft rolled for about 70 meters before overturning onto its back. The pilot exited the aircraft without sustaining any injuries.
Investigation Findings
The accident was not initially reported to the Junta de Seguridad en el Transporte (JST). The aircraft was disassembled at the site and transported to the operator's facilities without coordination with the investigation body, which hampered evidence collection. Upon arrival, the investigator found the aircraft loaded on a truck; the wing and fuselage fuel tanks were empty, preventing determination of the fuel quantity and condition at the time of the accident.
The engine was examined and showed no mechanical failures. The throttle, hot air, and mixture controls were continuous and free-moving. The air intake was unobstructed, and the air filter was in good condition, despite containing soybean plant debris from the emergency landing. The hot air system operated correctly.
The fuel system was inspected: the fuel filters and gascolator were checked, and fuel was present in the carburetor bowl. However, no fuel samples could be taken from the tanks as they had been drained.
The magnetos and spark plugs were bench-tested. The magnetos functioned properly. Of the 12 spark plugs, three were found to be short-circuited, showing electrical continuity between the positive electrode and ground. The failure mode was identical in all three: a conductive bead-like particle inside the plug bridged the electrodes. After removing the particles, the spark plugs regained normal function.
The technical representative of the repair workshop provided photographs confirming the good internal condition of all engine components.
Conclusion
No explicit probable cause was stated in the investigation report. The incident was attributed to a partial power loss resulting from three spark plugs being shorted by conductive particles.