What happened
On February 9, 2021, a Piper PA-A-25-235, registration LV-LXD, was returning to its base in Zaira, Córdoba, following an agricultural spraying mission. While cruising at approximately 500 feet, the aircraft experienced a partial loss of engine power accompanied by a drop in engine revolutions per minute (RPM).
Unable to maintain flight levels, the pilot attempted to manage the condition, but as RPM dropped to approximately 2000, an emergency landing was executed in a soybean field. During the landing sequence, the aircraft traveled roughly 70 meters before flipping onto its longitudinal axis. The pilot exited the aircraft without injuries.
The investigation
The investigation by the JST faced initial challenges as the accident was not promptly reported, and the aircraft was moved to a repair facility before investigators could arrive. Upon inspection, the fuel tanks were found empty, preventing a detailed analysis of the fuel quality.
Mechanical examinations of the engine revealed that the throttle, mixture, and hot air systems were functioning correctly. The air intake and filters were unobstructed, though they contained soybean residue from the landing. While the magnetos and mechanical components were in good condition, investigators focused on the ignition system. Testing of the 12 spark plugs revealed that three spark plugs were experiencing electrical shorts. These shorts were caused by a small, pearl-like conductive particle deposited between the electrodes. Once these particles were removed, the plugs returned to normal operation.