What happened
On May 6, 2023, at approximately 14:00 UTC, a Piper PA-25-235, registration LV-MNB, was performing agricultural spraying operations in a rural area near San José, Córdoba. The aircraft, operated by Aviación Agrícola AB S.R.L., was utilizing a temporary dirt runway measuring 650 meters in length.
During the takeoff roll, while carrying 360 liters of liquid spray, the aircraft traveled roughly 200 meters before abruptly veering to the left. The pilot attempted to correct the deviation using right rudder, but the aircraft failed to respond and drifted off the runway limits. The left wing subsequently struck a pile of stacked firewood located on the left side of the path. The impact caused the aircraft to rotate 180 degrees before coming to a stop. The aircraft sustained significant damage to the propeller, engine, wings, and fuselage, though the pilot escaped without injury.
The investigation
The JST investigation focused on the mechanical state of the landing gear and the operational environment. Inspectors noted that the left main wheel was no longer aligned with its axle. Upon searching the site, investigators found that several critical components of the wheel assembly were missing, including the outer half of the wheel, the cone bearing, and the adjustment nut. Only two of the three bolts securing the wheel halves remained in place, and the third showed signs of fracture at the threads.
Investigators also examined the temporary runway conditions. While the pilot had chosen a southward takeoff direction to avoid tall poplar trees at the northern end of the strip, the presence of the woodpile near the runway edge was identified as a factor that increased the severity of the impact.
Findings
- The primary trigger for the accident was the absence of a cotter pin (or the failure of such a pin), which is essential to prevent the axle adjustment nut from unscrewing.
- The rotation of the wheel during takeoff likely caused the adjustment nut to unscrew, allowing the wheel to shift laterally and eventually separate from the axle.
- There was a lack of documented traceability regarding the origin of the wheel components or recent maintenance performed on the assembly.
- The presence of obstacles (the woodpile) near the temporary runway significantly increased the magnitude of the aircraft damage during the excursion.