What happened
On May 7, 2002, at approximately 12:00 local time, a Piper PA-25-235 (registration EC-BGD) was performing agricultural spraying operations near Almo-harín, Cáceres. The pilot was conducting rice sowing missions using an improvised runway consisting of a livestock path. At the time of the incident, the aircraft was loaded with 250 kg of rice seed and approximately 80 kg of fuel.
During the takeoff roll toward the northeast, the aircraft experienced a sudden leftward veer as it approached rotation speed. This maneuver caused the aircraft to depart the runway and overturn, coming to rest in an inverted position. The impact triggered a fire in the engine compartment, which quickly spread throughout the airframe. The pilot sustained minor injuries (second-degree burns) but managed to evacuate the aircraft before it was destroyed by the flames.
The investigation
The investigation focused on the mechanical condition of the aircraft and the environmental conditions of the improvised runway. Investigators found no evidence of mechanical failure, such as a tire burst or landing gear breakage, to explain the sudden deviation.
Analysis of the runway revealed that the path was only 6 meters wide, flanked by cereal fields with 2-meter safety strips, totaling 10 meters of usable width. Because the Piper PA-25-235 has a wingspan of 11 meters, the wingtips extended beyond the safety margins. Furthermore, the investigation noted that the fuel tank in this model is located behind the firewall, making the aircraft highly susceptible to post-impact fires if spilled fuel reaches hot engine components.
Findings
- The primary cause of the accident was a wind variation acting on the aircraft.
- Moderate southeasterly winds were blowing at a 90-degree angle to the runway.
- This crosswind caused a directional imbalance and a slight roll, lifting the right wing and lowering the left wing.
- The left wingtip caught on the adjacent cereal crops, creating a torque that induced the sudden left turn and subsequent excursion.
Safety action
Following the accident, it was noted that agricultural operations often require using improvised fields that may lack adequate width, length, or surface quality. To mitigate these risks, operational manuals for aerial work should include specific procedures for selecting and preparing takeoff sites, including:
- Thoroughly examining the area around treatment zones to find the best possible improvised runway.
- Improving runway surfaces, width, or length, and removing obstacles whenever possible.
- Limiting operating conditions (such as crosswind components, temperature, or aircraft load) when using runways with known deficiencies.