What happened
On June 3, 2024, at 10:45 local time, an Air Tractor AT401, registration EC-IYL, operated by Martínez Ridao Aviación, failed to complete a takeoff from the Isla Mayor airstrip in Seville, Spain. The aircraft was engaged in specialized agricultural operations, specifically the sowing of rice, which involved frequent short cycles of loading seeds and water.
On the day of the accident, the pilot was preparing for the second flight cycle of the day. The aircraft was loaded with 365 liters of fuel, 500 kg of seeds, and 75 kg of water. The pilot noted that environmental conditions, including high temperatures and a significant tailwind, had worsened since the previous flight. To mitigate the tailwind, the pilot performed a static takeoff using brakes and a flap setting positioned between the second and third notch.
As the aircraft accelerated, it reached the midpoint of the runway without achieving liftoff. The pilot attempted an emergency discharge of the seed load to reduce weight; however, the seed discharge was slower than anticipated. Although the aircraft briefly reached an altitude of approximately 7 meters, it could not maintain flight. The aircraft subsequently rolled to the right, entered a stall, and impacted the terrain, coming to rest inverted in a nearby irrigation canal.
The investigation
The CIAIAC investigation examined the aircraft's performance capabilities under the specific environmental conditions present during the event. The investigation analyzed the runway characteristics, noting that the Isla Mayor strip is a partially paved, temporary runway where takeoff direction is often dictated by the location of ground support equipment.
Investigators reviewed the aircraft's flight manual, which specifies that for normal takeoffs, flaps should not be extended, and only a specific 10-degree setting should be used for short runways or maximum loads. The investigation also reviewed video footage of the takeoff, which confirmed the aircraft's trajectory, the presence of a tailwind, and the eventual loss of control.
Findings
- The high ambient temperature (34°C) and high humidity significantly reduced engine power and increased the required takeoff distance.
- The presence of a moderate tailwind (10-15 knots) further increased the necessary runway length by an estimated 24% to 48%.
- The pilot used a full flap configuration, which increased aerodynamic drag and lengthened the acceleration phase, contrary to the flight manual's recommendations for these conditions.
- The aircraft began its takeoff roll 40 meters ahead of the runway threshold, meaning the available runway was insufficient for the required takeoff distance.
- The incorrect calculation of aircraft performance before the flight meant the pilot was unaware that the takeoff was not viable under the existing weight, temperature, and wind conditions.