What happened
On May 6, 2005, at approximately 12:30 UTC, a Piper PA-36-285, registration CS-ASW, was performing agricultural rice sowing operations at the Herdade da Foz airstrip near Benavente, Portugal. After completing several successful dispersal missions, the pilot prepared for a final flight of the day.
During the takeoff from runway 16, the pilot applied maximum power and rotated the aircraft at approximately 65 MPH. The pilot then waited for the airspeed to reach 85 MPH before attempting to retract the 20-degree flaps. However, the aircraft struggled to accelerate and could not maintain a sufficient climb gradient to clear large trees located at the end of the runway.
In an attempt to clear these obstacles, the pilot initiated a left turn to approach the wind. This maneuver caused the aircraft to enter a power-off stall/sink condition, leading to a loss of altitude. The aircraft struck the ground in a controlled flight into terrain (CFIT) on a recently plowed field adjacent to the runway. The impact caused the left main landing gear to collapse and the propeller to strike the ground, resulting in significant damage to the engine, propeller, left wing, and the agricultural dispersal system. The pilot emerged from the accident uninjured.
The investigation
The GPIAAF investigation focused on the aircraft's performance capabilities and the operational parameters at the time of the accident. Investigators determined that the aircraft was significantly overweight. While the maximum takeoff mass (MTOM) was 1,996 kg, the actual takeoff mass was calculated at 2,177.80 kg due to a heavy load of wet rice seeds in the hopper.
Technical analysis of the engine revealed it was in good working order and producing normal power for the ambient temperature of 28°C. The investigation also reviewed the pilot's takeoff profile, noting that the use of 20-degree flaps and the decision to rotate at a lower speed, combined with the excessive weight, prevented the aircraft from meeting the required climb gradient to clear the 20-meter-tall trees.