What happened
On May 31, 2021, a Piper PA36-285 was performing agricultural seeding operations near Virtudes, Azambuja, Portugal. The aircraft, operated by Shamrock, Lda. with registration CS-DDL, was carrying approximately 600 kg of rice seeds. During the mission, the pilot attempted to realign the aircraft with a specific swath after receiving radio instructions from ground flaggers.
While executing a 180-degree left turn to reposition the aircraft, the pilot experienced a sensation of engine power loss and heard the stall buzzer. The aircraft entered a left-wing-low and nose-down attitude. Despite attempts to level the wings and increase airspeed, the aircraft could not be recovered and struck the ground at a steep nose-down angle of more than 60 degrees. The impact caused the engine, hopper, and landing gear to separate from the fuselage. The aircraft eventually came to rest in an inverted position. The pilot sustained only minor injuries and was able to exit the wreckage independently.
The investigation
The GPIAAF investigation established that the aircraft's total mass at the time of the accident was estimated at 2,096 kg, which was above its maximum authorized takeoff mass. The investigation also noted that the pilot was not wearing a flight suit or protective helmet, as these were not provided by the operator. Technical examination of the wreckage confirmed that all flight control surfaces were intact and there was no evidence of in-flight structural failure. The damage to the propeller was consistent with the engine producing power at the moment of impact.
Findings
- The primary cause of the accident was an abrupt asymmetric aerodynamic stall during a steep maneuvering turn.
- The aircraft was operating at a weight exceeding its maximum allowable takeoff mass.
- The pilot experienced a perceived loss of power and an aerodynamic stall while attempting to correct the flight path.
- The pilot's training and experience validation processes for specialized operations required more rigorous oversight.