What happened
On July 12, 2014, an Air Tractor AT301, registration HK4615, was performing an agricultural spraying mission over the El Retiro lot in Carepa, Antioquia. The aircraft, operated by Fumigaray S.A.S, departed from Los Almendros airfield carrying 300 gallons of fungicide and 75 gallons of fuel.
During the initial climb phase, the pilot noticed a progressive loss of power accompanied by a decrease in manifold pressure. The pilot immediately executed emergency checklists and, after receiving no positive response, decided to return to the departure runway. During the return maneuver, the engine emitted black smoke and subsequently failed. To avoid a row of trees, the pilot performed a forced landing in an unprepared field. During the descent, the aircraft struck the canopy of a tree before impacting the ground. The impact caused significant structural damage, including the separation of the engine from its mounts and damage to the landing gear.
The investigation
The GRIAA investigation focused on the engine, the carburetor, and the fuel system. Laboratory testing of the Pratt & Whitney R1304-AN1 engine showed that the engine performed normally during a ground run, and no contamination was found in the fuel samples. However, the investigation noted that the carburetor could not be functionally tested because its control system was damaged during the accident.
Investigators also examined the cockpit configuration, noting that the fuel selector valve lacked clear position markings (ON/OFF), which could potentially lead to pilot error during emergency procedures. Maintenance records for the aircraft and engine were found to be up to date.
Findings
- The pilot was uninjured and able to exit the aircraft on his own.
- The engine failed during the return maneuver after emitting black smoke.
- The possible failure in the air-fuel mixture supply system from the carburetor was identified as the primary cause of the power loss.
- The aircraft sustained heavy damage, including a fractured left main gear, a detached right wheel, and engine separation.
- The weather conditions were visual and did not contribute to the accident.