What happened
On August 13, 2016, an Air Tractor AT-301, registration HK-5162, was conducting aerial spraying operations near Ciénaga, Magdalena, Colombia. The aircraft had departed from the "La Lucha" airstrip for a scheduled mission at a nearby farm.
After reaching an altitude of approximately 400 feet, the pilot reduced power as part of the standard flight profile. At that moment, a loud noise was heard from the engine, followed by a significant loss of power. The pilot immediately initiated emergency procedures, which included the emergency discharge of the chemical payload, and attempted to return to the airfield. However, due to the engine failure at low altitude, the pilot was forced to perform a controlled landing in an unprepared banana plantation at Finca San José.
During the landing, the aircraft struck banana trees, causing the plane to pivot 90 degrees onto its engine side. The pilot sustained minor injuries and was assisted by local residents. The aircraft sustained substantial damage, including engine mount deformation and damage to the propeller and landing gear.
The investigation
The GRIAA investigation focused on the sudden loss of engine power. A specialized inspection of the Pratt & Whitney R1340-AN1 engine was conducted in Villavicencio. The examination revealed that the cylinder head of number two cylinder had fractured, leading to oil leakage and a significant drop in RPM, which rendered the engine inoperable.
The investigation also scrutinized the operator's maintenance practices. Investigators found that while the aircraft had a valid airworthiness certificate, the operator lacked clear procedures for the traceability of engine components. Furthermore, there was no evidence of a maintenance program specifically designed to account for the age of the engine components to prevent fatigue-related failures.
Findings
- The primary cause of the engine failure was the fracture of the number two cylinder head due to material fatigue or the expiration of the component's useful life.
- The forced landing was a direct consequence of the loss of engine power while flying at a low altitude.
- The operator's maintenance programs were deficient, as they did not implement preventive measures based on the age of the engine and its components.
- There was a lack of maintenance records regarding the traceability of specific engine components, making it impossible to determine the service history of the failed cylinder.