What happened
On December 19, 2018, a Rockwell S-2 Thrush Commander, registration HK5253, was conducting agricultural spraying operations over banana crops in the Zona Bananera region of Magdalena, Colombia. The aircraft, operated by Aero Agropecuaria del Norte, Aeropenort S.A.S., was flying at approximately 300 feet while en route to the Bonanza farm after completing a previous spray run.
During the flight, the aircraft experienced a sudden loss of engine power, with engine RPM dropping from 1,650 to 1,100. The pilot attempted standard cockpit procedures to recover power but was unsuccessful. Following emergency protocols, the pilot emptied the chemical payload to reduce weight and initiated an emergency landing in a banana plantation. The aircraft performed a controlled landing but struck banana palms during the landing roll, coming to a stop 30 meters further into the field. The pilot, who was the sole occupant, exited the aircraft uninjured.
The investigation
The GRIAA investigation focused on the mechanical integrity of the Pratt & Whitney R-1340-S3H1-G engine. While maintenance records indicated the aircraft was airworthy and compliant with all required services, investigators identified a fracture in cylinder number 7.
To determine the nature of the failure, the cylinder assembly was sent to the NTSB in the United States for metallographic inspection. The analysis revealed an intergranular fracture within the cylinder head housing. Investigators examined whether the failure resulted from operational stresses, improper maintenance, or manufacturing defects.
Findings
- The primary cause of the accident was a powerplant failure at low altitude caused by a fracture in the cylinder head housing.
- The fracture was identified as an intergranular failure, which likely originated from defects during the manufacturing process, specifically related to improper heat treatments or machining of the alloy.
- This structural failure led to a loss of combustion pressure within the cylinder, resulting in insufficient power to maintain flight speed.
- The pilot was found to be fully qualified, with valid medical certification and recent training, and acted appropriately to execute the emergency landing.