What happened
On November 21, 2015, a Cessna A188B, registration HK1820, was conducting an aerial spraying mission near Paratebueno, Cundinamarca. After completing pre-flight inspections and loading approximately 160 gallons of agricultural product, the pilot departed from the "El Vaticano" airstrip.
During the initial climb phase, the aircraft experienced a significant reduction in aerodynamic performance. In an attempt to recover flight conditions, the pilot activated the emergency release to jettison the chemical load. Despite this effort, the aircraft lost lift and struck a palm plantation. The impact caused substantial damage to the airframe, including the right wing, propeller blades, and landing gear. The pilot, who was the sole occupant, was uninjured and able to exit the aircraft on his own.
The investigation
The GRIAA investigation focused on the engine's performance during high-power settings. While the engine initially responded normally during ground tests and low-power operations, investigators observed a drop in RPM during power tests with a rich mixture.
Upon disassembling the fuel control unit, investigators discovered internal scratches on the contact faces of the control bushings and excessive tolerance in the control cam relative to the shaft. These physical defects caused an abnormal fuel flow during high-power demands, leading to an overly rich mixture that inhibited efficient combustion and caused the power loss.
Additionally, the investigation reviewed organizational factors, noting that the pilot had exceeded the monthly flight hour limits established by Colombian regulations and that the operator's safety management system implementation was still in a developmental phase.