What happened
On June 22, 2023, at approximately 10:32 local time, a Cessna A188B agricultural aircraft, registration HK-1971, was performing crop spraying operations near Puerto López, Meta. While executing the final pass of a field boundary at low altitude, the engine experienced a sudden loss of power.
The pilot attempted an emergency landing in an adjacent uncultivated field. During the approach, the aircraft's wingtips made contact with thin branches of young trees situated in a narrow gap. Although the pilot maintained control, the aircraft's main landing gear sank into the soft earth upon touchdown. This caused the nose to pitch forward, leading to propeller impact with the ground, a sudden stop, and the aircraft subsequently flipping onto its longitudinal axis, coming to rest in an inverted position.
Despite the significant structural damage to the airframe, propeller, and engine cowling, the pilot escaped the wreckage uninjured.
The investigation
The GRIAA investigation focused on the mechanical state of the Continental IO-520-D engine and the maintenance history of the aircraft. Investigators examined the engine components and found that the number 1 and 2 crankshaft support bearings were fractured and displaced from their seats. Additionally, the investigation identified a fractured rocker arm support bolt on cylinder number 6.
Technical analysis suggested that the fracture of the rocker arm bolt likely caused engine vibrations. These vibrations, combined with the bearing failures, led to restricted lubrication, which eventually caused the unrecoverable engine failure. The investigation also noted that a manufacturer service bulletin regarding the engine identification plate had not been implemented.
Findings
- The primary cause of the accident was an emergency landing in an unprepared field following a loss of engine power.
- A contributing factor was the fracture of the rocker arm shaft bolt on cylinder No. 6, which induced engine vibrations.
- The fracture and displacement of the number 1 and 2 crankshaft bearings resulted in insufficient lubrication, leading to the engine failure.
- The pilot reported low oil pressure (approximately 45 PSI) prior to the failure.