What happened
On December 29, 2021, a Cessna 188B, registration HK-2014, was conducting agricultural spraying operations over a rice crop near Yopal, Casanare. During its second flight of the day, approximately 15 minutes after takeoff, the engine experienced a sudden explosion accompanied by intense vibrations and the emission of white smoke.
Upon identifying the sudden loss of power, the pilot executed a controlled emergency landing in an unprepared field. The pilot, who was uninjured, was able to abandon the aircraft safely. While the airframe and landing gear remained intact, the engine sustained substantial damage, including a total fracture of the oil pan caused by internal components striking the casing.
The investigation
The GRIAA investigation focused on the mechanical failure of the engine, which had operated for 2/24 hours since its last overhaul. Investigators examined the internal components of the engine and identified that the connecting rods at positions 4 and 5 had fractured.
Technical analysis revealed evidence of material fatigue and discoloration caused by high temperatures and friction. The investigation established that the failure originated from a lack of adequate lubrication, which led to the premature aging of the metal and the eventual propagation of cracks in the rods. The investigation also reviewed maintenance records and the operator's quality control procedures regarding engine overhauls.
Findings
- The primary cause of the engine failure was the fracture of the connecting rods at positions 4 and 5, likely resulting from the incorrect installation of engine bearings.
- This improper installation likely caused the bearings to migrate, obstructing the engine's lubrication system.
- The maintenance workshop's inspection procedures were insufficient, as they did not provide adequate guidance for the critical installation and adjustment of bearings.
- The operator's General Maintenance Manual lacked specific, effective procedures to ensure technical control during special tasks, such as the removal and installation of internal engine components.
- The high temperatures and friction caused by the lubrication failure led to the premature fatigue of the connecting rod material.