What happened
On March 20, 2015, a Cessna TU206G, registration HK2327, was conducting a non-scheduled passenger flight from Mitú to the indigenous community of San José de Cananarí in the Vaupés department of Colombia. Shortly after takeoff from the Fabio León Bentley airfield, the aircraft began experiencing power fluctuations during the initial climb.
As the aircraft reached approximately 2,800 feet, the pilot noticed the manifold pressure indicator fluctuating. Despite attempts to regain power, the manifold pressure dropped significantly to 18 inches. Realizing the engine could no longer maintain altitude, the pilot declared an emergency and attempted to return to the airfield, but the aircraft continued to descend at a rate of 100 feet per minute.
To avoid a more catastrophic impact, the pilot executed an emergency landing on the Vaupés River near Puerto Corroncho. Upon impact with the water, the aircraft submerged rapidly. While the pilot and one passenger managed to evacuate the sinking aircraft with minor injuries, two other passengers were unable to escape and died in the accident.
The investigation
The GRIAA investigation focused on the mechanical failure of the Continental TSIO-520-M engine and the circumstances surrounding the emergency landing. Investigators examined the engine components and discovered that a section of an exhaust valve guide from cylinder number one had broken off and been ingested by the turbocharger. This ingestion caused the turbocharger to malfunction, preventing the engine from generating necessary manifold pressure.
Furthermore, the investigation looked into the operational procedures of the operator, Aerolíneas Llaneras - ARALL LTD. It was established that the engine had been subjected to prolonged periods of operating under lean mixture settings, which likely contributed to the fatigue of the valve guide component due to thermal cycling.