What happened
On September 8, 2014, a Cessna 182P, registration HK1921, was performing a commercial air transport flight from Mitú's Fabio Alberto León Bentley Airport (SKMU) to the Tapurucuara indigenous community in the Vaupés department, Colombia. After departing from runway 02, the aircraft was approximately ninety seconds into its flight when the engine began to fail and subsequently shut down.
The pilot attempted to return to the airport but was unable to maintain altitude, necessitating an emergency forced landing on the Vaupable River (Caño Cuduyari). Upon impact with the water, the aircraft underwent a dynamic rollover and sank into the riverbed. While the pilot and one passenger managed to evacuate the aircraft, a third occupant in the front right seat sustained a head injury that caused unconsciousness, leading to their death by drowning. The survivors were rescued by local fishermen.
The investigation
The GRIAA investigation focused on the mechanical failure of the engine and the condition of the fuel system. Investigators examined the fuel selector valve and discovered that the upper shaft had been modified with two off-center, non-standard holes. Metallographic analysis using a microscope revealed that the fracture occurred at the coupling of the upper shaft, where a 1 mm separation was present. The investigation established that the fracture pattern showed progressive deformation, characteristic of metal fatigue.
Findings
- The primary cause of the accident was a brittle fracture of the fuel selector valve's upper shaft due to material fatigue, which interrupted the fuel flow and caused the engine to shut down.
- Improper maintenance practices were identified, specifically the performance of aeronautical work that did not meet the standards required by the manufacturer's maintenance manuals.
- Inadequate supervision by the maintenance department allowed non-standard modifications (the off-center holes) to persist on a critical component.
- The geometry of the unauthorized holes created stress concentrations that accelerated the fatigue process.