What happened
On July 30, 2020, a Cessna 172K, registration HK2129, was operating a non-scheduled air taxi flight from Pacoa to Leticia, Colombia. The aircraft was carrying one pilot and two passengers. During the flight, the pilot noticed a burning smell and observed that the engine oil temperature had risen to 240°F, while oil pressure began to drop.
As the aircraft approached the Tarapacá area, the pilot attempted to manage the emergency by jettisoning baggage to reduce weight. At approximately 18:01 UTC, the pilot declared a "MAYDAY" via radio, stating the aircraft was entering the vicinity of the Ticuna population. The pilot intended to perform a controlled water landing on the Putum and River.
The aircraft successfully performed a controlled landing on the surface of the river. However, after coming to a stop, the aircraft began to submerge. While the two passengers were able to evacuate the aircraft on their own, the pilot was unable to escape and sustained fatal injuries due to the submersion.
The investigation
The GRIAA investigation focused on the mechanical failure of the power plant and the sequence of events leading to the engine's loss of performance. Investigators examined the engine components, specifically the lubrication system and the condition of the internal parts. The investigation also reviewed radio communications between the aircraft, a passing Cessna U206G, and a Colombian Air Force transport aircraft (FAC5078) to establish the timeline of the emergency.
Findings
- The primary cause of the accident was a forced water landing caused by abnormal engine operation, characterized by low oil pressure and high operating temperatures.
- The engine failure was driven by the fracture, detachment, and deformation of the bolts and the cap of the No. 1 connecting rod.
- This mechanical failure rendered the No. 1 cylinder inoperable, primarily due to the operation of dynamic parts under insufficient lubrication.
- It is believed the engine was operating with an insufficient quantity of oil, which progressively depleted during flight, leading to high friction and elevated temperatures.