What happened
On August 2, 2022, a Piper PA-28-161, registration HK-5382G, was conducting a solo student training flight departing from Ernesto Cortissoz International Airport in Soledad, Colombia. The flight plan involved a route from Barranquilla to Corozal and back.
During the cruise phase near Quinta del Río, the student pilot reported engine irregularities to Air Traffic Control and requested to return to the departure airfield. While approximately 5 nautical miles from the airport, the engine suffered a catastrophic failure characterized by an explosion and a significant oil leak. The pilot declared an emergency and executed a controlled power-off landing on runway 05. The pilot exited the aircraft uninjured, and while the engine sustained heavy damage, the airframe remained intact.
The investigation
The GRIAA investigation focused on the mechanical failure of the Lycoming O-320-D3G engine. Investigators examined the engine components, including the crankshaft, connecting rods, and the crankcase. The analysis revealed that the engine's internal components had suffered severe trauma, including perforations in the crankcase near cylinders 1, 2, 3, and 4, and fractures in the rod caps.
Additionally, the investigation noted procedural irregularities regarding the incident management. The flight school's maintenance organization performed an engine disassembly without the required authorization from the accident investigation authority. Furthermore, the school failed to notify the DIACC of the serious incident as required by Colombian aeronautical regulations, which hindered the transparency of the initial investigation process.
Findings
- The primary cause of the engine failure was the complete fracture of a connecting rod bolt, which created a catastrophic imbalance in the engine's rotating assembly.
- The fracture was likely driven by metal fatigue, potentially initiated by surface irregularities or corrosion.
- The failure caused perforations in the crankcase, leading to a rapid loss of lubrication.
- The resulting loss of oil exposed the crankshaft to extreme friction and overheating, evidenced by blue discoloration on the cylinder No. 4 rod bearing seat.
- Secondary internal damage to the rod caps and accessory housing further compromised the engine's integrity.