What happened
On October 10, 2014, a Cessna 172N, registration PR-NAR, was conducting a flight instruction mission from Carlos Prates (SBPR) to Divinópolis (SNDV). The flight involved two pilots and one additional crew member, performing touch-and-go training maneuvers. During the return leg to Carlos Prates, the aircraft experienced a drop in oil pressure accompanied by white smoke.
As the oil leaked, it came into contact with hot engine components, leading to an increase in internal temperatures. This thermal expansion eventually caused the engine to seize. The pilot performed a forced landing in a dry reservoir near the municipality of Juatube, MG. While the three occupants sustained light injuries, the aircraft suffered substantial damage to the engine, propeller, landing gear, and fuselage.
The investigation
CENIPA investigators identified oil trails on the right side of the fuselage, indicating a leak during flight. Upon removing the engine cowling, investigators found that an oil hose had become disconnected from its fitting. Technical analysis of the hose and the coupling elbow by the Department of Aerospace Science and Technology (DCTA) revealed no mechanical damage to the threads that would explain the detachment. The investigation concluded that the disconnection was likely caused by insufficient torque during installation combined with engine vibration.
The investigation also noted that the aircraft had undergone preventive maintenance just two days prior at a local maintenance facility. Following a separate incident involving a Robinson R22 that had also recently undergone maintenance at the same facility, CENIPA conducted a safety inspection of the maintenance provider. The inspection revealed that the fixed-wing maintenance team was understaffed, consisting of only one mechanic, one assistant, and an inspector who was also the company owner. The owner's dual role as manager and inspector led to a lack of oversight and an increased workload, which likely contributed to the improper installation of the oil hose.