What happened
On April 5, 2015, a Neiva 152, registration PR-CRL, was conducting a flight training mission from Bragança Paulista to Araras, Brazil. The aircraft was carrying two crew members, including an instructor and a student pilot. While cruising at 5,500 feet in the São Paulo Terminal sector, the engine suddenly ceased operation.
Following the failure, the instructor took control and attempted to restart the engine, but the attempt was unsuccessful. The crew performed an emergency landing in a field at Fazenda Marpland, near Itatiba, São Paulo. During the landing, the aircraft struck an uneven patch of terrain, resulting in a nose-down impact. Both occupants of the Neiva 152 escaped the accident without injury, though the aircraft sustained substantial damage.
The investigation
The investigation conducted by SERIPA IV focused on the mechanical failure of the engine. The engine was disassembled by a certified maintenance organization and inspected by specialists from the Institute of Aeronautics and Space (IAE).
Investigators identified radial and axial displacement of the bearings in the central main bearing of the engine semi-casings. This displacement restricted the flow of lubricating oil to the crankshaft journals, specifically affecting the third cylinder. The resulting lack of lubrication caused extreme overheating, which pushed the bearings, connecting rod caps, and bolts into the material's plastic temperature zone. This thermal stress led to the failure of the connecting rod cap bolts due to overload, triggering the total engine failure.
Findings
- The engine failure originated from the displacement of the central main bearing components.
- The overheating was caused by insufficient oil flow to the crankshaft journals.
- The investigation could not definitively determine if the displacement was caused by a loss of torque in the engine block studs or a dimensional error in the block bearings.
- A possible failure during the engine's last overhaul was suspected, as the displacement of the bearings may have been a result of improper assembly. However, a lack of records regarding the processes and parts used during the previous overhaul prevented investigators from confirming the exact origin of the faulty components.