What happened
On November 11, 2013, a Cessna 152, registration PR-EJW, was conducting a Private Pilot License (PPL) training flight departing from Jundia/SP (SBJD). While performing a series of maneuvers as outlined in the flight briefing, the crew experienced a significant increase in engine vibration, followed by a complete engine failure.
The instructor took control of the aircraft and attempted to restart the engine, but was unsuccessful. To avoid a more critical situation, the instructor executed an emergency traffic pattern to land in an unprepared area, specifically a plantation near Fazenda Campo Verde in Jarinu, SP. During the landing, the aircraft encountered uneven terrain at low speed, causing it to nose over (pilonar). Both the instructor and the student were uninjured, but the aircraft sustained substantial damage to the fuselage, wings, empennage, landing gear, and engine.
The investigation
The investigation focused on the Lycoming O-235-L2C engine, which was disassembled and inspected by professionals from the operator, EJ Escola de Aeronáutica LTDA, under the supervision of CENIPA investigators.
External inspection revealed that the impact of the emergency landing had torn the carburetor bowl from its mount. Within the lubrication system, investigators found scoring on the oil pump housing and a fractured tooth on the drive shaft. Metal shavings were also found in the oil filter, though the volume was deemed insufficient to have caused the failure.
Upon opening the engine block, investigators discovered fractures on the skirts of cylinders 3 and 4, along with damaged, deformed, and overheated connecting rod caps. The crankshaft inspection revealed that the cylinder 4 journal was darkened and misaligned. This misalignment caused an overload fracture in the oil pump drive shaft. Furthermore, the overheating at the journal likely led to the failure of the cylinder 4 connecting rod bolts, while excessive vibration may have loosened a nut on the cylinder 3 connecting rod bolt, initiating a failure sequence.
Fuel samples were tested and found to be clear, clean, and free of water or solid contaminants. The aircraft's maintenance records were up to date, and the aircraft was within weight and balance limits.
Findings
- The primary cause of the engine failure was a failure of the cylinder 4 journal, which led to crankshaft misalignment.
- The resulting misalignment caused an overload fracture of the oil pump drive shaft.
- Overheating at the journal likely caused the failure of the connecting rod bolts on cylinder 4.
- Excessive engine vibration likely caused the failure of the connecting rod bolt nut on cylinder 3.
- The engine failure was not caused by contaminated fuel or insufficient oil filtration.