What happened
On November 30, 2008, an EMB 711C, registration PT-NIQ, operated by Aeroclube de Ourinhos, departed from Estância Hércules in Foz do Iguaçu, Brazil, bound for Fortuna, São Paulo. The aircraft was carrying one pilot and three passengers.
Approximately 30 seconds after takeoff from runway 35, the engine suffered a failure, resulting in a significant loss of power and intense vibration. The pilot, unable to maintain altitude, chose to turn in the opposite direction of the standard departure procedure to avoid the high-voltage transmission lines of the Itaipu Dam. The pilot managed to maintain flight for approximately four minutes, during which time the electric fuel pump was activated and flaps were partially deployed. The flight concluded with an emergency landing on the Paraná River. The aircraft remained submerged for approximately 30 hours before being recovered, sustaining severe damage to the fuselage and empennage. All four occupants emerged from the wreckage uninjured.
The investigation
CENIPA investigators examined the wreckage of the engine after it was recovered from the river. During the disassembly of the engine, several components from cylinder number 3 were found to be missing, specifically the rocker arm shaft retaining cover, the shaft retaining cover nuts, and associated washers.
Analysis of the gasket on the retaining cover showed no signs of compression, suggesting that the nuts were either not tightened to the proper torque or the cover was never installed. The loss of this cover allowed the rocker arm shaft to dislodge, preventing the exhaust valve from opening and obstructing the necessary gas release for combustion. Furthermore, investigators noted the absence of torque paint on the cylinder 3 mounting nuts, indicating that maintenance had been performed on this cylinder, yet no record of such service existed in the aircraft's maintenance logs.
Findings
- Inadequate maintenance service was the primary cause of the engine failure, specifically the improper installation or failure to secure the rocker arm shaft retaining cover.
- Lack of proper management supervision allowed for discrepancies in maintenance records and a failure to verify the integrity of critical engine components.
- The engine failure was characterized by a loss of power in cylinder number 3 due to the inability to exhaust combustion gases.