What happened
On January 18, 2012, an Embraer EMB-720C, registration PT-EOT, was performing a taxi flight from Aeródromo Brig. Protás/de Oliveira, PA, to Chaves/Fazenda Santo Ambrósio, PA. Approximately 25 minutes into the flight, the pilot experienced significant engine vibration accompanied by a loss of power.
To ensure safety, the pilot decided to perform an emergency landing on a private airstrip at Fazenda Memória, located in the municipality of Muaná, PA. Before touchdown, the pilot coordinated with Belém Approach (APP-BE) via a third-party aircraft to relay the emergency status. The landing was completed without incident, and the pilot emerged uninjured. Following the landing, the crew moved the aircraft to a fenced area nearby with the help of a local resident.
The investigation
CENIPA investigators examined the engine components to determine the cause of the failure. Upon disassembly of the engine, investigators found that the fifth cylinder's connecting rod had fractured. The movement of the broken rod had damaged the cylinder walls and the piston skirt.
Analysis of the oil sump revealed metal fragments, including pieces of the fractured rod, bolts, and nuts. The investigation focused on the hardware used in the connecting rod assembly. While Lycoming Service Instruction (SI) No. 1469 recommended the use of high-strength bolts (P/N LW-12596), the investigation found that one of the bolts in use was P/N 75060.
Furthermore, investigators noted that the engine had undergone a 50-hour inspection only eight hours and 55 minutes prior to the accident. During this inspection, metal debris (shavings) in the oil and suction filters—which would have indicated the progressive wear of the bearing due to the loosening nut—was not identified.