What happened
On July 19, 2011, an Embraer EMB-711C, registration PT-NEX, was performing a ferry flight from São Luís, MA, to Belém, PA. The flight was being conducted under a Special Flight Authorization issued by ANAC to transport the aircraft to a maintenance facility for repairs. Although the authorization restricted the transport of passengers, a mechanic was on board alongside the pilot.
During the descent, approximately 20 nautical miles from the destination, the pilot noticed a significant engine oil leak. The leaking lubricant coated the windshield and other parts of the aircraft, leading to a drop in oil pressure, increased engine temperature, and noticeable engine vibration. To prevent further engine damage, the pilot executed an emergency landing in a pasture at Fazenda Guará, near Marituba, PA. The aircraft sustained light damage to the propeller, the left wing tip, and the landing gear, but the pilot and the passenger escaped without injury.
The investigation
CENIPA investigators examined the engine components and maintenance records of PT-N0X. The investigation revealed that the aircraft's airworthiness certificate had been suspended due to a previous wing defect. Investigators found that the engine's oil pressure line assembly contained an unauthorized repair weld and significant corrosion near the elbow connection.
Furthermore, the investigation identified that the elbow installed in the engine was made of aluminum (P/N MS20822-6D). However, Lycoming Mandatory Service Bulletin SB 240S required the use of a steel elbow (P/N MS208226) to prevent similar failures. Additionally, the investigation found that required mounting clamps specified in Airworthiness Directive 90-04-06 R1 and Service Bulletin 488A were missing from the oil pressure line assembly. Maintenance logs for the airframe, engine, and propeller were also found to be outdated.
Findings
- Improper maintenance of the engine oil pressure line assembly.
- Use of an incorrect aluminum elbow instead of the required steel version.
- Presence of an unauthorized weld and severe corrosion on the oil tube assembly.
- Failure to implement mandatory Lycoming Service Bulletins and Airworthiness Directives regarding component replacement and installation of securing clamps.
- Inadequate maintenance management and oversight regarding the execution of mandatory service instructions.