What happened
On December 11, 2010, an Embraer EMB 820C, registration PT-EPY, was conducting an aerial geophysical survey mission near Paulo Afonso, Bahia. The flight, operated by Microsurvey Aerogeof e Cons. Cient. Ltda., carried a pilot and one passenger.
Approximately 20 minutes into the flight, the left engine experienced a significant loss of power, prompting the pilot to shut the engine down. While attempting to return to the departure airfield, the pilot noted indications of overheating in the right engine. Consequently, the pilot executed a precautionary landing near kilometer 70 of the BR 423 highway in Água Branca, Alagoas. The aircraft sustained light damage, including a small dent in one of the right engine's propeller blades, likely caused by debris from the roadside. Both occupants were unharmed.
The investigation
CENIPA's investigation focused on the mechanical failure of the left engine. Investigators identified a fuel leak in the fuel lines (tube assembly PN LW 12098-0-100 and PN LW 1208-0-170). The failure was traced to a rupture in the internal part of fuel line number 3, caused by material fatigue, even though the exterior of the tube showed no visible damage.
The investigation examined the aircraft's maintenance history and found that while the aircraft had recently undergone a 100-hour inspection, there was no evidence that the required inspections for these specific fuel lines—mandated by Service Bulletin SB342E and Airworthiness Directive AD2008-14-07—had been performed. Furthermore, investigators noted that the difficult access required to install certain clamps on these lines could lead to omissions during field maintenance or inspections.
Findings
- Maintenance failure: The required inspections for the fuel lines, as specified by the manufacturer's Service Bulletin and the applicable Airworthiness Directive, were not verified as completed.
- Management supervision: Inadequate managerial oversight regarding maintenance processes contributed to the failure to implement necessary inspections.
- Material fatigue: The rupture of the fuel line assembly was caused by internal fatigue of the material.
- The pilot was properly qualified, and the aircraft was within weight and balance limits with valid airworthiness certification.