What happened
On July 28, 2014, an EMB 110P1, registration PT-TAW, departed from Fazenda Estância Hércules (SSFE) in Foz do Iguaçu, Brazil, bound for Curitiba. The flight was a repositioning mission carrying two pilots and two passengers. Shortly after takeoff, the crew detected abnormal vibrations that rapidly increased in intensity.
As the vibrations worsened, the crew attempted to divert to Cataratas Airport (SBFI). However, the intensity of the oscillations made maintaining aircraft control increasingly difficult. The crew eventually made the decision to perform a forced landing in a cornfield approximately 4 NM from SBFI. The aircraft sustained substantial damage to its engines, propellers, landing gear, fuselage, wings, and empennage. The pilot in command and two passengers were uninjured, while the second in command sustained minor injuries.
The investigation
CENIPA investigators determined that the mechanical failure originated from the rudder actuator terminal. The investigation revealed that severe corrosion had compromised the structural integrity of the terminal, leading to its rupture. This failure caused the rudder's balance mass (horn balance) to detach, triggering a flutter phenomenon that produced the intense vibrations experienced by the crew.
Investigators also examined the maintenance history and found that the aircraft's maintenance program did not require the disassembly of rudder compensator actuators to check for corrosion. Furthermore, the protective neoprene cover, which is intended to shield the internal parts of the actuator from contaminants, was missing from the failed component. The presence of a mixture of grease and soil inside the fractured component suggested that external elements had penetrated the assembly.
Findings
- The rupture of the rudder actuator terminal due to corrosion was the primary cause of the vibration and subsequent loss of control.
- The aircraft's maintenance program was inadequate as it did not include specific inspections for corrosion on this component.
- The absence of the protective neoprene cover on the actuator assembly allowed for the accumulation of contaminants.
- Potential issues with crew resource management were noted, as the crew's decision to shut down the left engine—which did not resolve the vibration—may have further complicated aircraft control.
Safety action
Following the investigation, Embraer issued Service Bulletin Alert No. 110-27-A095, providing instructions for inspecting rudder compensator actuator components and replacing parts if corrosion is detected. Additionally, the Brazilian National Civil Aviation Agency (ANAC) issued Airworthiness Directive No. 2014-09-01, mandating detailed inspections for corrosion in these components.