What happened
On August 30, 2009, an EMB-711ST aircraft, registration PT-NYL, was conducting an instrument flight rules (IFR) training mission from Itápolis to Jundiaability, Brazil. During the descent, while crossing 7,000 feet, the crew experienced a sudden engine failure accompanied by a loud metallic noise, the smell of burning, and white smoke inside the cabin.
In response to the emergency, the crew shut down the engine and the electrical system. After declaring an emergency with Air Traffic Services, the pilot attempted to reach the Jundiaí airport but determined the aircraft could not reach the runway. The pilot instead opted for an emergency landing in a plowed field near Limeira. During the final approach, the crew identified an obstacle—a fence—in their path. The instructor directed the pilot to use full flaps to gain momentary lift to clear the fence, followed by a command to retract the flaps. This maneuver caused the aircraft to lose lift and strike the ground with a high sink rate, resulting in severe damage to the aircraft. The instructor and the student pilot sustained light injuries, while the passenger remained uninjured.
The investigation
CENIPA investigators examined the engine components and found that the failure originated from the fracture of the connecting rod in cylinder number one. The investigation revealed that the fracture was caused by a fatigue mechanism. This process was likely accelerated by the presence of corrosion and micro-cracks, which acted as stress concentrators.
Technical analysis of the part showed that the rod's measurements were very close to the minimum threshold recommended for replacement. Furthermore, investigators noted that the crew and local air traffic services failed to promptly notify the regional investigation office (SERIPA IV) of the occurrence, as required by regulations.
Findings
- Fatigue failure of the cylinder number one connecting rod due to a fatigue mechanism.
- Presence of corrosion and micro-cracks that facilitated the fatigue process.
- Maintenance uncertainty regarding whether corrosion or micro-cracks could have been detected during previous inspections.
- The engine components were at the limit of their service life specifications.
- The emergency landing maneuver, specifically the retraction of flaps to clear an obstacle, contributed to the high sink rate upon impact.