What happened
On January 28, 2010, an EMB 202A, registration PT-UPW, was performing a ferry flight from Joaçaba, SC, to Ponta Grossa, PR, for scheduled maintenance. While cruising at flight level 075, the aircraft experienced intense engine vibrations accompanied by a significant loss of power.
The pilot attempted to divert to the aerodrome in União da Vitória, PR, but the loss of altitude and power made reaching the runway impossible. Consequently, the pilot performed a forced landing in a soybean plantation approximately 7 km from the runway. The aircraft slid 200 meters before coming to a complete stop. The pilot was uninjured, though the aircraft sustained damage to the engine and approximately 2,400 square meters of the soybean crop were affected.
The investigation
CENIPA investigators examined the engine components and the intake valve of cylinder number 6. The inspection revealed that the intake valve stem had fractured, the valve head had fragmented, and the valve stem was bent. Fragments from this valve had traveled through the intake ducts, causing secondary damage to the pistons and fuel injectors in cylinders number 2 and 4.
An analysis by the manufacturer, Embraer, identified fatigue mechanisms related to side-loading and bending loads at the valve end. Hardness testing also revealed discrepancies in material hardness between the valve body and the area near the fracture surface. Investigators also considered whether maintenance non-conformities, such as improper assembly of the split retaining washer or misalignment of contacting parts, could have contributed to the failure.