What happened
On August 24, 2004, a Cessna 210L, registration PT-KGG, was performing a flight from São Félix do Xingu to Aero Xingu in the state of Pará, Brazil. The aircraft was carrying one pilot and three passengers. Approximately 70 minutes into the flight, while cruising at 7,500 feet, the number one propeller blade fractured in flight. This failure triggered intense engine vibrations.
Recognizing the imminent loss of control, the pilot reduced power and shut down the engine to execute an emergency landing. The aircraft struck the canopy of trees in the Kuatine Indigenous Reserve, entered a dive, and collided with the ground. The impact caused severe damage to the airframe, engine, and instrument panel. The pilot sustained serious injuries, while the three passengers suffered minor injuries.
The investigation
CENIPA's investigation focused on the mechanical failure of the propeller and the maintenance history of the aircraft. The investigation revealed that the aircraft had recently undergone significant maintenance, including an engine replacement and a propeller overhaul.
Technical examinations of the fractured blade identified two distinct failure zones: a flat fracture surface indicative of fatigue and a 45-degree fracture surface characteristic of an overload. Scanning electron microscopy (SEM) confirmed that the fatigue originated from corrosion pits on the trailing edge, which acted as stress concentrators.
Furthermore, the investigation uncovered significant discrepancies in maintenance documentation and procedures. It was discovered that the propeller blades being serviced lacked proper traceability, as their serial numbers did not match the documentation provided to the maintenance facility. Additionally, the propeller pitch angles had been incorrectly adjusted for a different engine model, subjecting the blades to much higher operational stresses than intended.