What happened
On July 25, 2019, a Beechcraft 58, registration PR-RAU, was performing a taxi flight from Manaus to Itaituba, Brazil, transporting a funerary urn. Approximately 20 minutes after takeoff, a propeller blade on the right engine fractured. The separation of the blade caused intense vibrations and a heavy impact against the aircraft's nose, resulting in a hole in the forward fuselage. The pilot attempted to maintain single-engine flight, but the aircraft could not maintain altitude and descended into a forested area near the Novo Célar community in Autazes, Amazonas. The two crew members on board sustained serious injuries, and the aircraft suffered substantial damage.
The investigation
CENIPA investigators discovered that the propeller blade failure was linked to improper maintenance practices. Metallographic analysis of the fractured blade revealed a microstructure altered by heat, suggesting the blade had been superheated—likely during an unauthorized attempt to straighten it—which degraded the material's mechanical properties. Furthermore, investigators found that the serial numbers on all propeller blades had been tampered with.
Technical consultation with the manufacturer, Hartzell Propeller Inc., confirmed that the blades installed on the aircraft were not approved for this specific model. The use of the FC8465-6 model instead of the required FC8475-6 model created discrepancies in blade width and thickness. Additionally, the investigation revealed significant discrepancies in the aircraft's maintenance logs, including unrecorded flight hours, improper entries made in pencil, and a lack of traceability for several components. The aircraft was found to be unairworthy due to these non-compliant parts and inadequate maintenance oversight.
Findings
- Improper maintenance: The propeller blade was superheated to perform an unauthorized repair, compromising its structural integrity.
- Unapproved parts: The installed propeller blades were not certified for use on the Beechcraft 58.
- Maintenance management failures: The operator and the maintenance organization exhibited poor organizational culture, characterized by inadequate record-keeping and a lack of traceability for engines and propellers.
- Tampering: Serial numbers on the propeller blades had been intentionally altered.
- Inadequate oversight: Deficiencies in management processes and supervision allowed unapproved components and substandard maintenance practices to persist.