What happened
On January 21, 2004, an EMBRAER E-720C, registration PT-EYI, operated by Amazonaves Táxi Aéreo Ltda., was performing a scheduled flight from Fonte Boa to Santo Antonio do Içá, Amazonas. The aircraft was carrying three occupants and mail bags.
Approximately 15 minutes into the flight, the pilot experienced intense vibrations accompanied by fluctuating oil pressure and a loss of engine power. This was caused by the detachment of a 20 cm section of one of the propeller blade tips. In an attempt to reach an uncertified landing strip in Jutaí, the pilot diverted the aircraft. However, during the final approach, the engine failed completely. Unable to reach the intended runway, the pilot performed a forced landing in a wooded area near Jutaí. During the maneuver, the pilot applied full flaps, leading to an aerodynamic stall. The aircraft sustained severe damage to the fuselage, wings, and landing gear, and was subsequently declared a total loss. Two occupants sustained minor injuries, while the third remained uninjured.
The investigation
CENIPA's investigation focused on the mechanical failure of the propeller and the maintenance history of the aircraft. Investigators examined the propeller, a Hartzell model, and discovered that the serial numbers of the installed blades did not match the records in the aircraft's maintenance logs.
Technical analysis of the propeller revealed that the fracture originated from a cavity on the blade surface caused by Foreign Object Damage (FOD) sustained prior to the flight. This damage led to intergranular corrosion, which weakened the structure until the remaining section failed due to overstress during flight. Furthermore, the investigation found significant discrepancies in maintenance documentation: several 50-hour inspections were missing from the logs, and recent overhaul services were recorded at the maintenance shop but not updated in the aircraft's permanent records. The investigation also noted that a mechanic without a formal link to the primary maintenance provider had performed recent inspections without proper registration.
Findings
- The primary cause of the engine failure was the structural failure of a propeller blade due to a combination of intergranular corrosion and overstress.
- The corrosion was initiated by a notch caused by Foreign Object Damage (FOD) prior to the accident.
- Maintenance and supervision failures contributed to the accident, specifically the lack of traceability regarding the propeller blades and the failure to record essential maintenance tasks.
- The operator failed to ensure that periodic 50-hour inspections were properly documented and performed.
- The pilot failed to detect the visible damage to the propeller blade during the pre-flight inspection, which could have prevented the event.