What happened
On September 23, 2017, an EMB-720C operated by Aerotur Táxi Aéreo Ltda. departed from the Envira Aerodrome, Amazonas, bound for Tarauacá, Acre. Approximately twenty minutes into the flight, the pilot noticed irregular engine performance. Despite attempting to switch fuel tanks, the engine eventually ceased functioning entirely.
Recognizing the inability to maintain flight, the pilot performed an emergency landing on a beach along the banks of the Envira River. The impact caused substantial damage to the aircraft, including a broken nose gear, damaged main gear fairings, and various superficial damages to the fuselage. The two occupants on board, the pilot and a passenger, were uninjured.
The investigation
CENIPA investigators found that the engine's Lycoming IO-540-K1G5 had experienced significant power loss due to failures in the magneto system. The right magneto was found to be inoperable due to a broken capacitor terminal and a burnt rotor and output terminal. The left magneto was also performing poorly, with improper breaker gap settings and incorrect timing.
Investigation into the maintenance history revealed that the magnetos had undergone a general overhaul only 66 hours prior to the accident. However, the maintenance facility used an incorrect service manual for the S-1200 series magnetos. Furthermore, the investigation could not establish the traceability of internal components used during the overhaul. The operator had accepted parts without sufficient documentation to prove their origin, which may have contributed to the premature wear of the equipment.
Findings
- The right magneto was inoperable.
- The left magneto exhibited deficient sparking due to improper timing and gap settings.
- Lack of traceability for internal components used during the magneto overhaul.
- Use of an incorrect maintenance manual during the previous overhaul process.
- The aircraft was within weight and balance limits and had a valid airworthiness certificate.
- The pilot was properly licensed and rated for the flight.
Safety action
CENIPA issued recommendations to the National Civil Aviation Agency (ANAC) to:
- Ensure the maintenance organization uses only materials with assured traceability.
- Verify that the maintenance organization possesses and applies all necessary resources and technical manuals required for EMB-720C services.
- Instruct the operator to improve administrative and operational procedures for receiving and verifying maintenance services.