What happened
On August 21, 2020, an EMB-710C Embraer Turboprop, registration PT-NHW, was performing a ferry flight from Belém (SBJC) to Macapá (SJKI) with one pilot and two passengers on board. Approximately three minutes before reaching the destination, the aircraft's engine suffered a complete failure while at an altitude of approximately 1,000 feet. The pilot executed an emergency landing on the Amazon River, near the riverbank. While the aircraft sustained substantial damage due to the impact and the high salinity of the water, the pilot sustained only minor injuries, and both passengers were uninjured.
The investigation
CENIPA investigators examined the engine, the fuel, and the maintenance records of the aircraft. Fuel samples taken from the tanks showed no signs of contamination and met all required specifications. The engine, a Lycoming 0-540-B4B5, was inspected and disassembled. Although the engine was found to be seized due to internal oxidation caused by water ingress during the investigation process, investigators focused on the components present at the time of the failure.
Testing of the magnetos revealed that both units were inoperable due to carbonization and the presence of verdigris (copper oxidation) on the contact points. The investigation also noted that a recent maintenance event involving a propeller change had occurred, and a previous test flight had revealed a fuel pump leak that was subsequently repaired. Investigators also considered whether the pilot's decision to continue the flight, despite experiencing abnormal vibrations earlier in the flight, played a role in the outcome.
Findings
- The primary cause of the engine failure was the malfunction of both magnetos, which interrupted the electrical current to the spark plugs.
- The magneto contact points exhibited significant carbonization and verdigris, which hindered electrical flow and generated excessive heat.
- The pilot's decision-making process contributed to the event, as the flight continued toward the destination after an initial period of abnormal vibration was experienced.
- The aircraft was within weight and balance limits, and all required certifications and pilot licenses were valid.