What happened
On July 1, 2003, an EMB-711C aircraft, registration PT-NDX, departed from Tefé, Amazonas, en route to Coari, Amazonas, for a cargo flight. Approximately 40 minutes into the flight, as the pilot began the descent, the engine experienced two sudden jerks and ceased operation.
The pilot attempted standard in-flight engine restart procedures, but the engine failed to relight. Consequently, the pilot performed an emergency landing in a heavily forested area near Lake Coari. During the impact with trees, the aircraft sustained severe damage, including the separation of the wings. The pilot survived the accident without injuries.
The investigation
CENIPA investigators examined the engine components to determine the cause of the power loss. The inspection revealed that the locking pin of the central gear of the crankshaft was broken. Additionally, the crankshaft fastening bolt was found to be without proper torque, which allowed the gear to shift out of position. This misalignment caused a broken tooth and the total collapse of the gears responsible for transferring movement from the crankshaft to the magnetos, resulting in a loss of engine ignition.
Investigators also reviewed maintenance records and found discrepancies. While a 100-hour inspection had been performed recently, there was no documented record of a 50-hour inspection, and the owner could not provide documentation for the most recent engine overhaul. These gaps suggested potential inadequacies in maintenance execution and oversight.
Findings
- The engine failure was caused by a loss of magneto ignition due to mechanical gear failure.
- A broken locking pin and an improperly torquated bolt allowed the internal gears to shift, leading to mechanical collapse.
- Maintenance discrepancies indicated possible deficiencies in aircraft maintenance quality and management supervision.
- The pilot was properly qualified and the aircraft was within weight and balance limits at the time of the accident.