What happened
On October 28, 2009, an EMB-720D aircraft, registration PT-VMY, was performing a flight from the São Leopoldo do Tapajós community to the Jacareacanga aerodrome in Pará, Brazil. During the base leg of the approach to Jacareacanga, the pilot experienced a sudden loss of engine power. To avoid a more dangerous situation, the pilot executed a forced landing in an uninhabited, recently cleared area near the final approach path.
The impact with the terrain caused the aircraft to strike a small tree. The force of the landing on the irregular ground caused the main and nose landing gear to detach from the airframe, and the left wing also separated from the structure. Despite the severe damage to the aircraft, the pilot and the passenger were uninjured.
The investigation
CENIPA investigators examined the engine, magnetos, and fuel injection unit to determine the cause of the power loss. The investigation revealed that the engine was generally in good condition, with no signs of internal seizure, fire, or structural failure of the cylinders or pistons. However, several critical maintenance discrepancies were identified.
Investigators found that the fuel injector nozzle for cylinder number 3 was clogged, which likely induced engine vibrations. Furthermore, the investigation identified that a self-locking nut on the diaphragm stem of the fuel injection unit had become loose and was found inside the unit. The inspection also noted that the ignition cabling terminal for cylinder number 3 showed signs of overheating, likely due to improper cleaning methods that did not follow the manufacturer's service instructions.
Findings
- Improper maintenance of the fuel injection unit, specifically the failure to follow manufacturer procedures during the overhaul of the unit, led to the loosening of the diaphragm stem self-locking nut. This caused the interruption of fuel flow and the subsequent engine failure.
- Inadequate maintenance supervision, as the maintenance inspector failed to verify that the overhaul procedures were correctly executed.
- Maintenance practices, including the possible reuse of a previously used nut and the failure to apply appropriate thread-locking compound (Loctite), contributed to the component failure.
- Improper cleaning of ignition components, using unauthorized materials, contributed to high-voltage leakage and engine vibration.