What happened
On April 6, 2016, an EMBRAER EMB-202A, registration PT-VYL, departed from Fazenda Chaparral in Balsas, Maranhão, to perform millet seed spreading operations. Shortly after takeoff, while the pilot was executing a right-hand turn at a low altitude, the engine suffered a failure.
In an attempt to land, the pilot encountered a terrain contour that caused the aircraft to strike the ground, resulting in a broken landing gear. The aircraft slid approximately 40 meters along the surface and underwent a vertical axis rotation, which caused damage to the rear section of the fuselage. The pilot escaped the wreckage uninjured, and there was no fire.
The investigation
CENIPA investigators examined the engine and its accessories, including the fuel pumps, distributor, propeller governor, and magnetos. While the mechanical fuel pump was found to have exceeded its service life by 16.2 hours, bench tests showed its performance was within acceptable parameters.
However, the investigation revealed significant discrepancies in the magnetos. Testing of the right magneto showed insufficient spark due to a lack of necessary magnetization, while the left magneto exhibited current leakage and irregular spark distribution. Upon disassembly, the left magneto showed a cracked distributor block, play in the distributor drive shaft, and metal shavings caused by wear on the bronze bushing. This wear led to increased friction and heat, which melted the platinum fiber, preventing proper opening and causing inefficient sparking.
Furthermore, the investigation found that while maintenance records indicated that special inspections (such as the 500-hour magneto inspection) had been performed, the primary records documenting the actual execution of these tasks were missing from the maintenance facility's files. There was also a hypothesis that the engine might have been washed with aviation gasoline without properly isolating the magnetos, a practice that could cause premature wear, though this could not be definitively proven.
Findings
- Inadequate maintenance supervision regarding the inspection and servicing of the magnetos.
- Failure to perform or document the required 500-hour magneto inspection as specified by the manufacturer's service bulletin.
- Presence of a mechanical fuel pump that had exceeded its specified service life.
- Internal component failure within the left magneto due to excessive wear and heat.