What happened
On January 9, 2022, at approximately 15:30 UTC, an EMB-203 aircraft, registration PT-CYG, was performing a local agricultural spraying mission over a soybean plantation at Fazenda Kaiser in Balsas, Maranhão. The flight, operated for private agricultural purposes, was conducting fungicide application at an altitude of approximately 100 feet.
During the flight, the aircraft experienced a partial loss of engine power. The pilot attempted to maintain control by applying maximum power and extending the flaps to 30 degrees, while simultaneously attempting to return to the takeoff area. However, the aircraft could not maintain altitude and was forced to perform an emergency landing in a nearby crop field. The aircraft sustained substantial damage, but the pilot emerged from the wreckage uninjured.
The investigation
CENIPA investigators examined the engine, fuel, and maintenance records of the aircraft. Analysis of the ethanol fuel showed no signs of contamination. However, a detailed inspection of the Textron Lycoming IO-5-40-K1J5 engine revealed that cylinders #3, #4, and #5 showed external discoloration and internal marks characteristic of detonation.
Testing of the Teledyne Continental Motors magnetos revealed abnormal operation at low RPM and continuity issues within the wiring. Investigators determined that the ignition timing was advanced, which directly leads to detonation and reduced engine efficiency. The investigation traced this issue back to a previous maintenance event performed by a maintenance organization (OM) in September 2021. It was found that the technicians had reinstalled the magnetos without consulting the manufacturer's specific instructions for timing and installation. Additionally, the investigation identified discrepancies in the aircraft's Airworthiness Directive (AD) tracking logs, noting that some applicable directives had not been properly updated or recorded.
Findings
- Improper maintenance of the magneto timing was the primary factor leading to engine detonation and power loss.
- The maintenance organization failed to follow manufacturer-specific manuals for magneto installation.
- Inaccurate maintenance records regarding the compliance and tracking of Airworthiness Directives.
- The pilot was properly qualified, licensed, and medically certified for the operation.
- Weather conditions were favorable for flight at the time of the occurrence.