What happened
On May 18, 2018, a Piper PA-36-375, registration PR-PPJ, was conducting an agricultural spraying mission near Campo Florido, Minas Gerais. While en route to the application area, the pilot heard an unusual noise, followed by a complete engine failure.
In response to the loss of power, the pilot jettisoned the agricultural payload and performed an emergency landing in a field characterized by irregular terrain. The aircraft sustained substantial damage, including impacts to the left main landing gear, the right wingtip, the propeller, the lower part of the rudder, and the left wing root spar. The pilot emerged from the incident uninjured.
The investigation
CENIPA investigators examined the engine and fuel systems to determine the cause of the power loss. Fuel samples taken from both the aircraft tanks and the refueling truck were analyzed; the tests confirmed the use of ethanol, which met all ANP specifications and showed no signs of contamination.
Upon inspecting the engine, investigators discovered that the base of the dual magneto had fractured, leaving the component suspended only by its cables within the engine compartment. While bench tests showed the magneto was functioning normally, a specialized metallurgical analysis by the Institute of Aeronautics and Space (IAE) identified that the fracture was caused by fatigue. This fatigue was facilitated by porosities likely resulting from flaws in the material's manufacturing process.
Investigators also noted that the engine had been converted to operate on ethanol under a Special Flight Authorization (AEV). Because this conversion meant the engine was operating outside its original type certificate specifications, the investigation could not definitively determine if altered vibration, temperature, or compression levels contributed to the accelerated degradation of the component.
Findings
- The engine failure was caused by the fracture of the magneto base, which led to the loss of ignition.
- The fatigue fracture was facilitated by manufacturing porosities.
- The pilot was fully qualified, with valid medical and agricultural licenses, and possessed significant experience in the aircraft model.
- The aircraft was within weight and balance limits, and all maintenance logs were up to date.
- Meteorological conditions were favorable for the flight.