What happened
On November 29, 2022, at approximately 12:35 UTC, a Cessna A188B agricultural aircraft, registration PT-WMK, was performing pesticide application maneuvers over the Fazenda São Paulo area in Gaúcha do Norte, Mato Grosso. During the operation, the aircraft experienced an engine failure, forcing the pilot to perform an emergency landing into a wooded area.
The aircraft sustained substantial damage during the impact with the trees, though the pilot emerged from the wreckage uninjured.
The investigation
CENIPA investigators examined the aircraft's maintenance history and the condition of the powerplant. The Continental IO-540-K1G5D engine had flown only 50 hours since its last 50-hour inspection and 75 hours since its overhaul. The investigation included a teardown of the engine and a bench test of the ignition system.
While the fuel system was found to be functional—with the fuel injectors and pump in good condition—the investigation focused on the magneto. Although the magneto had undergone preventive maintenance in July 202 and was well within its 100-hour inspection interval, testing revealed significant irregularities. Using new ignition wires, investigators found that only four of the twelve wires provided full sparking, while others provided intermittent or no spark at all.
Findings
- The pilot was fully qualified, holding valid commercial licenses and medical certification.
- The aircraft was operating within weight and balance limits with a valid airworthiness certificate.
- Meteorological conditions were well above the minimum requirements for the flight.
- The ignition system malfunctioned due to an abnormal performance of the magneto, which led to the loss of engine power in flight.
- The cause of the magneto failure occurring so soon after its scheduled maintenance remains undetermined.