What happened
On October 30, 2018, an EMB-202 Ipanema, registration PT-UJI, was performing agricultural spraying operations near Miranda, Mato Grosso. The aircraft departed from Aeródromo Fazenda Pouso Alegre to conduct local pesticide application. During a turn intended to reposition the aircraft for the next spray run, the pilot experienced RPM oscillations and a significant loss of engine power. This power loss led to a degradation of airspeed and a loss of lift, forcing the pilot to perform an emergency landing in a plantation near the MS 339 state highway. The pilot escaped the wreckage uninjured, though the aircraft sustained substantial damage to the left wing, engine mount, empennage, fuselage, and landing gear.
The investigation
CENIPA investigators examined the engine, propeller, and maintenance records. While the engine itself showed no signs of internal malfunction, the investigation focused on the propeller governor. The investigation revealed that the maintenance organization had been performing operational tests without the correct manufacturer-specified parameters, as the proper Test Data Sheet (TDS) for this specific governor model was unavailable from the manufacturer, Ontic. Furthermore, investigators discovered that three pressure washers had been used as shims in the relief valve, which deviated from the manufacturer's manual. The investigation also noted that the aircraft was operating approximately 110 kg above its maximum takeoff weight of 1,800 kg. Additionally, the pilot had previously noted performance issues that were not formally recorded in the aircraft's logbooks.
Findings
- The primary cause of the power loss was a failure of the propeller governor, which caused uncommanded changes in propeller pitch.
- Maintenance practices were inconsistent with manufacturer specifications due to the lack of appropriate testing documentation.
- The aircraft was operating in excess of its maximum takeoff weight.
- There was a lack of formal reporting culture within the operator regarding observed aircraft performance discrepancies.
- Improper use of components (pressure washers instead of a single shim) was found within the governor assembly.