What happened
On February 27, 2014, at approximately 20:30 UTC, an NEIVA EMB-202 agricultural aircraft, registration PT-USY, was performing pesticide application over a corn plantation at Fazenda Trento, near Uruçu and Piauí. The aircraft was executing its first application pass when the engine suffered a sudden loss of power.
The pilot attempted to follow emergency procedures, including an attempt to jettison the chemical payload from the hopper, but was unsuccessful. During the subsequent forced landing attempt, the left main landing gear and the left wing struck the corn crops, causing the aircraft to pivot 90 degrees to the left. The aircraft then struck the ground, sliding approximately 65 meters through the plantation before coming to a complete stop. The pilot survived the impact without injuries, but the aircraft sustained substantial damage to the engine, propeller, fuselage, wings, and landing gear.
The investigation
CENIPA investigators examined the Lycoming IO-540-K1J5 engine at an ANAC-authorized workshop. While the engine's internal components—including the crankshaft, camshaft, pistons, and connecting rods—showed no signs of seizure, cracks, or significant wear, pressure testing revealed critical issues.
Testing showed that cylinder pressures in cylinders #1 and #6 were below the manufacturer's minimum limits. Investigators identified that the exhaust valve guides in these cylinders had become "ovalized," creating excessive clearance between the valves and the guides. This condition allowed air to leak through the exhaust ports during pressure testing. While the investigation could not confirm if specific cylinders had been recently replaced, the physical evidence suggested the engine's performance had been degrading over time due to this mechanical wear.
Findings
- Maintenance of the aircraft was a contributing factor.
- The ovalization of the valve guides led to a progressive loss of engine performance.
- The engine power loss eventually reached a point that resulted in the loss of flight capability during the application pass.