What happened
On December 15, 2016, a Cessna A188B, registration PT-WQR, was performing agricultural spraying operations near Santa Vitória do Palmar, Rio Grande do Sul. The aircraft, operated by PLA & Silva Aviação Agric. Ltda., had taken off from an improvised runway to apply urea to a rice crop.
Shortly after takeoff, while the pilot was executing a right-hand turn and preparing to transition into a left-hand turn to align with the application path, the engine ceased functioning. The pilot completed the left-hand turn, leveled the wings, jettisoned the load, and deployed full flaps to execute a forced landing. The aircraft sustained substantial damage, though the pilot remained uninjured.
The investigation
CENIPA investigators examined the Continental IO-520-L-C-D engine at a certified maintenance facility. Laboratory analysis of the fuel and ignition systems revealed no obstructions, debris, or ignition failures. While investigators noted a lack of torque on a hose clamp—indicating an air leak in the induction manifold—and observed a slightly leaner mixture in the even-numbered cylinders, these findings were not considered the primary cause of the engine failure.
Upon separating the engine crankcase halves, investigators discovered a fracture in the crankshaft between the cylinder 2 journal and the crankpin. Analysis by the Materials Division (AMR) confirmed that the fracture was caused by material fatigue, with no evidence of corrosion present. Records showed the component had been inspected via ultrasonic and magnetic particle testing in 2012 and had flown for 566 hours prior to the accident.
Findings
- The primary cause of the engine failure was a crankshaft fracture due to material fatigue.
- The pilot was properly qualified, held valid medical certification, and was experienced in this type of agricultural operation.
- The aircraft was within weight and balance limits, and all airworthiness documentation was up to date.
- Maintenance of the aircraft was listed as an undetermined contributing factor.