What happened
On January 21, 2016, a Cessna T1-88C, registration PR-JLA, was conducting agricultural spraying operations over a farm in Itobi, São Paulo. The aircraft had departed from the Casa Branca Aerodrome for the purpose of applying pesticides to a plantation.
While performing the application, the aircraft experienced a sudden engine failure. The failure resulted in smoke and oil being expelled onto the windshield, significantly obscuring the pilot's vision. Due to the loss of power, the pilot was forced to execute an emergency landing in a recently harvested sugarcane field. The aircraft sustained substantial damage, but the pilot emerged from the wreckage uninjured.
The investigation
CENIPA investigators examined the Continental TSIO-520-T engine to determine the cause of the power loss. The inspection revealed a crack in the external engine block near cylinder number five. Upon disassembly, investigators found a significant amount of metal shavings and fragments from internal components, including lifters and structural parts, inside the crankcase.
Technical analysis showed that the connecting rod head of cylinder five had been damaged by overheating. Additionally, one of the connecting rod bolts had broken into three pieces due to an impact overload. The investigation also identified evidence of fretting wear around the through-bolt holes in the front intermediate bearing. This wear suggested that the bearing halves were moving independently, likely due to dimensional inaccuracies following an engine overhaul or improper torque applied to the through-bolt nuts.
Findings
- The engine failure originated in cylinder number five.
- The investigation established that the primary contributing factor was inadequate maintenance procedures.
- Dimensional errors during the engine overhaul or improper torque application likely caused the bearing halves to move independently, leading to oil passage misalignment and subsequent overheating of the bearings and connecting rod.
- The breakage of the connecting rod bolt was a consequence of the engine failure rather than the initial cause.