What happened
On April 26, 2017, at approximately 10:05 local time, a Cessna A188 aircraft, registration HK2108, was performing agricultural spraying operations near the La Milagrosa airstrip in Maní, Casanare. After taking off for a subsequent spraying mission, the pilot initiated a left turn. During this maneuver, the aircraft suddenly banked sharply to the left. The pilot attempted to correct the attitude by applying right control, but the aircraft failed to respond to the inputs.
The aircraft continued an uncontrolled left turn until it impacted the terrain. The impact occurred at a low angle and low speed. The aircraft was destroyed, though the pilot, who was wearing a helmet and seatbelt, escaped the crash without injuries. No post-impact fire was reported.
The investigation
Investigators from the GRIAA examined the wreckage and the aircraft's maintenance records. The inspection of the wreckage revealed significant structural deformation on the left wing, including fractures and dents on the aileron. The right wing remained largely intact. The engine and the forward section of the empennage were found attached to the fuselage, and the propeller was embedded approximately 40 cm into the ground.
A detailed technical examination of the flight control cables was conducted. Investigators identified a condition known as a "frozen bearing" in the left aileron control pulley. This malfunction prevented the pulley from rotating freely, causing the control cable to rub against the surface. This friction led to excessive wear and a ductile, frayed fracture of the cable. Furthermore, the investigation revealed that the operator's maintenance interval for replacing these cables was 600 hours, exceeding the manufacturer's recommended 500-hour limit specified in Service Bulletin SE73-33.
Findings
- The primary cause of the accident was the fracture of the left aileron control cable caused by a seized pulley (frozen bearing), which jammed the aileron and prevented directional control.
- The operator's maintenance processes were deficient, failing to detect the pulley blockage and the resulting cable wear.
- The operator was performing cable replacements every 600 hours, which deviated from the manufacturer's 500-hour requirement.
- The pilot had limited experience on this specific aircraft type, with only 35 total flight hours in the model.