What happened
On 24 October 2021, a Cessna 402C II with registration ZS-KNG departed Wonderboom Aerodrome (FAWB) for a training flight. The flight, conducted under Part 141 regulations, included an instructor and a student pilot performing type familiarization maneuvers. After completing several touch-and-go circuits at The Coves Private Airstrip and Brits Aerodrome (FABS), the crew returned to FAWB for a full-stop landing on Runway 11.
During the landing roll, the aircraft began pulling sharply to the left. Although the instructor took control and applied increased braking to the right side, the aircraft's heading shifted by approximately 140 degrees. The excursion was caused by the left main landing gear becoming unstable due to a separated torque link. The aircraft eventually skidded to a halt at the left edge of the runway, resulting in substantial damage to the aircraft. No injuries were reported.
The investigation
SACAA AIID examined the maintenance history and the physical condition of the landing gear assembly. Records showed that a 100-hour mandatory periodic inspection (MPI) had been performed on the aircraft just five days prior to the incident. While the torque link, bolt, and castellable nut are considered on-condition items subject to regular inspection, the investigation found that the hardware had failed during the flight's maneuvers.
Physical examination of the components revealed that the split pin had sheared and the castellated nut had been stripped off the bolt. While the bolt remained at the aerodrome, the nut was missing entirely.
Findings
- The primary cause of the loss of control was the separation of the bolt and castellated nut connecting the torque link.
- The failure of the landing gear assembly was linked to improper maintenance or servicing.
- A contributing factor was identified as over-torquing during recent maintenance procedures.
Safety action
To prevent a recurrence, it is recommended that Approved Maintenance Organizations (AMOs) strictly adhere to all manufacturer technical specifications, particularly regarding precise torque measurements.