Incident Overview
On 24 October 2021 at approximately 0655Z, a Cessna 402C II twin-engine aircraft (registration ZS-KNG) departed from Wonderboom Aerodrome (FAWB) for a navigation training flight with an instructor and a student pilot on board. The flight, conducted under Part 141 of the South African Civil Aviation Regulations, included uneventful touch-and-go circuits at The Coves Private Airstrip and Brits Aerodrome (FABS) before proceeding to FAWB for a full-stop landing.
During the landing roll on Runway 11 after a smooth touchdown, the aircraft began pulling to the left. The instructor took control and applied right brake, but the aircraft’s heading changed by approximately 140° due to free movement of the left main landing gear. The aircraft skidded and came to a stop on the left edge of the runway. Substantial damage was reported; no injuries were recorded.
Investigation Findings
Examination revealed that the left main gear torque link had separated. The bolt and castellated nut connecting the torque link were found to be compromised: the nut had been stripped off and the split pin sheared. The aircraft’s 100-hour mandatory periodic inspection had been completed three days prior, at 1463.4 Hobbs hours. The torque link, bolt, and nut were considered on-condition items inspected during that inspection. Maintenance records indicated possible over-torque during servicing as a contributing factor.
Probable Cause
The investigation identified the probable cause as the pilot losing control and veering off the runway due to separation of the bolt and castellated nut connecting the torque link, resulting from landing gear failure and improper maintenance/servicing.