What happened
On August 9, 2001, at approximately 11:04Z, a CESSNA 402, registration ZS-NMV, was involved in a landing incident at Lanseria. The aircraft, operated by a commercial pilot, was undergoing a proficiency check with a second pilot when the event occurred. During the landing on Runway 06R, smoke was observed emanating from the right-hand undercarriage. This mechanical failure caused the aircraft to veer to the right of the runway centerline, eventually coming to a stop on the grass adjacent to the runway. There were no injuries and no fatalities resulting from the incident, though the aircraft sustained damage to its landing gear.
The investigation
An investigator present at the aerodrome for an unrelated matter witnessed the smoke and the subsequent excursion. Upon inspecting the aircraft at the scene, investigators determined that the center bolt of the right-hand undercarriage torque link had become dislodged. The investigation focused on the assembly of the bolt and the configuration of the washers used during maintenance. It was noted that the aircraft had flown only 17 hours since its last Mandatory Periodic Inspection.
Findings
The investigation established that the dislodgment of the torque link center bolt was caused by an improper installation of washers. Specifically, both large washers had been placed on the bolt head side of the assembly, rather than one washer being positioned on each side of the torque link. This imbalance allowed the bolt to be pulled through the eye end of the torque link, causing the wheel to turn sideways and forcing the aircraft off the runway.
Safety action
Following the findings, it was recommended that the Service Information Letter ME83-37 be converted into a South African Airworthiness Directive to prevent similar installation errors in the future.