What happened
While taxiing from the ramp toward the active runway, the pilot of a Cessna 402 reported that the aircraft's left main landing gear assembly collapsed. The incident occurred during the ground taxi phase of operations.
The investigation
A post-accident examination of the landing gear assembly was conducted to determine the cause of the collapse. Investigators found that the roll pin (part number NAS 561P4), which is responsible for retaining the attaching shaft (part number 0841011-1) to the trunnion assembly, had fractured. This failure allowed the landing gear attaching shaft to shift from its original installed position, which subsequently caused the trunnion assembly to separate from the landing gear support structure.
Following this event, the operator performed inspections on the remaining six Cessna 402 aircraft in their fleet. During these inspections, the operator identified two additional aircraft that also possessed broken landing gear shaft roll pins. As a result of these findings, the operator replaced the faulty roll pins and implemented a new maintenance protocol to reexamine the landing gear assemblies at six-month intervals.