What happened
The aircraft was conducting a standard approach and landing sequence. Upon touchdown, the pilot initiated the landing rollout as expected. During this phase, the right main landing gear suddenly collapsed, causing the aircraft to settle onto its right side. The event occurred without prior indication of mechanical failure during the descent or flare.
The investigation
Following the incident, maintenance personnel conducted a thorough examination of the landing gear system to determine the root cause of the collapse. The inspection focused on the hydraulic and electrical components responsible for gear extension and retention.
Technicians verified that the landing gear selector switch was correctly positioned in the down setting, ruling out pilot error regarding gear selection. A detailed check of the microswitches within the gear mechanism revealed significant contamination. The contacts were dirty, which likely prevented proper electrical continuity required to lock the gear in place. Despite the dirt accumulation, the switches themselves showed no signs of physical damage; they were neither cracked nor broken.
To resolve the issue, maintenance crews replaced the contaminated microswitches with new units. Post-replacement testing confirmed that the landing gear system functioned properly and extended/retracted as designed. The collapse was attributed to the failure of the dirty switches to maintain the locked position during the dynamic forces of rollout.