Event
The pilot reported that during the approach, he selected the landing gear to the down position. The landing gear indicator showed two green lights and the left gear light was off. After informing the tower, the pilot cycled the gear but the indication remained unchanged. He requested and was approved for a low approach to allow a visual check of the landing gear. After cycling the gear once more, three green lights appeared. The tower then confirmed that the gear appeared down and in place. The pilot was cleared to land on runway 13. The airplane touched down and rolled approximately 2,000 feet before the left main landing gear collapsed.
Investigation
An FAA inspector who responded to the accident site reported that the left main gear assembly was found retracted and up into the engine nacelle. The lock down assembly was unlocked and undamaged. The left main landing gear torque link was broken, and the left landing gear actuator gearbox assembly was detached from its mount box. The inspector noted that the accident airplane had accumulated about 148 hours since its last maintenance inspections on January 3, 2004. That inspection included checking the actuator support brackets for visible damage, wear, cracks, loose or missing rivets.
Findings
Examination of the fractured left gear actuator support box structure brackets revealed a crack that circumscribes the lower hi-shear rivet holes of the outboard bracket. The operator stated that during damage assessment, a structural failure of the left main landing gear actuator support box structure was discovered. They suspected that the structure had at least one existing crack, which allowed the actuator to "float" within the support structure, preventing complete spring compression from the actuator to engage the left main landing gear drag leg hooks.