Event Description
While taxiing after landing, the left main landing gear of an airplane collapsed.
Investigation
Disassembly of the left main gear actuator revealed that the lock ring had been installed upside-down. A radiograph of the lock piston and the ball bearing that operates the lock switch showed the ball bearing resting only halfway up the ramp on the lock piston. Despite this, the downlock switch indicated a locked condition.
Maintenance Background
Review of maintenance records showed that the actuator had been repaired by the Cessna Wichita Citation Service Center in Wichita, Kansas, on February 7, 1999. During that repair, the actuator was disassembled and reassembled.
A temporary replacement actuator, provided by the airplane manufacturer, had been installed when the original left main gear actuator was removed for overhaul.