Incident Overview
An aircraft on a flight from Flin Flon Airport, Manitoba, Canada, to Mason City, Iowa, made a stop at Grand Forks, North Dakota, for fuel and customs clearance. While taxiing for takeoff, the aircraft struck a 1-inch concrete lip on the ramp. The impact caused the right main landing gear to collapse.
Examination Findings
Post-accident examination of the landing gear system identified several anomalies. The actuator rod end was found to be bent. Additionally, one of the four springs on the overcenter cam device was detached from its proper attachment point and exhibited excessive stretching.
Functional Testing
With the aircraft placed on jacks, the detached spring was reattached, and the landing gear was extended. In this configuration, the spring became trapped between the downlock switch and the downlock overcenter mechanism. When weight was applied to the landing gear and firm upward pressure was exerted on the overcenter device, the right main landing gear retracted.
Selector Handle Behavior
Further tests on the landing gear selector handle revealed two issues. First, the handle did not always engage the safety latch when placed in the neutral position. Second, it was possible to move the selector from the down position to the up position without triggering the safety latch.