Incident Overview
The right main landing gear scissors separated while the aircraft was in the landing roll, leading to a ground loop and subsequent collapse of the right main landing gear. The separation occurred without prior indication.
Examination Findings
A post-accident examination of the right landing gear scissors assembly determined that a hinge bolt assembly had failed. Further inspection of the scissor assembly revealed two washers under the head of the scissors bolt that were damaged. These washers had diameters only slightly larger than the extreme hex points of the bolt head, significantly smaller than the recommended washers. The washers were extruded, or bent, towards the scissor bolt head, which allowed the upper and lower scissor assembly to disconnect.
Maintenance and Service Letters
Recent maintenance had reportedly been performed on both main landing gears. A Cessna Service Information Letter, ME83-37, dated November 23, 1983, recommended main landing gear scissor washer replacement for airplanes with serial numbers that included the accident aircraft. The Service Letter recommended replacing the two outer washers on the main landing gear scissor link for improved service life and main gear wheel alignment retention. It called for the installation of a new AN175-20 scissor bolt and one 5045018-2 washer under the head of the bolt for each main landing gear scissors.
Condition of the Washers
Contrary to the Service Letter recommendations, the examined scissor assembly contained two washers that were notably smaller than the specified 5045018-2 washer. The undersized washers were found extruded and bent, indicative of the failure sequence that led to the scissors separation.