NTSB Identification: LAX03LA106.
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Accident occurred Tuesday, March 04, 2003 in Crescent City, CA
Probable Cause Approval Date: 12/28/2004
Aircraft: Cessna 421C, registration: N26533
Injuries: 3 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The right main landing gear scissors separated during the landing roll, resulting in a ground loop and the collapse of the right main landing gear. Post accident examination of the right landing gear scissors assembly revealed that a hinge bolt assembly had failed. 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 airplane. The Service Letter recommended replacement of the two outer washers on the main landing gear scissor link for improved service life, and main gear wheel alignment retension. The Service Letter 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. Post accident examination of the scissor assembly revealed two damaged washers under the head of the scissors bolt, with diameters only slightly larger than the extreme hex points of the bolt head. The two washers were significantly smaller than the recommended washers, and were extruded, or bent towards, the scissor bolt head, which allowed the upper and lower scissor assembly to disconnect.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The separation of the upper and lower right main landing gear scissor links due to improper maintenance, which resulted in a ground loop, and the collapse of the right main landing gear during the landing roll.

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