The U.S. Army Research Laboratory-Weapons and Materials Research Directorate (ARL-WMRD) performed a dimensional inspection and metallurgical investigation of AH-64 Apache tail rotor strap pack assemblies and individual laminate sets. All of the dimensional critical characteristics were examined in an attempt to determine the cause of a buckling phenomenon within the strap pack assemblies. Conformance to the manufacturer's governing specifications with respect to the material, heat treatment, and marking requirements was also investigated. The cause of the buckling was attributed to a combination of factors. Dimensional nonconformances were identified. Most of the hole diameters were found to be well below the specified range, causing the assemblies to be forced together. Transposition of the laminates during manufacture was also highly likely to have occurred, adding to the misalignment of the assembly. All other characteristics of the laminates and assemblies were found to conform to the governing part drawings and specifications.
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