Study to Identify Stress Corrosion Prone Parts on the TA-7C Aircraft.

This program was aimed at determining which parts in the TA-7C aircraft are prone to stress corrosion cracking, and then establish corrective measures encompassing 1 inpsection criteria including NDI methods and intervals, 2 protection improvements, 3 material changes, and 4 design changes. The first task was the establishment of a stress corrosion cracking rating system based on evaluation parameters such as alloytemper, product form, thickness, grain direction, protective systems, assembly and applied stresses and other influencing factors. This rating was tested for sensitivity relative to known failures. The ratings are presented in three forms 1 numeric, 2 Criticality, and 3 Stress Corrosion-Failure Probability. The second task was to survey select stress corrosion cracking prone parts for measurement of residual stresses in suspect locations. Measurements were made within the stress analyzer physical limitations, and these measured stress values correlated with calculated stress. The third task was to recommend inspection procedures and intervals, protective system changes, materialtemper changes, and design changes. These are incorporated in the rating lists as a guideline to corrective action. Author