Permissible Defects in Hydraulic Tubing

Test methods and data are summarized to assist in establishing limits for defects in aircraft hydraulic tubing. The defects evaluated are (1) cracks as detectable by ultrasonic inspection after tube fabrication, and (2) service damage such as chafing and denting observed on aircraft. Permissible defect limits are listed for 6061T6 aluminum return lines, 3000 psi hydraulic tubing of 21Cr-6Ni-9Mn as well as 304 1/8 hard CRES, and 3A1-2.5V cold worked titanium. The performance requirements are outlined to which the defect samples were tested.