Section 27.605 - Fabrication methods(a) The methods of fabrication used must produce consistently sound structures. If a fabrication process (such as gluing, spot welding, or heat-treating) requires close control to reach this objective, the process must be performed according to an approved process specification.(b) Each new aircraft fabrication method must be substantiated by a test program.Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as amended by Amdt. 27-16, 43 FR 50599, Oct. 30, 1978 Secs. 313(a), 601, 603, 604, and 605 of the Federal Aviation Act of 1958 (49 U.S.C. 1354(a) , 1421 , 1423 , 1424 and 1425 ) ; sec. 6(c) of the Dept. of Transportation Act (49 U.S.C. 1655(c)