3 7 ▁( quality ▁system ▁requirements ▁for ▁production ▁certific ates ), ▁ 2 1 . 3 0 7 ▁( re qu iring ▁P MA ▁hold ers ▁to ▁establish ▁a ▁quality ▁system ▁that ▁meets ▁the ▁requirements ▁of ▁§ ▁ 2 1 . 1 3 7 ), ▁ 2 1 . 6 0 7 ▁( re qu iring ▁T SO A ▁hold ers ▁to ▁establish ▁a ▁quality ▁system ▁that ▁meets ▁the ▁requirements ▁of ▁§ ▁ 2 1 . 1 3 7 ). ▁ ▁Rel ations hip ▁to ▁repair ▁ ▁The ▁F AA ▁is ▁also ▁working ▁on ▁new ▁policies ▁concerning ▁parts ▁fabric ated ▁in ▁the ▁course ▁of ▁repair . ▁ ▁This ▁practice ▁has ▁histor ically ▁been ▁confused ▁with ▁P MA ▁manufact uring , ▁although ▁the ▁two ▁are ▁actually ▁quite ▁different ▁practices ▁supported ▁by ▁different ▁F AA ▁reg ulations . ▁ ▁Today , ▁F AA ▁Ad vis ory ▁Circ ular ▁ 4 3 . 1 8 ▁provides ▁guidance ▁for ▁the ▁fabric ation ▁of ▁parts ▁to ▁be ▁consum ed ▁purely ▁during ▁a ▁maintenance ▁operation , ▁and ▁additional ▁guidance ▁is ▁expected ▁to ▁be ▁released ▁in ▁the ▁near ▁future . ▁ ▁One ▁of ▁the ▁key ▁features ▁of ▁F AC ▁ 4 3 . 1 8 ▁is ▁that ▁it ▁recomm ends ▁implementation ▁of ▁a ▁quality ▁ass urance ▁system ▁quite ▁similar ▁to ▁the ▁fabric ation ▁ins pection ▁systems ▁that ▁P MA ▁manufact ur ers ▁are ▁required ▁to ▁have . ▁ ▁Indust ry ▁association ▁ ▁The ▁trade ▁association ▁representing ▁the ▁P MA ▁industry ▁is ▁the ▁Mod ification ▁and ▁Rep lacement ▁Part s ▁Association