M.A.304 Data for modifications and repairs
A person or organisation repairing an aircraft or a component, shall assess any damage. Modifications and repairs shall be carried out using, as appropriate, the following data:
(a) approved by the CAA;
(b) approved by a design organisation complying with Annex I (Part-21) to Regulation (EU) No 748/2012;
(c) contained in the requirements referred to in point 21.A.90B or 21.A.431B of Annex I (Part-21) to Regulation (EU) No 748/2012.