FAQ n.20095

Why and how must Parts and Appliances be marked, when are the letters EPA required, and which exceptions are acceptable?


To comply with EASA Part-21, Subpart D, 21.A.109, Subpart E, 21A.118A (b) and Subpart M, 21A.451(a) and (b), it is the obligation of the respective Holders of a Minor Change Approval, a STC, or a Major Repair Design Approval, to specify the required markings, including EPA letters as applicable, in their Design (read, ‘Approved Data’), according EASA Part-21, Subpart Q.

Subpart Q, 21.A.804(a), and related GM, require proper identification of each Part and Appliance that is designed or redesigned, including parts designed to be incorporated in repairs (21A.451), by ‘permanent and legible marking’ hereof, and is applicable for Design Organisations and Manufacturers.

21.A.804(a) 1 and 2  clearly require marking of Parts and Appliances with ‘name, trademark, or symbol identifying the Manufacturer’ and ‘Part number’, as defined in the applicable Design Data.

According to the GM the Design Approval Holder shall identify in all its Design (TC, STC, ETSO, Repair, Change) approved after 28 December 2009, how the Manufacturer has to mark subject Parts and Appliances in accordance with 21A.804(a) 1; which can be limited to identifying a marking field and the method, without prescribing the actual text or symbols.

21.A.804(a) 3 requires additionally marking with the letters ‘EPA’ of all parts produced (manufactured) in accordance with data ‘not belonging to the TC holder of the related product’.

Each interchangeable or removable Part or Appliance that is manufactured in accordance with a design issued by the Design Organisation, shall be permanently and legibly marked according to 21.A.804. The EPA marking was introduced in 2004; this was done to clearly identify any ‘not original’ Part, (which means any Part or Appliance not designed by the TC- or ETSO- Approval Holder), as a trigger for Maintenance Organisations and Accident or Incident investigators, in the light of Continuing Airworthiness. The intention was certainly not to require adding of the letters ‘EPA’ to mark repairs. In this context, EPA marking only applies to the new designed and manufactured parts to be incorporated in the repair. Especially where repairs have an impact on interchangeability, identification of incorporated new Parts is very important, and DO Procedures should address this item. Note that for parts referred to in 21.A.307(b), as amended with (EU)2021/699 (applicable from 18.05.2022), the EPA marking is not required as stated in 21.A.804(a)(3).

The only accepted exception with regard to Marking (including EPA), is defined in 21.A.804(b). This subparagraph offers the possibility to not physically mark the Part of Appliance, when it is too small or when marking hereof is otherwise impractical, but only after “Agency agreement”. This wording allows an Applicant/Holder of a Design and the Agency to further define in detail how this ‘agreement’ can be obtained and will be formalised. DOATL should however ensure that the DOA Applicant/Holder reflects this approach in its DO Handbook or Procedures, requiring at least a justification of the reason for not marking physically, and details of the alternative way chosen for the identification, in accordance with 21A.804(b), to know on the authorised release document accompanying the Part or Appliance, or on its container.

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