The official EASA position regarding ‘required’ application of SB instructions is as follows:
Through the DOA (Design Organisation Approval) oversight process, the Agency promotes that TC/STC holders designate a Service Bulletin (SB) as mandatory only if it is known to them that this SB will also be covered by an AD. In all other cases, the TC/STC holder should use a term like ’highly recommended‘ (or equivalent). However, this is not yet common practice and there are still cases where an SB is termed ’mandatory‘ by the TC/STC holder, although no AD is to be issued. The Agency has no legal tools to prohibit the use of the word ‘mandatory’ by TC/STC holders, but EASA Certification Memorandum CM-21.A-J-001 has been issued to provide advice and guidance on this subject.
The case of an SB for which an AD has been issued, irrespective of whether it is designated by the TC/STC holder as ‘mandatory’, ‘alert’ or ‘highly recommended’, is clear: these are part of the Mandatory Continuing Airworthiness Instructions and must be applied in all cases.
The case of SBs designated as ‘mandatory’, ‘alert’ or ‘highly recommended’ by the TC/STC holder for which no AD has been issued is more complex and the following cases should be considered:
- The TC/STC holder subsequently includes such SB (e.g. repetitive inspection instructions) in the manufacturer maintenance programme (Maintenance Review Board Report (MRBR) or Manufacturer Recommended Programme) for the aircraft concerned. In this case, the SB under consideration will need to be included in the aircraft maintenance programme as defined in Commission Regulation (EU) No 1321/2014, M.A.302(d) and (g) (see also AMC M.A.302(d)) to ensure compliance with instructions for continuing airworthiness issued by the TC/STC holder.
- The TC/STC holder does not include such SB in the manufacturer maintenance programme (MRBR or Manufacturer Recommended Programme) for the aircraft concerned. In this case, the final decision to apply such SB lies with the owner/operator or contracted CAMO, as M.A.302(g) does not apply.
- The TC/STC holder issues an SB defining a modification, the related embodiment instruction and the relevant scheduled maintenance requirements, where these may or may not be subsequently included in the manufacturer maintenance programme (MRBR or Manufacturer Recommended Programme) for the aircraft concerned. In case the SB will not be included in the manufacturer maintenance programme, the final decision to apply it or not lies with the owner/ operator or contracted CAMO. If the final decision is to apply the SB, then the aircraft maintenance programme needs to be updated to include the scheduled maintenance requirements.
Finally, in relation to points 2. and 3. above, for all non-mandatory modifications and/or inspections, including SBs classified by the TC/STC holder as ‘mandatory’, ‘alert’ or ‘highly recommended’ and not covered by a corresponding AD, for all large aircraft, or aircraft used in commercial air transport, an embodiment policy is to be established, as required by M.A.301(7.). That policy should then result in a substantiated (and recorded) operator’s decision for each SB to apply it, or not.