FAA: TSO Authorisation (TSOA)
• FAA - TSOA is A stand-alone approval. It is a combined design and production approval to manufacture an article that meets a specific TSO minimum performance standard (MPS). It does not grant installation approval on any aircraft.
• EASA: The equivalent is an ETSO Authorisation (ETSOA) issued under Part 21, Subpart O
>> EASA couples ETSO with organisational design capability shown via DOA (Part 21 Subpart J) or Alternative Procedures to DOA (ADOA/APDOA), and production is under POA (Subpart G) or Subpart F as applicable. So ETSO is not “covered under DOA”, but interlocks with DOA/ADOA and POA.
The Role of TSO & ETSO Parts
• TSO/ETSO are minimum performance standards for defined article types (avionics, seats, ELTs, etc.). A TSOA/ETSOA means the article’s design meets the applicable standard, and the manufacturer has an approved system to consistently produce conforming articles.
• Neither TSOA nor ETSOA is an installation approval. To use the article on a specific aircraft/engine/propeller, you still need TC/STC/minor-change approval against that product’s certification basis. (FAA says this explicitly; EASA/TIP materials say the same.)
Marking
• FAA requires TSO articles to be permanently marked with TSO number, holder ID and P/N;
• EASA requires ETSO marking with holder name/address, P/N/model, SN/DOM, and the applicable ETSO number.
FAA - TSOA = design + production approval. The holder controls design, quality, and suppliers; the FAA can inspect quality systems, facilities, data and tests. A quality manual is required. Minor changes may be made by the TSOA holder; major changes require a new authorisation.
• Installation is separate. You still need TC/STC/minor-change approval to install on a product.
• Delegation: FAA uses ODA (Organisation Designation Authorisation), including TSOA ODA, allowing qualified organisations to perform certain approval functions on the FAA’s behalf.
EASA (Part 21, Subparts O, J & G)
• ETSOA (Subpart O). The ETSOA holder is responsible for manufacturing (Through Part 21 G Approval) ETSO articles and must meet obligations, including DDP (Declaration of Design & Performance), change control (21.A.611), manual availability, and ETSO marking. Minor changes may be made by the holder; major changes need new authorisation.
• Design capability: Shown via DOA (Subpart J)—or ADOA/APDOA for specific projects. DOA holders have privileges) to classify and approve certain minor changes/repairs under approved procedures.
• OA interfaces are formalised.
• Special case (APUs): EASA materials highlight additional DOA requirements for APU ETSO authorisations.
Design authority
• FAA “design authority” model: For TSO articles, the TSOA holder is the design approval holder for the article (combined design/production). For aircraft/engine/propeller products and major mods, the TC/STC holder is the DAH. FAA can delegate findings/approvals to ODA organisations (e.g., a TSOA ODA).
• EASA “design authority” model: EASA recognises organisational design capability via DOA. The DOA holder (with named CVEs and a design assurance system) exercises privileges to classify/approve certain minor changes/repairs; for ETSO projects, applicants can use DOA or ADOA procedures. The ETSOA holder is responsible for the article and its documentation, while the POA controls production and release.
Capability
• FAA: A TSOA manufacturer may make minor design changes without prior FAA approval (must keep the original model designation and provide revised data); major changes require a new authorisation.
• EASA: an ETSOA holder may make minor design changes without further EASA authorisation (subject to data transmittal and traceability); major changes require a new ETSOA application.
Cross-Acceptance
• Under the FAA–EASA framework, reciprocal acceptance of TSOA/ETSOA is established: FAA accepts EASA ETSOA and vice-versa without issuing a duplicative LODA/ETSOA, streamlining transatlantic approvals. Technical Implementation Procedures (TIP) emphasises that TSO/ETSO does not imply installation approval.
Practical Differences
• Approval type: FAA’s TSOA inherently covers design + production; EASA’s ETSOA is an article authorisation that is integrated with DOA/ADOA (design capability) and POA for production.
• Delegation model: FAA uses ODA; EASA uses DOA (no ODA).
• Change control: Both allow minor changes by the authorisation holder; changes need a new authorisation.
• Installation: Always separate (TC/STC/minor change).
• Special cases: EASA imposes additional DOA conditions for APU ETSOs.
Additional Considerations
• FAA TSOA demands a robust quality system & manual; EASA requires demonstration of capability and POA controls.
• Whilst TSO/ETSO isn’t installation approval, creating installation instructions & limitations with the product-level certification provides a basis including wiring, cooling, EMI/EMC DO-160, HMI, safety analyses
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