Introduction to the Relationship Between FAA TSO and EASA ETSO

 What is a TSO / ETSO?

TSO is an FAA Term and stands for Technical Standard Order. ETSO is an EASA Term and stands for European Technical Standard Order.

A TSO / ETSO allows a common approach to the design of components which may be common to a number of different types of Aircraft, Engine or Auxiliary Power Unit (APU). This can also include avionic components as well as seats, seat belts, as well as emergency equipment.

A US company that wants to produce parts that meet the minimum standards of a TSO must apply for government approval and in the US this is called a TSOA or Technical Standard Order Authorization.

The TSOA applicant must self-certify design compliance, although the FAA is permitted to check compliance to the extent that the FAA believes necessary.

In addition, the TSOA applicant must have a production quality assurance system that meets FAA regulatory requirements and that will be subject to FAA inspection through FAA Manufacturing Inspection District Offices, known as MIDOs.

An FAA-approved production quality assurance system helps to ensure that each component that is produced under the TSOA design, will meet the specifications of the TSOA design.

Because a TSOA article is theoretically installable in any aircraft, it carries no inherent installation eligibility.

A ETSO (European Technical Standard Order) ensures that a part or appliance complies with a minimum performance standard. In all cases, the installer must apply for an installation approval on-board the aircraft. He/she can use the ETSO authorization and he/she complements it to demonstrate that the installation complies with the applicable certification basis for the changed aircraft.

European Technical Standard Order authorizations are covered by Subpart O of Part-21 which is the Annex to Commission Regulation (EU) No 748/2012. A list of the ETSO standards in the published list ETSO Index.

There has been a long-standing support for the initiative to drive mutual recognition between the FAA, TCCA, and EASA thus allowing the acceptance of the exporting authority’s TSO approval.

Such a process serves to eliminate the importing authority’s approval and validation activities, believing that no additional added value related to the safety of the article is achieved by this practice.


With tripartite acceptance and recognition:

a) FAA will accept a TCCA CAN-TSO design approval (DA) for articles from Canada and will no longer issue a Letter of TSO design approval (LODA) for the same article.

b) TCCA will accept the FAA’s TSOA for an article from the United States (U.S.) without issuing a CAN-TSO DA for the same article.

c) FAA will accept an EASA ETSOA for an article from the European Union (EU) and will no longer issue a LODA for the same article

d) EASA will accept the FAA’s TSOA for an article from the U.S. without issuing an ETSOA for the same article.

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