Technical Standard Orders (TSO)
A TSO is a minimum performance standard, defined by the Federal Aviation Administration, used to evaluate an article. An article can be a material, part, component, process, or appliance (see Title 14, Code of Federal Regulations, 21.1(b)(2)). Each TSO covers a certain type of article. When authorized to manufacture an article to a TSO standard, this is referred to as a TSO Authorization (TSOA). Receiving a TSO Authorization is both a design and production approval.
Receiving a TSO Authorization is not an approval to install and use the article in the aircraft. It means that the article meets the specific TSO, and the applicant is authorized to manufacture it.
Receiving a TSO authorization is approval to manufacture an article that may be installed on an aircraft only after showing that the article meets the specific airworthiness requirements (certification basis) of a particular aircraft model. In other words, receiving a TSO authorization means that an article meets a minimum performance requirement independent of the article's intended installation on an aircraft. A separate FAA approval is required to install the article on an aircraft.
Contact your local FAA office to request an application for TSO Authorization.
What is the difference between a "Canceled TSO" and "Withdrawal of a TSO Authorization?"
A "Canceled TSO" means that the TSO has been rendered inactive, and the FAA will no longer issue new TSO Authorizations (TSOA) against that particular TSO. However, any existing TSOA obtained prior to the cancellation of the TSO are still valid and may continue to be manufactured and marked in accordance with that authorization.
The "Withdrawal of a TSO Authorization" means that a specific authorization letter (TSOA) is withdrawn by the FAA and the approval to manufacture that particular article is terminated.
In summary, if the TSO is canceled, you can still make the article but you can't apply for a new authorization (TSOA) to that particular TSO revision level. If the TSOA is withdrawn, you can't even manufacture the article under the TSO system (i.e., the FAA won't let you put a TSO label on it).
What is a letter of design approval?
A letter of design approval is an FAA design approval for an article manufactured outside the United States which meets a specific TSO.
How do I obtain a letter of TSO design approval?
The FAA will issue a letter of design approval only to manufacturers located in a country with which the U.S. has concluded a bilateral agreement applicable to the article in question. The exporting Civil Aviation Authority (CAA) is responsible for oversight of both the design and production of such articles.
An applicant for a FAA letter of TSO design approval should apply through the exporting CAA with a request that the application and required data be forwarded to the FAA. The exporting CAA should contact the FAA for information concerning the latest FAA technical policy and procedures whenever the CAA receives an application for an FAA letter of TSO design approval to a TSO performance standard for which the CAA has not previously made compliance findings.
The FAA issues a letter of TSO design approval only for articles of a kind for which a minimum performance standard has been published in an FAA Technical Standard Order (TSO).
Title 14 Code of Federal Regulations (14 CFR)
- Part 21, Certification Procedures for Products, Articles, and Parts
Advisory Circulars
- 20-41, Substitute Technical Standard Order (TSO) Aircraft Equipment
- 21-43, Production Under 14 CFR Part 21, Subparts F, G, K, and O
- 21-46, Technical Standard Order Program
- 21-50, Installation of TSOA Articles and LODA Appliances
Orders
Search Technical Standard Orders in the FAA Dynamic Regulatory System (DRS)
2023 FAA TSO Workshop, September 20-21, 2023
The Federal Aviation Administration hosted the 2023 FAA TSO Workshop on September 20-21 in Denver, CO. Briefings and presentations from the Workshop are available on our Information for Applicants and Design Approval Holders site.