FAR 21.601 — TSO Authorizations
FAR 21.601 explains TSO authorizations, letters of TSO design approval, and key definitions for FAA-approved articles used on civil aircraft.
In Plain English
FAR 21.601 is the opening section of Subpart O, which governs Technical Standard Order (TSO) authorizations. It tells you what the subpart covers and defines the terms you'll see throughout it.
The subpart prescribes:
- Procedural requirements for issuing TSO authorizations
- Rules for holders of those authorizations
- Procedural requirements for issuing letters of TSO design approval
Key definitions you should know:
- A TSO is a minimum performance standard set by the FAA for specified articles (like avionics, seats, or life vests) used on civil aircraft.
- A TSO authorization is a combined FAA design and production approval issued to a manufacturer whose article meets a specific TSO.
- A letter of TSO design approval is design-only approval issued under § 21.621.
- An approved article is one made under a TSO authorization, an FAA letter of acceptance under § 21.613(b), or a letter of TSO design approval.
- An article manufacturer is the person who controls the design and quality of the article, including outsourced parts and processes.
Why it matters: when a regulation requires an "approved" article, this section tells you what that approval actually means.
Regulation Text
14 CFR § 21.601§ 21.601 Applicability and definitions.
(a) This subpart prescribes—
(1) Procedural requirements for issuing TSO authorizations;
(2) Rules governing the holders of TSO authorizations; and
(3) Procedural requirements for issuing letters of TSO design approval.
(b) For the purposes of this subpart—
(1) A TSO issued by the FAA is a minimum performance standard for specified articles used on civil aircraft;
(2) A TSO authorization is an FAA design and production approval issued to the manufacturer of an article that has been found to meet a specific TSO;
(3) A letter of TSO design approval is an FAA design approval for an article that has been found to meet a specific TSO in accordance with the procedures of § 21.621;
(4) An article manufactured under a TSO authorization, an FAA letter of acceptance as described in § 21.613(b), or an article manufactured under a letter of TSO design approval described in § 21.621 is an approved article for the purpose of meeting the regulations of this chapter that require the article to be approved; and
(5) An article manufacturer is the person who controls the design and quality of the article produced (or to be produced, in the case of an application), including any related parts, processes, or services procured from an outside source.
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Oral Exam Questions a DPE Might Ask
Q1What is a TSO, and what does a TSO authorization grant the manufacturer?
Per FAR 21.601, a TSO is a minimum performance standard issued by the FAA for specified articles used on civil aircraft, and a TSO authorization is an FAA design and production approval issued to a manufacturer whose article has been found to meet that TSO.
Q2How does an article qualify as 'approved' when regulations require an approved article?
FAR 21.601(b)(4) states an article is approved if manufactured under a TSO authorization, under an FAA letter of acceptance per § 21.613(b), or under a letter of TSO design approval per § 21.621.
Q3Who is considered the 'article manufacturer' under the TSO rules?
FAR 21.601(b)(5) defines the article manufacturer as the person who controls the design and quality of the article produced, including any related parts, processes, or services procured from an outside source.
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§21.15 Type Certificate Application
FAA application form, aircraft drawings, and engine data
§21.17 Certification Basis
Applicable airworthiness, noise, and emission rules
§21.20 Compliance Showing
How applicants show compliance to the FAA
§21.31 Type Design
Drawings, specifications, dimensions, and limitations
§21.41 Type Certificate
What the certificate includes once the design is approved
§21.47 Type Certificate Transferability
Transfer and licensing notices for FAA type certificates
Related Sections in Part 21