TSO Authorization Duration

FAR 21.613 — TSO Authorization Duration

FAR 21.613 explains how long a TSO authorization or letter of TSO design approval remains effective and what happens if a TSO is revised or canceled.

In Plain English

FAR 21.613 sets out how long a Technical Standard Order (TSO) authorization or letter of TSO design approval stays valid, and what happens when the underlying TSO changes.

The key points:

A TSO authorization or letter of TSO design approval stays in effect indefinitely — until the holder surrenders it, the FAA withdraws it, or it is otherwise terminated by the FAA.
If the FAA later revises or cancels a TSO, holders of an affected letter of acceptance of a statement of conformance, TSO authorization, or letter of TSO design approval may keep manufacturing articles built to the original TSO without getting a new approval.
Those manufacturers still have to comply with all other applicable requirements of the chapter.

Why it matters operationally: this rule protects manufacturers (and the supply chain pilots rely on for parts like avionics, seatbelts, and instruments) from being forced to redesign every time a TSO is updated, while keeping FAA oversight in place.

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Regulation Text

14 CFR § 21.613

§ 21.613 Duration. (a) A TSO authorization or letter of TSO design approval is effective until surrendered, withdrawn, or otherwise terminated by the FAA. (b) If a TSO is revised or canceled, the holder of an affected FAA letter of acceptance of a statement of conformance, TSO authorization, or letter of TSO design approval may continue to manufacture articles that meet the original TSO without obtaining a new acceptance, authorization, or approval but must comply with the requirements of this chapter.

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Oral Exam Questions a DPE Might Ask

Q1How long is a TSO authorization or letter of TSO design approval effective?

Per FAR 21.613(a), it is effective until surrendered by the holder, withdrawn, or otherwise terminated by the FAA — there is no fixed expiration date.

Q2If the FAA revises or cancels a TSO, must the holder stop production or reapply?

No. Under FAR 21.613(b), the holder may continue manufacturing articles that meet the original TSO without obtaining a new acceptance, authorization, or approval, as long as they comply with the other requirements of the chapter.

Q3What FAA actions can end a TSO authorization?

FAR 21.613(a) lists three: the holder surrenders it, the FAA withdraws it, or the FAA otherwise terminates it.

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