FAR 21.614 — TSO Transferability

FAR 21.614 is a short but important rule in the certification world. It states that if a manufacturer holds a TSO authorization (Technical Standard Order authorization) or a letter of TSO design approval, that approval cannot be transferred to another party.

In plain terms:

• A TSO is an FAA-issued minimum performance standard for specific articles (like avionics, seatbelts, or oxygen masks) used on civil aircraft.
• When a manufacturer earns a TSO authorization, it's tied specifically to that manufacturer — not to the part itself or to a buyer of the company's assets.
• If another company wants to produce the same article under TSO, it must apply for and obtain its own TSO authorization.

Why it matters operationally: As a pilot, you generally won't deal with TSO paperwork directly, but understanding this rule helps you grasp why TSO-marked parts are linked to a specific manufacturer and why substitutions during maintenance must come from properly authorized sources.