Definition
A Technical Standard Order (TSO) is a minimum performance standard issued by the FAA for specific materials, parts, processes, and appliances used on civil aircraft. A manufacturer who designs an article meeting a TSO and is granted TSO authorization may produce and mark the article as TSO-approved, certifying that it meets that minimum performance standard.
Plain English
An FAA-issued rulebook for a specific aircraft part, telling manufacturers the minimum quality and performance the part must meet. If a part carries a TSO marking, the FAA has confirmed the maker built it to that standard.
Context Anchor
Seen in equipment approvals, aircraft maintenance records, parts catalogs, electronic equipment documents, and discussions about whether a part is approved for a specific aircraft.
Derivation
Standard comes from the Old French estandart, meaning a fixed flag or rallying point — something that does not move and that others measure themselves against. A Technical Standard Order is exactly that: a fixed technical benchmark that a manufactured article must meet.
Why Pilots Care
It guarantees that the equipment installed in an aircraft meets established safety and performance criteria.
Intuition Check
Do not read “order” as something someone buys. Here, “order” means an official FAA standard that manufacturers build to.
Example Sentence 1
The replacement altimeter the shop ordered is TSO-approved, so it can be installed in the certificated aircraft without further design approval.
Example Sentence 2
Pilots check the Technical Standard Order markings on instruments to ensure they comply with regulatory standards.