- Approval of Modified Seating System Initially Approved Under a Technical Standard Order
- Date issued
- Office of Primary Responsibility
This advisory circular (AC) provides information, clarification, and procedural guidance for the approval and installation of modified technical standard order (TSO)approved seating systems in U.S. type-certificated aircraft. In this AC, we address modifications that result from design changes, repairs, and alterations pursuant to Title 14 of the Code of Federal Regulations (14 CFR) parts 21 and 43.
This AC is not mandatory and does not constitute a regulation. This AC describes an acceptable means, but not the only means, to modify TSO seating systems. However, if you use the means described in this AC, you must follow it in all important respects.
- AC 21-25B (PDF)