Technical Standard Orders: A Breakdown

If you work in aviation, you will undoubtedly have heard the term TSO. In an industry with so many different technical terms, parts, and practices, acronyms and abbreviations like TSO can become difficult to remember. This blog will cover TSOs, or technical standard orders, in detail.

A TSO is a minimum performance standard issued by the United States Federal Aviation Administration for specified materials, parts, processes, and applications used on civil aircraft. When an entity is authorized to manufacture a material, part, or appliance to a TSO standard, this is known as TSO authorization. TSO authorization serves as both a design and production approval. Nevertheless, there are a few conditions that go along with TSO authorization. For one, TSO authorization is only an approval to manufacture an item after proving that the item meets specific airworthiness requirements of a given aircraft model. More simply put, TSO authorization means that an item also meets a minimum performance requirement independent from the item’s intended installation on an aircraft.

Furthermore, receiving a TSO is not necessarily an approval to install and use an item on an aircraft. It simply means that the item adheres to a TSO and the applicant is authorized to manufacture it. It is ultimately the responsibility of the applicant to assure the authorized item is appropriate for use on the aircraft and adheres to all installation and operational standards set in place by the FAA. A separate approval from the FAA is required before the item can be installed on the aircraft.

A Parts Manufacturer Approval, or PMA, is a combined design and production approval for modification and replacement items. Therefore, a PMA allows manufacturers to produce and sell these items for use on type certificated products. This differs from a TSO in that the approval is solely valvid for a specific aircraft or aircraft model for which the item is approved. The design approval phase of PMA certifies that an item complies with the airworthiness standard of eligible products (such as an aircraft, engine propeller, etc.).

Each part of an aircraft, regardless of its size or importance to the function of the aircraft, must have authorization to show that it meets the minimum standards necessary for operation. The TSO represents the highest level of standardization. Below it are the type certificate and supplemental type certificate. The type certificate is issued to the manufacturer of an aircraft part when the FAA determines that the part adheres to performance criteria. A supplemental type certificate is administered when an aircraft undergoes significant modification, addition, or repairs. For example, if a passenger aircraft was converted into a freight aircraft, it would require a supplemental type certificate.

Though TSOs are issued by the FAA, they often do so in conjunction with SAE International. SAE International provides consultation on the establishment and implementation of the FAAs standards. The company comprises a broad range of groups with expertise in areas such as airlines and manufacturing to help create transparent standards. Some of the criteria they enforce includes electrical, safety, and environmental standards. This includes how the parts respond to different temperatures, charges & discharges, insulation resistance, and different altitudes, humidities, and more.

At NSN Sphere, owned and operated by ASAP Semiconductor, we can help you find all types of TSO parts in addition to many other parts for the aerospace, civil aviation, and defense, electronics, and IT hardware markets. Dedicated account managers are always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at or call us at 1-714-705-4780.


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