TSO stands for Technical Standard Order & TSOA stands for Technical Standard Order Authorization.
What is a TSO
A TSO is a minimum performance standard for specified materials, parts, and appliances used on civil aircraft. TSOs represent FAA standardization that reflects standards that the FAA has deemed to be both safe and beneficial.
A TSO, is an FAA published specification identifying a minimum performance standard for specified materials, parts and appliances used on civil aircraft.
It may specify additional factors or operating parameters as well as other minimum specifications that apply to an article.
TSO articles may in principle be used on a wide variety of aircraft. However the installation of a new TSO article will require modification approval which could be for example supplemental type certificate (for alterations that are also major changes to the type design) and field approval.
What is a TSOA
A Technical Standard Order Authorization, (TSOA) is the approval that authorizes a manufacturer to produce a material, part or appliances to a TSO standard.
When authorized to manufacture a material, part, or appliances to a TSO standard, this is referred to as TSO authorization.
Receiving a TSO authorization is both design and production approval, however receiving a TSO Authorization is not in itself an approval to install and use the article in the aircraft, rather it means that the article meets the specific TSO and the applicant is authorized to manufacture it.
TSOAs reflect FAA approvals of both design and production systems, means the design is in compliance with the FAA’s standards & the production approval means that the company has a quality system in place designed to assure that articles are be airworthy.
In order to obtain a TSOA, the manufacturer must develop an article design that meets the TSO specifications and is airworthy and must also develop a manufacturing quality system that will assure that each part released from the system meets the approved design requirements.
Within the TSOA application, the applicant must certify that the design is in full compliance with the appropriate standards.
The FAA will then evaluate the application to confirm this compliance. The FAA typically responds to a TSOA application within 30 days of the application.
Difference between TSOA & PMA Process
There is no installation authority inherent in the TSOA. A parts manufacturing approval (PMA) on the other hand provides at least one aviation product (such as an aircraft or engine) into which the PMA part can be installed.
TSOAs do not provide this sort of installation eligibility because they are meant to reflect standard specifications for articles that can be used in a wide variety of aircraft.
A Parts Manufacture Approval (PMA) is a combined design and production approval for modification and replacement articles. It allows a manufacturer to produce and sell these articles for installation on type certificated products.
The design approval phase of PMA certifies that a replacement or modification article complies with the airworthiness standards of eligible products (aircraft, engine, or propeller).
The applicant shows this compliance through tests and computations unless the article is identical to the article design on a type-certificated product. Identicality means that an article is the same in all respects to an article design in a type-certificated product.
TSO Revision Process
TSOs are updated from time to time. They usually will receive a letter to reflect their revision level. A subsequent “revision” to a TSO may a change in suffice to identify the change.
A TSO may also cancel previous revision levels (It will be stated within the TSO)
Cancellation means that no one can obtain TSOA in the future under that TSO.
When there is no explicit cancellation or withdrawal of the prior revision level of the TSO, that means that the prior revision level is still a valid TSO. In some cases, the FAA permits the prior revision level of a TSO to coexist with the current revision level. (For example, if there is no safety reason for cancelling the prior revision level.)
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