Avionics News March 2012 - 19

FREQUENTLY ASKED QUESTIONS United States
Follow-on Installation to an STC
The following information is from Federal Aviation Regulations Part 21 and Part 43. QUESTION: Does the follow-on installation of a previous supplemental type certificate have any bearing on the criterion that current installation must be approved under? ANSWER: There are no automatic rules for the follow-on installation of a previous STC. If the installation and subsequent modification constitutes a major change in type design, then the modifier must apply for an STC. If the installation constitutes a major alteration, then the modifier must use approved data and follow the regulations for a major alteration; however, if the installation constitutes neither of these, then, by regulation, the installation must be a minor alteration, and the appropriate regulations should be followed. Most avionics systems are approved via an approved model list STC for business reasons, rather than because the installation is a major change in type design. The AML STC was developed to facilitate the installation of avionics systems previously performed under the individual approvals of a field approval. So, one cannot make an automatic assumption about the appropriate certitude level for a follow-on installation of an AML. In many cases, the follow-on installation may even be a minor alteration. § 21.113 (b) If a person does not hold the TC for a product and alters that product by introducing a major change in type design that does not require an application for a new TC under § 21.19, that person must apply to the appropriate aircraft certification office for an STC. The vast majority of supplemental type certificates, including approved model list STCs, are not issued because the avionics installation meets the criterion of 14 CFR Part 21, but rather, the applicant chose the STC route to meet business needs or to facilitate follow-on field installations.

The repair station performing an installation must evaluate the alteration (modification) to determine the appropriate approval level. If the avionics installation is a major change in type design, then it must apply for an STC; and if the installation is a major alteration, then it must meet the requirements for a major alteration. § 145.201 (c) (2) (A certificated repair station may not approve for return to service) any article after a major repair or major alteration unless the major repair or major alteration was performed in accordance with applicable approved technical data. However, if the installation is not a major change in type design or a major alteration then, by regulations, it must be a minor alteration and should be accomplished accordingly. § 1.1 An alteration other than a major alteration (is a minor alteration). Does this analysis change for an STC issued by a foreign national aviation authority? No. The U.S. is the only country with three levels of modifications: major change in type design, major alteration and minor alteration. Most countries only have two levels: a major change in type design and a minor change in type design. But, in both cases, the modifications normally require approved data. Not unlike the U.S., many foreign businesses may also choose the STC route for marketing purposes. So, again, there is no automatic rule for a current installation of an installation previously performed under an STC. Each alteration must be evaluated against the criterion unique to this installation. The previously issued STC is an indicator that extra care should be taken during the evaluation of the data; however, there are no automatic approval standards for these installations.
Note: The AEA offers “Frequently Asked Questions” to foster greater understanding of the aviation regulations and the rules governing the industry. The AEA strives to ensure FAQs are as accurate as possible at the time of publication; however, rules change. Therefore information received from an AEA FAQ should be verified before being relied upon. This information is not meant to serve as legal advice. If you have particular legal questions, they should be directed to an attorney. The AEA disclaims any warranty for the accuracy of the information provided.

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Avionics News March 2012

Table of Contents for the Digital Edition of Avionics News March 2012