Avionics News May 2012 - 17

Installation of Wireless Local Area Network using IEEE 802.11 Protocols in Part 23 Aircraft
This policy statement addresses the certification of 14 CFR Part 23 aircraft that include a wireless local area network, using institute of electrical and electronics engineers 802.11 a/b/g/n protocols. More specifically, the policy clarifies the guidance regarding cabin WLAN equipment installation that creates a radio frequency

network and provides connectivity (i.e., Internet connection and email services) through access point(s) to users with IEEE 802.11 compliant portable electronic devices. The primary concern of the subject WLAN certification is the aircraft systems immunity and compatibility with RF energy from transmitting PEDs (T-PEDs). Comments are due no later than May 9, 2012. These documents can be viewed online at www.faa. gov/aircraft/draft_docs/.

FREQUENTLY ASKED QUESTIONS United States
Removing Previous Modifications
The following information is from Federal Aviation Regulations Part 21 and Part 43.

QUESTION: If a modification was installed via a supplemental type certificate, does this require an STC or field approval to remove it? ANSWER: Maybe – but only if the removal (independent of the installation) constitutes a major change in type design or a major alteration – otherwise, no. There is no automatic criterion for removal of a previous installation. The vast majority of STCs, including approved model list STCs, are not issued because the avionics installation meets the criterion of 14 CFR Part 21. Rather, the applicant chose the STC route to meet business needs or to facilitate follow-on field installations. § 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. Note: While there is FAA policy that encourages the agency to only issue STCs when required by a major change in type design, the establishment of AML STCs for avionics systems (AC 23-22) was actually based on standardizing major alterations. In addition, many parts manufacturing approval projects begin with an STC, and other FAA policy requires many avionics systems, such as GPS, to be initially approved via STC. The repair station removing a previous installation is performing an alteration (modification) independent of the initial installation. As a result, the repair station must evaluate its

alteration to determine the appropriate approval method. If the alteration is a major change in type design, then it must apply for an STC; and if the alteration is a major alteration, then it must meet the requirements for a major alteration. However, if the alteration 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. § 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. In each case, there is no indication this requirement is reciprocal; or that all STCs are a major change in type design or every alteration performed with approved data is a major alteration. There are dozens of reasons why repair stations choose to utilize a higher level of approval for a given installation. The technology may have been “new and novel” at the time of initial installation, or the customer may have intended to export the aircraft to a country that only recognizes a higher level of approval. Or, the installer may have opted for a particular installation level because of incorrect guidance from someone else. In fact, the basis of an AML STC was to replace avionics installation previously performed via field approval in an effort to add consistency to the thousands of installations performed annually, not to change the approval level of the alteration. It doesn’t matter why the original installer chose the path that they did, if not relevant to the current modification.
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 May 2012

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