4-3 Malfunctions, failures, or defects in the flight control system including 4.3.1.7 interference with normal control; and Malfunctions or failures of attitude, airspeed, or altitude instruments. 4.3.1.8 Note: Review § 21.3(c) for the complete and accurate list of your responsibilities.
If we determine during an accident investigation or service difficulty that your article is 4.3.2 unsafe, you must report to us at our request any results you find or actions you plan to take to correct the deficiencies. You will also have to submit to us any data we need to help the FAA issue an airworthiness directive (pursuant to § 21.3).
4.4 Design Changes.
As a TSOA holder, you are responsible for any design changes you make to your article 4.4.1 and for updating the descriptive and substantiation data. Design changes to your article are classified as either minor or major. We require that you evaluate all design changes to determine if they are minor or major changes.
Pursuant to § 21.601, it is the responsibility of the TSOA holder or LODA holder to 4.4.2 control the design relative to the applicable TSO requirements, including all parts, processes, or services procured from an outside source. Similarly, it is the responsibility of the TC/STC holder to ensure the TSO articles that have undergone design changes continue to meet the applicable airworthiness requirements of the aircraft.
Minor Design Changes Under a TSOA. 4.4.3 We permit TSOA holders to make minor design changes to their articles without further approval. However, all minor design changes must be substantiated to show compliance with the applicable TSO MPS requirements (pursuant to § 21.619(a)). We encourage you to propose to your ACO what constitutes a minor change, including the changes made by your suppliers, for the particular TSO article being manufactured and work with your ACO to establish a mutually agreed upon process for managing minor design changes. Sometimes minor changes may require significant substantiation (including testing) to ensure the article still meets the TSO requirements. However, unless the change results in a “substantially complete investigation” to the TSO, it can be classified as minor pursuant to § 21.619(a). Note that a major/minor design change classification under § 21.619(a) or (b) is made at the article level relative to the TSO standard and should not be confused with a major/minor design change classification under § 21.93. Design change classifications under § 21.93 are made at the product level.
We encourage you to use a partnership for safety plan to formalize the 4.4.3.1 agreement discussed in 4.4.3.1 with your ACO. You can find more information on this process in the FAA and Industry Guide to Product
4-4 Certification. The manufacturer must maintain and submit to the FAA, on request, minor change substantiation data (pursuant to § 21.619(a)).
The article model and/or part number are used for configuration 4.4.3.2 management at the aircraft level. You should change the part number of any article where a minor change to a previously manufactured article may affect the interchangeability at the product level, the use or installation of the article, or the minimum performance standards specified in the TSO.
Update any associated documentation, such as the installation instructions, to identify the difference between the previous and new part number versions of the article.
Pursuant to § 21.619(a), you must substantiate and document all minor 4.4.3.3 design changes. You must notify your ACO within the timeframe agreed upon with them. We recommend the data be submitted before shipping any articles. This will prevent you from distributing potentially noncomplying articles in the event the ACO finds that a minor change claim is improperly substantiated. You must state in your minor change notification letter that the changed article complies with the TSO. This statement reaffirms your compliance with part 21, subpart O. You can send this letter to the ACO by email.
If we determine a minor design change submittal is not sufficiently or 4.4.3.4 properly substantiated, you must provide additional substantiation or other data as requested by your ACO. This could require you to retest the article to show compliance with the TSO standard. If, after review of the substantiation, the ACO determines that the article no longer meets the TSO MPS, you must immediately stop marking and shipping any changed articles and comply with the TSO requirements.
If we determine a minor design change is really a major design change, 4.4.3.5 as defined in § 21.619(b), you must immediately stop marking and shipping any changed articles and comply with the criteria for major design changes.
Major Design Changes Under a TSOA. As stated in § 21.619(b), the FAA requires a 4.4.4 new TSO application for all major design changes to TSO articles under a TSOA.
If the applicable TSO is revised while the application is being evaluated, 4.4.4.1 you should provide an OPR summary with functional impacts to applicants for installation approval of the article;
A sufficient description should be provided for proper assessment; 4.4.4.2 Any OPRs with potential safety impact should be corrected; 4.4.4.3 OPR information should be provided in the installation manual or 4.4.4.4 supplemental data;
4-5 There should be a means for updating OPR summary if necessary; 4.4.4.5 The TSOA holder should provide contact information in case installer 4.4.4.6 needs more information; and The TSOA holder should have a means to accept problems reported from 4.4.4.7 the field.
Only need to demonstrate compliance with the TSO in effect at the time of 4.4.4.8 the original application, not the revised TSO.
The ACO can give up to a 6 month relief period to applicants with 4.4.4.9 pending applications provided the specific TSO being applied for contains provisions for doing so. If the applicant does not submit a complete application within this time, it must comply with the most recent TSO version.
Note: Some revised TSOs may contain a statement that the older version of the TSO will remain effective for a period of months after a revision becomes effective. During this time, the ACO may accept applications for either version of the TSO.
Design Changes Under a LODA. 4.4.5 Design changes to articles that have been issued a LODA are subject to the requirements defined in the applicable bilateral agreement. Generally, when the CAA considers a design change minor, it is approved without any FAA involvement. Design changes the CAA considers major require the LODA holder to apply for a new LODA.
Design Change by a Person Other Than the Manufacturer - TSOA and LODA. 4.4.6 Pursuant to § 21.619(c), we permit design changes to a TSO article by a person other than the original manufacturer who holds the TSO authorization, such as the product operator, the installer of the article, or the maintenance personnel. If the person seeking approval is another article manufacturer (refer to § 21.601(b)(5)), they must apply under a separate TSOA or LODA and obtain approval before modifying the article. The article may also be altered as part of an installation in an aircraft or engine, and approved under part 43 or the applicable airworthiness regulations in 14 CFR parts 23, 25, 27, 29, 31, 33, and 35. In all cases, the article must be permanently marked to indicate it has been modified.
The determination of whether a design change, repair, or alteration is major or minor 4.4.7 varies, and depends on which FAA approval is being affected. These changes are classified differently within their specific regulatory basis, and this classification depends on whether the FAA approval is a TSOA, STC, repair, or alteration. Minor changes under a TSOA may be a major change for other types of FAA approval and vice versa. Regardless of the classification of the modification, all modifications must be substantiated relative to the applicable requirements (pursuant to § 21.619).
4-6
4.5 Transferability.
As stated in § 21.614, the holder of a TSO authorization or letter of TSO design approval may not transfer the TSO authorization or letter of TSO design approval.
However, they may submit a request to the FAA for a transfer. The term “transfer” applies only to the TSO design approval. The production approval process that the MIDO accomplishes during a transfer is the same process for a new applicant or an applicant that is adding additional capability to an existing facility. TSOA transfer requests must be made by the current holder of the TSO authorization or letter of TSO design approval.
Examples of a Transfer. 4.5.1 When the sale or liquidation of a company that holds TSOA or LODA causes a change in the company’s legal status, those TSOA or LODA must be transferred. TSOA or LODA design data may be sold from one company to another, and this is also considered a transfer.
For example, the acquisition of a company with a TSOA or LODA by a 4.5.1.1 holding company would require a transfer of the TSOA or LODA if the acquired company is disbanded or absorbed into the purchasing company.
In this case, the legal entity that received the TSOA or LODA will no longer exist, so the original holder would be required to request a transfer of the TSOA to the purchasing corporation before being disbanded or absorbed. A company can transfer a TSOA or LODA only when we grant them an exemption to § 21.614.
As another example, assume XYZ Company holds a TSOA, and 4.5.1.2 ABC Corporation purchases XYZ Company. ABC Corporation plans to disband and absorb XYZ Company. In this case the legal status of XYZ has changed (for example, the company no longer exists as a legal entity) and the acquisition of the XYZ Company would necessitate a transfer of the TSOA or LODA.
Example of What Is Not a Transfer. 4.5.2 A company changing its name or relocating its facilities does not 4.5.2.1 necessitate the TSOA or LODA to be transferred. The acquisition of a company with a TSOA or LODA by a holding company would not necessitate the transfer of the TSOA or LODA if the acquired company continues to exist as the same legal entity to which the original TSOA or LODA was issued under the following conditions:
4.5.2.1.1 The acquired company retains possession of the TSOA or LODA, substantiating data, and responsibilities under the original authorization or approval; and
4.5.2.1.2 The acquired company retains the same quality system (TSOA only).
4-7 Example: ABC Corporation purchases XYZ Company. XYZ Company 4.5.2.2 holds a TSOA and will continue to operate under the same name, in the same location, with the same management, and under the same production system. In this case the legal status of XYZ has not changed and therefore the TSOA is not transferred.
Articles Approved With a TSOA. 4.5.3 Pursuant § 21.614, if you are changing your name, relocating your facilities, or being acquired by another company, you must inform your ACO before the action occurs, and you:
Should expect your ACO to forward this information immediately to your 4.5.3.1 MIDO/MISO;
Must not ship any articles from a new facility until the MIDO has 4.5.3.2 inspected and approved the new facility, and the ACO has reissued your TSOA; and Should expect your ACO to reissue the TSOA at the same level as the 4.5.3.3 original TSO after the MIDO determines your QS meets the requirements of § 21.137 pursuant to § 21.607 and you can produce each article to conform to your approved design.
Articles Approved With a LODA. 4.5.4 Pursuant to § 21.621, if you are a foreign manufacturer who holds a LODA and you are changing your name, relocating facilities, or being acquired by another company, you:
Must ensure your CAA provides the FAA written confirmation that your 4.5.4.1 legal status remains unchanged after an acquisition;
Must not mark or ship any articles with the TSO marking until the FAA 4.5.4.2 has reissued the LODA for name changes or facility relocations; and Should expect the FAA to reissue the LODA at the same level as the 4.5.4.3 original TSO after receiving written confirmation from the CAA that your article meets the TSO after a name change or facility relocation.
Converting a TSOA to a LODA. 4.5.5 Our regulations do not contain a provision for a manufacturer currently holding a TSOA to become a foreign manufacturer by relocating its design and production facilities outside the United States. In this case, your foreign facility should apply for a separate LODA as described in this AC. As the design approval holder (DAH) for the original TSOA, you will retain continued operational safety (COS) responsibilities.
Converting a LODA to a TSOA. 4.5.6
4-8 Our regulations do not contain a provision for a foreign manufacturer holding a LODA and wanting to become a U.S. manufacturer by relocating its design and production facilities into the United States. In this case, the manufacturer’s facility in the United States should apply for a new TSOA as described in this AC, applying for the current version of the applicable TSO(s). As the DAH for the original LODA, you will continue to have COS responsibilities.
5-1 CHAPTER 5. ADDITIONAL TSO TOPICS
5.1 Receiving a Parts Manufacturer Approval (PMA) to Modify a TSOA Article.
We do not issue PMA to modify TSO articles; we issue PMA to modify products (aircraft, engines, and propellers). PMA approves replacement and modification articles for specific type-certificated products. These articles may reside in an assembly approved under a TSOA on these specific products, but the PMA limits installation of these articles to those specific products. PMA cannot approve replacement articles solely for original articles approved solely under a TSOA.
5.2 Shipping a Subcomponent of an Article Independent of the Complete Article.
You can ship a subcomponent of an article independent of the complete article, but you must complete an FAA Form 8130-3, Airworthiness Approval Tag, or other acceptable document. This tag will help make clear that the subcomponent is only a piece of an article and to clarify the article in which it is intended to be installed.
5.3 Incomplete TSO Article.
An incomplete TSO article is one that provides only part of the performance and/or functionality specified in the applicable TSO. For us to approve and issue a TSOA or LODA for an incomplete TSO article, all of the following conditions must be met:
The incomplete article provides a major and independent TSO function. There must be 5.3.1 TSO requirement(s) that are specific to the function provided by the incomplete article (that is, in addition to general requirements related to software or environmental qualification).
Example of an incomplete article that provides a major and independent 5.3.1.1 function: TSO-C4, Bank and Pitch Instruments, contains requirements that apply to an electronic flight instrument system (EFIS). The EFIS displays “bank and pitch” information, but does not include a vertical gyro.
Because the EFIS provides a major independent TSO-C4 function that meets specific TSO requirements pertaining to a display, you may be granted an incomplete TSOA to TSO-C4.
Example of an incomplete article that does not provide a major and 5.3.1.2 independent function: a cooling fan for a global positioning system (GPS) covered by TSO-C196b, Airborne Supplemental Navigation Sensors for the Global Positioning System (GPS) Equipment using Aircraft-Based Augmentation. Because the cooling fan does not provide a major contribution of the TSO-C196b function, it is not eligible to be qualified as an incomplete TSO article.
5-2 The TSO MPS provides appropriate and adequate standards for evaluation of the article 5.3.2 as an incomplete article. You must identify and meet all the specific performance standards in the TSO that apply to the incomplete article (pursuant to § 21.603(a)(1)).
In the installation drawings and/or installation manual, you must adequately document 5.3.3 detailed instructions and limitations, pursuant to § 21.50 and § 43.13, for the installation and use of the incomplete article. For example, company “ABC” manufactures under TSO-C119c, Traffic Alert and Collision Avoidance System (TCAS) Airborne Equipment, TCAS II with Optional Hybrid Surveillance, a traffic alert and collision avoidance system (TCAS) antenna with an interface that is interoperable with a Company “XYZ” Model “123” TCAS computer. The installer must substantiate the interoperability between these two components when showing compliance with the applicable airworthiness requirements.
You must list in the installation manual the specific MPS that your article meets. This 5.3.4 should be provided by referencing the specific paragraphs of the TSO (a single reference can frequently be used to include a parent paragraph and all of its subparagraphs). This information will assist the installer of the TSO article in knowing the limitations of the article’s capabilities, to comply with § 21.50.
When not obvious from the component, you should permanently and legibly mark the 5.3.5 article with at least “INCOMP” adjacent to the TSO number marking (for example, “Meets TSOC69c INCOMP”) and include detailed instructions in the installation drawings or installation manual. Marking an article “INCOMP” or “Incomplete” will eliminate ambiguity about the article’s level of compliance.
5.4 Multiple TSO Authorizations for the Same Article.
If you elect to apply for a TSO Authorization, you must apply for all applicable TSO pertinent to the functions your article provides. You also need to request a deviation from § 21.15(b) to establish one TSO as the primary TSO to mark the article having multiple TSO approval.
Marking. 5.4.1 After having TSOA and the deviation approval, you can:
Mark the primary TSO number on the nameplate (marking each individual 5.4.1.1 TSO number on the article’s nameplate may be impractical).
Mark the primary article permanently and legibly with a statement that the 5.4.1.2 remaining TSO marking requirements are in the installation manual (IM),
(e.g., “See Inst Mnl for Addtl TSO approvals and/or markings.”).
List the other TSOs (and marking requirements for each TSO) in the front 5.4.1.3 section of the IM for the article’s primary TSO.
5-3 Multiple TSO Authorizations With Incomplete TSO. 5.4.2 You should apply for multiple TSO authorizations even when the article does not meet the entire TSO but meets the requirements for an incomplete TSO article, as explained in paragraph 5.3 of this AC. In cases where the article does not completely meet any TSO, a primary TSO must be established for marking. Typically this is the TSO that the article comes closest to meeting in full. The requirements listed in paragraph 5.3 of this AC must be followed when applying for an incomplete TSO. The article or the installation manual must list each TSO authorization and identify its associate deviation approval, as applicable.
5.5 Non-TSO Functions (NTF).
Definition of a Non-TSO Function 5.5.1 An NTF is a function provided by an article that is not covered by the 5.5.1.1 TSO MPS, does not support or affect the hosting article’s TSO function(s), and could technically be implemented outside of the TSO article.
When you design and manufacture an article, the article functions may be 5.5.1.2 addressed by the MPS of the TSO, or the article may provide additional functions that are not covered by any TSO. With FAA acceptance of your TSOA application, you are authorized to certify that the design and manufacturing of the article meet the MPS of the applicable TSO. NTF are accepted on a “non-interference” basis relative to the compliance of the TSO requirements for a given article.
FAA Guidance on NTFs. 5.5.2 You may choose to integrate an NTF into a TSO article to support a foreign airspace requirement, minimize the amount of line replaceable units and interconnected wiring systems in an aircraft installation, address a specific customer/industry need, or for product differentiation. NTFs may be included and accepted on a non-interference basis, as part of your TSO submittal. A TSOA may be issued for the article, if you demonstrate that it meets all of the following conditions:
The hosting article is eligible for a TSOA and meets the applicable 5.5.2.1 TSO performance requirements;
There is no applicable TSO for the NTF; 5.5.2.2 The added NTF does not affect or interfere with the hosting TSO article’s 5.5.2.3 ability to meet the TSO MPS or violate any limitations imposed by the hosting TSO; and
5-4 The hosting TSO article’s environmental qualification, and hardware and 5.5.2.4 software design assurance levels adequately support the NTF, as applicable.
Note: The criticality of the NTF should not exceed that of the hosting TSO article. Conversely, if the integrated NTF criticality is lower than the hosting TSO article, you may choose to adopt the higher design assurance levels throughout or to employ proper partitioning techniques.
5.5.2.4.1 The NTF descriptive and substantiation data are evaluated by the FAA for compliance with the MPS (for example, structural, environmental, or flammability requirements) of the TSO.
5.5.2.4.2 Substantiation data from the TSO testing showing compliance with TSO requirements is also applicable to the NTF components. For example, an in-flight entertainment system integrated into a seat design provides non- TSO functionality for the seat. The components that make up the in-flight entertainment system are required to meet the structural and flammability MPS of the seat TSO. The related substantiation data that is generated to meet the TSO MPS can be used by the TC or STC applicant without retesting the components that enable the NTF. Additional substantiation data that is not required by the seat TSO MPS may be required by the TC or STC applicant to show compliance with the applicable aircraft airworthiness requirements.
5.5.2.4.3 NTF descriptive or substantiation data that is not needed to show compliance with the TSO MPS is evaluated separately during the aircraft installation design approval (for example, TC/STC). Guidance for the approval of non-TSO functions relative to the aircraft airworthiness regulations is contained in paragraph 5.d of AC 21-50, Installation of TSOA Articles and LODA Appliances.
Non-TSO Function Evaluation Procedures. 5.5.3 The installer of the article in an aircraft is responsible for obtaining regulatory compliance approval of the TSO article and its NTFs before installation. This task is difficult because the installer generally may not have the equipment, or the expertise available to the TSO manufacturer to accomplish a thorough equipment performance evaluation, especially when the performance of an NTF must be determined by laboratory simulation or under stress conditions. This AC provides a procedure for you to help the ACO evaluate NTFs at the time of TSO application. If you follow this procedure, the FAA ACO can acknowledge the design assurance levels and environment testing accomplished on NTFs, if required by the TSO MPS, to preclude the need for repeated evaluation for each installation approval.
Project Planning Considerations. 5.5.3.1 Since the TSO minimum performance requirements do not cover the integrated NTF, the ACO will need adequate time to review the
5-5 manufacturer’s declared performance requirements to verify that the non- TSO function can reasonably be accommodated within the hosting TSO article. Manufacturers intending to integrate non-TSO functions in a proposed TSO article should plan accordingly and coordinate with their ACO at the earliest opportunity and well in advance of their TSO application, to avoid potential delays to their project. Use of a Partnership for Safety Plan (PSP) should be encouraged to formalize and adapt integrated non-TSO function to each manufacturer’s internal TSO procedures. Each project specific certification plan should address any specific ACO test and validation requirements.
Data Submittal. 5.5.3.2 Data submitted to the ACO to permit review of an NTF should include, as a minimum, the following:
5.5.3.2.1 A clear definition of the intended function and any anticipated operational credit that may be sought at the time of installation so your justification for the proposed hazard classification of failure condition(s) can be evaluated;
5.5.3.2.2 Your declared performance requirements. Where possible, you are encouraged to adopt existing industry-accepted standards, such as RTCA, European Organization for Civil Aviation Equipment (EUROCAE), SAE, or Aeronautical Radio, Incorporated (ARINC);
5.5.3.2.3 Your proposed test procedures to validate the performance requirements for the non-TSO function, including RTCA Document RTCA/DO-160 (revision level same as hosting TSO article) environmental test conditions;
5.5.3.2.4 Installation and operating instructions/limitations and maintenance instructions for the non-TSO function(s) as applicable;
5.5.3.2.5 If the TSO article includes software and/or complex custom airborne electronic hardware, your verification of the hosting TSO article’s software and/or airborne electronic hardware design assurance levels;
5.5.3.2.6 The manufacturer’s verification that the hosting TSO article’s software and hardware design assurance levels, including RTCA/DO-254 complex electronic hardware requirements in accordance with AC 20-152, RTCA, Inc., Document RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware, remain appropriate for the non-TSO function. If the non-TSO function includes software components, all RTCA/DO-178 (revision level same as hosting TSO article) software artifacts normally furnished to the ACO or retained by the manufacturer must clearly describe the non-TSO function software components and demonstrate compliance with the requirements of paragraph 5.5.3.2.3.
5-6 ACO Evaluation Criteria. 5.5.3.3 If, following early coordination with the ACO, it is determined the NTF is of a simple nature, where descriptive and substantiation data compliance with the MPS of the TSO is easily understandable, your NTF will be evaluated on a non-interference basis during the normal application process. However, the ACO will require a concurrent TC or STC project evaluation if it is determined that the added NTF(s):
5.5.3.3.1 Are complex and difficult to review and to fully understand without a concurrent installation evaluation;
5.5.3.3.2 Have a high degree of system flight deck to pilot interface;
5.5.3.3.3 Are of a simple nature individually, but combined in such a way or in sufficient quantities to become complex and difficult to review and fully understand without a concurrent installation evaluation; or
5.5.3.3.4 Incorporate new or novel technology.
Note: If a TC/STC project is being accomplished at an ACO that is different than the ACO responsible for issuing the TSOA, both offices will coordinate in the review of your declared NTF performance requirements.
NTF Acceptance and Installation Data. 5.5.3.4
5.5.3.4.1 The TSOA that the FAA letter issues to you documents the TSOA(s) being granted, including the integrated NTF that was evaluated by the ACO in conjunction with the hosting TSO article.
5.5.3.4.2 It is essential to note that the TSO article and any integrated NTF are inseparable at the article level, and should be covered by a common manufacturer’s hardware and/or software part number. The TSOA letter conveys design and production approval for the TSO function as well as design acceptance on a non-interference basis and production approval for the NTF. For example, if the TSO has MPS for functional performance, hardware and software design assurance, and environmental qualification, then the TSOA letter will also convey the ACO acceptance of your statement of conformance to these requirements for the NTF. Because the NTF is not covered under the TSO authority granted by § 21.603(a), AC 21-50 provides additional guidance for the acceptable use of TSO data for installation approval. The following additional information must be included in your article installation manual, component maintenance manual, and/or operating manual to support the aircraft installation approval requirements:
5.5.3.4.2.1 A description of the NTF, including key performance specifications, as well as qualification levels, such as software, hardware, and environmental;