Appendix E
c. Part 25, Appendix H, Section H25.5.
(1) Regulation.
“H25.5 Electrical Wiring Interconnection System (EWIS) Instructions for Continued Airworthiness.
(a) The applicant must prepare Instructions for Continued Airworthiness (ICA) applicable to EWIS as defined by § 25.1701 that are approved by the FAA and include the following:
(1) Maintenance and inspection requirements for the EWIS developed with the use of an enhanced zonal analysis procedure that includes:
(i) Identification of each zone of the airplane.
(ii) Identification of each zone that contains EWIS.
(iii) Identification of each zone containing EWIS that also contains combustible materials.
(iv) Identification of each zone in which EWIS is in close proximity to both primary and back-up hydraulic, mechanical, or electrical flight controls and lines.
(v) Identification of— (A) tasks, and the intervals for performing those tasks, that will reduce the likelihood of ignition sources and accumulation of combustible material, and (B) procedures, and the intervals for performing those procedures, that will effectively clean the EWIS components of combustible material if there is not an effective task to reduce the likelihood of combustible material accumulation.
(vi) Instructions for protections and caution information that will minimize contamination and accidental damage to EWIS, as applicable, during performance of maintenance, alteration, or repairs.
(2) Acceptable EWIS maintenance practices in a standard format.
(3) Wire separation requirements as determined under § 25.1707.
(4) Information explaining the EWIS identification method and requirements for identifying any changes to EWIS under § 25.1711.
(5) Electrical load data and instructions for updating that data.
(b) The EWIS ICA developed in accordance with the requirements of H25.5(a)(1) must be in the form of a document appropriate for the information to be provided, and they must E-3
Appendix E be easily recognizable as EWIS ICA. This document must either contain the required EWIS ICA or specifically reference other portions of the ICA that contain this information.”
(2) NPRM Preamble Discussion for Section H25.5 (70 FR 58532, October 6, 2005).
“Appendix H to Part 25—Instructions for Continued Airworthiness As previously noted, improper maintenance, repair, and modifications often hasten the “aging” of EWIS. To properly maintain, repair, and modify airplane EWIS, certain information must be available to the designer, modifier, and installer. This information should be part of the ICA as required by current § 25.1529 and the proposed § 25.1739.
This proposal would amend Appendix H by adding a new section, H25.5, to require TC applicants to develop maintenance information for EWIS as part of the ICA as a requirement for getting a design approval. The proposed rule would also apply to applicants for design change approvals (supplemental TCs and amended TCs).
The proposal would require applicants for TCs to prepare ICA for EWIS that are approved by the FAA Oversight Office, in the form of a document that is easily recognizable as an EWIS ICA. To prepare these instructions, they must use an EZAP such as the one described in AC120-XX, “Program to Enhance Aircraft Electrical Wiring Interconnection System Maintenance” to perform a review of their representative airplane covering all areas, including the flightdeck (also known as the cockpit), electrical power center, fuel tank wiring and powerfeeder cables, as well as the engine. Applicants for design change approvals would have to perform a similar review for their proposed design changes.
A zonal analysis procedure is an assessment of the structures and systems within each physical zone of the airplane. It is used to develop an inspection program to assess the general condition and security of attachment of all system components and structures items contained in the zone, using general visual inspections (GVI). An enhanced zonal analysis procedure (EZAP) is an enhanced version of the zonal analysis procedure. It focuses on EWIS components. An EZAP-generated inspection program might call for the use of stand-alone GVI and detailed inspections (DET). A stand-alone GVI is one that is performed separately from the regularly scheduled GVI (typically more frequently) and is focused on a particular area or component. In this case, the focus would be wiring. So while the zonal analysis procedure would result in a regularly scheduled GVI for the entire zone, in which each of its systems and structures are inspected at the same time, the EZAP could result in additional GVIs or DETs for the EWIS in that zone, which occur more frequently. These inspection techniques are discussed later in this section.
An EZAP identifies the physical and environmental conditions contained in each zone of an airplane, analyzes their effects on electrical wiring, and assesses the possibilities for smoke and fire. From such an analysis, maintenance tasks can be developed to prevent ignition sources and to minimize the possibilities for combustion by minimizing the accumulation of combustible materials. Such a procedure would involve dividing the airplane into physical areas, or zones, including actual physical boundaries such as wing spars, bulkheads, and cabin floor, and access provisions for the zone, and identifying which of those zones contain EWIS components. For E-4
Appendix E those zones with EWIS components, characteristics and components of all systems installed in the zone would be listed. The EWIS in the zone would be described, including information on the full range of power levels carried in the zone. And the presence or possibilities for ignition sources or accumulation of combustibles would be noted.
Combustibles are any materials that could cause a fire to be sustained in the event of an ignition source. Examples of combustible materials would be dust or lint accumulation, contaminated insulation blankets, and fuel or other combustible liquids or vapors. Wire contaminants are foreign materials that are likely to cause degradation of wiring. Wire contaminants can also be combustibles. Some commonly used airplane liquids, like engine oils, hydraulic fluids, and corrosion prevention compounds, might be readily combustible, but only in vapor or mist form. In that case, an assessment must be made of conditions that could exist within the zone that would convert the liquid to that form. Combustibles appearing as a result of any single failure must be considered. An example would be leaks from connection sites of unshrouded pipes. For the purposes of this new requirement, the term combustible does not refer to material that will burn when subjected to a continuous source of heat as occurs when a fire develops. Combustibles, as used here, will sustain a fire without a continuous ignition source.
An EZAP must address:
• Ventilation conditions in the zone and the density of the installations that would affect the presence and build-up of combustibles and the possibilities for combustion. Avionics and instruments located in the flightdeck and equipment bays, which generate heat and have relatively tightly packed installations, require cooling air flow. The air blown into the area for that cooling tends to deposit dust and lint on the equipment and EWIS components.
• Liquid contamination on wiring. Most synthetic oils and hydraulic fluids, while they might not be combustibles by themselves, could be an aggravating factor for accumulation of dust or lint. This accumulation could then present fuel for fire. Moisture on wiring may increase the probability of arcing from small breaches in the insulation, which could cause a fire.
Moisture on wires that contain insulation breaches can also lead to “arc tracking.” As discussed previously, arc tracking is a phenomenon in which an electrical arc forms a conductive carbon path across an insulating surface. The carbon path then provides a short circuit path through which current can flow. Short circuit current flow from arc tracking can lead to loss of multiple airplane systems, structural damage, and fire.
• EWIS in close proximity to both primary and back-up hydraulic, mechanical, or electrical flight controls.
• The type of wiring discrepancies that must be addressed if they are identified by general visual or detailed inspections. A listing of typical wiring discrepancies that should be detectable during EZAP-derived EWIS inspections is given in AC120-XXX, Section B “Guidance for Zonal Inspections.”
• Proper cleaning methods for EWIS components.
E-5
Appendix E Once information about such contaminants and combustibles within an airplane zone is collected, each identified possibility for combustion would then be addressed to determine whether a specific task could be performed to reduce that possibility. An example of a specific task to reduce build-up of combustibles on EWIS components is the use of temporary protective covers (such as plastic sheeting) over EWIS components in a zone where corrosion prevention fluids are being used. This would minimize the amount of fluid contamination of the EWIS components. Preventing fluid contamination reduces the probability of other contaminants, like dust and dirt, accumulating on the EWIS components. If no task can be developed to prevent accumulation of combustibles in a zone, such as the dust blown through the air by cooler fans, then tasks must be developed to minimize their buildup, such as scheduled cleaning.
Developing an ICA to define such tasks would include assessing whether particular methods of cleaning would actually damage the EWIS components. Although regular cleaning to prevent potential combustible build-up would be the most obvious task for an EWIS ICA, other procedures might also be called for. A detailed inspection of a hydraulic pipe might be appropriate, for instance, if high-pressure mist from a pinhole caused by corrosion could accumulate on a wire bundle in a low ventilation area, creating a possibility for electrical arcing.
Proximity of EWIS to both primary and back-up hydraulic, mechanical, or electrical flight controls within a zone would affect the criticality of inspections needed, their level of detail, and their frequency. Even in the absence of combustible material, wire arcing could adversely affect continued safe flight and landing if hydraulic pipes, mechanical cables, or wiring for fly-by-wire controls are routed close to other wiring.
The EZAP-generated ICA must be produced in the form of a single document, easily recognizable as EWIS ICA for that specific airplane model. The single document is relevant to the maintenance and inspection aspects of the ICA, and not the standard wiring practices manual or electrical load analysis, etc.
The ICA must define applicable and effective tasks, and the intervals for performing them, to:
• Minimize accumulation of combustible materials.
• Detect wire contaminants
• Detect wiring discrepancies that may not otherwise be reliably detected by inspections contained in existing maintenance programs.
As noted earlier, among the types of tasks to be developed from an EZAP are general visual inspections (GVI) and detailed inspections (DET). A GVI is defined as a visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made from within touching distance of the inspected object unless otherwise specified. It is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or droplight and may require removal or opening of access panels or doors. It may be necessary to use a mirror to improve visual access to all exposed surfaces in the inspection area. Stands, ladders, or platforms may be required to E-6
Appendix E gain proximity to the area being checked. It is expected that the area to be inspected is clean enough to minimize the possibility that accumulated dirt, grease, or other contaminants might hide unsatisfactory conditions that would otherwise be obvious. It is also expected, as an outcome of the EZAP applied to EWIS, that any cleaning considered necessary would be performed in accordance with procedures that minimize the possibility of the cleaning process itself introducing anomalies. The EZAP must identify guidelines to assist personnel performing a GVI in identifying wiring discrepancies and in assessing what effect such discrepancies, if found, could have on adjacent systems, particularly if these include wiring. As discussed previously, a list of typical wiring discrepancies that should be addressed is contained in proposed AC120-XX, Section B, “Guidance for Zonal Inspections.”
A DET is an intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity considered appropriate. Inspection aids, such as mirrors, magnifying lenses, or other means, may be necessary. Surface cleaning and elaborate access procedures may be required. A DET can be more than just a visual inspection. It may include tactile assessment to check a component or assembly for tightness and security. Such an inspection may be needed to ensure the continued integrity of installations such as bonding jumpers, terminal connectors, etc.
A DET would be required when the developer of the EZAP determines that a GVI is inadequate to reliably detect anomalies or degradation of EWIS components. Any detected discrepancies must be corrected according to the operator’s approved maintenance procedures.
It is not intended that the EZAP ICA identify how to correct detected discrepancies.
To prevent improper modification and repair of existing EWIS or the improper installation of a new EWIS, modification designers and modification personnel must know the applicable standard wiring practices, EWIS identification requirements, and electrical load data for the airplane undergoing modification. The proposed Appendix H25.5 would also require that the following information be included in ICA applicable to EWIS:
• Standard wiring practices data.
• Wire separation design guidelines.
• Information to explain the airplane’s EWIS identification method required by the proposed § 25.1711.
• Electrical load data and instructions for updating that data. Such information will help ensure that those modifying, repairing, or installing new EWIS will not perform any action that will adversely affect previously certified systems and unintentionally introduce potential hazards.
Standard wiring practices are defined as standards developed by the specific airplane manufacturer or industry-wide standards for the repair and maintenance of EWIS. They include procedures and practices for the installation, repair, and removal of EWIS components, including information about wire splices, methods of bundle attachment, connectors and electrical terminal E-7
Appendix E connections, bonding, and grounding. Although a standard wiring practices manual is not a design manual, and those designing a new EWIS modification for a specific model airplane should not use it as such, it does provide the designer with insight into the types of EWIS components used by the TC holder and the procedures recommended by the manufacturer for maintenance or repair that supports continued airworthiness of the components.
EWIS separation guidelines are important for maintaining the safe operation of the airplane. Maintenance and repair personnel need to be aware of the type certificate holders’ separation requirements so they do not compromise separation in previously certified systems.
In fuel tank systems, the separation of certain wires may be critical design configuration control items and therefore qualify as an airworthiness limitation. Maintenance personnel need to be aware of these guidelines and limitations because many times wire bundles must be moved or removed to perform necessary maintenance. They must be able to readily identify EWIS associated with systems essential to the safe operation of the airplane.
Similarly, those who design and install new EWIS need to be aware of separation requirements so they can use the same methods to develop the required separation for the EWIS they are adding to the airplane. This would help to ensure both that newly added EWIS is adequately separated from other EWIS, airplane system components, and structure so they do not damage the added EWIS, and that the addition of the new EWIS does not invalidate separation for previously certified EWIS.
Electrical load data and the instructions for updating that data are necessary to help ensure that future modifications or additions of equipment that consume electrical power do not exceed the generating capacity of the onboard electrical generation and distribution system. The existing § 25.1351(a)(1) mandates that the required generating capacity, and the number and kinds of power sources, must be determined by an electrical load analysis. Typically, after an airplane is delivered and enters service, it is modified numerous times throughout its service life.
Each addition or deletion of an electrical-power-consuming system changes the electrical load requirements. The only way to ensure that the capacity of the overall generating and distribution system, as well as individual electrical buses, is not exceeded is to have an up-to-date electrical load analysis. The best way to ensure that an up-to-date electrical load analysis is maintained is for the type certificate holder to include such data in the ICA provided with the airplane when it is first delivered to a customer, along with recommended practices for keeping it updated as electrical loads are deleted and added.”
3. Part 26
a. Section 26.3.
Ҥ 26.3 Definitions For the purposes of this part:
FAA Oversight Office is the aircraft certification office or office of the Transport Airplane Directorate with oversight responsibility for the relevant type certificate, supplemental type certificate, or manufacturer, as determined by the Administrator.”
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Appendix E
b. Section 26.11.
Ҥ 26.11 Electrical wiring interconnection systems (EWIS) maintenance program
(a) Except as provided in paragraph (g) of this section, this section applies to transport category, turbine-powered airplanes with a type certificate issued after January 1, 1958, that, as a result of the original certification, or later increase in capacity, have—
(1) A maximum type-certificated passenger capacity of 30 or more or
(2) A maximum payload capacity of 7,500 pounds or more.
(b) Holders of, and applicants for, type certificates, as identified in paragraph (d) of this section must develop Instructions for Continued Airworthiness (ICA) for the representative airplane’s EWIS in accordance with part 25, Appendix H paragraphs H25.5(a)(1) and (b) of this subchapter in effect on [effective date of this final rule] for each affected type design, and submit those ICA for review and approval by the FAA Oversight Office. For purposes of this section, the “representative airplane” is the configuration of each model series airplane that incorporates all variations of EWIS used in production on that series airplane, and all TC-holder-designed modifications mandated by airworthiness directive as of the effective date of this rule. Each person specified in paragraph (d) of this section must also review any fuel tank system ICA developed by that person to comply with SFAR 88 to ensure compatibility with the EWIS ICA, including minimizing redundant requirements.
(c) Applicants for amendments to type certificates and supplemental type certificates, as identified in paragraph (d) of this section, must:
(1) Evaluate whether the design change for which approval is sought necessitates a revision to the ICA required by paragraph (b) of this section to comply with the requirements of Appendix H, paragraphs H25.5(a)(1) and (b). If so, the applicant must develop and submit the necessary revisions for review and approval by the FAA Oversight Office.
(2) Ensure that any revised EWIS ICA remain compatible with any fuel tank system ICA previously developed to comply with SFAR 88 and any redundant requirements between them are minimized.
(d) The following persons must comply with the requirements of paragraph (b) or (c) of this section, as applicable, before the dates specified.
(1) Holders of type certificates (TC): [insert date 24 months after effective date]
(2) Applicants for TCs, and amendments to TCs (including service bulletins describing design changes), if the date of application was before [effective date of final rule] and the certificate was issued on or after [effective date of final rule]: [insert date 24 months after effective date], or the date the certificate is issued, whichever occurs later.
(3) Unless compliance with § 25.1729 of this subchapter is required or elected, applicants for amendments to TCs, if the application was filed on or after [effective date of final E-9
Appendix E rule]: [insert date 24 months after effective date], or the date of approval of the certificate, whichever occurs later.
(4) Applicants for supplemental type certificates (STC), including changes to existing STCs, if the date of application was before [effective date of final rule] and the certificate was issued on or after [effective date of final rule]: [insert date 30 months after effective date], or the date of approval of the certificate, whichever occurs later.
(5) Unless compliance with § 25.1729 of this subchapter is required or elected, applicants for STCs, including changes to existing STCs, if the application was filed on or after [effective date of final rule], [insert date 30 months after effective date], or the date of approval of the certificate, whichever occurs later.
(e) Each person identified in paragraphs (d)(1), (d)(2), and (d)(4) of this section must submit to the FAA Oversight Office for approval a compliance plan by [insert date 90 days after effective date of final rule]. The compliance plan must include the following information:
(1) A proposed project schedule, identifying all major milestones, for meeting the compliance dates specified in paragraph (d) of this section.
(2) A proposed means of compliance with this section, identifying all required submissions, including all compliance items as mandated in part 25, Appendix H paragraphs H25.5(a)(1) and (b) of this subchapter in effect on [effective date of this final rule], and all data to be developed to substantiate compliance.
(3) A proposal for submitting a draft of all compliance items required by paragraph
(e)(2) of this section for review by the FAA Oversight Office not less than 60 days before the compliance time specified in paragraph (d) of this section.
(4) A proposal for how the approved ICA will be made available to affected persons.
(f) Each affected person must implement the compliance plan, or later approved revisions, as approved in compliance with paragraph (e) of this section.
(g) This section does not apply to the following airplane models:
(1) Lockheed L-188
(2) Bombardier CL-44
(3) Mitsubishi YS-11
(4) British Aerospace BAC 1-11
(5) Concorde
(6) deHavilland D.H. 106 Comet 4C
(7) VFW-Vereinigte Flugtechnische Werk VFW-614 E-10
Appendix E
(8) Illyushin Aviation IL 96T
(9) Bristol Aircraft Britannia 305
(10) Handley Page Herald Type 300
(11) Avions Marcel Dassault - Breguet Aviation Mercure 100C
(12) Airbus Caravelle
(13) Lockheed L-300”
b. NPRM Preamble Discussion (70 FR 58526, October 6, 2005). Part 26 was proposed as a new Subpart I to Part 25. The placement of these requirements was changed in the final rule.
“B. Part 25 Subpart I—Continued Airworthiness and Related Part 25 Changes As discussed below, the following proposals are applicable to holders of existing TCs for transport category airplanes and applicants for approval of design changes to those certificates. On July 12, 2005, we issued policy statement PS-ANM110-7-12-2005, “Safety – A Shared Responsibility – New Direction for Addressing Airworthiness Issues for Transport Airplanes” (70 FR 40166). The policy states, in part, “Based on our evaluation of more effective regulatory approaches for certain types of safety initiatives and the comments received from the Aging Airplane Program Update (July 30, 2004), the FAA has concluded that we need to adopt a regulatory approach recognizing the shared responsibility between design approval holders (DAH) and operators. When we decide that general rulemaking is needed to address an airworthiness issue, and believe the safety objective can only be fully achieved if the DAHs provide operators with the necessary information in a timely manner, we will propose requirements for the affected DAHs to provide that information by a certain date.”
We believe that the safety objectives contained in this proposal can only be reliably achieved and acceptable to the FAA if the DAHs provide the operators with the EWIS- and fuel tank-system-related maintenance information required by the proposed operational rules for Parts 91, 121, 125, and 129. Our determination that DAH requirements are necessary to support the initiatives contained in this proposal is based on several factors:
• Developing EWIS and fuel tank system ICA is complex. Only the airplane manufacturer, or DAH, has access to all the necessary type design data needed for the timely and efficient development of the required EWIS and fuel tank system maintenance tasks.
• FAA-approved EWIS and fuel tank system ICA need to be available in a timely manner. Due to the complexity of these ICA, we need to ensure that the DAHs submit them for approval on schedule. This will allow the FAA Oversight Office having approval authority to ensure that the ICA are acceptable, are available on time, and can be readily implemented by the affected operators. Additionally, accurate and timely information is necessary to ensure alignment with the requirements of the Fuel Tank Safety Rule (FTSR). The compliance deadline for the operational requirements of the FTSR was extended to facilitate this alignment, as stated E-11
Appendix E in the Federal Register notice “Fuel Tank Safety Compliance Extension (Final Rule) and Aging Airplane Program Update (Request for Comments)” (69 FR 45936).
• The proposals in this NPRM affect a large number of different types of transport airplanes. Because the safety issues addressed by this proposal are common to many airplanes, we need to ensure that technical requirements are met consistently and the processes of compliance are consistent. This will ensure that the proposed safety enhancements are implemented in a standardized manner.
• The safety objectives of this proposal need to be maintained for the operational life of the airplane. We need to ensure that future design changes to the type design of the airplane do not degrade the safety enhancements achieved by the initial incorporation of EWIS and fuel tank system ICA. We need to be aware of future changes to the type designs to ensure that these changes do not invalidate the maintenance tasks assigned to a particular type design when the ICA are first developed under the requirements of this proposal.
Based on the above reasons and the stated safety objectives of FAA policy PS-ANM110-7-12-2005, we are proposing to implement DAH requirements applicable to EWIS and fuel tank system ICA.
In the past, we have issued a similar requirement in the form of a special federal aviation regulation (SFAR). But SFARs appear in various places in the CFR and are difficult to reference as a whole. The FAA believes that placing these types of requirements in a new subpart of part 25, which contains the airworthiness standards for transport category airplanes, would provide a single, readily accessible location for this type of requirement. Therefore, we are proposing new subpart I to part 25 to contain these requirements.
In preliminary discussions with foreign airworthiness authorities of the concept of this new subpart, they have expressed concerns that their regulatory systems may not be able to accommodate these types of requirements in their counterparts to part 25. While agreeing on the need for these types of requirements, they have suggested that it may be more appropriate to place them in part 21 or another location. As discussed below, because we expect these new subpart I requirements to be similar to new part 25 airworthiness standards, we have tentatively decided to place them in part 25. However, we specifically request comments on the appropriate location of these requirements, particularly from the foreign authorities. If, based on comments received, we conclude that another location is more appropriate, we may move them in the final rule. Because such a move would not affect the substance of the requirements themselves, we would not consider this to be an expansion of the scope of this rulemaking that would require additional notice and comment procedures.
Section 25.1 Applicability.
As stated in § 25.1, part 25 currently prescribes airworthiness standards for issuance of TCs, and changes to those certificates, for transport category airplanes. As discussed in more detail above, with this NPRM the FAA is proposing to expand the coverage of part 25 to include a new subpart I containing requirements that must be complied with by current holders of these certificates. Therefore, we are proposing to amend § 25.1, “Applicability,” to state that part 25 E-12
Appendix E also includes requirements for holders of these design certificates. As discussed in the FAA’s final rule, “Fuel Tank Safety Compliance Extension and Aging Airplane Program Update” (69 FR 45936), this NPRM is one of several proposals for adoption of these kinds of requirements for current holders of type certificates.
A theme common to this and other possible subpart I proposed rules is that the rulemaking projects include proposals for changes to operational rules to require operators to implement programs or take other actions that the FAA has determined are necessary for safety.
In several recent rules we have adopted operational requirements without a corresponding requirement for design approval holders to develop and provide the necessary data and documents to support the operators’ compliance. The difficulty encountered by operators in complying with these rules has convinced us that the corresponding design approval holder requirements are necessary to enable operators to comply by the regulatory deadlines.
Section 25.2 Special retroactive requirements.
Section 25.2 currently contains “special retroactive requirements.” These requirements are “retroactive” in the sense that they require applicants for changes to TCs to comply with requirements that were not applicable to the original TC. As discussed below, proposed subpart I would have a similar effect, in that it would impose new requirements on both existing design certificate holders and applicants for changes to those certificates. Therefore, we are proposing to amend § 25.2 to make reference to proposed subpart I.
Section 25.1801 Purpose and Definition.
Paragraph (a) of this section states that this subpart would establish requirements for holders of TCs to take actions necessary to address particular safety concerns or to support the continued airworthiness of transport category airplanes. Such actions may include, but are not limited to, performing assessments, making design changes, developing revisions to ICA, and making necessary documentation available to affected persons.
The specific applicability of each subpart I rule will be established as part of the rulemaking adopting each rule. Generally this subpart would also apply to applicants for type certificates and changes that are pending as of the effective date of this rule. It would also apply to future applicants for changes to existing type certificates. Under § 21.101, the FAA may determine that it is not appropriate to require such applicants to comply with new airworthiness standards, such as proposed new subpart H. However, it is appropriate for them to comply with the same requirements as existing certificate holders. Otherwise, the safety improvements that result from type certificate holder compliance with these requirements could be undone by later modifications.
For example, in the case of this proposed rule, as discussed below, operators would be required to revise their maintenance programs based on EWIS ICA developed by the type certificate holder. Unless future STC applicants are required to provide similar ICA for their modifications, the TC holder’s ICA could become obsolete or, in some cases, even provide incorrect and potentially unsafe information as applied to the STC holder’s modification. In other cases, because subpart I rules accompany corresponding operating requirements, failure of E-13
Appendix E an STC applicant to comply with a subpart I rule could make it impossible for an operator to comply with the corresponding operating requirement. Subpart I does not apply to future applicants for TCs, because those applicants will be covered by other proposed changes to part 25, including Appendix H.
Therefore, adoption of a new subpart I rule would also necessitate new requirements for certification of changes to TCs that are in addition to the requirements that are specified under § 21.101. Under that section, if a change is “significant” and certain other criteria are met, the applicant would have to show compliance with the latest airworthiness requirements. For example, an applicant applying for such a change after this final rule becomes effective would have to comply with the proposed EWIS requirements in subpart H. Even if we determine that these broader regulations do not apply, the applicant for a change must still comply with the subpart I rule.
Paragraph (b) of this section provides a definition of the term “FAA Oversight Office.”
The FAA Oversight Office is the aircraft certification office or office of the Transport Airplane Directorate with oversight responsibility for the relevant TC or STC, as determined by the Administrator. As stated later in the discussion of the proposed operating rules, the primary means for operators to comply with those requirements would be by implementing programs or taking other actions developed by the TC and STC holders under this proposed subpart. In each case, to ensure compliance with the relevant subpart I rule, the TC and STC holder’s compliance documentation (for example, in this case, EWIS ICA) must be submitted to the FAA Oversight Office. Because we expect this will be a standard approach to compliance with the requirements of this subpart, we are including this definition in this section to avoid having to repeat it in each section within this subpart.
25.1805 Electrical Wiring Interconnection Systems (EWIS) Maintenance Program.
This proposal would apply to holders of TCs and to applicants for new TCs, amended TCs, and supplemental TCs if the application was filed before the effective date of this rule and the certificate was issued on or after the effective date of this rule. It would also apply to future applicants for approval of changes to existing TCs.
Paragraph (a) states that this rule would apply, with some exceptions, to transport category turbine-powered airplanes with a maximum type-certificated capacity of 30 or more passengers, or a maximum payload capacity of 7500 pounds or more resulting from the original certification of the airplane or later increase in capacity. This would result in the coverage of airplanes where the safety benefits and the public interest are the greatest.
The reference to the originally certificated capacity, or later increase in capacity, is intended to address two situations:
• In the past, some designers and operators have tried to avoid applying requirements mandated only for airplanes over specified capacities by getting a design change approval for a slightly lower capacity. By referencing the capacity resulting from original certification, this proposal would remove this possible means of avoiding compliance.
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