(3) Protections and cautions. This AC provides guidance for developing actions and cautionary statements to be added to maintenance instructions for the protection of wire and other EWIS components. Maintenance personnel will use these enhanced procedures to minimize contamination and accidental damage to EWIS while working on an airplane.
(4) “Protect and clean as you go” philosophy. This philosophy is applied to airplane EWIS through inclusion in operators’ maintenance and training programs. This philosophy stresses the importance of protective measures when working on or around wire bundles, connectors, and other EWIS components. It stresses how important it is to protect EWIS during structural repairs, STC installations, or other alterations by making sure that metal shavings, debris, and contamination resulting from such work are removed. The “protect and clean as you go” philosophy is translated into specifics by the protection and caution recommendations described in section 15 of this AC. More information is contained in section 13 of this AC, Causes of Wire and Other EWIS Component Degradation.
(5) Consolidation with fuel tank requirements. The FAA has developed an extensive program to address safety problems associated with fuel tanks. Fuel tank systems contain EWIS that may be routed independently or may be integrated with other airplane systems’ EWIS. One part of the Fuel Tank Safety Rule, SFAR 88, requires development of maintenance and inspection instructions to ensure the safety of the fuel tank system. Other sections of the Fuel Tank Safety Rule require operators to include fuel tank safety maintenance and inspection instructions in their maintenance or inspection programs. An objective of this AC is to ensure that fuel tank system ICA developed to comply with SFAR 88 are compatible with the EWIS ICA, including minimizing redundant requirements. See section 2 of this AC for details.
b. To fully realize the objectives of this AC, type certificate holders, STC holders, air carriers, air operators, maintenance providers, and repair stations will need to redefine their current approach to maintaining and altering airplane wiring and systems. This redefinition must reach both overall philosophy and specific maintenance tasks. This may require more than simply updating maintenance manuals and work cards and improving training. Maintenance personnel need to be aware that airplane EWIS must be maintained in an airworthy condition.
They also need to recognize that a visual inspection of EWIS has inherent limitations. Small defects such as breached or cracked insulation, especially in small-gage wire, may not always be apparent. Therefore, effective EWIS maintenance combines good visual inspection techniques with improved wiring maintenance practices and training.
c. General Compliance Information. Sections 5 through 12 of this AC provide general information regarding the performance of the EZAP. The EZAP process is described in detail in appendix A and appendix B of this AC.
d. EWIS Degradation and Maintenance Information. Sections 13 through 15 of this AC contain general information on (1) causes of wire and other EWIS component degradation,
(2) EWIS maintenance guidance, including the levels of inspection applicable to EWIS maintenance, and (3) protection and caution recommendations. The information in these sections can be used by manufacturers in developing EWIS maintenance guidance and by operators to improve EWIS maintenance practices.
5. Enhanced Zonal Analysis Procedure (EZAP)—General Guidance.
a. The EZAP described in this AC was developed to identify tasks to (1) minimize accumulation of combustible materials, (2) detect EWIS component defects, and (3) detect EWIS installation discrepancies that may not be reliably detected by inspections contained in existing maintenance programs. An EZAP logic diagram and an accompanying step-by-step explanation are contained in appendix A of this AC. The EZAP process outlined in appendix A is to be used by type certificate holders. It is also to be used by modifiers such as STC holders/applicants to determine if the design change requires new EWIS ICA, or revisions to existing EWIS ICA. If the STC applicant/holder does not have access to the data required to perform the EZAP outlined in appendix A, then the process outlined in appendix B of this AC may be used.
b. An EZAP will result in safety improvements for airplanes operated with a maintenance or inspection program that includes a zonal inspection program (ZIP). It is unlikely that ZIPs developed in the past considered wire or other EWIS components, except for the most obvious damage that could be detected by a GVI.
c. For airplane models without a ZIP, the EZAP logic is likely to identify a large number of EWIS-related tasks that will need to be consolidated into the existing systems maintenance or inspection program. DAHs who have airplane models without a ZIP might find it worthwhile to develop a ZIP in accordance with an industry-accepted method, such as Maintenance Steering Group 3 (MSG-3), in conjunction with an EZAP.
d. When performing the EZAP, evaluate items such as plumbing, ducting, control cables, and other system installations located in the zone for possible contributions to wiring or other EWIS component degradation or failures. The results of the analysis will indicate whether a restoration task, a zonal GVI, a stand-alone GVI, or a detailed inspection (DET) is required to inspect the EWIS in the zone. The way to determine the best type of inspection is graphically represented in figure 2, step 8, of appendix A of this AC. The type of inspection is determined by completing EZAP Worksheet 3A or EZAP Worksheet 3B of appendix A of this AC. EZAP Worksheet 3A is used for airplanes with a ZIP. EZAP Worksheet 3B is used for airplanes without a ZIP.
e. New tasks identified by the EZAP logic should be compared against existing tasks in the maintenance program to ensure that they are compatible with each other. Also, existing maintenance task type and frequency should not affect the outcome of the EZAP analysis. The analysis for a particular zone should be completed to identify appropriate EWIS tasks and their frequency. After the analysis is complete, these new EWIS tasks should be compared to existing maintenance program tasks to assess where the new tasks and the existing maintenance program tasks can be logically combined. The EZAP analysis should not be adjusted in order to make the tasks and intervals fit the existing maintenance program just for the sake of aligning tasks. Refer to the description in figure 1, step 9, of appendix A of this AC for a detailed discussion on task consolidation and alignment.
f. Operators may want to use the EZAP logic to identify additional inspection and cleaning tasks for any design changes on their airplanes for which EZAP ICA are not available. EWIS ICA developed by a DAH might not have taken into account modifications made to the airplane 8
by someone other than the DAH who developed the EWIS ICA. Also, when an STC is no longer supported by the STC holder, operators may want to perform an EZAP on the zone(s) affected by the modification.
6. EWIS ICA Developed Using an EZAP.
a. An EWIS ICA task is either an inspection task or a restoration task. The inspection task can be a zonal general visual inspection (GVI), stand-alone GVI, detailed inspection (DET), or a combination of these. A restoration task is usually a cleaning task, but it can also be a task such as replacing an air filter in order to reduce the likelihood of contamination build-up within a zone. EWIS ICA are comprised of all the data required to perform these inspection or restoration tasks. The EWIS ICA can be, and almost always are, comprised of several different data components. It is all of these data components put together that define any particular EWIS ICA. The data components of EWIS ICA can be, and often are, located in multiple documents produced by the applicant or DAH.
b. As an example, EWIS ICA data components can be located in a Maintenance Review Board Report (MRBR), a maintenance planning document (MPD), a maintenance implementation document (MID), an airplane maintenance manual (AMM), a standard wiring practices manual/electrical standards practices manual (SWPM/ESPM), or a stand-alone ICA document produced by a DAH or STC applicant. These data components are items such as:
• Task reference number(s).
• Task type (for example, DET, stand-alone GVI).
• Task interval.
• Task description (for example, perform a DET inspection of the power feeders and connected EWIS components).
• Task procedure (in other words, instructions on how to perform the actual task(s)).
Note: The task procedure should describe how to accomplish the maintenance task. For example, if the task description states to perform a stand-alone GVI of the EWIS in the zone, then the procedure should instruct the maintenance technician to inspect the EWIS within the zone. In the past, some task procedures have instructed the technician to merely inspect the “wires” or “wiring” in the zone.
Such a procedure would not be acceptable since wire is only one component of an EWIS. An EWIS includes many components such as clamps, connectors, bundle ties, and stand-offs as defined by § 25.1701. However, in certain cases it may be acceptable for the inspection task to specify a particular EWIS component, such as a wire bundle or high current carrying cable, as being the focus of a specific inspection. For example, service history may show that on a particular airplane model, the power feeders in a specific zone should be the focus of an inspection.
Therefore, specifying to perform a DET or stand-alone GVI of the power feeders 9
and their connected EWIS, instead of a DET or stand-alone GVI of the EWIS in the zone, would be more effective in aiding the maintenance technician to detect possible defects in the power feeder rather than instructing them to inspect all the EWIS within the zone. Such an approach should be considered on a case-by-case basis.
• Task applicability (in other words, model, engine type).
• Airplane zone identification.
Note: According to Air Transport Association (ATA) iSpec 2200, Information Standards for Aviation Maintenance, zones are identified by the airplane manufacturer “to facilitate maintenance, planning, preparation of job instructions, location of work areas and components, and a common basis for various maintenance tasks.” ATA iSpec 2200 contains guidelines for determining airplane zones and their numbering. The EZAP process uses these manufacturer-identified zones. The zones are not created uniquely for EZAP.
• Access instructions.
• Supporting procedures as necessary.
c. Both airplane manufacturers and STC holders/applicants produce EWIS ICA but the process they use is different, and each of these DAHs produce the EWIS ICA in different forms.
It is not possible to provide a one-size-fits-all answer for what comprises EWIS ICA. The DAH must identify all of the components comprising the EWIS ICA and identify all of these components in a single document. This single document has become known as the source document. The regulatory requirement for the source document is contained in part 25, appendix H, paragraph H25.5(b) and is discussed in section 7 of this AC.
7. EWIS ICA Source Document as Required Part 25, Appendix H, Paragraph H25.5(b).
a. Paragraph H25.5(b) imposes some specific requirements for documentation and identification of EWIS ICA. It requires that the EWIS ICA developed in accordance with paragraph H25.5(a)(1) must be in the form of a document appropriate for the information to be provided, and that they must be easily recognizable as EWIS ICA. This document must either contain the required EWIS ICA, or specifically reference other documents that contain this information. The document required by paragraph H25.5(b) is referred to as the source document (SD). The entire EWIS ICA must be contained or referenced in the SD. However, paragraph H25.5(b) does not prescribe a specific data form for either the EWIS ICA or the SD (if they are not one and the same). The form the EWIS ICA data takes, and the form of the SD, is at the discretion of the DAH or applicant, as long as it meets the requirements of paragraph H25.5(b) and the data it contains (or references) meets the requirements of paragraph H25.5(a)(1). Some airplane manufacturers plan to use existing documents as their SD.
This could be an MRBR, MPD, MID, or some other document. Others are planning to develop new forms of documentation to specifically address the new EWIS ICA SD requirement.
Whatever form the DAH uses to document the EWIS ICA, the SD must clearly identify the data that comprise the EWIS ICA or contain the actual data in order to be in compliance with paragraph H25.5(b).
(1) As described above, paragraph H25.5(b) requires that each EWIS ICA be easily recognizable as EWIS ICA. This means that the EWIS ICA will need to be uniquely identified as such. As an example, some DAHs place “(EZAP)” or “(EWIS)” after each task description to signify that the task is a part of the EWIS ICA. Keep in mind that the purpose of this requirement is to enable easy identification of ICA tasks after they have been incorporated into an operator’s maintenance program. The requirement is meant to ensure traceability. The identification requirement is not for the benefit of the technician who performs the actual maintenance task, but rather for the people who must keep track of the EWIS ICA, such as personnel at an operator or maintenance facility who track maintenance tasks, or an FAA principal inspector.
(2) There are some unique requirements regarding operator-requested revisions to approved EWIS ICA that necessitate they be easily identifiable. Refer to section 12 of this AC for information regarding operator-requested revisions to EWIS ICA.
b. Future Revisions to the FAA-Approved Source Document (SD). After initial approval of the source document, a DAH will likely need to revise the document at some point in order to account for any new or revised EWIS inspection or restoration procedures developed due to production changes or design changes mandated by ADs. Revisions to EWIS ICA such as task deletion, addition, or interval escalation could also occur due to a request by the Industry Steering Committee (ISC) and can be addressed by a specific airplane model’s Zonal Working Group. Any agreed to revisions would be reflected in an update to the MRBR. Proposed revisions to the SD should be submitted to the FAA oversight office, ACO, or office of the Transport Airplane Directorate, as applicable, for review and approval. Upon approval, the FAA oversight office will issue a formal FAA-letter approving the new SD revision. A DAH can then use that approval letter as proof that the EWIS ICA contained in, or referenced by, the SD has been FAA approved. The SD should be revised and submitted for FAA approval when an existing EWIS inspection or restoration task type or task interval is proposed, as well as any proposed task deletions. The revised SD should also be submitted for review and approval if any of the referenced procedures, such as an AMM procedure or procedures referenced within the AMM procedure, is revised such that that any references to that procedure by the SD would no longer be valid. An example of this would be a change to the AMM procedure number or title of the procedure.
8. EWIS ICA Developed by Type Certificate Holders or Applicants. For EWIS ICA data1 identified in the MRBR, MPD, MID, or other type of SD, the items listed below are considered to constitute EWIS ICA. The FAA oversight office must review this material for its 1 The MRBR, MPD, or other document used as the SD may reference the information comprising the actual EWIS ICA. The airplane manufacturer or operators would use this referenced information to develop the task cards (sometimes referred to as job cards) or other documents that are used by maintenance technicians.
acceptability before issuing an approval. The items listed below are also the data that airplane manufacturers and/or operators (or other FAA-approved maintenance providers) will use to develop the task, or job, cards used by the maintenance technician to perform the EWIS inspection or restoration tasks.
a. Controlling reference numbers for the individual EWIS ICA tasks as listed in the MRBR, MPD, MID, or other SD. These reference numbers can be referred to as MRBR reference number, Maintenance Manual (MM)/MPD reference number, Maintenance Significant Items (MSI) reference number, task number, and so forth. The nomenclature and the documents called out by the reference numbers can vary among DAHs. Also, tasks may have been given more than one number by the manufacturer to identify them as parts of different documents. So one task, for example, may have an MPD reference number as well as an MRBR reference number.
If more than one number identifies any single EWIS task, then each of those numbers must be considered part of the EWIS ICA. All numbers considered necessary to fully identify and track the EWIS ICA should be considered part of the ICA.
b. Type of task (for example, restoration/cleaning, stand-alone GVI, zonal GVI, and DET as identified in the SD).
c. Task interval (in other words, how often the maintenance task must be accomplished— for example, every 16,000 flight cycles or 3,000 days).
d. Applicability (for example, 767-200, A340, EMB-145) as identified in the SD. Some models within the same family of airplanes may have differing maintenance requirements based on available options (for example, freighter versus passenger version, engine types).
e. Airplane zone identification for airplanes with a zonal program (for example, Zone 201).
f. Task description as given in the SD (for example, Inspect (General Visual) all exposed EWIS in the wheel well. NOTE: Gear extended, doors in open position.)
g. Task procedure(s). These are the actual instruction(s) on how to perform the zonal GVI, stand-alone GVI, DET, and restoration/cleaning tasks that support the task description listed in the SD.
h. Supporting task procedure(s), if any, necessary to perform the task procedure in any other document referenced by the task procedure.
i. Instructions for protections and caution information that will minimize contamination and accidental damage to EWIS. (This can appear in different places, such as in the AMM or in the SWPM/ESPM.) If contained in the SWPM or ESPM (or other similar document), this information will be contained in chapter 20. Sometimes this information is repeated in the standard practices chapter (chapter 20) of the AMM. In any case, it is general caution and protection information, and we do not expect that unique procedures will be developed for individual EWIS ICA for a particular airplane model or even models produced by the same manufacturer. Any protection and caution information specific to EWIS ICA must be referenced in the SD.
9. EWIS ICA Developed by an STC Applicant/Holder or Applicant.
a. Unlike TC applicants/holders, STC applicants do not use the Maintenance Review Board (MRB) process to develop maintenance tasks. However, an STC applicant, like a TC holder, is required to develop EWIS ICA with an EZAP. Therefore, nearly everything that comprises the EWIS ICA for a TC holder’s airplane will also comprise the EWIS ICA for an STC applicant’s modification. Obviously the volume of EWIS ICA for the STC applicant will be smaller and the tasks will be confined to the modified area of the airplane. The following are considered to constitute EWIS ICA for an STC and, therefore, would need FAA oversight office approval:
(1) Controlling reference number(s) contained in the SD for the individual EWIS ICA tasks if those numbers are used to identify a specific EWIS ICA task. All information referenced in the SD that is considered necessary to fully identify and track the EWIS ICA tasks should be considered part of the ICA.
(2) Type of task (for example, restoration/cleaning, stand-alone GVI, zonal GVI, and DET) as identified in the SD.
(3) Task interval (in other words, how often the maintenance task must be accomplished—for example, every 16,000 flight cycles or 3,000 days).
(4) Applicability as identified in the SD (for example, 767-200, A340, EMB-145).
Some models within the same family of airplanes may have differing maintenance requirements based on available options (for example, freighter versus passenger version, engine types).
(5) Airplane zone identification for airplanes with a zonal program (for example, Zone 201).
(6) Task description as given in the SD (for example, Inspect (General Visual) all exposed EWIS in the wheel well. NOTE: Gear extended, doors in open position.)
(7) Task procedure(s). These are the instruction(s) on how to perform the GVI, DET, and restoration/cleaning tasks that support the task description listed in the SD. These will sometimes appear in a referenced document, rather than in the SD itself.
(8) Supporting task procedure(s) (if any) necessary to perform the task procedure in any other document referenced by the task procedure.
(9) Instructions for protections and caution information that will minimize contamination and accidental damage to EWIS—unless the modification is using some unique materials or EWIS components, this information will be the same as that developed by the airplane manufacturer. In this case, the applicant should make a statement, along with the appropriate justification, that the existing protection and caution information is adequate.
b. Applicants may submit actual task cards for FAA oversight office approval. The task card is what the maintenance technicians (in other words, persons actually performing the EWIS ICA task) use on the shop floor to tell them what the task is and how to accomplish it. Refer to section 7 of this AC for further discussion on EWIS ICA documentation.
10. FAA and FAA Oversight Office Approval of EWIS ICA.
a. The requirements for the FAA to approve EWIS ICA are contained in § 25.1729 and in § 26.11(b) and (c). Section 25.1729 requires applicants to prepare EWIS ICA in accordance with part 25, appendix H, sections H25.4 and H25.5, and to have them approved by the FAA. In this case, approval by the FAA means approval by the ACO or office of the Transport Airplane Directorate with oversight responsibility for the company or person requesting the approval.
Section 26.11(b) and (c) require that DAHs and applicants prepare EWIS ICA in accordance with paragraphs H25.5(a)(1) and (b) of appendix H. These also must be approved by the FAA, but in this case by the FAA oversight office. In summary, there are three different compliance scenarios that require FAA approval of EWIS ICA:
(1) Section 26.11(b) requirements for TC holders.
(2) Section 26.11(c) EWIS ICA requirements for STC and amended TC holders/applicants.
(3) Section 25.1729 EWIS ICA requirements for TC, amended TC, and STC applicants.
b. The following guidance is related only to paragraphs H25.5(a)(1) and (b) of appendix H to part 25. Guidance for the other EWIS ICA requirements in appendix H may be found in AC 25.1701-1, Certification of Electrical Wiring Interconnection Systems on Transport Category Airplanes.
c. The FAA oversight office will approve the SD required by paragraph H25.5(b).
Approval of the SD signifies approval of the actual EWIS ICA contained either in the SD itself, or in other documents referenced in the SD. If the SD references data contained in other documents, the FAA oversight office, ACO, or office of the Transport Airplane Directorate must review that data to ensure compliance with paragraphs H25.5(a)(1) and (b). Please note that this includes all task procedures related to the tasks descriptions. This means that approval of the SD also signifies approval of any referenced data. It does not, however, necessarily signify approval of the entire referenced document. For example, EWIS ICA task procedures contained in the AMM will be considered FAA approved, but the entire AMM is not considered FAA approved.
This is because the AMM contains maintenance data other than EWIS maintenance data. Once the SD has been submitted by an applicant or DAH and found to be in compliance by the ACO in the case of an ICA developed for § 25.1729, or by the ACO or office of the Transport Airplane Directorate (FAA oversight office) in the case of ICA developed for § 26.11, a letter will be issued signifying approval of the EWIS ICA. The DAH may communicate the approved version of the EWIS ICA (in other words, attach the FAA approval letter to the EWIS ICA source document) to the operators to show that the EWIS ICA are approved.
Note: FAA Aircraft Evaluation Group (AEG) approval of MRBRs that contain EWIS ICA tasks does not signify FAA approval of the EWIS ICA as required by § 25.1729 or § 26.11.
The FAA oversight office (ACO or office of the Transport Airplane Directorate) will issue this approval.
d. A DAH located outside of the United States should submit the required regulatory material to the FAA through that DAH’s civil aviation authority (CAA). This applies to the draft 14
and final EWIS ICA, as well as to any necessary supporting documentation such as the EZAP for the airplane model or design change for which approval is sought. The FAA oversight office ACO, or office of the Transport Airplane Directorate, will coordinate with the CAA regarding review and approval of the data.
e. The following are meant to represent the general types of activity that may occur when EWIS ICA are developed and approved. These sequences of events are presented as examples and may not necessarily represent the exact order in which these actions will occur every time or all the actions necessary for every situation. However, the actions listed are consistent with the MRB procedures outlined in AC 121-22A, Maintenance Review Board.
(1) The following are typical actions for holders of, or applicants for, type certificates as they develop EWIS ICA to comply with the requirements of part 25, appendix H, paragraphs H25.5(a)(1) and (b) (as required by § 25.1729 and § 26.11).
Note: The steps below are focused on the development, review, and approval of the EZAP-derived EWIS ICA. Other EWIS ICA tasks and non-EWIS ICA may also be addressed during the review process, but, for clarity, they are purposely left out of the following sequence of events.
(a) The DAH conducts the preliminary EZAP analysis.
(b) The DAH presents the results of the EZAP analysis to the Industry Steering Committee (ISC) working group (WG) assigned to review the analysis. Typically this will be the Zonal WG. FAA personnel from ACO and AEG offices will participate in the WG.
(c) The WG and the DAH agree on any necessary revisions to the analysis, and the DAH updates the analysis based on these agreements.
(d) The DAH presents the revised EZAP analysis results to the ISC.
(e) The ISC reviews the EZAP analysis results and identifies any necessary revisions.
(f) The DAH updates the analysis based on ISC review and prepares the MRB report, which includes EZAP-derived EWIS ICA.
(g) The DAH transmits the MRB report to the applicable FAA AEG office for approval.
(h) The AEG MRB chairperson reviews and approves the MRBR and reviews the acceptability of other relevant EWIS ICA documentation, such as task procedures contained in the AMM, and then transmits the MRBR approval letter to the DAH. This could be an iterative process if the MRB chairperson identifies any additional changes he or she believes are necessary.
Note: The MRB chairperson’s signature does not indicate approval of compliance with the requirements of §§ 26.11 and 25.1729. Those compliance findings must be issued by the FAA oversight office.
(i) The DAH prepares instructions for continued airworthiness, which include EZAP-derived EWIS ICA based upon the content of the approved MRBR.
(j) The DAH produces the SD (required by paragraph H25.5(b)), which either contains or identifies the location of the EWIS ICA. (The SD can either contain the EWIS ICA or reference its location in other documents—it is the DAH’s choice.)
(k) The DAH submits the SD and any referenced ICA documents to the FAA oversight office for approval.
(l) The FAA oversight office, in conjunction with the applicable AEG office, reviews and approves the SD, which indicates approval of the EWIS ICA referenced or contained in that document.
(2) Following are the typical steps that DAHs or applicants will need to go through in determining whether the design change for which they seek approval requires revisions to previously approved EWIS ICA or the development of new EWIS ICA, or both. A design change can be accomplished through an amended TC (including service bulletins describing design changes), an STC, or changes to an existing STC. These actions apply to applicants who must comply with § 25.1729 (in other words, paragraphs H25.5(a)(1) and (b) of appendix H) or § 26.11(c), or both.
Note: The steps below are focused on the development, review, and approval of the EZAP-derived EWIS ICA. Other EWIS ICA tasks and non-EWIS ICA may also be addressed during the review process, but, for clarity, they are purposely left out of the following sequence of events.
(a) The applicant determines whether the proposed design change requires a revision to the existing EWIS ICA or development of new EWIS ICA, or both. Guidance on making this determination is contained in appendix B of this AC. If required, the applicant develops a new or revised EWIS ICA.
(b) If new or revised EWIS ICA are required, the applicant produces a SD (required by paragraph H25.5(b)) containing the EWIS ICA (developed using the procedure outlined in appendix B of this AC) or identifying their location in other documents. (Whether the SD contains the EWIS ICA or references their location in other documents is the applicant’s choice).
(c) The DAH submits the SD, any referenced ICA documents, and any supporting documentation to the FAA oversight office for approval.
Note: Supporting documentation may be the result of the procedure as outlined in appendix B, previously approved EWIS ICA applicable to the airplane zone(s) 16
being modified, or other documentation that supports the applicant’s position as to the necessity of creating new or revised EWIS ICA.
(d) The FAA oversight office, in conjunction with the applicable AEG office, reviews and approves the SD, which indicates approval of the EWIS ICA referenced or contained in that document.
11. Making EWIS ICA Available to Operators and Other Persons. Section 26.11(e)(4) requires that the compliance plan submitted by the DAH or applicant contains a proposal for how the approved EWIS ICA will be made available to affected persons. Section 26.11(f) requires that the compliance plan be implemented in accordance with § 26.11(e). The rule does not specify the manner in which the DAH must make the EWIS ICA available. It simply requires the DAH to make them available. The “affected persons” that the rule refers to are operators and others required to comply with the requirements of §§ 26.11, 25.1729, 121.1111, and 129.111.
12. Operator Changes to EWIS ICA. Sections 121.1111 and 129.111 require that the EWIS maintenance program be based on EWIS ICA that have been developed in accordance with provisions of appendix H and approved by the FAA oversight office. Guidance for air carriers and air operators on how to make changes to FAA-approved EWIS ICA is contained in AC 120-99, Incorporation of Electrical Wiring Interconnection System (EWIS) Instructions for Continued Airworthiness into an Operator’s Maintenance Program.
13. Causes of Wire and Other EWIS Component Degradation. The following are considered principal causes of wiring degradation and should be used to help focus maintenance programs.
a. Vibration. High vibration areas tend to accelerate degradation over time, resulting in “chattering” contacts and intermittent symptoms. High vibration of tie-wraps or string-ties can cause damage to insulation. In addition, high vibration will exacerbate any existing wire insulation cracking.
b. Moisture. High moisture areas generally accelerate corrosion of terminals, pins, sockets, and conductors. It should be noted that wiring installed in clean, dry areas with moderate temperatures appears to hold up well.
c. Maintenance. Scheduled and unscheduled maintenance activities, if done improperly, may contribute to long-term problems and degradation of EWIS. Certain repairs may have limited durability and should be evaluated to ascertain if rework is necessary. Repairs that conform to manufacturers’ recommended maintenance practices are generally considered permanent and should not require rework. Care should be taken to prevent undue collateral damage to EWIS while performing maintenance on other systems.
(1) Metal shavings and debris have been discovered on wire bundles after maintenance, repairs, modifications, or STC work has been performed. Take care to protect wire bundles, connectors, and all other EWIS components during maintenance, repairs, or modification work.
Work areas should be cleaned while the work progresses to ensure that all shavings and debris are removed. The work area should be thoroughly cleaned after work is complete, and the area should be inspected after the final cleaning.
(2) Repairs should be performed using the most effective methods available. Since wire splices are more susceptible to degradation, arcing, and overheating, the recommended method of repairing a wire is with an environmentally sealed splice.
d. Indirect Damage. Events such as pneumatic duct ruptures or duct clamp leakage can cause damage that, while not initially evident, can later cause wiring problems. When events such as these occur, surrounding EWIS should be carefully inspected to ensure that there is no damage or potential for damage evident. Indirect damage caused by these types of events could be broken clamps or ties, broken wire insulation, or even broken conductor strands. In some cases, the pressure of the duct rupture could cause wire separation from the connector or terminal strip.
e. Contamination. EWIS contamination refers to either of the following situations:
(1) presence of a foreign material that is likely to cause degradation of EWIS or (2) presence of a foreign material that is combustible or capable of sustaining a fire after removal of the ignition source. An EWIS contaminant may be in solid or liquid form.
(1) Solid contaminants. Solid contaminants such as the following can accumulate on wiring and other EWIS components and could degrade or penetrate wiring or other EWIS components.
• Metal shavings/swarf
• Debris
• Livestock waste
• Lint
• Dust
(2) Fluid contaminants. Chemicals in fluids such as the following can contribute to degradation of wiring and other EWIS components.
• Hydraulic fluid
• Battery electrolytes
• Fuel
• Corrosion inhibiting compounds
• Waste system chemicals 18