AC 120-102B

U.S.

Department of Transportation Federal Aviation Administration Advisory Circular Subject: Incorporation of Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness into an Operator’s Maintenance Program Date: 6/3/24 AC No: 120-102B Initiated by: AFS-300 Change:

On November 8, 2007, the Federal Aviation Administration (FAA) published the Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety (EAPAS/FTS) Final Rule. The intent of the rule is to help ensure the continued safety of commercial airplanes by improving the design, installation, and maintenance of electrical wiring systems. Title 14 of the Code of Federal Regulations (14 CFR) part 121, § 121.1111, and part 129, § 129.111 include requirements for operators to have their maintenance programs include inspections and procedures for electrical wiring interconnection systems (EWIS). This advisory circular (AC) is not mandatory and does not constitute a regulation. This AC describes an acceptable means, but not the only means, to comply with the applicable sections of 14 CFR. However, if you use the means described in this AC to show compliance, you should follow it in all important respects unless alternate means or deviations are proposed and are accepted by the FAA. The contents of this document do not have the force and effect of law and are not meant to bind the public in any way, and the document is intended only to provide information to the public regarding existing requirements under the law or agency policies.

H ugh Thomas for Lawrence Fields Executive Director, Flight Standards Service

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CONTENTS Paragraph Page

Chapter 1. General1-1

1.1 Purpose of This Advisory Circular (AC)1-1

1.2 Audience1-1

1.3 Where You Can Find This AC1-1

1.4 What This AC Cancels1-2

1.5 Background1-2

1.6 Related Title 14 CFR Parts1-3

1.7 Related Reading Materials1-4

1.8 FAA Policy Statements1-5

1.9 AC Feedback Form1-6

Cha pter 2. Enhanced Airworthiness Program for Airplane Systems (EAPAS)

Requirements2-1

2.1 Requirements2-1

2.2 Description of EWIS ICA Required by 14 CFR Part 26, § 26.112-1

2.3 EWIS ICA Development Required by § 25.17292-3

2.4 DAH Activities for Compliance with § 26.112-4

2.5 Why the EWIS ICA Approval is Necessary2-4

2.6 TCH-Developed EWIS Recommended Maintenance Requirements2-4

2.7 STC Holder-Developed EWIS ICA2-6

2.8 STC Limitation2-6

2.9 Requirement to Ensure Compatibility Between Fuel Tank System and EWIS ICA2-7

Table 2-1. I ntegrated Enhanced Airworthiness Program for Ai rplane

Systems/Fuel Tank Safety Task2-9

2.10 Operator-Developed EWIS ICA2-9

Cha pter 3. Operational Requirements3-1

3.1 Operator Incorporation of Federal Aviation Administration (FAA)-Approved Electrical Wiring Interconnection System (EWIS) Instructions for Continued

Airworthiness (ICA) into the Maintenance Program3-1

3.2 Operator Changes to Enhanced Zonal Analysis Procedure (EZAP)-Developed

EWIS Task or Task Intervals3-2

3.3 Operator Changes to EWIS ICA Developed Under 14 CFR Part 25, § 25.17293-3

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3.4 EAPAS Maintenance Training3-3

3.5 Operator’s Maintenance Program Approval Under §§ 121.1111 and 129.1113-4

3.6 Operations That are Authorized OpSpec D0973-4

Table 3-1. Sample D097 Table 1 – Aging Aircraft Maintenance Programs3-5

Appendix A. A cronymsA-1

Appendix B. D efinitionsB-1

Appendix C. C ontact Information for Questions Regarding Responsible Aircraft

Certification Service OfficesC-1

1-1 CHAPTER 1. GENERAL

1.1 Purpose of This Advisory Circular (AC). This AC is not mandatory and does not constitute a regulation. This AC describes an acceptable means, but not the only means, for Title 14 of the Code of Federal Regulations (14 CFR) part 121 certificate holders (CH) and part 129 operators (part 129, § 129.14) of U.S.-r egistered airplanes (hereafter both are referred to as “operators”) to comply with the applicable sections of 14 CFR.

However, if you use the means described in this AC to show compliance, you should follow it in all important respects unless alternate means or deviations are proposed and are accepted by the Federal Aviation Administration (FAA). The contents of this document do not have the force and effect of law and are not meant to bind the public in any way, and the document is intended only to provide information to the public regarding existing requirements under the law or agency policies.

1.1.1 Requirements. The electrical wiring interconnection system s (EWIS) instructions for continued airworthiness (ICA) have been developed using an enhanced zonal analysis procedure (EZAP). See Appendix B, Definitions, for the definition of EZAP. The requirements to develop these EWIS ICA are contained in 14 CFR part 25, § 25.1729 and 14 CFR part 26, § 26.11. Section 25. 1729 refers to the EWIS ICA requirements contained in part 25 appendix H, §§ H25.4 and H25.5, while § 26.11 refers only to the EWIS ICA requirements contained in § H25.5(a)(1) and (b). This AC provides guidance for the EWIS ICA that have been developed in accordance with § 26.11 and AC 25- 27, Development of Transport Category Airplane Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness Using and Enhanced Zonal Analysis Procedure.

1.2 A udience. This AC applies to operators of transport category turbine-powered airplanes with a type certificate (TC) issued after January 1, 1958 that, as a result of original type certification or later increase in capacity, have a maximum type-certificated passenger capacity of 30 or more, or a maximum payload capacity of 7,500 pounds or more. This AC can also be used as a method of compliance for any transport category airplane that has § 25.1729 in its certification basis.

Note: The phrase “original type certification or later increase in capacity” addresses two situations. In the past, some designers and operators avoided applying requirements mandated only for airplanes over a specific capacity by receiving a design change approval for a slightly lower capacity. By referencing the capacity resulting from original certification, the rule removes this means of avoiding compliance. Also, the FAA could have originally certified an airplane design with a capacity slightly lower than the minimum specified in the rule, but through later design changes, the capacity could be increased above this minimum. The reference to later increase in capacity in the rule ensures that, if this occurs, the design would have to meet the requirements of the rule.

1.3 Where You Can Find This AC. You can find this AC on the FAA’s website at https://www.faa.gov/regulations_policies/advisory_circulars and the Dynamic Regulatory System (DRS) at https://drs.faa.gov.

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1.4 What This AC Cancels. AC 120-102A, Incorporation of Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness into an Operator’s Maintenance Program, dated September 12, 2012, is canceled.

1.5 Background.

1.5.1 Trans World Airlines, Inc. (TWA) Flight 800. Since 1959, there have been at least 18 fuel tank explosions. Most notably, on July 17, 1996, a 25-year-old Boeing 747-100 series airplane was involved in an in-flight breakup after takeoff from John F. Kennedy International Airport in New York, resulting in 230 fatalities. The National Transportation Safety Board (NTSB) determined that the probable cause of the TWA Flight 800 accident was an explosion of the center wing fuel tank (CWT) resulting from ignition of the flammable fuel and air mixture in the tank. The NTSB could not conclusively determine the source of ignition energy for the explosion, though the most likely cause was a wiring failure outside the CWT. This failure allowed excessive electrical energy to enter the CWT through electrical wiring associated with the fuel quantity indicator system (FQIS).

1.5.2 S wissair Flight 111. Two years after the TWA accident, in September 1998, an MD-11 airplane, Swissair Flight 111, crashed into the Atlantic Ocean off the coast of Nova Scotia, Canada. In its final accident report, the Transportation Safety Board of Canada (TSB) determined that there was smoke and a fire above the ceiling in the cockpit. In the report, the TSB could not identify the exact cause of the fire; however, the TSB stated that “a segment of in-flight entertainment network… power supply unit cable… exhibited a region of resolidified copper on one wire that was caused by an arcing event.” The TSB determined that this resolidified copper was in the area where the fire most likely originated.

1.5.3 I nvestigation. Investigation of these two accidents, and subsequent examinations of many other airplanes, showed that deteriorated wiring, corrosion, and improper wire installation and repairs were common conditions in the EWIS. In addition, wire bundles contaminated with metal shavings, dust, and fluids were also common conditions in representative examples of transport airplanes. These contaminants could damage the EWIS and also provide fuel for an electrical fire.

1.5.4 F AA’s Conclusions.

1.5.4.1 The FAA concluded that the following ICA for the EWIS are too general, and not described in enough detail in maintenance manuals:

• Wiring maintenance practices,

• Wiring components,

• Wiring inspection criteria, and

• Wiring repair and installation instructions.

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1.5.4.2 Therefore, the FAA determined that to correct these deficiencies, future ICA developed for the EWIS must define:

• What has to be done,

• When it has to be done,

• How it will be accomplished, and

• That the EWIS ICA must be FAA-approved.

1.5.5 E nhanced Airworthiness Program for Airplane Sy stems/Fuel Tank Safety (EAPAS/FTS) Final Rule. On November 8, 2007, the FAA published the EAPAS/FTS Rule. This rule helps ensure the continued safety of commercial airplanes by improving the design, installation, and maintenance of the airplanes’ EWIS. The rule also includes certification (§ 26.11 and §§ 25.1701 through 25.1733) and operational (§§ 121.1111 and 129.111) requirements. Part 26 subpart A establishes design approval holder (DAH) requirements for support of the continued airworthiness and safety improvements for turbine-powered transport category airplanes.

Note 1: F or the purposes of this AC, a DAH refers to the TC and Supplemental Type Certificate (STC) holder when used in context.

Note 2: For the purposes of this AC, the responsible Aircraft Certification Service office or the office of the Transport Airplane Directorate (TAD) with oversight responsibility for the relevant TC, STC, or manufacturer as determined by the Administrator may be one in the same.

1.5.6 Title 14 CFR Subparts. Sections 121.1101 (part 121 subpart AA) and 129.101 (pa rt 129 subpart B) require operators to support the continued airworthiness of each airplane.

These requirements may include revising the maintenance program, incorporating design changes, incorporating revisions to ICA, and making necessary documentation available to affected persons (see Appendix B). These subparts will also improve the reader’s ability to readily identify rules pertinent to continued airworthiness.

1.6 Re lated Title 14 CFR Parts. DRS ( https://drs.faa.gov) provides a comprehensive knowledge center of regulatory guidance material. It contains searchable databases that contain regulatory, guidance, CFR, and Special Federal Aviation Regulations (SFAR) current, historical, and pending versions and aviation product information. The following sections of 14 CFR apply:

• P art 21, § 21.50, Instructions for Continued Airworthiness and Manufacturer’s Maintenance Manuals Having Airworthiness Limitations Sections.

• P art 25, § 25.1529, Instructions for Continued Airworthiness.

• Part 25, § 25.1729, Instructions for Continued Airworthiness: EWIS.

• Part 25 Appendix H, § H25.5, Electrical Wiring Interconnection System (EWIS) Instructions for Continued Airworthiness.

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• Part 26 , Continued Airworthiness and Safety Improvements for Transport Category Airplanes.

• Part 26 Subpart A, General.

• Part 26, § 26.11, Electrical Wiring Interconnection Systems (EWIS) Maintenance Program.

• Part 43, § 43.13, Performance Rules (General).

• Part 121 Subpart AA, Continued Airworthiness and Safety Improvements.

• Part 121, § 121.1111, Electrical Wiring Interconnection Systems (EWIS) Maintenance Program.

• Part 129 Subpart B, C ontinued Airworthiness and Safety Improvements.

• Part 129, § 129.111, Electrical Wiring Interconnection Systems (EWIS) Maintenance Program.

• SFAR 88, Fuel Tank System Fault Tolerance Evaluation Requirements.

1.7 Related Reading Materials (current editions):

1.7.1 ACs. You c an locate each of the following ACs on the FAA website at https://www.faa.gov/regulations_policies/advisory_circulars and on DRS:

• AC 25-8, Auxiliary Fuel System Installations.

• AC 25-19, Certification Maintenance Requirements.

• AC 25-27, Development of Transport Category Airplane Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness Using an Enhanced Zonal Analysis Procedure.

• AC 25.981- 1, Fuel Tank Ignition Source Prevention Guidelines.

• AC 25.981-2, Fuel Tank Flammability Reduction Means.

• AC 25.1701-1, Certification of Electrical Wiring Interconnection Systems on Transport Category Airplanes.

• AC 26- 1, Part 26, Continued Airworthiness and Safety Improvements.

• AC 120-16, Air Carrier Maintenance Programs.

• AC 120-94, Aircraft Electrical Wiring Interconnection Systems Training Program.

• AC 120-97, Incorporation of Fuel Tank System Instructions for Continued Airworthiness into Operator Maintenance and/or Inspection Programs.

• AC 121- 22, Maintenance Review Boards, Maintenance Type Boards, and OEM/TCH Recommended Maintenance Procedures.

• AC 129- 4, Maintenance Programs for U.S.- Reg istered Aircraft Operated Under 14 CFR Part 129.

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1.7.2 FAA Orders.

• Order 8110.54, Instructions for Continued Airworthiness Responsibilities, Requirements, and Contents.

• Order 8110.104, Responsibilities and Requirements for Implementing Part 26 Safety Initiatives.

1.7.3 I ndustry References. The use of the term “ATA coded sections” within this AC refers to the Air Transport Association of America (ATA) codes that are standardized for each aircraft system. The ATA changed its name to Airlines for America (A4A) in 2011;

however, the acronym “ATA” is still used for coded aircraft systems. The acronyms “ATA” and “A4A” are considered interchangeable. The alternate format for aircraft system coding is the Joint Aircraft System/Component (JASC) Code. For additional information on JASC coding, refer to the FAA JASC Code Table and Definitions, which is accessible via https://sdrs.faa.gov/documents/JASC_Code.pdf. Refer also to A4A Maintenance Steering Group – 3rd Task Force (MSG-3), Operator/Manufacturer Scheduled Maintenance Development, and DAH-developed publications.

1.8 FAA Policy Statements (available for download at https://drs.faa.gov).

1.8.1 PS-ANM110-7-12-2005, Safety—A Shared Responsibility—New Direction for Addressing Airworthiness Issues for Transport Airplanes.

1.8.1.1 On July 12, 2005, the FAA issued policy statement PS-ANM110-7-12-2005.

The policy states, in part: “Based on our evaluation of more effective regulatory approaches for certain types of safety initiatives…the FAA has concluded that we need to adopt a regulatory approach recognizing the shared responsibility between DAHs 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…”

1.8.1.2 Section 26.11 implemented this policy for the EAPAS/FTS rule.

Section 26.11 requires the design approval holders (DAH) to develop ICA for EWIS for certain transport category airplanes and submit them for review and approval to the responsible Aircraft Certification Service office.

1.8.2 PS-AIR-100-2009-05-27, Adding Part 26 to Type Certificate Data Sheets and Supplemental Type Certificates. On October 22, 2007, 14 CFR adopted a new part 26, Continued Airworthiness and Safety Improvements for Transport Category Airplanes.

1.8.3 PS -AIR-100-2007-12-27B, Enhanced Airworthiness Program for Airplane Systems (EAPAS) Supplemental Type Certificate (STC) Limitation. On June 10, 2009, the FAA issued revised policy statement PS-AIR-100-2007-12-27B. This memo was revised to remove the paragraph on certification basis, which is included in a separate policy memorandum, PS-AIR-100-2009-05-27.

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1.8.4 ANM-08-113-001, Policy Statement on Clarification of Maximum Payload Capacity Definition in Design Approval Holder Rules. On September 12, 2008, the FAA issued policy statement ANM-08-113-001. This policy states that the “maximum payload capacity criterion is used, along with other criteria, to determine whether a rule is applicable to a DAH. However, there has been confusion on the use and definition of the term. This policy memorandum clarifies the maximum payload capacity criterion when used with regard to these DAH rules and their corresponding operational rules.”

1.9 AC Feedback Form. For your convenience, the AC Feedback Form is the last page of this AC. Note any deficiencies found, clarifications needed, or suggested improvements regarding the contents of this AC on the Feedback Form.

2-1 CHAPTER 2. ENHANCED AIRWORTHINESS PROGRAM FOR AIRPLANE

SYSTEMS (EAPAS) REQUIREMENTS

2.1 Requirements. This advisory circular (AC) provides guidance to support operator compliance with the electrical wiring interconnection system (EWIS) maintenance program requirements contained in the Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety (EAPAS/FTS) Rule. Title 14 of the Code of Federal Regulations (14 CFR) part 121, § 121.1111 and part 129, § 129.111 require operators to incorporate into their maintenance program inspections and procedures for EWIS contained in instructions for continued airworthiness (ICA) approved by the Federal Aviation Administration (FAA) responsible Aircraft Certification Service office. The design approval holder (DAH) develops and revises the ICA using AC 25-27, Development of Transport Category Airplane Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness Using and Enhanced Zonal Analysis Procedure.

The ICA for the EWIS consist of inspections and procedures to accomplish those tasks, and may include, in addition, maintenance of other natures (e.g., overhaul, repair, etc.), intervals, and “protections and caution” instructions and information. (Refer to 14 CFR part 1 for the definition of “maintenance” and “preventive maintenance.”)

2.2 Description of EWIS ICA Required by 14 CFR Part 26, § 26.11.

2.2.1 Overview. The EWIS ICA required by § 26.11 are developed in accordance with 14 CFR part 25 appendix H, § H25.5(a)(1) and (b). These ICA are:

1. Maintenance tasks to reduce the likelihood of ignition sources and accumulation of combustible material. There may be inspections under the form of a zonal General Visual Inspection (GVI), standalone GVI, Detailed Inspection (DET), overhauls, repairs, replacements, or a combination of these;

2. Procedures to effectively clean the EWIS components of combustible material if there is not an effective maintenance task to reduce the likelihood of combustible material accumulation; and

3. Instructions for protections and caution information to minimize contamination and accidental damage to EWIS, as applicable, during the performance of maintenance or alteration. The EWIS ICA can include other instructions (refer to §§ H25.4 and H25.5(a)(2) through (5)).

2.2.2 M ultiple Items and Components . The EWIS ICA include multiple items and can be, and almost always are, comprised of several different components. All of these items and components define a particular EWIS ICA. These items and components are in multiple DAH-produced documents.

2.2.2.1 These EWIS ICA items include:

1. Type of task (e.g., overhaul, replacement, standalone GVI, DET, or standard zonal GVI).

2. Task interval (e.g., every 16,000 flight cycles or 3,000 days).

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3. Airplane zone identification for airplanes with a zonal program

(e.g., Zone 201).

4. Task description (e.g., Inspect (General Visual) all exposed EWIS in the wheel well).

Note: The gear is extended with the handle down and gear locked in the down position and doors in open position).

5. Airplane applicability. Some models within the same family of airplanes may have differing maintenance requirements based on available options

(e.g., freighter versus passenger version engine types).

6. Task procedure(s) as described in the referenced Aircraft Maintenance Manual (AMM) or other documents that contain the procedure(s). These are the actual instructions on how to perform the GVI, DET, restoration/cleaning tasks that support the task description listed in the Maintenance Review Board Report (MRBR) and Maintenance Implementation Document (MID), and maintenance tasks that support the task description.

7. Supporting task procedure(s), if any, necessary to perform the task procedure in any other document referenced by the task procedure.

8. Instructions for protections and caution information that will minimize contamination and accidental damage to the EWIS (these can appear in different places, such as in the AMM or in the Standard Wiring Practice Manual (SWPM)/Electrical Standard Practices Manual (ESPM)). This information, if contained in the SWPM/ESPM (or other similar documents), should be in its chapter 20. Sometimes, this information is repeated in the standard practices chapter 20 of the AMM. In any case, it is general protections and caution information, and it is not expected that unique procedures will be developed for individual EWIS ICA for a particular airplane model or models produced by the same manufacturer.

The AMM or SWPM/ESPM will reference any protections and caution information specific to the EWIS ICA.

2.2.2.2 As an example, the EWIS ICA components can be located in one or more of the following documents:

• Document required by § H25.5(b);

• Maintenance Review Board Report (MRBR);

• Maintenance Planning Document (MPD);

• Maintenance Implementation Document (MID);

• Aircraft Maintenance Manual (AMM);

• Standard Wiring Practice Manual (SWPM);

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• Electrical Standard Practices Manual (ESPM) (a term used by some type certificate holders (TCH)); or

• Standalone ICA document produced by a Supplemental Type Certificate (STC) applicant.

2.2.3 EWIS Source Document. Section H25.5(b) states that 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 provided, and must be easily recognizable as the EWIS ICA or specifically reference other sections of the EWIS ICA that contain this information. This document is referred to as the source document. The form is at the discretion of the DAH, as long as it meets the requirements of §§ H25.2 and H25.5(b).

The entire EWIS ICA can be in the source document, or the source document can point to a series of other documents, such as the MRBR, MPD, MID, AMM, or SWPM/ESPM, which contain the EWIS ICA.

Note: The source document referenced above is approved by the responsible Airc raft Certification Service office. The operational rules require operators to incorporate into their maintenance program EWIS ICA approved by the responsible Aircraft Certification Service office. The source document provides the information necessary for the operator to comply with §§ 121.1111 and 129.111.

2.2.4 Controlling Reference Numbers. C ontrolling reference numbers for the individual EWIS ICA tasks are listed in the MRBR, MPD, MID, or other maintenance documents. An example of a controlling reference number in an MRBR is “MM/MPD ref.

20-XXX-XX.” This number correlates to a cross-reference number in the source document and the AMM, which is the actual maintenance task with all associated instructions to accomplish it. The DAH may refer to these reference numbers as Maintenance Review Board (MRB) reference, AMM/MPD reference, Maintenance Significant Items (MSI) reference, task number, etc. It can vary. The TCH may consider one or all of the reference numbers part of the EWIS ICA. The DAH will identify all reference numbers necessary to fully track and identify the EWIS ICA. All reference numbers considered necessary to fully identify and track the EWIS ICA should be considered part of the EWIS ICA.

2.2.5 DAH Revi sions to EWIS ICA. The DAH will revise the source document in order to account for any new or revised EWIS inspection or procedures required by § H25.5(a)(1) and developed due to production changes, or design changes mandated by an Airworthiness Directive (AD). They will provide the revised source document to operators after the document has been approved by the responsible Aircraft Certification Service office.

2.3 EWIS ICA De velopment Required by § 25.1729. In addition to the EWIS ICA that are required and developed under § 26.11 for existing in service airplanes, there will also be the EWIS ICA developed under § 25.1729 for new airplane type certificates (TC), or when 14 CFR part 21, § 21.101 requires the holder of an amended TC or an STC to comply with a corresponding amendment to part 25 that was issued on or after the date of