Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety (EAPAS/FTS)
Federal RegisterNov 8, 2007
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Parts 1, 21, 25, 26, 91, 121, 125, and 129.
[Docket No.: FAA-2004-18379; Amendment Nos. 1-60, 21-90, 25-123, 26-0, 91-297, 121-336, 125-53, 129-43]
RIN 2120-AI31
Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety (EAPAS/FTS)
AGENCY:
Federal Aviation Administration (FAA), DOT.
ACTION:
Final rule.
SUMMARY:
This final rule amends FAA regulations for certification and operations of transport category airplanes. These changes are necessary to help ensure continued safety of commercial airplanes. They improve the design, installation, and maintenance of airplane electrical wiring systems and align those requirements as closely as possible with the requirements for fuel tank system safety. This final rule organizes and clarifies design requirements for wire systems by moving existing regulatory references to wiring into a single section of the regulations specifically for wiring and by adding new certification rules. It requires holders of type certificates for certain transport category airplanes to conduct analyses of their airplanes and make necessary changes to existing Instructions for Continued Airworthiness (ICA) to improve maintenance procedures for wire systems. It requires operators to incorporate ICA for wiring into their maintenance or inspection programs. And finally, this final rule clarifies requirements of certain existing rules for operators to incorporate ICA for fuel tank systems into their maintenance or inspection programs.
DATES:
These amendments become effective December 10, 2007.
FOR FURTHER INFORMATION CONTACT:
If you have technical questions about the certification rules in this action, contact Stephen Slotte, ANM-111, Airplane & Flight Crew Interface, Federal Aviation Administration, 1601 Lind Avenue, SW., Renton, WA 98057-3356; telephone (425) 227-2315; facsimile (425) 227-1320, e-mail
steve.slotte@faa.gov
. If you have technical questions about the operating rules, contact Fred Sobeck, AFS-308, Aircraft Maintenance Division, Federal Aviation Administration, 800 Independence Avenue, SW., Washington, DC 20591; telephone: (202) 267-7355; facsimile (202) 267-7335, e-mail
frederick.sobeck@faa.gov
. Direct any legal questions to Doug Anderson, Office of Regional Counsel, Federal Aviation Administration, 1601 Lind Avenue, SW., Renton, WA 98057-3356; telephone (425) 227-2166; facsimile (425) 227-1007, e-mail
Douglas.Anderson@faa.gov
.
SUPPLEMENTARY INFORMATION:
Authority for This Rulemaking
The FAA's authority to issue rules regarding aviation safety is found in Title 49 of the United States Code. Subtitle I, Section 106 describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the agency's authority.
This rulemaking is promulgated under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, the FAA is charged with promoting safe flight of civil aircraft in air commerce by prescribing minimum standards required in the interest of safety for the design and performance of aircraft; regulations and minimum standards in the interest of safety for inspecting, servicing, and overhauling aircraft; and regulations for other practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it prescribes—
• New safety standards for the design of transport category airplanes, and
• New requirements necessary for safety for the design, production, operation, and maintenance of those airplanes, and for other practices, methods, and procedures relating to those airplanes.
Contents
I. Executive Summary
II. Background
A. Summary of the NPRM
1. The Proposed Rule
2. Related Activities
B. Differences Between the NPRM and the Final Rule
C. Summary of Comments
III. Discussion of the Final Rule
A. Overview
B. Design Approval Holder (DAH) Requirements (part 26)
1. Requirements To Develop ICA
2. Changes to Location of Design Approval Holder Requirements
3. Interaction Between New Design Approval Holder Requirements and Part 21
4. Compliance Dates
5. The Design Approval Holder Compliance Plan
6. Defining the Representative Airplane
7. Impact on Operators
8. EZAPs Already Completed
9. Wire Inspections
10. Protections and Cautions
11. Alignment of EWIS and Fuel Tank ICA
12. Approval of ICA
13. Rule Applicability
14. Non-U.S. Manufacturers
15. General Comments About Design Approval Holder Requirements
16. Airplanes Excluded From Design Approval Holder and EWIS Operating Requirements
C. Electrical Wiring Interconnection System (EWIS) Certification Rules (part 25 subpart H)
1. New Subpart for EWIS
2. The Definition of EWIS (§ 25.1701)
3. Functions and Installation: EWIS (§ 25.1703)
4. Systems and Functions: EWIS (§ 25.1705)
5. System Separation: EWIS (§ 25.1707)
6. System Safety: EWIS (§ 25.1709)
7. Component Identification: EWIS (§ 25.1711)
8. Fire Protection: EWIS (§ 25.1713)
9. Electrical Bonding and Protection Against Static Electricity: EWIS (§ 25.1715)
10. Accessibility Provisions: EWIS (§ 25.1719)
11. Protection of EWIS (§ 25.1721)
12. Flammable Fluid Shutoff Means: EWIS (§ 25.1727)
13. Powerplant and APU Fire Detection System: EWIS (§ 25.1731)
14. Fire Detector Systems, General: EWIS (§ 25.1733)
15. Engine, Nacelle, and APU Wiring
16. Designated Fire Zones
17. Goal of the New Wiring Subpart
18. Harmonization
D. Instructions for Continued Airworthiness: EWIS (§ 25.1729 and Appendix H)
1. Requirements for EWIS ICA
2. ICA as a Single Document
3. Standard Wiring Practices Manuals
4. Mandatory Replacement Times
5. Wire Identification Method Information
6. Electrical Load Data
E. Continued Airworthiness and Safety Improvements Subparts for Operating Rules (parts 91, 121, 125, 129)
1. Establishment of New Subparts
2. Continued Airworthiness Subparts and Airworthiness Directives
3. Type and Scope of Requirements
F. Operating Requirements for EWIS (parts 121 and 129)
1. Requirements for Maintenance and Inspection Program Revisions
2. ICA Developed by Design Approval Holders
3. Different Requirements for Existing and Future Designs
4. ICA for Alterations
5. Alaska Operations
6. EWIS Inspections
7. Non-U.S. Registered Airplanes
8. Taking Airplanes Out of Service
9. Training
10. Reporting Requirements
G. Operating Requirements for Fuel Tank Systems (parts 91, 121, 125, and 129)
1. Requirements for Maintenance and Inspection Program Revisions
2. Airplanes Excluded From Fuel Tank System Operating Requirements
3. Change in Operator Compliance Date for Auxiliary Fuel Tank ICA
4. Original Configuration and Auxiliary Fuel Tanks
5. Inspection and Maintenance Program Terminology
H. Regulatory Evaluation
1. Engine Costs
2. Wiring System Safety Analysis for Engines
3. Labor Rates
4. The Regional Airplane Fleet
5. Measure of Effectiveness
6. Operational Impacts
7. Training Costs
8. Costs for EZAP Analysis and Inspection of Engines
9. Engine Costs of § 25.1362
10. Wire Labeling Costs
11. Additional Certification and Operator Costs
12. Previous Rulemaking
13. Relevance to the Current Fleet
14. Accidents Indirectly Initiated by EWIS
I. Harmonization Changes to Transport Category Certification Rules (Part 25)
1. FAA/JAA (Joint Aviation Authority) Harmonization
2. Circuit Protective Devices (§ 25.1357)
3. Precautions Against Injury (§ 25.1360)
4. Electrical Supplies for Emergency Conditions (§ 25.1362)
5. Electrical Appliances, Motors, and Transformers (§ 25.1365)
J. Additional Certification Rule Changes (part 25)
1. Rules Changed To Accommodate Subpart H
2. Electrical Equipment and Installations (§ 25.1353)
IV. Regulatory Notices and Analyses
V. The Amendments
I. Executive Summary
Safety concerns about wiring systems in airplanes were brought to the forefront of public attention by a midair explosion in 1996 involving a 747 airplane. Ignition of flammable vapors in the fuel tank was the probable cause of that fatal accident, and the most likely source was a wiring failure that allowed a spark to enter the fuel tank. All 230 people aboard the airplane were killed. Two years later, an MD-11 airplane crashed into the Atlantic Ocean, killing all 229 people aboard. Although an exact cause could not be determined, the presence of resolidified copper on a portion of a wire of the in-flight entertainment system cable indicated that wire arcing had occurred in the area where the fire most likely originated.
Investigations of those accidents and later examinations of other airplanes showed a collection of common problems. Deteriorated wiring, corrosion, improper wire installation and repairs, and contamination of wire bundles with metal shavings, dust, and fluids (which would provide fuel for fire) were common conditions in representative examples of the “aging fleet of transport airplanes.”
The FAA has concluded that current maintenance practices do not adequately address wiring components, wiring inspection criteria are too general, and maintenance instructions do not describe unacceptable conditions, such as improper repairs and installations, in enough detail.
With this final rule we are introducing new maintenance, inspection, and design criteria for airplane wiring to address conditions that put transport airplanes at risk of wire failures, smoke, and fire. We are adding requirements for type certificate holders and applicants for type certificates and supplemental type certificates to analyze the zones of their airplanes for the presence of wire and for the likely accumulation of contaminant materials. This final rule also requires them to develop maintenance and inspection tasks to identify, correct, and prevent wiring conditions that introduce risk to continued safe flight. We are requiring that these tasks be included in new Instructions for Continued Airworthiness for wiring and that they be compatible with Instructions for Continued Airworthiness for fuel tank systems. The EWIS ICA must not conflict with the ICA for fuel tanks, and must avoid duplication and redundancy. Too frequent disturbance to electrical wiring by repeated moving, pulling, and flexing of the wire bundles will induce unnecessary stress on the wiring and its components, which in turn could lead to degradation, expedited aging, and failures. Thus it is important that redundant tasks and unnecessary disturbances to the electrical wiring be minimized. We are amending Title 14 Code of Federal Regulations (CFR) parts 91, 121, 125, and 129 operating rules to require operators of transport category airplanes to incorporate maintenance and inspection tasks for wiring into their regular maintenance programs and we are clarifying existing requirements for fuel tanks.
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We are creating a new subpart of part 25 to contain the majority of the certification requirements for airplane wiring, including new rules to improve safety in manufacture and modification. Finally, we are creating a new part 26 for design approval holder requirements relating to continued airworthiness and safety improvements and new subparts in parts 91, 121, 125, and 129 for the same types of requirements for operators.
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We are not amending 14 CFR part 135 because presently there are only 20 airplanes with sufficient passenger or payload capacity to be affected by this rule that fly in part 135 operations. Should part 135 be amended to permit widespread usage of these larger transport category airplanes, we may extend the operating requirements of today's rule to part 135 at that time.
Accompanying this final rule are guidance materials in the form of advisory circulars (AC), which present one way, but not the only way, to comply with specific parts of these regulations.
One of the ACs presents a suggested curriculum for electrical wiring interconnection system (EWIS) training. Existing § 121.375 requires that certificate holders or anyone performing maintenance have a training program. This requirement ensures that anyone determining the adequacy of maintenance work (including inspectors) is fully informed about the procedures and techniques involved and is competent to perform them. AC 120-94 provides guidance for complying with § 121.375 as it applies to EWIS maintenance and inspection. In AC 120-94 we provide a suggested training program to address the informational needs of the various people who come in contact with airplane EWIS, and we encourage operators to include this training voluntarily. While the Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) had recommended some form of EWIS training be required for anyone likely to come into contact with EWIS, we have determined the associated cost would be unduly burdensome. There are 11 other ACs accompanying this rule which provide guidance on different requirements contained here. A few of them have been revised for clarification. In those instances, this will be noted in section III. Otherwise, except for minor editorial changes, the guidance accompanying this rule is being published in the same form in which it was proposed and will not be discussed here.
Since the Notice of Proposed Rulemaking (NPRM), the National Transportation Safety Board (NTSB) has issued Safety Recommendations A-06-29 through -35 pertaining to fires on one particular model of regional jet. In the 6 months between October 2005 and March 2006, there were a total of 6 fires on regional jets. A seventh fire occurred prior to that 6-month period. The NTSB stated that, in addition to the danger posed by the fires, 2 of the incident airplanes temporarily lost all flight displays. The NTSB's investigation
revealed that all of the fires originated from the same electrical component—an electrical contactor located in the avionics compartment beneath the floor of the captain's seat. The fires were caused by moisture-induced short circuits between the electrical terminals of the contactors. We have issued airworthiness directives (AD) to correct this unsafe condition. However, if the requirements in this final rule had been in effect, the type of failure that caused these 7 fires would not have occurred. This is because several of the new requirements directly address design issues that led to the fires. This final rule is meant to proactively address wiring conditions existing in the transport airplane fleet that we now know affect safe flight and can be detected, corrected, or prevented.
We express present value benefits and costs using a 7% discount rate. The total estimated benefits of this final rule, $801 million ($388 present value) over a 25-year period, are comprised of operational benefits and safety benefits. The operational benefits are estimated at $506.3 million ($237.5 million present value). The safety benefits are estimated at $294.6 million ($150.6 million present value). This final rule will prevent a portion of fatal and non-fatal incidents and accidents while decreasing the impact that EWIS discrepancies have on airline operations.
The estimated total cost of this final rule is $416 million ($233 million present value) over 25 years. The majority of these costs ($292.2 million, or $147.6 million present value) will be borne by operators. The remainder of the projected costs will be borne by aircraft and engine manufacturers, and, to a much lesser extent, the FAA Oversight Offices.
II. Background
A. Summary of the NPRM
1. The Proposed Rule
On October 6, 2005 (70 FR 58508), the FAA published in the
Federal Register
the Notice of Proposed Rulemaking (NPRM) entitled Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety (EAPAS/FTS), which is the basis of this final rule.
In that NPRM, we proposed development of Instructions for Continued Airworthiness (ICA) for wiring systems and subsequent incorporation of those ICA into operators' maintenance programs. We also proposed alignment of the compliance times for operators to incorporate wire and fuel tank system ICA into their maintenance programs.
We proposed changes in the certification rules to require more attention during the design and installation of airplane systems to conditions that could compromise wire safety and accessibility. And we proposed a new part 25 subpart that would be dedicated to current and new regulations about airplane wiring systems.
If you would like more details about the proposal, you can get a copy by following the instructions under the Availability of Rulemaking Documents heading at the end of this preamble.
2. Related Activities
On July 12, 2005, the FAA published in the
Federal Register
a statement of policy for future management of the shared responsibility between design approval holders (DAH) and operators in achieving certain types of safety objectives. That stated policy is reflected in the requirements of this final rule for DAHs to develop ICA for airplane wiring systems.
Also published in the July 12, 2005
Federal Register
was a disposition of comments on a previous notice to extend the date for operators to comply with special maintenance requirements for fuel tank systems. That date was extended from December 6, 2004 to December 16, 2008.
On July 7, 2006, we published notice in the
Federal Register
stating that, although we had originally proposed to align compliance times for operator incorporation of ICA for wiring and for fuel tanks, we later found it impractical to do so. This notice notified operators that their compliance date for incorporation of fuel tank ICA is still December 16, 2008.
Twelve draft ACs on different aspects of the rule accompanied the NPRM and were made available for public comment at the same time. On November 8, 2005, the comment period for the ACs was extended to February 3, 2006, so that it would align with the comment period for the NPRM.
B. Differences Between the NPRM and the Final Rule
We have revised the numbering for 14 CFR part 25 subpart H Electrical Wiring Interconnection Systems (EWIS). We did this to harmonize as much as possible with the planned European Aviation Safety Agency (EASA) version of these rules. As discussed later, the design approval holder requirements proposed in the NPRM as subpart I are now contained in new part 26, again to harmonize more easily with the regulatory structure of other national airworthiness authorities. We also have made some changes to the compliance planning sections of those rules. In response to comments, we have increased the compliance time for the design approval holder requirements to 24 months from the effective date of this rule. We have increased the time for operator compliance with the EWIS requirements to 39 months from the effective date of this rule. Because our regulatory process exceeded the time we had originally planned for issuance of this rule, it is no longer practical to align the operator compliance dates for the EWIS ICA with those for fuel tanks. Coordination of the timing of the maintenance tasks within those ICA is still desirable and possible, so that aspect of our proposal remains unchanged in the final rule. We have, however, extended the date for operators to submit ICA for auxiliary fuel tanks to the FAA Oversight Office.
We have removed some airplanes from the exclusion lists of the DAH requirements and the operating rules. This was either because they were already excluded as a result of the definition of the affected airplanes or because we have reconsidered the rationale for certain exclusions. We have also made other, minor, changes in wording to the proposed rules for the purposes of clarification or harmonization. We discuss all of the changes in section III of this preamble.
C. Summary of Comments
The FAA received 39 comment letters about the proposed rule and guidance material. The comments covered a wide spectrum of topics and a range of responses, which we discuss more fully below. There was much support for the general intent of the rule and the guidance material. There were also requests for changes and for clarification.
III. Discussion of the Final Rule
A. Overview
This rule is a result of years of study, data gathering, and collaboration with industry. It has been developed as a solution to the problem of wire contamination and wire damage on airplanes, which can result in system failures, smoke, and fire, and can threaten continued safe flight.
Examinations by the Aging Systems Task Force of representative airplanes from the fleet of aging transports revealed wiring that was deteriorated, corroded, improperly installed and repaired, and contaminated with materials such as metal shavings, dust,
and fluids.
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The NTSB, as well as working groups of the FAA, industry, and other Civil Aviation Authorities, found these conditions to be common across the fleet, not just isolated instances of poor maintenance. While systems have always been subject to careful scrutiny of their safety and reliability during the certification process, the wires that connect those systems had been considered appropriately cared for when fitted and maintained according to standard industry practices.
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Transport Aircraft Intrusive Inspection Project final report dated December 29, 2000.
Now we know that airplane wiring needs more attention. It needs to be considered as a discrete system, and given the same careful scrutiny as other systems. The design of wiring systems is important for creating safe separation from other wires and systems and protecting it from damage. Inspection and maintenance is important in uncovering and repairing wire damage and preventing buildup of contaminants that can cause damage and that also provide fuel for fire. Wire must be inspected regularly and contaminant buildup must be prevented.
In considering the problems found on transport category airplanes, we explored various alternatives. One alternative was to do nothing. But the result of that approach would be a continuation of incidents and accidents caused by deteriorated wiring systems. Once we knew there was a problem affecting safe flight, doing nothing was not really an option. We could have asked for voluntary support. But voluntary programs in the past have not always resulted in complete participation, and a voluntary program could not guarantee the level of safety we want to ensure. Accordingly, we decided to develop a rule to correct potential safety problems with airplane wiring, and to require compliance of all those whose participation is necessary to achieve that goal.
This rule enlists the aid of design approval holders in assessing the wiring on their airplanes and in developing inspection and maintenance tasks that operators can use to maintain wire safety. It requires operators to incorporate into their inspection and maintenance programs tasks for maintaining wire safety that are based on those developed in accordance with requirements. It introduces new certification rules for wire separation, identification, system safety, protection from damage, access, and other aspects of wire safety. It creates a new subpart in the certification rules for wire certification so that the many existing requirements are more easily found. It also requires that design approval holders align inspection and maintenance tasks for wiring with those for fuel tank systems, to avoid duplication and to ensure that the most rigorous task is accomplished. As an example, if the EWIS ICA calls for a general visual inspection of a certain wire and the fuel tank ICA calls for a detailed inspection of the same wire, the general visual inspection task would be removed from the EWIS ICA and the detailed inspection would be retained in the fuel tank ICA, identified as both a fuel tank task and an EWIS task.
B. Design Approval Holder (DAH) Requirements (Part 26)
For design approval holders this final rule differs from the proposal in the following four ways.
• The physical location of the rule has changed, from the proposed location in part 25, subpart I, to a new part 26.
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Since the comments refer to the NPRM, however, the commenters' original references are retained, including references to proposed ACs.
• The compliance date has been changed from December 16, 2007, to 24 months after the effective date of the rule.
• Two changes were made to the compliance plan requirement.
• The definition of the “representative airplane” has been clarified.
We have also made minor wording revisions to section 26.11 for clarification. They do not change the requirements.
1. Requirements To Develop ICA
As discussed above, this rule introduces requirements for design approval holders (DAH) to assess their airplanes in relation to wiring. The assessment must be performed with an enhanced zonal analysis procedure (EZAP), which is outlined in a part-25-series advisory circular accompanying this rule entitled AC 25-27 “Development of Transport Category Airplane Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness Using an Enhanced Zonal Analysis Procedure.” This AC was originally titled AC 120-XX “Program to Enhance Aircraft Electrical Wiring Interconnection System Maintenance.” The material contained in that proposed AC is now presented in two separate ACs. Guidance for carrying out an EZAP analysis, as required in the new parts 25 and 26 regulations in this final rule, is presented in the newly titled No. 25-27 AC named above, which will be referred to in the rest of this document as the DAH EZAP AC. Guidance for the operator requirements will be presented in a separate 120-series AC titled “Incorporation of Electrical Wiring Interconnection System (EWIS) Instructions for Continued Airworthiness into the Operator's Maintenance Program.”
For each zone on the airplane that contains wiring, DAHs must develop maintenance and inspection tasks to prevent contaminant buildup on that wiring and maintain safety. They must then make those tasks available to operators in the form of ICA readily identifiable as pertaining to wiring. They must also assess those wiring ICA in relation to ICA for fuel tank systems to make sure there are no conflicts or redundancies between the two. The rule includes requirements for the DAH to submit a compliance plan to the FAA outlining how it intends to meet these requirements.
2. Changes to Location of Design Approval Holder Requirements
In the NPRM, we noted that we had not decided on the final location of the continued airworthiness and safety improvements design approval holder requirements of part 25, subparts A and I. We requested comments on this issue, and received 7 comments on the rule location. Transport Canada and British Airways stated that they wanted the requirements in part 21. This was to keep the procedural requirements of the new subpart with the present procedural requirements of part 21 and out of the airworthiness standards parts of the regulations. EASA, Airbus, Boeing, Aerospace Industries Association, and the General Aviation Manufacturers Association stated that they wanted the requirements in a new part or in part 21. EASA said these requirements must be in a mandatory part of its system and CS (Certification Specifications) -25, its equivalent to our part 25, is not mandatory. Others who commented wanted to maintain part 25 as strictly an airworthiness standard.
Based on these comments and on discussions with Transport Canada, EASA, and the Brazilian Agencia Nacional de Aviacao Civil, we decided to create a new part 26 and move the enabling regulations out of part 25 and into part 21—Certification Procedures for Products and Parts. We did this for several reasons.
First, moving these requirements to a new part keeps part 25 as strictly an airworthiness standard for new transport category airplanes. This is important because it maintains
harmonization and compatibility among the United States, Canada, and the European Union regulatory systems. Second, integrating the requirements into part 21 improves the clarity of how the part 26 requirements will address existing and future design approvals.
In creating the new part 26, we renumbered the previous sections of part 25, subpart I, and we incorporated the changes discussed in this preamble. A table of this renumbering follows:
Table 1.—Relationship of Proposed Subpart I to Final Rules in Part 26
Part 26
Part 25, Subpart I
Subpart A—General
§ 26.1 Purpose and Scope
§ 25.1801(a) Purpose and definition.
§ 26.3 Definitions
§ 25.1801(b) and 25.1803.
§ 26.5 Applicability Table
New.
Subpart B—Enhanced Airworthiness Program for Aging Systems
§ 26.11 Electrical Wiring Interconnection Systems (EWIS) Maintenance Program
§ 25.1805 Electrical Wiring Interconnection Systems (EWIS) Maintenance Program.
As noted in the table above, we have added a new § 26.5 to provide an applicability table that will facilitate identifying those provisions of part 26 that apply to affected persons at any given time. As we add subparts to part 26, we will update this table to identify the applicability of those new subparts. As with new subpart B of part 26 in this final rule, we will specify the details of applicability for each new subpart in the new subparts themselves.
3. Interaction Between New Design Approval Holder Requirements and Part 21
It was our intent to treat those provisions of the requirements establishing standards for design changes and revisions to the ICA as airworthiness requirements. Adding a statement to the new § 26.1(a) that the requirements of part 26 are airworthiness requirements clearly integrates these requirements with the procedures specified in part 21. The result of treating these requirements as airworthiness requirements is that any design changes that may be required by part 26 rulemaking become part of the type design of the aircraft. This makes clear that the full flexibilities allowed in part 21, such as equivalent level of safety findings and special conditions, may be applied. Also, we added § 26.1(c) to make a distinction in part 26 between type certificates and supplemental type certificates. Typically, for interpreting part 21, reference to type certificates includes supplemental type certificates unless usage of that term clearly indicates otherwise. While the usage of those terms in part 26 is contrary to the usage in part 21, we did this to make clear distinctions in requirements within part 26.
To address the change to “Special retroactive requirements” originally proposed in § 25.2(d) and to fully integrate the new rule with part 21, we made four changes to part 21. First, § 21.7 replaces proposed § 25.2(d) by establishing the applicability of continued airworthiness and safety improvement requirements. This section establishes the general applicability of part 26 to design approval holders, pending and future applicants for design approval, and type certificate holders and licensees for newly produced transport category airplanes.
While § 21.7 makes part 26 applicable to pending applications, § 21.17(a) clarifies this applicability by adding part 26 to the exception list of those requirements of the subchapter that are not established by date of application for a type certificate but by date that the type certificate is issued.
For changed products, in the case when the exceptions of § 21.101(b)(1), (2) or (3) apply, new § 21.101(g) makes clear that, even if an applicant may use an early amendment to part 25, the applicant must still comply with any applicable provisions of part 26. For each applicable part 26 provision, an applicant may elect to comply with a corresponding amendment to part 25 that is issued on or after the date of the part 26 amendment. Under the normal application of § 21.101, if the exceptions of § 21.101(b) do not apply, the applicant would be required to comply with the latest amendments of part 25 in lieu of the requirements of part 26.
Sections 21.31 and 21.50 are revised to make it clear that the Airworthiness Limitations section of the ICA is part of the type design and that changes to the ICA generated under part 26 must be made available as part of the total ICA.
These changes to part 21 do not change or add any new requirements to those proposed in the NPRM. Rather, they clarify the relationship between existing part 21 and new part 26.
4. Compliance Dates
Several commenters proposed changes to the DAH compliance dates for subpart I (now part 26) requirements. The proposal would have required DAHs of existing airplanes to submit ICA for approval to the FAA Oversight Office by December 16, 2007. This was based on an expected effective date of June 30, 2006 for the final rule, and would have allowed DAHs 18 months to complete compliance. The proposed operator requirements would have allowed operators 12 months from the date DAHs completed their ICA to incorporate EWIS tasks into their maintenance program. The compliance date for operators (again based on an expected final rule effective date of June 2006) was December 16, 2008.
Avions de Transport Regional (ATR), Aerospace Industries Association and General Aviation Manufacturers Association (AIA/GAMA), General Electric (GE), and Boeing requested a longer compliance time for the DAH requirements. ATR specifically proposed 30 months because it said it will need to review and update all of its maintenance documentation. GE requested 36 months. Boeing and AIA/GAMA requested the compliance time for DAHs be increased to 24 months. Boeing and AIA/GAMA noted that industry, through ATSRAC, originally identified 24 months as the time needed to conduct the EZAP analysis for their existing airplane configurations. But the FAA has now proposed additional requirements, such as evaluating type certificate (TC) holder changes mandated by airworthiness directives (AD) and compliance plan activities. The commenters noted that the original schedule and resource analysis did not account for these additional activities. Additionally, Boeing and FedEx requested that the rule include required time periods for FAA review and approval activities involved in the compliance plans. Boeing and Airbus noted that the rules do not currently limit the amount of time the FAA will take to review and approve documents, which will negatively impact their compliance time. Boeing stated that most DAHs will require the full 90 days for developing a compliance plan, and will not initiate that plan until they obtain FAA approval. So to ensure that they have an appropriate time for compliance activities, they'll need FAA approval immediately, which is impractical.
Boeing and AIA/GAMA also said that the hard compliance dates and an expected final rule issuance in early 2007 will leave DAHs with less than 12 months to comply with the subpart I requirements. Along with Airbus and GE, they requested that we revise the compliance dates to represent a number
of months after the effective date of the rule, rather than a hard date. AIA/GAMA noted that this approach would prevent our process and schedule for issuing the final rule from impacting DAH compliance dates.
We agree with the commenters that additional time should be allowed for DAH compliance with 26.11. While we understand that ICA for EWIS have already been developed for a number of affected airplanes, we also understand that not all DAHs have begun this activity. In addition, as discussed later, DAHs that have already developed EWIS ICA may not have addressed the “representative airplane” configurations, as required by this rule. However, because DAHs would need to plan and coordinate with the FAA anyway, we do not believe the requirements to do so will significantly increase the amount of time needed to comply. In consideration of these factors, we believe that 24 months will allow sufficient time for DAHs to develop and submit the necessary compliance plan, draft data and documents, and final data and documents to show compliance with today's rule.
We have made a minor revision to section 26.11(d)(3), (d)(4) and (d)(5). This is to clarify that the affected pending or future applicants must comply either by a date based on the effective date of the rule, or by the date of approval of the related certificate. Even though we specifically discussed the intent of these dates in the NPRM preamble, we believe that using the term “approval of the application,” which appeared in the proposal (in proposed § 25.1805(c)(3), (c)(4), and (c)(5)) indicating dates for compliance, may have caused confusion. So, we have replaced the term “application” with the term “certificate” in 26.11(d)(3), (d)(4) and (d)(5).
We are not including FAA-required time periods for review and approval of the required compliance plans. Instead, expectations for FAA personnel have been defined in a new FAA order
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that directs the Aircraft Certification and Flight Standards Services in their roles and responsibilities for implementing these initiatives. The order includes expected times (6 weeks) for reviewing and approving DAH compliance plans, plans to correct deficiencies, and draft and final compliance data and documents. To facilitate implementation, we will also train affected personnel in their roles and responsibilities and provide in-depth familiarization with requirements of the regulations and associated guidance. The FAA's Aviation Safety organization's recent registration as an ISO (International Organization for Standardization) -9001-compliant organization will also facilitate standardized and timely implementation of the review and approval process.
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Order 8110.26, “Responsibilities and Requirements for Implementing Part 26 Safety Initiatives,” will be released concurrently with this rule.
Several operators also requested revisions to the DAH compliance dates, noting the potential adverse impact on them because of the time it could take for FAA review and approval. Air Transport Association (ATA) recommended that § 25.1805(c)(1) (now 26.11(d)(1)) be rewritten to provide a reasonable period of time (90 days) for the necessary FAA review and approval activities. ATA noted that the amount of time the FAA will take to review and approve TC holders' EWIS/FTS ICA could reduce operator compliance time significantly. FedEx made similar comments and noted that compliance dates should acknowledge time for approval of compliance documents, distribution of those documents, operator planning for addressing the requirements, and final release of the changes in the operator's program. Royal Dutch Airlines (KLM) was also concerned about FAA review and approval impacting operators' compliance time and requested that the operator compliance date be one year after ICA are approved. Boeing, ATR and U.S. Airways also stated that the compliance time for the operational rules should be based on availability of needed data.
Continental requested that operators be allowed 18 months rather than 12 months to comply. It said a thorough training program would be needed for maintenance personnel not familiar with wiring and its components. This would require additional effort by the operator not contemplated by simply having ICA incorporated into a maintenance task or inspection program. Additionally, Continental stated that contract maintenance personnel must also be trained for systems they maintain.
The National Air Carrier Association (NACA) requested that operators have two years for compliance, dependent on DAHs complying with their requirements on time.
Based on rationale the ATA provided for requesting the change, we infer that ATA would like additional time (90 days) added to the operator's compliance time rather than to the DAH's compliance time. While it is inappropriate to put requirements for the FAA in a rule applicable to DAHs, we have, as discussed previously, identified expectations for FAA review and approval (including timeframes) in an internal FAA order. The length of time to review plans, data, and documents depends largely on the quality of the submittals. Acceptable documents will take less time to review.
We have structured the requirements of the DAH rule and developed complementary guidance to facilitate timely review and approval of DAH submittals (compliance planning, draft document reviews, etc.). We do agree, however, that a modest increase in operator compliance time would help ensure that operators are not impacted by the FAA review and approval process. We have revised the EAPAS compliance date for operators from 12 months to 15 months.
Regarding the NACA request for a two-year compliance time, in the past we have imposed numerous maintenance program revision requirements through operational rules and ADs. Twelve months has been the typical compliance time for these changes and has been sufficient for operators to comply. The maintenance actions described in the maintenance program changes would be accomplished sometime later, as specified in the maintenance program. So operators will have sufficient time to plan and conduct the necessary EWIS training.
On July 30, 2004, (69 FR 45936), we extended the Fuel Tank Safety Operational Rule compliance dates to December 16, 2008, for reasons outlined in that final rule. Because of the similar timelines for operator incorporation of the FTS and EAPAS maintenance actions into their programs, we had determined that aligning the compliance dates for the FTS and EAPAS maintenance program changes would allow operators to revise their maintenance program once to address both safety initiatives. However, given delays in issuing the EAPAS rulemaking proposal and the expectation for industry to have the FTS ICA developed for compliance with the EASA rule (December 2007) and the FAA rule (December 2008), we have determined that the benefits of aligning the FTS and EAPAS compliance dates are not substantial enough to justify further delay in implementing FTS maintenance actions. As previously discussed, we are not extending the FTS operational rule compliance date in this final rule.
5. The Design Approval Holder Compliance Plan
As noted above, in the NPRM we contemplated submission of a proposed means of compliance, identifying all required submissions to the FAA. The NPRM proposed submission of—
• A project schedule identifying all major milestones.
• A detailed explanation of how the proposed means of compliance would be shown to comply if it differed from that described in advisory material.
• A proposal for submitting a draft of all compliance items no less than 60 days before the compliance due date.
• A proposal for how the approved ICA would be made available to affected persons (operators and others required to comply with this rule).
The proposal stated that if the FAA notified the DAH of deficiencies in its proposed compliance plan or in its implementation of that plan, the DAH must submit a corrected plan to the FAA Oversight Office within 30 days. All of these compliance plan requirements were contained in proposed § 25.1805(d) and (e).
Airbus requested that § 25.1805(d) and (e) be removed because, it said, these requirements are unnecessary. Airbus believes the only important compliance date is the final date for DAHs to submit the data and documents necessary to support operator compliance. Boeing recommended we remove the § 25.1805(d)(3) requirement to identify deviations to methods of compliance identified in FAA advisory material because it does not agree that proposed methods of compliance should be compared to other methods. Instead, it said, they should be evaluated on their own merits.
The FAA agrees that some provisions of proposed § 25.1803(d) and (e) could be removed without adversely affecting our ability to facilitate TC holder compliance. Specifically, proposed paragraph (d)(3) would require TC holders to identify intended means of compliance that differ from those described in FAA advisory materials. While this is still a desirable element of any compliance plan, we have concluded that an explicit requirement is unnecessary and it is not included in this final rule. As with normal type certification planning, we expect that TC holders will identify differences and fully discuss them with the Oversight Office early in the compliance period to ensure that these differences will ultimately not jeopardize full and timely compliance. Because we believe that timely review and approval is beneficial and will save both DAH and FAA resources, the advisory material recommends that if the DAH proposes a compliance means differing from that described in the advisory material, the DAH should provide a detailed explanation of how it will demonstrate compliance with this section. The Oversight Office will evaluate these differences on their merits, and not by comparison with FAA advisory material.
Similarly, proposed paragraph (e) contains provisions that would have authorized the Oversight Office to identify deficiencies in a compliance plan or the TC holder's implementation of the plan and require specific corrective actions to remedy those deficiencies. While we anticipate that this process will still occur in the event of a potential non-compliance, we have concluded that it is unnecessary to adopt explicit requirements to correct deficiencies and have removed them from the final rule. Ultimately, TC holders are responsible for submitting compliant EWIS ICA by the specified date. This section retains the requirements to submit a compliance plan and to implement the approved plan. If the Oversight Office determines that the TC holder is at risk of not submitting compliant EWIS ICA by the compliance date because of deficiencies in either the compliance plan or the TC holder's implementation of the plan, the Oversight Office will document the deficiencies and request TC holder corrective action. Failure to implement proper corrective action under these circumstances, while not constituting a separate violation, will be considered in determining appropriate enforcement action if the TC holder ultimately fails to meet the requirements of this section.
Additionally, in reviewing the comment, we realized that the rule text could more clearly state our intent to allow DAHs flexibility to modify their approved plan if necessary. So the final text of proposed § 26.11(f) has been modified to read “each affected person must implement the compliance plan,
or later approved revisions
* * *.” In response to Airbus' comment that the only important compliance date is the final date for DAHs to submit the data and documents, we must reiterate that we believe a compliance plan is important. The purpose of a 90-day compliance date for the compliance plan is to allow all parties to be informed about how the DAH will be meeting its requirements and to ensure that the all necessary data will be provided to the operators on time. Early development of a compliance plan will give assurance of development of all the necessary data in time for the operators to comply with their requirements.
6. Defining the Representative Airplane
Boeing requested that we define in advance of the final rule which TC holder configuration changes mandated by ADs should be considered in the EZAP. Boeing and AIA/GAMA noted that the DAH must consider airplane configurations representative of each airplane model plus DAH-developed modifications mandated by AD. Boeing stated that because ADs are applicable to operators and not DAHs, and because most ADs are not applicable to all airplanes within a specific model range, it is difficult to define a representative airplane. Boeing does not believe the proposed § 25.1805 (now § 26.11) compliance time allows enough time to properly define the representative configuration.
As previously discussed, we have increased the proposed DAH compliance time for a number of reasons, one of which was to allow sufficient time for the DAH to identify the representative configuration for each affected airplane model.
As discussed in the NPRM, the purpose of the requirement to address all TC-holder-developed modifications mandated by AD is to make the EZAP as complete and accurate as possible. It would serve no purpose to require the TC holder to analyze an airplane configuration no longer in service because an AD has mandated its modification. Therefore, TC holders must assess all these modifications to determine whether they affect the results of the EZAP. Because TC holders own the design data for both the original configurations and these modifications, they are the only entities capable of performing these assessments. When TC holders develop AD-mandated modifications for airplanes still in production, they normally incorporate these same modifications into new airplanes. So this requirement imposes little additional burden for these airplanes. At the same time, we recognize that it would be unreasonable to require the TC holder to analyze modifications developed by third parties. Accordingly, this requirement is limited to TC-holder-developed modifications.
In reviewing Boeing's comment, we recognized that the proposed definition of “representative airplane,” i.e., “the configuration of each model series airplane that incorporates all variations of EWIS used on that series airplane * * *,” could be interpreted in different ways. It could be interpreted as applying to all post-production
modifications, not just those mandated by AD and those DAH-developed modifications introduced into production. It could also refer to variations used for post-production modifications, as well as those used in production. Boeing correctly understands that we intended to require evaluation only of variations used in production and those post-production modifications mandated by AD. Section § 26.11(b) has been revised to clarify this. For those design changes made in production for which the TC holder has issued service bulletins describing post-production equivalents, the ICA should identify those service bulletins with the corresponding production configurations. This will enable operators that have incorporated these service bulletins to determine that the ICA for the production modification also applies to them.
7. Impact on Operators
Boeing asked that we separate the operational rule from DAH requirements, with a separate comment period, so that defined service information and associated costs can be evaluated by the operators. Boeing contended that consolidating DAH and operational requirements into one rulemaking action with one comment period prevents the FAA from obtaining accurate cost estimates and prevents operators from determining the true impact of the proposal on their operations. NACA also expressed concern that operators cannot know the full impact of this rule until DAHs develop the required ICA.
We have decided against separating the operational rules from the DAH requirements. Separating the rules would not change the technical requirements contained in this final rule but would substantially delay implementation of the EAPAS safety initiative. Thus, it is essential to include both certification and operational requirements in the final rule to ensure maximum safety benefits to the flying public.
In addition to issues of timeliness, we note that while some operators will not know the precise effects of the ICA developed by TC holders on their maintenance programs, they should have a good understanding of the nature and scope of the program from the NPRM and the guidance material provided in the DAH EZAP AC (AC No. 25-27). As discussed, both of these were derived from ATSRAC's recommendations, which operators played a major role in developing. In addition, since 2004, multiple operators have been involved with several airplane manufacturers in developing EWIS ICA using the EZAP analysis described in the DAH EZAP AC. This has been accomplished by integrating EWIS ICA development into the airplane manufacturer's normal maintenance development program. Operators of the airplane model for which a maintenance program is being developed (or revised) are always involved in the development of that program. Therefore, these operators do know the impact of integrating these new EWIS ICA into their maintenance programs.
8. EZAPs Already Completed
Boeing asked that we include a statement in the final rule indicating that EZAP analyses conducted prior to the effective date of the final rule, and resultant ICA, comply with subpart I (now part 26) requirements. Boeing questioned the statement that the proposed time frames are supported by experience gained by EZAPs already performed, when the NPRM did not discuss the acceptability of those analyses. It noted that several EZAP analyses were conducted using MSG-3
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methods, which differ slightly from those contained in proposed AC 120-XX (now the DAH EZAP AC, No. 25-27). Boeing noted that, for those cases, it must show the FAA Oversight Office how the previous analyses were conducted, make any necessary changes, obtain industry agreement, and have the FAA approve the resulting ICA.
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Air Transport Association (ATA) Maintenance Steering Group 3 (MSG-3) is a document containing a logic process used by the airlines and manufacturers to develop scheduled maintenance programs for an airplane.
We believe that work done before adoption of the rule will reduce the level of effort required for DAHs to comply with the rule. But we also recognize that some additional work may be necessary for DAHs to show compliance. For example, EWIS ICA may not have been aligned with FTS ICA or may not have been developed for the “representative airplane” as defined in the rule. Therefore previous work cannot automatically be considered compliant. Because we cannot say with any confidence that no more work will be required, we are not adopting Boeing's recommendation.
9. Wire Inspections
The National Air Traffic Controllers Association (NATCA) called the proposal inadequate because it relies on enhanced zonal inspections to detect latent failures in the wiring system, and it said that zonal inspections detect only visible deteriorated wire.
The commenter said that without periodic or real-time monitoring of airplane wiring, there is no way to predict a degraded state and prevent future wire failures. NATCA recommended that we include requirements for either continuous on-board detection of airplane wiring faults, such as that provided by system self-test features, or periodic maintenance tasks, to detect both visible and hidden degradation in the wiring system.
The requirements adopted today do not prevent use of wire monitoring or fault detection technology. Multiple non-destructive inspection (NDI) tools and real-time monitoring techniques are being developed for use in aircraft wiring inspection. However, current NDI reflectometry technology is not yet mature enough for its use to be mandated by the FAA. Although real-time monitoring technology, such as arc fault circuit breaker technology, is further along in development, it too is not yet mature enough to address all circuit types. We expect that these technologies, when available, may be relatively more expensive than conventional methods, so the need for visual inspection of EWIS would remain even if this technology were widely available. We made no change based on this comment.
10. Protections and Cautions
Boeing requested that we remove from subpart I (now part 26) the requirement to include ICA instructions for protection and caution information to minimize contamination and accidental damage during maintenance activities. It suggested this language should be added to the operating rule. Boeing considers the methods of protecting wiring during maintenance to be best determined by the maintenance provider and dependent on the type of maintenance activity underway. Boeing also noted that operators who have already developed protection schemes based on their experience will be required by the operational rules to replace this with the one provided by the TC holder. Boeing does not believe this is a positive step towards increased protection of EWIS.
United Airlines stated its support for requiring airplane manufacturers to include specific recommendations for when and how to protect wire bundles from damage during different phases of maintenance.
We infer that Boeing is referring to the requirement in H25.5(a)(1)(vi). That requirement applies both to new type certificates complying with § 25.1729
(proposed as § 25.1739) and existing type certificates complying with part 26. The requirement is consistent with ATSRAC's recommendations. These recommendations were based on recognition that the TC holder will have the best understanding of EWIS material properties and vulnerabilities, and will be in the best position to identify what protection and caution measures are needed. If operators have developed their own instructions, they may be used as alternatives or as supplements to those provided by the TC holder, if approved by their Principal Inspector (PI). We have provided guidance to the FAA field offices to allow for consideration of an operator's alternative to that approved by the FAA Oversight Office. We made no rule change based on this comment.
11. Alignment of EWIS and Fuel Tank ICA
AIA/GAMA and GE requested that the last sentence of proposed § 25.1805(b) (now § 26.11(b)), requiring minimization of redundant requirements between EWIS and fuel tank ICA, be deleted. The commenters stated that this is an economic and customer service issue beyond the scope of the FAA's safety interest.
Boeing requested we include, within proposed § 25.1805(b), the levels of alignment of FTS and EWIS maintenance actions that will be acceptable for compliance. While Boeing sees the benefit of eliminating redundant maintenance activities, it considers itself unable to determine how to show compliance with this requirement.
Minimizing redundant requirements is not just an economic issue for operators. One of ATSRAC's findings is that repeated disturbance of EWIS during maintenance is itself a source of safety problems. Therefore, while ensuring that all necessary maintenance is performed, it is also our objective to minimize disturbance by eliminating redundant requirements. Too frequent disturbance to electrical wiring by repeated moving, pulling, and flexing of the wire bundles will induce unnecessary stress on the wiring and its components, which in turn could lead to degradation, expedited aging, and failures. Thus it is important that redundant tasks and unnecessary disturbances to the electrical wiring be minimized. Operators will review their maintenance tasks and coordinate with the DAHs to ensure that tasks are incorporated into their maintenance program for the highest level of safety and performed in the manner most suitable for their operation.
As discussed earlier, Boeing and other TC holders have been required to develop ICA since 1981, and maintenance manuals even before that. In developing ICA, TC holders routinely review individual tasks to align them with other tasks being developed. This is done both to avoid redundancy and to eliminate confusing or conflicting instructions that could inadvertently lead to improper maintenance with unsafe consequences. The purpose of the requirement to align the ICA is no different. The intended “levels of alignment” are the same as would be expected for ICA developed in connection with original type certification. The MSG-3 and Maintenance Review Board (MRB) processes, with which Boeing and other affected TC holders are familiar, have the same objectives. The DAH EZAP AC, “Development of Transport Category Airplane Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness Using an Enhanced Zonal Analysis Procedure,” No. 25-27, describes means of compliance that will achieve these objectives. It provides a step-by-step process to assist applicants in compliance with the electrical wiring interconnection system (EWIS) maintenance requirements. This process includes a step requiring an analysis of the related maintenance tasks to ensure that they are consolidated and/or aligned to maximize effectiveness and eliminate redundancies and duplications between the EWIS and fuel tank ICA.
The airplane manufacturer will align the ICA requirements to the greatest extent possible. No change to the final rule is necessary.
12. Approval of ICA
Boeing and AIA/GAMA requested further clarification of proposed §§ 25.1739 (now § 25.1729) and 25.1805(b) (now § 26.11(b)) requirements that ICA prepared in accordance with paragraph H 25.5 of Appendix H be submitted to the FAA Oversight Office for approval. AIA/GAMA, Airbus, and FedEx recommended that EWIS ICA be accepted by the FAA, rather than approved, with the exception of any applicable airworthiness limitation items (ALI), which should be approved. The commenters were concerned that the proposed requirements are not consistent with the current requirement in § 25.1529 that ICA be found acceptable to the FAA (except for ALI, which must be approved). FedEx also stated that creation of separate “FAA-approved” ICA will lead to confusion and fragmentation of what should be an integrated inspection program.
As discussed earlier, one of the primary objectives of these DAH rules is to ensure that operators have at least one source of FAA-approved data and documents that they can use to comply with operational requirements. This objective would be defeated if the required data and documents were not, in fact, approved. Only by retaining authority to approve these materials can we ensure that they comply with applicable requirements and can be relied upon by operators to comply with operational rules. We believe that there are differences between EWIS ICA and other ICA that necessitate approval of EWIS ICA:
• EWIS ICA are the means for compliance with some of the technical requirements of new subpart H (§ 25.1707 relating to system separation and § 25.1711, component identification).
• EWIS ICA contain highly technical information such as electrical loads data and wiring practices standards that are more complex than typical maintenance instructions.
• EWIS ICA require a degree of consistency and standardization that may not be necessary for other ICA.
We agree that further clarification is needed regarding FAA Oversight Office approval of EWIS ICA. We do not intend to approve all documents that contain EWIS ICA details, such as the airplane maintenance manual. We do intend to review references in all documents that are referred to in the EWIS ICA source documents. We have made changes to the AC guidance information (AC 25.1701-1) to clarify exactly what documents the FAA Oversight Office will approve. No change to the final rule is necessary.
13. Rule Applicability
Today's rule is applicable to airplanes with a passenger capacity of 30 or more passengers or a payload capacity of at least 7,500 pounds operating in parts 121 and 129. NATCA requested that we consider revising the rule applicability to address all transport airplanes regardless of size or type of operation. It stated that all transport airplanes are subject to the same aging safety concerns, and passengers should have one level of safety.
The FAA has used these size criteria for the applicability of other rulemakings because they capture the airplanes carrying the vast majority of passengers and cargo. Similarly, by limiting applicability of the EAPAS operational rules to parts 121 and 129, we focus these requirements on the
airplanes that transport most passengers and cargo. Based on our analysis, the additional safety benefit of extending the operational requirements to all transport airplanes would not justify the additional costs of doing so. We will continue to review this issue and, as this rule is implemented, if we can demonstrate that it can be applied cost effectively to smaller airplanes or other operators, we may consider further rulemaking.
Several commenters requested revisions and clarification of applicability with respect to supplemental type certificates (STC). EASA requested we revise the applicability of § 25.1805 (now § 26.11(d)) to include STCs that significantly affect EWIS.
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British Airways stated its support for the existing applicability, agreeing that the analysis performed by the DAH would cover the EWIS they are responsible for as well as the wiring changed or added by others. FedEx requested clarification on means of compliance for STCs.
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EASA plans to address STCs in its NPA.
Additionally, the ATA requested we revise proposed § 25.1805(c)(4) (now § 26.11(d)) to clarify its applicability only to new STCs issued after the effective date of the final rule and not to existing STCs that may be modified after the effective date of the rule. The ATA noted that some STCs are modified to expand the STC effectivity as an operator's fleet grows and should not be evaluated for compliance with § 25.1805(c)(4).
Section 26.11 will apply to future applicants for STCs and to existing TCs. As explained in the NPRM, we decided not to include existing STCs in this section for two reasons. First, most existing STCs do not provide detailed instructions for wiring installation, relying on the judgment and expertise of the individual installer. In most cases it would not be possible for the current STC holder to evaluate these wiring installations. Second, in most cases, installers have followed the TC holder's wire routing and installed STC wiring in or adjacent to existing wiring. In these cases, implementing the maintenance programs developed by the TC holder should adequately address the safety issues identified in this rule that may exist in the STC wiring. Our conclusion here is consistent with ATSRAC's recommendations.
However, we will not revise § 26.11 to exclude modifications to existing STCs. As discussed, one reason we are not applying this rule to existing STCs is that in many cases existing STCs do not include data for EWIS that can be evaluated. As discussed in the NPRM, we believe it is important that EWIS ICA be provided for all future STCs, including changes to existing STCs. We have revised § 26.11(d) to clarify that “if an existing STC is amended, this section would apply to the amendment.”
The extent of the review required for changes to existing STCs would be limited to the newly proposed changes. Applicants would not be required to evaluate the entire design change approved under their existing STC. For example, if an applicant proposed to add additional monitors to an existing in-flight entertainment STC, only the EWIS supporting the additional monitors would need to be evaluated for the impact to the ICA. If an applicant were merely adding airplane models of the same configuration to an existing STC, they would not need to evaluate their STC.
Boeing Wichita asked whether it would be required to evaluate EWIS for an entire airplane in order to comply with requirements of § 25.1805 (now § 26.11) when applying for an STC.
We do not intend to require applicants for design changes approval to evaluate the EWIS of the entire airplane. Rather, these applicants must evaluate whether their proposed design change would require revision of the ICA developed by the TC holder (and any previous STC applicants) in compliance with § 26.11 to correctly address the design change. An example would be if an STC applicant proposed to add EWIS to a zone that did not previously have EWIS. The applicant would need to develop an ICA revision providing for any maintenance actions within that zone that may be necessary to comply with Appendix H to part 25. We have revised § 26.11 by adding a new paragraph (c) to clarify this requirement.
14. Non-U.S. Manufacturers
Airbus also commented that proposed § 25.1805 paragraphs (b), (d), and (e) (now § 26.11(b) and (e)) fail to acknowledge that non-U.S. manufacturers will likely have to comply with similar regulations issued by their own authorities. Airbus said that discussion of the compliance plan and review of the compliance items should be delegated to the relevant foreign authority, as far as permitted by existing Bilateral Aviation Safety Agreements.
We recognize the important role other national authorities are likely to play in implementation of this rule. In addition to the on-going efforts to harmonize these requirements, we have been working closely with the other national authorities to define appropriate roles, responsibilities, and relationships among all affected authorities. As discussed in the NPRM, the compliance planning provisions are equally important for foreign TC holders, and we expect to have mutually agreeable arrangements with their authorities on how this planning will be overseen.
15. General Comments About Design Approval Holder Requirements
We received a number of general comments responding to the concept of DAH requirements rather than to the DAH requirements in this specific rulemaking. We responded to these types of comments in the comment disposition document accompanying our policy statement titled “Safety—A Shared Responsibility—New Direction for Addressing Airworthiness Issues for Transport Airplanes.” Both were published in the
Federal Register
on July 12, 2005. As a result, we will not respond to such comments again here. We have included them, and our responses, in a separate document in the docket. That document is titled “General Comments about DAH Requirements Sent to Docket Number 18379.”
Boeing and AIA/GAMA did not agree with our assessment that DAH rules are necessary to support this initiative. They requested we remove proposed § 25.1805 (now § 26.11) from the rule. They contended that
• The required material is neither complex nor limited to the DAH,
• Operators have the option of developing an enhanced zonal inspection program without participation of the DAH, and
• Operators will not be required to adopt maintenance programs developed by the DAH.
Both commenters stated that developing EWIS ICA is not complex. They noted the EZAP process is based on MSG-3 maintenance program development procedures, which are neither complex nor limited to the DAH. They believe that the DAH type design data needed for development of maintenance tasks is also available to operators.
Boeing and AIA/GAMA also said that use of the MSG-3 process by the DAH alone will only account for airplane configurations certified by the DAH and some, but not all, AD-mandated modifications. Unique configurations that evolved after delivery will not be considered by the DAH. Boeing contended that operators are capable of assessing their airplane configurations using proposed AC 120-XX (now the DAH EZAP AC) and developing an
enhanced zonal inspection program without DAH involvement. Additionally, Boeing stated that operators could develop ICA more efficiently because they could concurrently address the baseline configuration and any configuration changes made in service.
As discussed previously, the policy statement provides criteria for deciding when DAH regulations are necessary.
Appendix H paragraph H25.5(a)(1) identifies information required to perform the analysis and develop maintenance tasks. While some of this information may be available to operators without assistance from the DAH, operators would not have access to all of it.
Also, the methodology described in the AC may appear to be relatively simple, but applying it properly requires considerable expertise and judgment and can be quite complex. DAH involvement is necessary to ensure it is applied properly. We believe that DAH regulations are necessary for this safety initiative to ensure all of the representative type design configurations are addressed in a timely manner. The “representative” airplane is defined as the configuration of each model series airplane that incorporates all the variations of EWIS used on that model, and that includes all TC-holder-designed modifications mandated by AD, as of the effective date of this rule.
Existing regulations regarding ICA as adopted in Amendments 21-50 and 25-54 require DAHs to provide ICA for the airplane as a whole. This rule simply applies that same policy to EWIS, which were not specifically addressed by those amendments.
We note that in the form in which the rules were proposed, operators would be required to implement EWIS ICA based on those “developed by the type certificate holder.” That statement did not clearly articulate our intent and we have corrected that language in the final rule to reference “in accordance with the provisions of Appendix H of part 25 of this chapter applicable to each affected airplane * * *.”
Both Boeing and AIA/GAMA requested that we establish, within the final rule, all requirements for the DAHs regarding consistency, standardization of process and requirements, and technical guidelines. They do not believe the rule or guidance material is comprehensive enough to enable DAHs to comply. Boeing stated that the root cause of past difficulties with voluntary compliance lies with unclear regulatory requirements and lack of appropriate guidance. Boeing noted that the FAA attempted to address this problem in the proposed rule, but said those attempts have fallen short of what is needed. It quoted draft AC 25-XX: “* * * the Compliance Team, as soon as possible after issuance of the safety initiative rule, will provide the DAHs with our expectations for the required analysis content [and] describe to the DAHs our expectations for the content and format of their data * * * .” Boeing contends that visibility of requirements, expectations, and technical requirements would ensure uniformity of application and inform operators of what information they would receive from DAHs.
We partially agree. The program plan for the aging airplane rules was to release associated guidance and policy for public comment upon release of the NPRMs. We believe this approach should have helped clarify our expectations of what is considered an acceptable approach to compliance.
For this initiative, both the performance standards and guidance materials were developed by ATSRAC, which had representatives from the affected industry. We must presume that industry, in helping to develop these materials, understood what would be expected for new TCs. We consider these same materials to be sufficient for application to existing TCs.
The comprehensiveness and level of detail of requirements and related advisory material is at least equivalent to that for other ICA currently in Appendix H, which DAHs have successfully complied with for 25 years. The purpose of compliance planning provisions is to ensure that DAHs work closely with the FAA, as they do for initial certification, in developing compliant data and documents. We made no change to the rule due to this comment. However, we will clarify in AC 26-1 that the compliance team will meet with DAHs as soon as possible after issuance of the final rule to ensure that guidance materials and expectations related to rule implementation are clear.
16. Airplanes Excluded From Design Approval Holder and EWIS Operating Requirements
The DAH requirements and the EWIS requirements for operators do 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
(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
The airplanes excluded from these rules are not currently operating under parts 121 or 129, so there is no need for DAHs to develop data to support the operational rules for these airplane models. The Vickers Viscount airplane appeared on this exclusion list in the NPRM. But since the Vickers Viscount was originally type certificated before January 1, 1958, this airplane is not subject to these rules because of the general exclusion of airplanes type certificated before that date. Thus it has been removed from the exclusion list. Similarly, the Convair and DC-3 models that have been modified to incorporate turbine-powered engines are also covered by this general exclusion, so they too have been removed from the originally proposed exclusion list. The Lockheed L-300 has been added to the exclusion list. There is only one qualified aircraft, which was modified, used, and later retired by the National Aeronautics and Space Administration (NASA) in 1995. It would not be cost effective to bring it into 121 operations. Thus it has been excluded from the requirements of these rules.
C. Electrical Wiring Interconnection System (EWIS) Certification Rules (Part 25 Subpart H)
1. New Subpart for EWIS
This final rule creates a new subpart H within part 25 of 14 CFR addressing electrical wiring interconnection systems (EWIS). Its purpose is to be the single place in the regulations where the majority of certification rules pertaining to transport airplane wiring can be found. Many of the rules contained in this new subpart are previously-existing requirements that have been moved from different parts of the regulations. Some have been reworded to make it clear that they apply to wiring. Several of the rules in subpart H are new. As a whole, the rules in subpart H are meant to improve the safety of transport airplane wiring by making sure that it is designed to be safe. Individually, the rules address different aspects of wiring design safety, and they are discussed individually below.
To better harmonize with foreign airworthiness authorities, the numbers of many of the rules in subpart H have been changed from those originally proposed. The following table indicates the revised numbers. Since commenters referred to the proposal when they
wrote to the FAA, however, their references below are the originally proposed rule numbers. Similarly, if a commenter references a proposed AC, the original draft AC number is retained, as used by the commenter. Several of the proposed subpart H rules received no comments and remain unchanged except for their numbers. Those will not be discussed here. The following table indicates the rule number changes.
Table 2.—Subpart H Rule Renumbering
Title in subpart H
Final rule section
NPRM
section
Definition
25.1701
25.1701
Functions and Installation: EWIS
25.1703
25.1703
Systems and Functions: EWIS
25.1705
25.1719
System Separation: EWIS
25.1707
25.1709
System Safety: EWIS
25.1709
25.1705
Component Identification: EWIS
25.1711
25.1711
Fire Protection: EWIS
25.1713
25.1713
Electrical Bonding and Protection against Static Electricity: EWIS
25.1715
25.1717
Circuit Protective Devices: EWIS
25.1717
25.1721
Accessibility Provisions: EWIS
25.1719
25.1725
Protection of EWIS
25.1721
25.1727
Flammable Fluid Protection: EWIS
25.1723
25.1729
Powerplants: EWIS
25.1725
25.1731
Flammable fluid shutoff means: EWIS
25.1727
25.1733
Instructions for Continued Airworthiness—EWIS
25.1729
25.1739
Powerplant and APU fire detector system: EWIS
25.1731
25.1737
Fire detector systems, general: EWIS
25.1733
25.1735
[Reserved]
deleted
25.1707
[Reserved]
deleted
25.1715
Instruments using a power supply: EWIS
deleted
25.1723
2. The Definition of EWIS (§ 25.1701)
Section 25.1701 is a new requirement. It defines electrical wiring interconnection systems (EWIS). The final rule differs from the proposal in the addition of the words “and external wiring of equipment,” discussed below.
Boeing commented that EWIS is not limited to the numbered items in § 25.1701(a). EWIS components might also include terminal blocks, circuit protective devices, and contactors. Boeing requested we indicate that EWIS may include these and other items as well.
We agree with Boeing that the EWIS components listed in § 25.1701(a) are not a comprehensive list. There may be other devices that would be considered part of an EWIS, as indicated by the phrase in the lead-in sentence to the list of § 25.1701(a)(1)-(13); “* * * this includes:” A determination of whether a component is considered to fall under the definition of EWIS must be made on specific design details of a certification program.
Airbus commented that the phrase “and external wiring of equipment” should be added to the list in proposed § 25.1701(b) of components covered by the EWIS definition. Airbus stated that for completeness and consistency, external wiring of equipment should be considered, since it can be part of the aircraft installation (e.g., galley connection wiring and seat connection wiring). Continental asked if wire installed in seats is covered by the proposal.
We have added the phrase “and external wiring of equipment” to the list of equipment in § 25.1701(b). We consider this a clarification of what constitutes an EWIS component and not an increase in scope over the proposal. If an airplane component, such as a galley or a seat, is manufactured with connection cables external to it, then the external connection cables would be considered an EWIS component.
An individual commenter stated that the word “interconnection” in the phrase “electrical wiring interconnection systems” is redundant and should be eliminated. This commenter also requested that we cite the numerous examples of airplane electrical wiring systems that are not a part of the EWIS. This commenter further requested that we define the term EWIS in the definition section and cite examples of components included in and excluded from the system.
We do not concur with the request to remove “interconnection” from the term “electrical wiring interconnection system” (EWIS). The EWIS certification and operational requirements in the final rule apply to wires that “interconnect” airplane systems, as opposed to wiring located solely within the enclosure of a piece of avionics equipment, for example. Thus the word interconnection is integral and important in describing what electrical wiring interconnection system means.
The definition of EWIS contained in § 25.1701 does include examples of airplane wiring and its associated components that are not part of the EWIS. We believe that these examples are sufficient to adequately articulate the regulatory definition of EWIS and that further examples are unnecessary. We made no change due to this comment.
We do not agree with the commenter's proposal to define EWIS in the definition section. Although not specifically identified by the commenter, we are assuming that he wants the definition to appear in 14 CFR part 1. Section 25.1701 contains the EWIS definition and clearly states that the definition applies to “The Chapter.” This includes all applicable certification and operational subchapters such as parts 25, 121, and 129 where the EWIS requirements are located. We have revised the final rule to include a reference to § 25.1701 in § 1.2.
Continental Airlines quoted § 25.1701 (definition) and the preamble discussion to emphasize the following statements:
The term EWIS means any wire, wiring device, or combination of these, including termination devices, installed in the airplane for
transmitting electrical energy
between two or more termination points * * *
* * * but any electrical connection used to support power and/or
signal transmission
that is part of the airplane TC, and that is used for the laptop or other carry-on items, is covered by the proposed definition.
The commenter requested that the phrase “signal transmission” be defined.
As used in the context of the proposal, signal transmission refers to data transmitted through wired means, as opposed to wireless signal transmission.
GE and AIA/GAMA commented that proposed § 25.1701(c), which provides for exceptions to the definition of an EWIS, means that the equipment inside shelves, panels, etc. will have to show compliance with EWIS requirements even if they are qualified to the standards of Radio Technical Commission for Aeronautics (RTCA) document number RTCA/DO-160. These commenters believe this would be the opposite of the rule's intended meaning. They request that the following phrase be deleted from the final rule: “Except for the equipment indicated in paragraph (b) of this section”.
As discussed in the NPRM, the definition of EWIS includes electrical wiring interconnection system components inside shelves, panels, racks, junction boxes, distribution panels, back-planes of equipment racks including circuit board back-planes, and wire integration units. This EWIS, unlike wiring within avionics equipment, is typically designed and made for a particular airplane model or series of models. Avionics components must be sent back to their manufacturer or a specialized repair shop for service. But this type of equipment is maintained, repaired, and modified by the same personnel who maintain, repair, and modify the other EWIS in the airplane. In an electrical distribution panel system, for example, separation must be designed and maintained within the panel just as in the EWIS leading up to that panel. Identification of components inside the panel is just as important as for those outside the panel since the wiring inside the panel is treated much the same. We have retained the first sentence of proposed § 25.1701(c).
3. Functions and Installation: EWIS (§ 25.1703)
Section 25.1703 (whose number is unchanged from that in the proposal), is essentially derived from requirements of existing § 25.1301. It requires that applicants select EWIS components that are of a kind and design appropriate to their intended function. Factors such as the components' design limitations, functionality, and susceptibility to arc tracking and damage from moisture must be considered in selecting EWIS components.
The final rule differs from the proposal in that words were changed to clarify meaning and words inadvertently left out of the proposal were put back in. We also removed the word “adequately” in response to a comment from Boeing, as noted in the discussion elsewhere under the heading System Separation (§ 25.1707).
Boeing commented that proposed § 25.1703(a)(3) states that EWIS must “function properly when installed.” Boeing proposed the final rule be rewritten to say that EWIS must “perform the function for which it was intended without degrading the airworthiness of the airplane.”
The commenter stated that it has had difficulty in the past with the term “function properly” when applied to complex or non-essential systems. It stated the suggested revision will help clarify the regulation's intent.
We agree that in the past the term “function properly” has been applied to complex or non-essential systems in a nonstandardized manner. We have revised the final rule text as proposed.
Airbus, Boeing, General Electric, and Honeywell requested that we add the words “in the fuselage” to § 25.1703(c) so it is consistent with the original regulation, § 25.869 (a)(3). They said that this will ensure that the requirements of § 25.1703(c) are consistent with the original requirement.
We agree. We mistakenly omitted the phrase “in the fuselage” in the proposed wording. We have revised the final rule to include it.
EASA and Airbus commented that ATSRAC recommended that § 25.1703 include the following requirement:
Electrical wiring interconnection system modifications to the original type design must be designed and installed to the same standards used by the original aircraft manufacturer or other equivalent standards acceptable to the Administrator (for 14 CFR)/authorities (for JAR).
EASA stated that this requirement will be included in the EASA notice of proposed amendment (NPA) that will propose to adopt ATSRAC's recommendations. Airbus said such a requirement is consistent with the proposal's preamble and advisory material (reference proposed AC 25.17XX, paragraph 5.b.(8)(b)). Airbus said that including this language in the final rule will ensure EWIS minimum compatibility for modifications made after an airplane is delivered.
Similarly, the International Aviation Safety Association (IASA) commented that airplane and wiring manufacturers should be required to approve the type of wiring used in modifications to an approved type design.
To add this additional requirement would essentially delegate to the type certificate holder authority to establish standards that go beyond the minimum safety standards required by part 25. The FAA does not have legal authority to make such a delegation. As with other airworthiness standards, an applicant who shows compliance with our standards is entitled to design approval (reference § 21.117). The rationale for this is that our standards provide an acceptable level of safety, so exceeding them is not necessary for safety. However, the referenced advisory material does contain the following statement:
Only the components listed in the applicable manual or approved substitutes should be used for the maintenance, repair, or modification of the aircraft. EWIS modifications to the original type design should be designed and installed to the same standards used by the original aircraft manufacturer or other equivalent standards acceptable to the FAA. This is because the manufacturer's technical choice of an EWIS component is not always driven by regulatory requirements alone. Sometimes specific technical constraints would result in the choice of a component that exceeds the minimum level required by the regulations.
We believe such a statement meets the intent of the ATSRAC recommendation. Therefore, we made no changes based on this comment.
Airbus requested that the term “hazard” replace “hazardous effects” in proposed § 25.1703(d). Airbus said this would eliminate ambiguous interpretation due to inappropriate use of what is a system safety classification term in § 25.1309(b). Airbus stated that the effect on the component itself needs to be covered instead of the effect on the function.
We infer from this comment that Airbus objects to the phrase “hazardous effects” because it believes this phrase implies that a numerical probability analysis would be necessary to show that moisture on EWIS components in known areas of moisture accumulation would not create a hazard not shown to be improbable. A numerical probability analysis is not necessary when demonstrating compliance with § 25.1703(d). The intent is that good engineering and manufacturing judgment be used when designing and installing EWIS components in areas of known moisture accumulation to minimize potential for moisture to cause an EWIS component failure. Such a failure could in turn lead to a functional failure of the system it is associated with. Or it could lead to accelerated
degradation of the component and localized electrical arcing could occur. This in itself could lead to a hazardous condition. It is important to protect the EWIS component from moisture damage. But it is the possible safety hazard from failure of the component that the rule is addressing, and not strictly the effect on the component, or its function. The advisory material for § 25.1703(d) states, in part, the following:
This section requires that EWIS components located in areas of known moisture build-up be adequately protected to minimize moisture's hazardous effects. This is to ensure that all practical means are used to ensure damage does not occur from fluid contact with components.
We believe that this statement prevents confusion about whether or not a numerical probability analysis is required for demonstrating compliance with this requirement. It is not. We made no changes due to this comment.
Boeing and AIA/GAMA commented that the preamble discussion of § 25.1703(d) states that the rule proposes to ensure that “all practical means” are used to prevent damage due to fluid contact. They noted that one could interpret this guidance to mean that multiple means must be used. Another interpretation could be that all practical means must be considered and the most appropriate method used to address potential for fluid impinging on wiring. For purposes of clarification, Boeing requests that the term “used” be changed to “considered.”
This rule is meant to require that all practical means be considered and the most appropriate method used to address potential damage from fluid contact with EWIS components. The advisory material for this requirement has been clarified to state this.
4. Systems and Functions: EWIS (§ 25.1705)
Section 25.1705 was proposed as § 25.1719. This section adds to the regulations the concept that EWIS associated with systems required for type certification or by operating rules must be considered an integral part of those systems and considered in showing compliance with all applicable requirements. In addition to this general requirement, the rule lists other specific certification rules (for example § 25.773 Pilot compartment view and § 25.981 Fuel tank ignition prevention) for which the applicant must include consideration of the EWIS that is part of the subject system in demonstrating compliance.
There are two differences between the proposal and the requirement as adopted: The section number has been changed, and a reference to § 25.1331(a)(2) (as discussed below) has been added.
EASA and Airbus requested that § 25.1723 be deleted and references to §§ 25.1303(b) and 25.1331(a)(2) be moved to § 25.1719 (now § 25.1705).
We partially agree to this request. There is no need to list both rules in § 25.1705(b). It is necessary to refer to § 25.1331(a)(2) because that requirement specifically applies to instruments required by § 25.1303(b). To list both §§ 25.1303(b) and 25.1331(a)(2) would be redundant. Therefore we have revised § 25.1705(b) to include 25.1331(a)(2) and we have deleted proposed § 25.1723 from the final rule.
EASA suggested that references to §§ 25.854 and 25.858 be included in § 25.1719 (now § 25.1705). The subjects of these two requirements are lavatory fire protection and cargo or baggage compartment smoke or fire detection systems, respectively. EASA stated that if we add §§ 25.854 and 25.858 to § 25.1719(b), § 25.1735 can be deleted, because its intent would be addressed in § 25.1719(a) and (b).
Requirements of § 25.1705(a) apply to EWIS associated with systems required for type certification or by operating rules. This is slightly different from those in § 25.1735, which apply to EWIS associated with any installed fire protection system, whether or not it is required for type certification or by operating rules. Therefore, we cannot delete § 25.1735. We have revised it, however, to include references to §§ 25.854 and 25.858. We included these two requirements in the preamble discussion for the proposed § 25.1735 and to avoid future confusion we believe they should be referenced within the final rule.
5. System Separation: EWIS (§ 25.1707)
Section 25.1707 System Separation: EWIS was proposed as § 25.1709. This rule requires applicants to design EWIS with appropriate separation to minimize possibility of hazardous effects upon the airplane or its systems.
Aside from the section number change, the difference between the proposal and this final rule is that word changes have been made to clarify meaning, and the reference in paragraph (a) has been changed.
EASA commented that proposed § 25.1709 (now § 25.1707) uses the phrase “any EWIS component failure” in several places throughout the requirement. EASA believes this implies that an exhaustive list of possible EWIS component failures not related to the design under review would have to be produced. It believes this goes beyond the intent of the rule, and states that the equivalent EASA requirement will use the wording “an EWIS component failure * * *” as was recommended by ATSRAC. EASA recommended that the final rule language be revised to adopt ATSRAC's recommended wording.
We have made the change EASA requested. The intent of the requirement is that applicants assess all EWIS components that could have a reasonable likelihood of failing in such a manner as to create a hazardous condition. We believe the revised rule language is clearer and will not cause an applicant to unreasonably consider EWIS component failures that could not adversely impact required separation.
Boeing requested that the words “adequately” be removed from the text of proposed § 25.1703(d) (rule number unchanged) and “adequate” from § 25.1709 (a), (c), (d), (e), (f), (g), (k), and (l) (§ 25.1709 is now § 25.1707). Boeing contends that inclusion of these terms does not enhance interpretation of the rules. It requested that we either delete them or add performance criteria that define the term “adequate.”
We believe the word “adequate” is necessary to the intent of § 25.1707. Paragraph (a) of that section provides objective criteria outlining how adequate physical separation must be achieved. We have also described various means of providing adequate physical separation in the associated advisory material. Because each system design and airplane model can be unique, and because manufacturers have differing design standards and installation techniques, § 25.1707 does not mandate specific separation distances. The advisory material provides the criteria each airplane manufacturer should consider when developing adequate physical separation for EWIS. These criteria include the following factors:
• The electrical characteristics, amount of power, and severity of failure condition of the system functions performed by the signals in the EWIS and adjacent EWIS.
• Installation design features, including the number, type, and location of support devices along the wire path.
• The maximum amount of slack wire resulting from wire bundle build tolerances and other wire bundle manufacturing variabilities.
• Probable variations in the installation of the wiring and adjacent wiring, including position of wire support devices and amount of wire slack possible.
• The intended operating environment, including amount of deflection or relative movement possible and the effect of failure of a wire support or other separation means.
• Maintenance practices as defined by the airplane manufacturer's standard wiring practices manual and the ICA required by § 25.1529 and § 25.1729.
• The maximum temperature generated by adjacent wire/wire bundles during normal and fault conditions.
• Possible electromagnetic interference, high intensity radiated fields, or induced lightning effects.
Although not related to this comment, we believe that the requirements of § 25.1707(c) could be stated more clearly. We have revised § 25.1707(c) in the final rule to state that
* * * damage to circuits associated with essential functions will be minimized under fault conditions.
We have removed the word “adequately” from § 25.1703(d). As used in proposed § 25.1703(d), that word does not add clarity to the requirement's intent and is therefore unnecessary.
GE suggested that for clarification we revise proposed § 25.1709(l) (now § 25.1707(l)) to read as follows:
§ 25.1709(l) Each EWIS must be designed and installed so there is adequate separation between it and other aircraft components, in order to prevent abrasion/chafing, vibration damage, and other types of mechanical damage.
We agree with GE that the wording of this rule could be improved to help clarify its requirements. We have revised § 25.1707(l) to state that
* * * EWIS must be designed and installed so there is adequate physical separation between it and other aircraft components and aircraft structure, and so that the EWIS is protected from sharp edges and corners, to minimize potential for abrasion/chafing, vibration damage, and other types of mechanical damage.
Boeing requested that the reference to § 25.1309(b)(1) and (b)(2) in § 25.1709(a) (now § 25.1707(a)) be deleted. It commented that the applicable guidance material does not include a numerical probability analysis. EASA commented that proposed § 25.1709(a) limits applicability of § 25.1309 to EWIS addressed by subparagraphs (b)(1) and (b)(2). EASA believes that for administrative purposes the final § 25.1709(a) should simply reference § 25.1309 because § 25.1309 could be revised in the future or the requirements of those paragraphs could be moved to a different paragraph within § 25.1309, making it necessary to also change § 25.1709. It stated that the equivalent EASA requirement will just reference § 25.1309.
We agree with Boeing's request to delete the reference to § 25.1309(b)(1) and (b)(2) and do not agree with EASA's request to modify the reference. The intent of the reference to failure conditions as defined by § 25.1309(b)(1) and (b)(2) was to require that an EWIS, under normal and failure conditions, would not create an unsafe condition. The failure conditions we were intending to reference are “hazardous” or “catastrophic,” used in EASA CS-25.1309 and in § 25.1709. In reviewing the text of the proposal, however, we realized that this reference could cause confusion as to the intent of the requirement and that the reference to the “catastrophic” failure condition is not necessary for the purposes of this requirement. To better align the requirement of paragraph (a) with the requirements of paragraphs (e) through (j), and to ensure adequate separation between EWIS and other airplane systems not specifically addressed by those paragraphs and paragraph (k), we have revised the first sentence of 25.1707(a). That sentence now reads: “Each EWIS must be designed and installed with adequate physical separation from other EWIS and airplane systems so that an EWIS component failure will not create a hazardous condition.” We discuss the term “hazardous condition” in our response to the next two comments.
General Electric and Honeywell commented that the wording of § 25.1709 (now § 25.1707) should be revised to clarify the meaning of “hazardous conditions,” so that a contained and detectable engine nacelle or auxiliary power unit (APU) enclosure fire is clearly distinguished from a fire within the pressurized fuselage as not being hazardous. In a similar comment, Airbus requested that the language for § 25.1709(b) (now § 25.1707(b)) be revised to reflect the original ATSRAC recommendation as follows:
Each EWIS must be designed and installed so that any electrical interference likely to be present in the airplane will not result in hazardous effects upon the airplane or its systems unless shown to be extremely remote.
Airbus stated that the ATSRAC-proposed words “unless shown be to extremely remote,” should not be removed unless it can be interpreted that the word “likely” excludes cases that are extremely remote and this is expressed in the advisory material.
In our NPRM preamble discussion of this issue, we said that the phrase “hazardous condition” in § 25.1709 (now § 25.1707) is used in a different context than it is when associated with the EWIS safety analysis requirements of § 25.1705 (now § 25.1709.) While that statement remains true, we now realize that framing the discussion around what a hazardous condition means in different rules may have caused confusion. The meaning of the term “hazardous condition” remains the same, whether used in § 25.1707, in § 25.1709, in current § 25.1353, or in CS 25.1309. Here is the definition for a hazardous failure condition, and also for a catastrophic failure condition.
Hazardous Failure Condition:
Failure condition that would reduce the capability of the airplane or the ability of the flightcrew to cope with adverse operating conditions to the extent that there would be, for example:
• A large reduction in safety margins or functional capabilities; or
• Physical distress or excessive workload such that the flightcrew cannot be relied upon to perform their tasks accurately or completely; or
• Serious or fatal injuries to a relatively small number of persons other than the flightcrew.
Catastrophic Failure Condition:
Failure condition that would result in multiple fatalities, usually with the loss of the airplane.
Hazardous and catastrophic failure conditions are descriptive terms for situations that could occur in the airplane because of failures (safety margins reduced, the flightcrew unable to perform accurately because of adverse operating conditions, injuries to passengers, etc.). These are situations that result from unsafe conditions and must be avoided. Therefore, when an airplane is certified, the applicant must show that the kinds of failures that could result in these kinds of situations have been considered, and measures put in place to prevent them.
In the System Separation rule, § 25.1707, separation distances or a barrier must be used to ensure that none of the types of failures described in the rule will create a situation that would fit the definition of a hazardous condition. The operative term in this rule is that such failures will not create a hazardous condition. To show that a given failure, such as fuel leakage onto EWIS components, will not create a hazardous condition, the applicant may use a qualitative analysis, consisting of expert engineering judgment, manufacturing judgment, and an assessment of any relevant service history.
In the EWIS System Safety rule, § 25.1709, the applicant must show that each EWIS system is designed and installed so that each hazardous failure
condition is extremely remote. The definition of a hazardous failure condition remains the same. In this rule, however, a numerical probability is required to demonstrate that the possibility for such an occurrence is extremely remote.
Section § 25.1709 uses both the terms “hazardous” and “catastrophic” and says that the applicant must not only show that each hazardous failure condition is extremely remote, but that each catastrophic failure condition is extremely improbable and does not result from a single failure. This would normally require a combination of qualitative and quantitative analyses to demonstrate compliance.
The requirements of § 25.1707 do not preclude use of valid component failure rates if the applicant chooses to use a probability argument in addition to the design assessment to demonstrate compliance. It also does not preclude the FAA from requiring such an analysis if the applicant cannot adequately demonstrate that hazardous conditions will be prevented solely by using the qualitative design assessment. However, we did not include the words “unless shown to be extremely remote” in § 25.1707 because we did not want to imply that a numerical probability assessment was required to comply with this rule.
The engine nacelles and APU enclosures are designated as fire zones and this is taken into account in the design and installation of EWIS in those areas. But we do not agree with GE and Honeywell that a fire in the engine nacelle or APU enclosure could never create a hazardous condition. There is always the possibility that the fire could not be suppressed and could result in a safety hazard. We made no changes because of these comments.
The National Air Carrier Association (NACA) commented that the proposed EWIS system separation requirements in § 25.1709 (now § 25.1707) are necessary for new aircraft. However, it said that imposing these requirements and those of § 25.1711 on existing airplanes would be a significant economic burden.
The separation and identification requirements of §§ 25.1707 and 25.1711 are applicable to new designs and do not apply to previously certified products.
In a comment relating to proposed § 25.1709 (now § 25.1707), IASA requested that specific mention be made of wiring that is required to regularly flex in position (such as that in doors and hatches).
We agree that designers and installers should address the additional stresses placed on wires and cables that are required to regularly flex, such as those in doors and hatches. We have revised the advisory material for §§ 25.1703 and 25.1709 to reflect this. However we do not concur that a change to § 25.1707 is necessary. As stated, these requirements are performance based. Applicants would have to demonstrate that any wiring required to regularly flex in operation would be able to maintain its designed separation distance from other EWIS, components, or airplane structure as applicable.
Boeing and GE requested that we clarify § 25.1709(d) (now § 25.1707(d)). They asked whether an “independent airplane power source” is considered to be an airplane level power source as is related to an APU, battery, etc., or whether it is
any
power source that transmits power. If it is the latter, they recommended that there be some differentiation in the associated guidance material for the differences between ground blocks and ground studs, and for the differences between static grounds terminating at ground blocks and ground studs. The commenters did not consider ground blocks “a common terminating location” for non-redundant grounds.
As used in § 25.1707(d), “independent airplane power sources” means a general source of power for the whole of the airplane or for major subsystems (such as the permanent magnet generators that provide power for fly-by-wire systems ). Examples include engine-or APU-driven generators, batteries, and ram air turbines. We have revised the AC to reflect this.
GE requested that the word “physical” be deleted from the text of § 25.1709(d) (now § 25.1707(d)). It stated that adequate separation should be all that is required and that using physical separation is only one means of achieving this.
The FAA believes that the word “physical” is necessary, as recommended by ATSRAC, to ensure that necessary separation is not achieved solely by electrical isolation and use of control logic via hardware or software implementation. We made no changes due to this comment.
Airbus requested that the phrase “will not create a hazardous condition” be replaced by the phrase “will not create a hazard” in proposed § 25.1709 (e), (f), (g), (h), (i), and (j) (proposed § 25.1709 is now § 25.1707). Airbus commented that this would eliminate ambiguous interpretation from inappropriate use of what is a system safety classification term used in § 25.1309(b).
We believe the word “hazard” is ambiguous and could cause confusion in the context of the requirement. We believe that the preamble discussion in the NPRM (which refers to this rule as § 25.1709), the additional clarification given in this final rule, and the advisory material for final § 25.1707 clearly articulate what is meant by the term “hazardous condition.”
6. System Safety: EWIS (§ 25.1709)
This rule requires applicants to perform a system safety assessment of the EWIS on their airplane. The current regulation requiring system safety assessment for certification is § 25.1309. But current § 25.1309 only covers systems and equipment that are “required by this subchapter,” and wiring for non-required systems is sometimes ignored. The objective of new § 25.1709 is to apply the concepts of § 25.1309 to all wiring.
The safety assessment required by § 25.1709 must consider effects that both physical and functional failures of EWIS would have on the airplane's safety. Based on that safety assessment, the applicant must show that each EWIS failure considered to be hazardous is extremely remote. Each EWIS failure considered to be catastrophic must be shown to be extremely improbable and may not result from a single failure.
This rule was proposed as § 25.1705. That number has been changed to § 25.1709, to harmonize with foreign airworthiness authorities. With the exception of that number change, this rule remains unchanged from the form in which it was proposed.
Airbus suggested that use of the words “extremely remote” and “extremely improbable” should be avoided. It pointed out that the preamble discussion for § 25.1705 (now § 25.1709) is based on a qualitative approach and this was the basis of ATSRAC's recommendation. Airbus said that no calculated number should be necessary for compliance with this rule. It also said, with reference to the NPRM preamble discussion, that “jamming” cannot be a justification for creating § 25.1705 because an EWIS cannot cause flight control surface or pilot controls jamming.
The analysis required by § 25.1709 is not purely a qualitative assessment of the effects of EWIS failures. Nor was this the basis of the ATSRAC recommendation. The analysis required by § 25.1709 is based on a qualitative and quantitative approach to assessing EWIS safety, as opposed to a purely numerical, probability-based quantitative analysis. This is consistent with existing § 25.1309 assessments, where a qualitative analysis is always necessary, and the quantitative
probability analysis is a means of compliance for the hazardous and catastrophic failure conditions.
Section 25.1709 is based on the recommendation from ATSRAC. The § 25.1709 safety assessment must consider effects that both physical and functional failures of EWIS would have on airplane safety. The physical analysis is meant to be a qualitative assessment and its results are to be integrated into the analysis required by § 25.1309 (or other required assessments such as § 25.671 as applicable), which is both a qualitative and quantitative assessment.
In response to Airbus's comment that creation of EWIS requirements should not be predicated on flight control surface or pilot controls jamming, the NPRM preamble reference is in the context of explaining that certain airplane systems are exempt from § 25.1309. EWIS associated with those exempt systems are thus also excluded, even though those EWIS could create hazardous conditions in the same way as any other EWIS. As a result, there is a need for a requirement to address all the EWIS on an airplane. We made no changes based on these comments.
While acknowledging that the aim of proposed § 25.1705 (now § 25.1709) is to make the requirements of § 25.1309 more explicitly applicable to EWIS, Airbus requested that the text of this rule be revised to read as follows:
Each EWIS must be designed and installed so it does not lead to a catastrophic failure condition as a consequence of a single EWIS failure. EWIS failure should be understood as failure affecting from one to all EWIS components within a single bundle.
Airbus's rationale for this change is based on the originally estimated 32.8 accidents that adoption of the proposed rules will prevent over the next 25 years. When combined with the number of airplanes projected to be in service and their combined operating hours, the probability of an EWIS causing a hazardous or catastrophic failure condition will be less than is required to demonstrate compliance with § 25.1709. The commenter contended that if this rationale is accepted by the FAA, then all an applicant should have to do is show in a qualitative manner that an airplane's EWIS will not be the cause of a catastrophic event.
The purpose of § 25.1709 is to ensure that the same analytical rigor applied to other systems for compliance with § 25.1309 is applied to EWIS. That is why the proposal specified the same criteria as § 25.1309(b). Airbus's request would impose lesser criteria for analysis of EWIS, even though the consequences of EWIS failures may be just as severe as any other system failures. Airbus's justification for its request relies on the estimated numbers of incidents in the initial regulatory evaluation and an apparent assumption that this number would meet the computed risk threshold required by § 25.1309. This is not the case. The analytical methods used for an economic evaluation are very different from methods required for risk assessment by § 25.1309 (or § 25.1709). The regulatory evaluation is a projected incident rate based on historical data. Estimating possible failures for compliance requires a detailed evaluation of the modes and effects of potential failures in a specific system design. We made no change because of this comment.
Boeing requested that proposed § 25.1705 (now § 25.1709) be included as a reference within § 25.1309(b) as previously proposed by industry. Boeing stated that duplicating the regulations leaves open the possibility of deviations in application. GE commented that proposed § 25.1705 is not acceptable. It said the discussion of this proposal, and the accompanying AC, contain several misstatements regarding current use and means of compliance with § 25.1309. According to GE, this misunderstanding of § 25.1309 has led to a perception by the FAA that a new rule is needed, when in fact, § 25.1309 already addresses the area of concern. The NPRM preamble states that § 25.1309 does not address single wire chafing or arcing as a cause of failure: “the physical portion has been neglected in past system safety analyses.” GE contended this is not true, because § 25.1309 safety assessments have addressed wiring failures as sources of fire. GE recommended that proposed § 25.1705 be removed. It suggested that the AC material for proposed § 25.1705 be provided to ARAC for incorporation into the § 25.1309 AC.
As stated in the preamble discussion of the NPRM, and in its related draft advisory material, the § 25.1709 analysis may be accomplished in conjunction with § 25.1309 assessments. Having a separate requirement for EWIS safety assessments will ensure that all airplane EWIS are assessed for potential impact on safe operation. This cannot be accomplished if § 25.1709 is simply included as a reference in § 25.1309. Nor can we delete § 25.1709 and incorporate its means of compliance into future versions of advisory material for § 25.1309, as GE suggests. As discussed in the NPRM, the requirements of § 25.1709 are necessary. Current safety analysis practice has been proven—by accidents and service history—to be insufficient with respect to safety assessments of wire designs and installations, including wire failures that can cause fires. The requirements of § 25.1709 are such that they complement those of § 25.1309 and address its shortcomings when it comes to safety assessments of EWIS. Section 25.1309 does not allow any single failure to result in catastrophic consequences, regardless of the failure probability. The requirements of § 25.1709 are consistent with those of § 25.1309. We made no changes due to these comments.
Federal Express referred to this statement in the preamble discussion of proposed § 25.1705 (now § 25.1709):
If this information [what systems and functions the other wires in the same and surrounding bundles support] is not available to the modifier, then the EWIS system must be designed to accommodate this lack of knowledge * * *.
FedEx said this would typically mean that wire being added for the modification would need to be routed separately from existing airplane wiring. It requested that, prior to adoption of this concept into any advisory material or design standard, detailed guidance on separation in confined areas such as equipment racks or breaker panels be developed.
We believe that the advisory material for post-TC modifications provides clear guidance for the case cited by Federal Express. When separation cannot be maintained because of physical constraints (in terminal strips and connectors, for instance), the applicant should conduct the appropriate analysis to show that no adverse failure conditions result from sharing the common device. This analysis requires knowledge of the systems or system functions sharing that device (again, the example would be terminal strips and connectors). If a modifier cannot identify the systems or system functions in the congested area, then the new EWIS would have to be routed through a different area if an acceptable alternative method of providing adequate separation is not provided. We made no changes to the final rule because of this comment. However, we have expanded the final advisory material for this requirement to provide clear guidance on the specific scenario contained in FedEx's comment.
Boeing commented on the part of the § 25.1705 (now § 25.1709) discussion in the NPRM that states that an in-flight entertainment (IFE) system installed on an airplane with subpart H as part of its type certification basis would be subjected to a more rigorous safety
assessment. Boeing noted its understanding that subpart H is applied to applicants for type certificates, amended type certificates, and supplemental type certificates. It asked whether it is correct that “an application for that or another IFE system to be installed on any airplane following the implementation of subpart H would be subjected to a more rigorous safety assessment.”
Boeing asked whether an existing STC applicable to an existing airplane model, applied to a new airplane of the same model but with subpart H as part of its certification basis, would be subjected to requirements of subpart H. It referred to the statement in the NPRM that post-type certificate modifications have repeatedly introduced wiring safety problems. Boeing asked for clarification of whether an existing amended or supplemental type certificate would be subjected to subpart H requirements prior to installation on an airplane with or without subpart H as its basis of certification.
In the case of a previously certified IFE system being considered for installation on an airplane model with subpart H in its certification basis, the answer is yes. The IFE system would have to be certified to the EWIS requirements of subpart H. To do otherwise could compromise the safety of the airplane by applying a lesser certification standard to the IFE system. After the effective date of the final rule, if a modification is proposed for an existing airplane model without subpart H in its certification basis, whether or not the modification will need to have subpart H in its certification basis will be decided on a case-by-case basis, and the requirements of § 21.101, Designation of applicable regulations, will apply.
7. Component Identification: EWIS (§ 25.1711)
This rule requires applicants to identify EWIS components using consistent methods that facilitate easy identification of the component, its function, and its design limitations. For EWIS associated with flight-essential functions, identification of the EWIS separation requirement is also required.
The number of this rule remains unchanged from its number as proposed. In response to comment, we have revised wording to clarify its intent, as discussed below.
Boeing requested that we clarify § 25.1711(a) by revising it as follows:
EWIS components must be labeled or otherwise identified using a consistent method that facilitates identification of the wire
EWIS component,
its function, and its design limitations, if any.
GE requested we revise the same paragraph to read as follows:
EWIS components must be labeled or otherwise identified using a consistent method that facilitates identification.
Boeing and GE also requested that we remove the requirement in § 25.1711(b) that, for systems requiring redundancy, components must be identified with component part number, function, and separation requirement for bundles. They stated that all wiring should be treated with the same level of care. The commenters contended that as the proposed requirement was written, the regulation was impractical to implement, since there are many redundancy separation categories in the aircraft. A given bundle might have different separation requirements from multiple other bundles, from hydraulic systems, and from air ducts, and the requirement could vary with axial distance along the fuselage. There would not be room to add all this data to the bundle label.
We have clarified § 25.1711(a) as requested by Boeing. It is the intent of this rule to require identification of all EWIS components and not just the wire (which is one component of an EWIS). We have revised that section by replacing the word “wire” with the phrase “EWIS component.”
We have decided against deleting the phrase “of the wire, its function, and its design limitations, if any” from § 25.1711(a). It is important that the EWIS component's function and design limitation information be easily and readily available to maintainers and future modifiers. Labeling components with this information will help ensure that the level of safety provided by the original design is not degraded. It will also prevent potential safety hazards from improper maintenance and from replacement of original parts with parts not designed or intended for that particular use.
We have also decided against deleting § 25.1711(b). We agree that all wiring must be treated with care. But we are especially concerned that wires and other EWIS components associated with flight-essential or flight-critical systems be easily identifiable by those designing and installing modifications, as well as by technicians performing maintenance or repair. If a wire bundle has different separation requirements as it is routed throughout the airplane, then those varying separation requirements must be identified on the bundle at the appropriate location where a particular separation requirement is applicable. It would not be necessary to have each label on the bundle contain all the differing separation requirements.
IASA suggested that using a color-coding approach to identifying critical systems would help post-TC modifiers easily identify critical airplane systems. We agree with the need to help ensure easy identification of these systems so that post-TC modifications and repairs do not inadvertently introduce unintended failure modes. However, the EWIS identification requirements of § 25.1711 do not prescribe the means by which EWIS is identified. It only requires that the identification scheme be consistent throughout the airplane and that modifications follow the same scheme. Color coding of EWIS may be an acceptable means to comply with the requirements. We made no changes because of this comment.
US Airways stated that mandating identification for all terminals, switches, connectors, or any component mounted in an area with limited space could cause tags or something similar to be used. These would in turn become contaminants.
We agree that some EWIS components may be so small that it would be impractical to label the component directly with textual data, and that excessive use of tags could become a source of future contamination. However, § 25.1711 states that other means of identification can be used if the component cannot be physically marked. For example, the manufacturer's consistent marking scheme may be such that a color code is used to mark these types of components. Applicants will have to collaborate with their FAA Aircraft Certification Office to work out the details. The method of identification is not mandated by the rule. It is left up to the applicant to propose a method of identification. We made no changes based on this comment.
8. Fire Protection: EWIS (§ 25.1713)
This rule requires that EWIS components meet the applicable fire and smoke protection requirements of § 25.831(c). It further requires that EWIS located in designated fire zones be fire resistant. Insulation on electrical wires and cables is required to be self-extinguishing when tested in accordance with the applicable portions of Appendix F, part 1, of part 25. Section 25.1713 is adopted as proposed, except that we removed the phrase “at least” that preceded “fire resistant.”
EASA and Airbus commented that § 25.1713(a) should also reference § 25.863. Airbus stated that this reference is common practice for fire
protection compliance demonstration for EWIS components. EASA stated that the equivalent EASA requirement, CS 25.1713, will reference CS 25.863.
Because § 25.1723 already requires EWIS components to meet requirements of § 25.863, it is not necessary to state the same requirement in § 25.1713.
Boeing commented that proposed § 25.1713(c) repeats and replaces § 25.869(a)(4), except with the change underlined below:
(c) Insulation on electrical wire and electrical cable,
and materials used to provide additional protection for the wire and cable,
installed in any area * * *
Boeing requested that we change § 25.1713(c) and/or Appendix F to Part 25 to clarify which test article configurations (test components individually or test components installed on the wire), and which flammability tests are required for “materials used to provide additional protection for the wire and cable.”
Boeing noted that Appendix F only refers to electrical conduit. It said the rule is clear on how electrical conduit and insulation on wire must be tested, but not on how to test the “materials used to provide additional protection for the wire and cable.”
Boeing said that the rules should make clear what testing is required for materials such as tight-fitting protective sleeve ( heat shrinkable material, for example), loose-fitting protective sleeve (such as spiral wrap or Varglas), or, for that matter, clamps, grommets installed in holes, or other devices used to protect wire and cable.
We have not revised § 25.1713(c) and/or Appendix F because we believe the requirements of § 25.1713(c) are clear and unambiguous. A material used to protect wire such as heat shrinkable material, or loose fitting protective sleeving such as spiral wrap or Varglas, must be tested in accordance with the requirements of part 25, Appendix F, part I, in the same manner as electrical wire is tested. As stated in Appendix F, Part 1(a)(v), it is not necessary to test small parts such as clamps and grommets because they would not contribute significantly to the propagation of a fire.
9. Electrical Bonding and Protection Against Static Electricity: EWIS (§ 25.1715)
Section 25.1715 requires that EWIS used for electrical bonding and protection against static electricity meet the requirements of § 25.899. It requires that EWIS components used for any electrical bonding purposes (not just those used for protection against static electricity) provide an adequate electrical return path under both normal and fault conditions.
Section 25.1715 was proposed as § 25.1717. Its number was changed to better harmonize with foreign airworthiness authorities. In response to comments, we have revised the wording of § 25.1715 and expanded it to clarify meaning, as discussed below.
Boeing stated that the term “adequate electrical return path” as used in § 25.1717 (now § 25.1715) is difficult to define, and should be replaced with performance criteria, such as the following:
On airplanes having grounded electrical systems, electrical bonding provided by EWIS components must provide an electrical return path capable of carrying both normal and fault currents without creating a shock hazard.
GE requested clarification of what constitutes a fault condition for compliance with proposed § 25.1717. It asked if a fault condition includes failure of the bonding path, such as physical breakage.
We have revised § 25.1715 as requested by Boeing but have added the phrase “or damage to the EWIS components, other airplane system components, or airplane structure.” to the end of the suggested revision.
In response to GE's comment, the intent of the requirement is to ensure that the current return paths are sized so they can accommodate fault currents due to component failure. One example would be shorted integrated drive generator power feeder cables where electrical bonding is used for the fault current path.
10. Accessibility Provisions: EWIS (§ 25.1719)
This rule requires access be provided to allow for inspection of EWIS and replacement of their components, as necessary for continued airworthiness.
Section 25.1719 was proposed as § 25.1725. Its number has been changed to facilitate harmonization. No other changes have been made.
EASA and Airbus commented that the wording of proposed § 25.1725 (now § 25.1719) is slightly different from that recommended by ATSRAC. ATSRAC recommended that it state:
Means
must be provided to allow for inspection of EWIS and the replacement of its components as necessary for continued airworthiness.
The NPRM proposed § 25.1725 to read as:
Access
must be provided to allow inspection and replacement of any EWIS component as necessary for continued airworthiness.
Airbus said that the word “access” is ambiguous. For example, it said, it is almost impossible to access the inside of a conduit. U.S. Airways noted that the rule needs to be revised because there are areas where access to cables and wire runs is not possible.
EASA suggested we change the rule to ATSRAC's original wording and stated that it will use this wording in its equivalent requirement, CS 25.1719.
We have decided to retain the wording of this requirement as proposed. However, it should be noted that it is not the intent of the rule to require human physical access in all cases. If such access is not possible because of physical design, then other inspection techniques could be allowed, such as use of a remote optical device. However, in response to U.S. Airways' statement, § 25.1719 does require that access be provided to allow for inspection and replacement for any EWIS component if it is necessary for continued airworthiness. Therefore there will not be areas where EWIS components are inaccessible for airplanes with § 25.1719 in their type certification basis.
We have revised AC 25-1701-1 to reflect the fact that other types of inspection techniques could be approved when human physical access is not possible. Other types of emerging inspection techniques may not require physical access.
11. Protection of EWIS (§ 25.1721)
Section 25.1721 requires that cargo or baggage compartments not contain any EWIS whose failure would adversely affect safe operation. It also requires that all EWIS be protected from damage by movement of people and from damage from items carried on the airplane by passengers or cabin crew.
Section 25.1721 was proposed as § 25.1727. Its rule number was changed to harmonize with regulations of foreign airworthiness authorities. No other changes have been made.
Boeing suggested that this rule be revised to state that EWIS should be protected so it “* * * cannot be damaged by normal movement of cargo or baggage in the compartment.” It said this change will clarify requirements. Boeing, GE, and AIA/GAMA stated that maintenance personnel need to be trained in proper EWIS handling.
We have decided against revising § 25.1721 in the manner Boeing suggests. This requirement is not limited to “normal movement.” EWIS in cargo or baggage compartments must be designed and installed so it is protected in both normal and non-normal situations, such as when cargo
containers come loose and strike compartment walls during flight because of cargo system malfunctions.
We agree that training personnel in proper handling of EWIS is also necessary. Although we have not mandated this training, except for technicians and inspectors working directly with EWIS, we have outlined a training program for a wide variety of personnel who work on airplanes. This training program is outlined in Advisory Circular 120-YY, Aircraft Electrical Wiring Interconnection Systems Training Program. We made no changes due to these comments.
GE requested that the phrase “risk of damage” be deleted from proposed § 25.1727 (now § 25.1721). It stated that risk of damage implies control of the failure effect of damage that is assumed to occur, as in § 25.901(c). It said that because 14 CFR 25.1309 already adequately controls the relationship between probability of a failure condition and its effect, risk of damage should be deleted from proposed § 25.1727.
We believe it is necessary to address both damage and risk of damage. Design and installation must be such that they preclude damage to EWIS to the extent possible when all design and installation factors are considered. We recognize, however, that it is not always possible to prevent possible damage because of design or installation considerations. EWIS components should be robust enough to minimize the damage that could occur if they come into contact with cargo, baggage, or personnel. We made no changes due to this comment.
12. Flammable Fluid Shutoff Means: EWIS (§ 25.1727)
Section 25.1727 requires that EWIS associated with each flammable fluid shutoff means and control be “fireproof” (as defined in § 1.1) or located and protected so that any fire in a fire zone will not affect operation of the flammable fluid shutoff means, in accordance with § 25.1189.
Section 25.1727 was originally proposed as § 25.1733. We have changed its number to facilitate harmonization with foreign airworthiness authorities. No other changes have been made.
Boeing recommended that the word “fireproof” in § 25.1733 (now § 25.1727) be replaced with “fire resistant” to be consistent with terminology used in § 25.869(a) and proposed § 25.1735 (now § 25.1733). AIA/GAMA stated that fire resistant and fireproof are not synonymous.
AIA/GAMA is correct. “Fireproof” is a more stringent standard than “fire retardant.” The basis for proposed § 25.1727 is the requirement of § 25.1189(d) that “each flammable fluid shutoff means and control must be fireproof or must be located and protected so that any fire in a fire zone will not affect its operation.”
To ensure the effectiveness of flammable fluid shutoff means and controls, the requirement for EWIS associated with those systems must be as stringent as the requirement for other components of those systems.
13. Powerplant and APU Fire Detection System: EWIS (§ 25.1731)
This rule requires that EWIS that are part of a fire or overheat detector system located in a fire zone be fire resistant, as defined in § 1.1. It also requires that EWIS components of any fire or overheat detector system for any fire zone may not pass through another fire zone unless:
• They are protected against the possibility of false warning caused by fire in the zone through which they pass, or
• Each zone involved is simultaneously protected by the same detector or extinguishing system.
This rule also requires that EWIS that are part of a fire or overheat detector system in a fire zone meet requirements of § 25.1203. Section 25.1203 requires approved, quick acting, fire or overheat detectors in each designated fire zone, and in the combustion, turbine, and tailpipe sections of turbine engine installations, to provide prompt indication of fire in those zones.
Section 25.1731 was originally proposed as § 25.1737. Its number was changed for purposes of harmonization. No other changes have been made.
EASA requested that the reference to § 25.1203 be moved to § 25.1719 (now § 25.1705 Systems and Functions: EWIS).
The intent of § 25.1731 is to ensure that any EWIS components associated with powerplant and auxiliary power units' fire detector systems be as robust and fire resistant as the other components making up these systems. The requirements of § 25.1731 are based on those contained in § 25.1203. It could create confusion if the requirements in § 25.1731 were split between two separate subpart H regulations as requested by EASA. Therefore we have retained the originally proposed § 25.1731 in this final rule.
14. Fire Detector Systems, General: EWIS (§ 25.1733)
Section 25.1733 requires that EWIS associated with any installed fire protection system be considered in showing compliance with the applicable requirements for that particular system. This is a new requirement that has not previously existed in part 25. Current part 25 regulations contain fire detection system requirements for powerplants, lavatories, and cargo compartments. Each of these fire detection systems requires electrical wire, and failure of this wire could lead to inability of the detection system to function properly. This rule applies to all required fire protection systems with the exception of those for powerplants and APUs. Requirements for EWIS associated those systems are contained in § 25.1731.
Section 25.1733 was originally proposed as § 25.1735. Its number was changed to better harmonize with foreign airworthiness authorities. As stated previously in the discussion under the heading of Systems and Functions: EWIS (§ 25.1705), we have revised this rule to include references to §§ 25.854 and 25.858, in response to comments from EASA.
Boeing and GE requested that proposed § 25.1735 (now § 25.1733) be removed from subpart H, because it is not directly related to EWIS certification. The commenters noted that any system, not just fire detection systems, which uses wiring in its design will be required to meet requirements of subpart H.
We have decided to adopt this requirement as proposed. Fire detection systems need wire and other EWIS components to operate. Failure of an associated EWIS component could lead to inability of the detection system to function properly. Therefore EWIS components must be considered an integral part of the fire detection system and meet requirements of the applicable regulation.
15. Engine, Nacelle, and APU Wiring
GE, Honeywell, and AIA/GAMA commented that engine, nacelle, and APU wiring should be exempt from the proposed EWIS certification and maintenance requirements. They said wiring in these areas is extremely rugged, has excellent reliability in service, and is easily accessible for inspection. They further stated that it is physically impossible for a wiring failure or deterioration in the propulsion system to cause a hazardous or catastrophic effect. They expressed the view that existing regulations are
adequate, as demonstrated by service experience, and application of these rules to engine, nacelle and APU wiring confers no safety benefit and would result in significant cost to industry.
We agree that EWIS components installed on the engine are very robust. This is because the harsh environment in which they are installed and the critical function engines play in the safe operation of the airplane dictate such robust design and installation. However, we do not agree that it is impossible for an engine wiring failure to cause a hazardous or catastrophic condition. The following quote is from the “Lauda Air B767 Accident Report,” dated July 21, 1993, issued by the Aircraft Accident Investigation Committee Ministry of Transport and Communications, Thailand—
Investigation of the accident disclosed that certain “hot-short” conditions involving the electrical system occurring during an auto-restow command, could potentially cause the DCV to momentarily move to the deploy position.
This illustrates that, in the past, there have been designs where an engine wiring failure could cause a catastrophic accident. Application of these requirements to all wiring on part 25 airplanes will help ensure that in the future we will minimize EWIS designs and installations that could lead to serious safety issues. Our position is consistent with ATSRAC's recommendation that engine wires not be excluded from compliance with these new requirements. Additionally, our regulatory analysis indicates that these rules are cost effective. We made no rule change due to these comments.
16. Designated Fire Zones
General Electric (GE) commented that the entire rulemaking package was written from the perspective of wiring contained in the pressurized fuselage, and then extrapolated to other areas. It stated as an example the assumption made throughout the NPRM that an electrical fire is catastrophic. GE stated that this is not the case in a designated fire zone, because such zones contain specific design measures to safely detect, contain, and put out a fire. The commenter stated that unpressurized portions of the airplane spend much of the flight at ambient pressures which will not easily support combustion. GE suggested that itemizing fuel sources that are isolated from the pressurized portion of the airplane—engine oil, engine fuel—as if they coexisted with the heated and air-conditioned section of the aircraft is very misleading.
We believe that a fire in a fire zone is a safety issue. Fire zones are designated as such because they are areas that have a higher potential for a fire to occur. These zones do have fire detection and suppression systems or other design features to mitigate effects of fire. But these features are designed to meet a limited set of test conditions for a limited duration of time and are not designed to meet all anticipated sets of conditions that may exist in a fire zone. Any fire on board an airplane, no matter where it occurs, has the potential for serious safety consequences.
The rule package was written with the objective of ensuring the safety of wiring in the entire airplane, consistent with the intent of ATSRAC.
17. Goal of the New Wiring Subpart
GE and AIA/GAMA commented that many of the proposed subpart H EWIS certification requirements are duplicative of existing part 25 rules. They asserted that repeating a requirement in multiple locations promotes differences in interpretation and confusion over acceptable means of compliance. They recommended that the proposed subpart contain new applicable requirements and act as a collector with references or points to the existing applicable rules. They said this packaging technique would provide the benefit of the common location sought by the FAA to bring focus to the importance of EWIS design and certification while minimizing the confusion, interpretation, and divergence that challenges use of duplicate rule sets.
We do not agree with the opinion that the proposed certification requirements of subpart H are duplicates of existing part 25 requirements. To be a duplicate implies that the requirement exists in both the new subpart H and in other places within part 25. This is not the case. As described in the proposal's preamble, some of the subpart H requirements previously resided in other part 25 subparts. But they have been relocated to the new subpart H, and in some cases enhanced, and no longer exist elsewhere in part 25. Also, many requirements of subpart H are new requirements. In some cases (for instance in § 25.1705 in this final rule), we reference existing part 25 requirements that are applicable to EWIS but have not been moved into subpart H because they do not lend themselves to division into wire and non-wire portions. The goal of collecting existing part 25 wire-related requirements and developing new requirements is to make them easy to locate, ensure their application to EWIS, and highlight the importance of considering wiring and its associated components as an airplane system. Eliminating the majority of the proposed subpart H requirements and simply referencing other wire-related requirements in a new § 25.1700 series paragraph would not support this goal.
18. Harmonization
British Airways, Royal Dutch Airlines (KLM), Airbus, and the Association of Asia Pacific Airlines requested that the proposed FAA and European Aviation Safety Agency's (EASA) EWIS requirements and advisory material be fully harmonized and made identical where possible.
Harmonization of these requirements with EASA has been our goal from the beginning. We have coordinated extensively with EASA and other national civil aviation authorities to achieve this common objective. While there may be some differences in wording because of our differing regulatory procedures, our intent is to harmonize the substantive requirements to the extent possible.
D. Instructions for Continued Airworthiness: EWIS (§ 25.1729 and Appendix H)
1. Requirements for EWIS ICA
Section 25.1729 requires that applicants prepare EWIS ICA in accordance with requirements of Appendix H to part 25. Section 25.1729 was originally proposed as § 25.1739. Its number has been changed to facilitate harmonization with the regulations of foreign airworthiness authorities. Otherwise, this rule remains unchanged from the form in which it was proposed.
This final rule also revises paragraph H25.4 and adds a new paragraph H25.5 to Appendix H—Instructions for Continued Airworthiness. Section H25.5 is a new requirement. It requires TC applicants and applicants for design change to develop maintenance information for EWIS as part of the ICA that are required for design approval. The EWIS ICA must be developed through the use of an enhanced zonal analysis procedure (EZAP). The ICA must include tasks, and intervals for performing those tasks, to reduce the likelihood of ignition sources and accumulation of combustible material and tasks to clean the EWIS of combustible material if there is not an effective task to reduce the likelihood of its accumulation. The ICA must also include—
• Instructions for protections and cautions to prevent accidental damage or contamination to EWIS during maintenance, alteration, or repairs.
• Acceptable maintenance practices in a standard format.
• Wire separation requirements as determined under § 25.1707.
• Information explaining the EWIS identification method and requirements for identifying any changes to EWIS under § 25.1711.
• Electrical load data and instructions for updating that data.
The ICA developed through the use of an EZAP must be in the form of a document appropriate for the information to be provided, easily recognizable as EWIS ICA, and either contain required EWIS ICA or specifically reference other portions of the ICA that contain this information.
The amendment to section H25.4 requires that the Airworthiness Limitations section of the ICA include any mandatory replacement times for EWIS components.
The final wording for the requirement for ICA as a single document was revised from its proposed form, to clarify intent, as discussed below. No other changes have been made to these rules.
2. ICA as a Single Document
Boeing and AIA/GAMA requested we delete paragraph H25.5(b) of Appendix H. This paragraph requires that EWIS ICA be contained in a single document, easily recognizable as EWIS ICA. They said their current approach is to produce several documents, including the maintenance planning data document, airplane maintenance manual, and standard wiring practices manual, with appropriate cross-references. These documents may not be EWIS specific. Boeing and AIA/GAMA believe separating EZAP-generated maintenance activities from those required by Special Federal Aviation Regulation (SFAR) 88 defeats the intent of the rule and is impractical.
Additionally, Airbus, and GE suggested we revise H25.5(b) to say “the ICA must be provided in a manner acceptable to the Administrator, where instructions specific to EWIS are easily recognizable.” They believe there is no safety benefit in uniquely identifying ICA related to, but not specific to, EWIS. They also requested that proposed § 25.1739 (now § 25.1729) be revised with a reference back to § 25.1529 or deleted in its entirety. They stated that § 25.1529 already requires Instructions for Continued Airworthiness to be developed in accordance with Appendix H.
We do not agree that paragraph H25.5 (b) should be deleted or revised as requested. The requirements of paragraph (b) do not preclude incorporation by reference of detailed information. However, we expect the DAH to provide a document appropriate for the information provided, in other words, a single or source document that either includes the EZAP-generated EWIS ICA or specifies where those EWIS ICA can be located. This also means that, if incorporation by reference is the approach taken by the DAH, all referenced documents are available at the same time as the EWIS ICA source document. We have revised the text of final H25.5(b) to clarify that the requirement only applies to EWIS ICA developed in accordance with requirements of H25.5(a)(1) and that the “document must either contain the required EWIS ICA or specifically reference other portions of the ICA that contain this information.” This does not change the meaning of the requirement, but clarifies it.
We also do not agree with the request to delete or revise § 25.1729. Having a separate requirement for EWIS ICA located within subpart H is consistent with the purpose of creating the new subpart. The goal was to collect existing part 25 wire-related requirements and develop new requirements, make them easy to locate, ensure their application to EWIS, and highlight the importance of considering wiring and its associated component as an airplane system. We made no changes due to this comment.
3. Standard Wiring Practices Manuals
Airbus commented about the requirement to include acceptable maintenance practices in a standard format. Airbus made the point that electronic standard wiring practices manuals (SWPM), in which such maintenance practices can be found, are easily searchable. It requested that manufacturers who publish their SWPMs electronically be either exempt from the requirement for a standard format for SWPMs, and/or an interim master breakdown index (which was outlined in the AC as an approach to standardizing SWPM formats without rewriting them), or able to adopt a similar approach.
We are rejecting Airbus's request to exempt electronic versions of the SWPM from requirements of part 25, Appendix H, H25.5. The objective of this requirement is to ensure that maintenance personnel can readily access necessary information. They may work on many different models, so having a standard format will facilitate this. An applicant may propose an alternative “standard” format to that described in the AC, as long as it achieves the same objective (again, taking into account that maintenance personnel will be working on a range of models). The master breakdown index described in AC 25-26 was developed so that existing non-electronic SWPMs would not have to be reformatted. An electronic SWPM, by definition, can be easily indexed to align with the master breakdown index format as depicted in the AC. We made no changes due to this comment.
4. Mandatory Replacement Times
Airbus requested that the requirement in section H25.4 to include mandatory replacement times for EWIS in Airworthiness Limitations of ICA be deleted because it is not related to any requirements to define mandatory EWIS replacement times.
We are retaining H25.4. The intent of this requirement is not to mandate life limits for EWIS components, but to ensure that the designer consider whether EWIS life limitations are applicable to a particular design and identify those limits in the Airworthiness Limitations section of the ICA. Such limitations, if any, would be identified when demonstrating compliance with § 25.1703. That rule requires that EWIS be installed according to limitations specified for that EWIS component, and this might include life limits under certain circumstances. For example, a given EWIS component may be well suited for a particular environment, but because of technological limitations, the material it is made of may degrade over time when exposed to certain environmental stresses. The component manufacturer may recommend that certain tests be performed at given intervals to ensure that its material properties are still within its qualification limits, and if they are not, recommend that the component be replaced. Life limits might also be identified when demonstrating compliance with the EWIS safety assessment requirements of § 25.1705, as part of identifying acceptable mitigation strategies to prevent hazardous or catastrophic failures. We made no changes due to this comment.
5. Wire Identification Method Information
Airbus, AIA/GAMA, and GE suggested we delete the requirement in proposed H25.5 for information explaining wire identification methods and requirements for identifying changes to EWIS. They stated that changes to EWIS, including future identification, are the modifier's responsibility, and a DAH cannot anticipate all possible future changes and give instructions for identification methods for changed components.
This requirement is intended to ensure that EWIS components added or changed due to post-TC modifications retain the same identification scheme used by the design approval holder. It is not necessary for the original DAH to anticipate future changes to EWIS. The original DAH is only required to describe the original identification scheme used. An example could be a particular color used to identify EWIS components associated with a fly-by-wire system. It is the responsibility of the future modifier to follow that EWIS identification scheme as required by § 25.1711.
6. Electrical Load Data
GE requested confirmation that H25.5(a)(2), (3), (4), and (5) do not apply to the existing fleet. Also, AIA/GAMA and GE contended that electrical load data is a certification issue, not a continued airworthiness issue, and future changes or updates to that information is the modifier's responsibility. They requested that paragraph H25.5(a)(5) be deleted.
The requirements of H25.5(a)(2), (3), (4), and (5) do not apply to the existing fleet unless a modification is introduced that would require that these requirements be part of the type certification basis of the modification, in accordance with 14 CFR 21.101.
We agree that it is the responsibility of modifiers (e.g., STC applicants) to ensure that they update the actual load data of the airplane they are modifying and document the electrical load data as required by H25.5(a)(5). However, we have decided against deleting paragraph H25.5(a)(5). We are using this requirement as a means to ensure that accurate electrical load data is available to those who need it. Accurate electrical load data is necessary to help ensure continued airworthiness. It is important that the load demand of an airplane's systems not exceed the generation and distribution capacity of its electrical power system. By ensuring this, the necessary levels of electrical power will always be available for those airplane systems needed for safe operation. We made no changes due to this comment.
E. Continued Airworthiness and Safety Improvements Subparts for Operating Rules (Parts 91, 121, 125, 129)
1. Establishment of New Subparts
This rule establishes new subparts in parts 91, 121, 125, and 129. These new subparts will contain operator requirements for continued airworthiness and safety improvements, just as the new part 26 will contain requirements for continued airworthiness and safety improvements applicable to DAHs. As we stated in the NPRM:
The FAA believes that inclusion of certain rules under th
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