Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety (EAPAS/FTS), 58508-58561 [05-19419]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 70, Number 193 (Thursday, October 6, 2005)]
[Proposed Rules]
[Pages 58508-58561]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-19419]



[[Page 58507]]

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Part II





Department of Transportation





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Federal Aviation Administration



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14 CFR Parts 1, 25, 91, etc.



Enhanced Airworthiness Program for Airplane Systems/Fuel Tank Safety 
(EAPAS/FTS); Proposed Advisory Circulars; Proposed Rule and Notices

Federal Register / Vol. 70, No. 193 / Thursday, October 6, 2005 / 
Proposed Rules

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 1, 25, 91, 121, 125, 129

[Docket No. FAA-2004-18379; Notice No. 05-08 ]
RIN 2120-AI31


Enhanced Airworthiness Program for Airplane Systems/Fuel Tank 
Safety (EAPAS/FTS)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The intent of this proposal is to help ensure the continued 
safety of commercial airplanes by improving the design, installation, 
and maintenance of their electrical wiring systems as well as by 
aligning those requirements as closely as possible with the 
requirements for fuel tank system safety. This proposed rulemaking 
consists of regulatory changes affecting wiring systems and fuel tank 
systems in transport category airplanes. First, it proposes to organize 
and clarify design requirements for wire systems by moving existing 
regulatory references to wiring into a single section of the 
regulations specifically for wiring and adding new certification rules. 
It also proposes to require 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 would require operators to incorporate those ICA for wiring into 
their maintenance or inspection programs. And finally, this proposed 
rulemaking would clarify requirements of certain existing rules for 
operators to incorporate ICA for fuel tank systems into their 
maintenance or inspection programs.

DATES: Send your comments on or before February 3, 2006.

ADDRESSES: You may send comments [identified by Docket Number FAA-2004-
18379] using any of the following methods:
     DOT Docket Web site: Go to https://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to https://
www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: Docket Management Facility; U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, 
Washington, DC 20590-001.
     Fax: 1-202-493-2251.
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    For more information on the rulemaking process, see the 
SUPPLEMENTARY INFORMATION section of this document.
    Privacy: We will post all comments we receive, without change, to 
https://dms.dot.gov, including any personal information you provide. For 
more information, see the Privacy Act discussion in the SUPPLEMENTARY 
INFORMATION section of this document.
    Docket: To read background documents or comments received, go to 
https://dms.dot.gov at any time or to Room PL-401 on the plaza level of 
the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Stephen Slotte, ANM-111, Airplane & 
Flight Crew Interface, Federal Aviation Administration, 1601 Lind 
Avenue SW., Renton, WA 98055-4056; telephone (425) 227-2315; facsimile 
(425) 227-1320, e-mail steve.slotte@faa.gov (certification rules) or 
Fred Sobeck, AFS-304, 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 (operating rules).

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites interested persons to participate in this 
rulemaking by submitting written comments, data, or views. We also 
invite comments relating to the economic, environmental, energy, or 
federalism impacts that might result from adopting the proposals in 
this document. The most helpful comments reference a specific portion 
of the proposal, explain the reason for any recommended change, and 
include supporting data. We ask that you send us two copies of written 
comments.
    We will file in the docket all comments we receive, as well as a 
report summarizing each substantive public contact with FAA personnel 
about this proposed rulemaking. The docket is available for public 
inspection before and after the comment closing date. If you wish to 
review the docket in person, go to the address in the ADDRESSES section 
of this preamble between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. You may also review the docket using the 
Internet at the Web address in the ADDRESSES section.
    Privacy Act: Using the search function of our docket Web site, 
anyone can find and read the comments received into any of our dockets, 
including the name of the individual sending the comment (or signing 
the comment on behalf of an association, business, labor union, etc.). 
You may review DOT's complete Privacy Act Statement in the Federal 
Register published on April 11, 2000 (65 FR 19477-78) or you may visit 
https://dms.dot.gov.
    Before acting on this proposal, we will consider all comments we 
receive on or before the closing date for comments. We will consider 
comments filed late if it is possible to do so without incurring 
expense or delay. We may change this proposal in light of the comments 
we receive.
    If you want the FAA to acknowledge receipt of your comments on this 
proposal, include with your comments a pre-addressed, stamped postcard 
on which the docket number appears. We will stamp the date on the 
postcard and mail it to you.

Availability of Rulemaking Documents

    You can get an electronic copy using the Internet by:
    (1) Searching the Department of Transportation's electronic Docket 
Management System (DMS) Web page (https://dms.dot.gov/search);
    (2) Visiting the FAA's Regulations and Policies Web page at https://
www.faa.gov/regulations_policies/; or
    (3) Accessing the Government Printing Office's Web page at https://
www.gpoaccess.gov/fr/.
    You can also get a copy by submitting a request to the Federal 
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence 
Avenue SW., Washington, DC 20591, or by calling (202) 267-9680. Make 
sure to identify the docket number, notice number, or amendment number 
of this rulemaking.

Organization of This NPRM

    Discussion of the proposal in this NPRM is organized under the 
following headings. Material supplementary to this discussion, but not 
included in it, appears in appendices at the end of the discussion, 
before ``List of Subjects.'' Whenever there is a reference to a 
document being included in the docket

[[Page 58509]]

for this NPRM, the docket referred to is Docket Number FAA-2004-18379. 
A list of acronyms used is included as Appendix A. Unless stated 
otherwise, rule sections referenced in this NPRM are part of Title 14 
of the Code of Federal Regulations.

Table of Contents

I. Executive Summary
II. Background
    A. Flight 800 Accident
    B. Flight 111 Accident
    C. FAA Aging Transport Nonstructural Systems Plan
    D. Fuel Tank Safety Rule
    E. Existing Wiring Certification Regulations
III. General Discussion of the Proposal
    A. Nature of the Problem
    B. Relationship of this Proposal to Other Aging Aircraft 
Initiatives
    C. Alternatives to Rulemaking
IV. Overview of Proposal
V. Section-by-Section Discussion of Proposed Rules
    A. Part 25 Subpart H-Electrical Wiring Interconnection Systems 
(EWIS)
    B. Part 25 Subpart I--Continued Airworthiness and Related Part 
25 Changes
    C. Other Proposed Changes to Part 25
    D. Part 25 Electrical System Harmonization Rules
    E. Proposed Changes to Part 91, 121, 125, and 129 Operating 
Rules for Fuel Tank Systems and EWIS and Other Existing Continued-
Airworthiness-Related Rules
    F. Proposed Changes to Parts 121 (Subpart Y) and 129 (Subpart 
B)-EWIS Maintenance Programs
    G. Proposed Changes to Parts 91 (Subpart L), 121 (Subpart Y), 
125 (Subpart M), and 129 (Subpart B) ( Fuel Tank Maintenance 
Programs
    H. Advisory Circulars
VI. Regulatory Analyses and Notices
Appendices
    Appendix A--List of Acronyms
    Appendix B--Correlation Between Proposed New Part 25 Regulations 
and Existing Regulations
    Appendix C--Correlation Between Existing Part 25 Regulations and 
Proposed New Regulations
    Appendix D--Existing Part 25 Requirements Requiring Revision to 
Support the New Proposed Regulations
    Appendix E--Flowchart 1: Pre- and Post-Type Certification Safety 
Analysis Concept--Flowchart 2: Post-TC Safety Analysis Concept

I. Executive Summary

    Safety concerns about wiring systems in airplanes were brought to 
the forefront of public and governmental attention by a mid-air 
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 determined to be a wiring failure 
causing a spark to enter the fuel tank. All 230 people aboard 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, a region of resolidified copper on 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 subsequent examinations of 
other airplanes showed that 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 concluded that current maintenance 
practices do not adequately address wiring components, wiring 
inspection criteria are too general, and unacceptable conditions, such 
as improper repairs and installations, are not described in enough 
detail in maintenance instructions. Wiring failures result in airplane 
delays, unscheduled landings, in-flight entertainment system problems, 
nonfatal accidents, and fatal accidents.
    Up until this time, airplane wiring has never been singled out for 
special attention during maintenance inspections. Although close 
attention is paid to safe design within systems, we had assumed that 
for the wiring providing power to those systems, standard industry 
practice was appropriate, and modifications have often been performed 
without scrutiny for the effect their wiring additions may have on 
other systems in the airplane. Damaged wire and insulation can cause 
electrical arcing, providing the spark that can cause fire. Dust, dirt, 
lint, contamination, and vapors provide fuel for fire. Recent rules 
have established requirements for wiring connected to fuel tank 
systems. This proposal goes further, to address all the wiring 
contained in an airplane as systems on their own and provide scrutiny 
to the conditions that affect their safe functioning. It aligns with 
the requirements for fuel tank wiring.
    We are proposing 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 proposing 
requirements for type certificate holders and applicants for type 
certificates and supplemental type certificates to analyze all the 
zones of their airplanes for the presence of wire and for the 
likelihood of contaminant materials. The proposal would also require 
them to develop maintenance and inspection tasks to identify, correct, 
and prevent wiring conditions that cause risk to continued safe flight. 
We are proposing 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. We are 
further proposing to amend Title 14 Code of Federal Regulations (CFR) 
parts 91, 121, 125 and 129 operating rules to require operators of 
transport airplanes to incorporate those tasks for wiring and fuel 
tanks into their regular maintenance programs. Finally, we are creating 
a new subpart of part 25 to contain all applicable certification 
requirements for airplane wiring, including new rules to improve safety 
in manufacture and modification.
    The total estimated benefits of the proposal are comprised of 
efficiency benefits and safety benefits. The efficiency benefits are 
$192.3 million ($78.3 million present value). The safety benefits are 
$563 million ($262.4 million present value). From 1995-2002, 397 wiring 
failures were reported. We used industry estimates to determine that 
68% of those failures would be detectable. The 7 most common--burned, 
loose, damaged, shorted, failed, chafed, and broken wires--account for 
84% of all wiring failures. Wiring failures cause 22.1 flight delays 
per year, with an average time of 3.5 hours and an estimated cost of 
approximately $35,639 each, and without this proposal, we believe that 
wiring delays will increase proportionately with the growth of the 
fleet. Wiring failures cause 27.5 unscheduled landings per year at an 
average cost of approximately $200,461 per unscheduled landing. We 
estimate that, based on expected fleet growth of 3.82% per year, there 
will be 1,118 unscheduled landings caused by wiring failures over a 25-
year period, of which approximately 760 would be prevented by this 
proposal, resulting in a total benefit of averting unscheduled landings 
of $152.4 million. Delays and unscheduled landings contain safety risks 
for passengers and crew and increase the likelihood of a more serious 
event. We estimate 32.8 wiring-related incidents or accidents could be 
prevented by this proposal in the next 25 years, for a total safety 
benefit of $563 million ($262.4 million present value). This includes 
1.2 fatal accidents that can be prevented.
    The estimated total cost of this NPRM is $474.4 million ($209.2 
million present value) over 25 years. The total estimated benefits are 
$755.3 million

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($340.7 million present value) over the same period. This proposal 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.

II. Background

A. Flight 800 Accident

    Safety concerns about wiring systems in airplanes were brought to 
the forefront of public and governmental attention by a 1996 accident 
over the Atlantic Ocean near East Moriches, New York, involving a 747-
131 airplane, operated as TWA Flight 800. That accident was 
investigated extensively by the National Transportation Safety Board 
(NTSB). It also prompted the FAA to investigate fuel tank wiring, and 
to focus on aging wiring in general. On May 7, 2001, the FAA published 
a final rule titled ``Transport Airplane Fuel Tank System Design 
Review, Flammability Reduction, and Maintenance and Inspection 
Requirements'' (66 FR 23086) to specifically address safety of the fuel 
tank, including wiring, which was determined to be the probable cause 
of the TWA Flight 800 accident. This NPRM addresses safety concerns 
related to aging wiring in general, and incorporates maintenance 
requirements specific to fuel tanks.
    The NTSB determined the probable cause of the TWA Flight 800 
accident, in which the airplane broke up in flight, was an explosion of 
the center wing fuel tank (CWT) resulting from ignition of the 
flammable fuel and air mixture in the tank. The source of ignition 
energy for the explosion could not be determined with certainty. 
However, of all the sources evaluated, the most likely was a wiring 
failure outside the CWT. This failure allowed excessive electrical 
energy to enter the CWT through electrical wiring associated with the 
fuel quantity indication system (FQIS).
    During its investigation, the NTSB found several potentially unsafe 
conditions in and near the electrical wiring of the accident airplane. 
The findings included cracked wire insulation, metal shavings adhered 
to a floor beam where FQIS wires would have been routed (consistent 
with maintenance records describing compressed air being used to blow 
metal shavings off avionics units), other debris, and sulfide deposits. 
In addition, it found evidence of several repairs that did not comply 
with the guidelines in Boeing's ``Standard Wiring Practices Manual'' 
(SWPM). Noncompliant repairs included:
     Use of an oversized strain relief clamp on the terminal 
block of the number 1 fuel tank compensator. The clamp did not 
adequately secure the wires.
     Many open-ended (rather than sealed) wire splices, which 
exposed conductors to possible water contamination.
     Several wire bundles containing many wire splices on 
adjacent wires at the same location.
     Excessive solder on the connector pins inside the fuel 
totalizer gauge. The solder had apparently caused inadvertent joining 
of connecting pins/wires from the right main fuel tank and CWT FQIS.
    Some of these conditions may suggest the need for improved 
maintenance. However, the NTSB found that deterioration, damage, and 
contamination of aircraft wiring and related components, such as those 
found on the accident airplane, were common in other transport category 
airplanes inspected as part of the accident investigation. This was 
especially true in older airplanes. The NTSB concluded that ``the 
condition of the wiring system in the accident airplane was not 
atypical for an airplane of its age and one that had been maintained in 
accordance with prevailing industry practices.''
    The NTSB expressed concern about the damage and contamination found 
on electrical wiring and components during their examinations of 
numerous transport category airplanes, including the accident airplane. 
The conditions found were especially disturbing because it was clear 
from those examinations that much aircraft wiring is difficult, if not 
impossible, to inspect and test because of its inaccessibility.
    The NTSB concluded that inadequate attention to the condition of 
aircraft electrical wiring had resulted in potential safety hazards. 
The conclusions from the accident investigation brought a heightened 
awareness to the FAA, other government agencies, and the general public 
of the importance of maintaining the integrity of aircraft wiring. A 
copy of the NTSB findings (NTSB Aircraft Accident Report Number AAR-00/
03) can be found on the NTSB Web site https://www.NTSB.gov, and is 
contained in the docket.

B. Flight 111 Accident

    Two years after the Flight 800 accident, in September 1998, an MD-
11 airplane, operated as Swissair Flight 111, crashed into the Atlantic 
Ocean off the coast of Nova Scotia, Canada. There were no survivors. 
Within approximately 53 minutes of the airplane's departure from New 
York to Geneva, Switzerland, the flightcrew smelled an abnormal odor in 
the cockpit. The cockpit voice recorder indicates that they thought the 
smell was coming from the air-conditioning system. A short time after 
the flightcrew noticed the smell, there was smoke in the cockpit, and 
they diverted the airplane to the Halifax airport.
    While preparing for landing, the flightcrew were unaware that fire 
was spreading above the ceiling in the front of the aircraft. They 
declared an emergency and signaled a need to land immediately. About 
one minute later, radio communications and secondary radar contact with 
the aircraft were lost, and the flight recorders stopped functioning. 
About five and one-half minutes later, the aircraft crashed into the 
ocean.
    In its final report, ``Aviation Investigation Report, In-Flight 
Fire Leading to Collision with Water,'' Report Number A98H0003, the 
Transportation Safety Board of Canada (TSB) (the Canadian governmental 
body charged with aircraft accident investigation) could not identify 
the exact cause of the fire. As part of its 11 findings of causes and 
contributing factors, however, the TSB stated that: ``A segment of in-
flight entertainment network power supply unit cable exhibited a region 
of resolidified copper on one wire that was caused by an arcing event. 
This resolidified copper was determined to be located in the area where 
the fire most likely originated. This arc was likely associated with 
fire initiation event; however, it could not be determined whether this 
arced wire was the lead event.'' That report can be found in the 
docket.
    In the section of the report entitled ``Findings as to Risk,'' the 
TSB cited 24 separate risks that had the potential to degrade aviation 
safety but could not be shown to have played a direct role in the 
event, or are unrelated to this event but were found during the 
investigation. Among those findings of risks are the following 
statements. (The numbers under which each finding appears in the TSB 
report are indicated.)
     ``Regulations do not require that aircraft be designed to 
allow for the immediate de-powering of all but the minimum essential 
electrical systems as part of an isolation process for the purpose of 
eliminating potential ignition sources.'' (3.2.3)
     ``Examination of several MD-11 aircraft revealed various 
wiring discrepancies that had the potential to result in wire arcing. 
Other agencies have found similar discrepancies in

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other aircraft types. Such discrepancies reflect a shortfall within the 
aviation industry in wire installation, maintenance, and inspection 
procedures.'' (3.2.7)
     ``The consequence of contamination of an aircraft on its 
continuing airworthiness is not fully understood by the aviation 
industry. Various types of contamination may damage wire insulation, 
alter the flammability properties of materials, or provide fuel to 
spread a fire. The aviation industry has yet to quantify the impact of 
contamination on the continuing airworthiness and safe operation of an 
aircraft.'' (3.2.8)
     ``There is no guidance material to identify how to comply 
with the requirements of Federal Aviation Regulation (FAR) 25.1353(b) 
[relating to cable routing] in situations where physical/spatial wire 
separation is not practicable or workable, such as in confined areas.'' 
(3.2.10)
     ``Inconsistencies with respect to CB (circuit breaker) 
reset practices have been recognized and addressed by major aircraft 
manufacturers and others in the aviation industry. Despite these 
initiatives, the regulatory environment, including regulations and 
advisory material, remains unchanged, creating the possibility that 
such ``best practices'' will erode or not be universally applied across 
the aviation industry.'' (3.2.12)
     ``FAR 25.1309 requires that a system safety analysis be 
accomplished on every system installed in an aircraft; however, the 
requirements of FAR 25.1309 are not sufficiently stringent to ensure 
that all systems, regardless of their intended use, are integrated into 
the aircraft in a manner compliant with the aircraft's type 
certificate.'' (3.2.21)
    In addition to the two accidents discussed above, multiple 
incidents and accidents that have occurred over the years illustrate 
the types of wire malfunctions that can affect flight safety. A 
discussion of some of those, titled ``EAPAS NPRM Supplemental Material, 
Other Incidents and Accidents Involving Electrical Wiring,'' is 
included in the docket for this NPRM.

C. FAA Aging Transport Nonstructural Systems Plan

    After the Flight 800 accident, at the recommendation of the White 
House Commission on Aviation Safety and Security (WHCSS), the FAA 
expanded its Aging Aircraft Program, which in the past had focused on 
structures, to cover nonstructural systems. We formed a team to study 
aging nonstructural systems and conduct detailed physical evaluations 
of aging airplanes. We reviewed the report from that study team, along 
with information from meetings with FAA principal inspectors and 
representatives of major airplane manufacturers, as well as an analysis 
of airplane service histories. From this combined information, we 
developed the Aging Transport Nonstructural Systems Plan (included in 
the docket for this NPRM). The plan's primary focus is on electrical 
wiring systems. There are other on-going research and development 
activities that address mechanical and avionics systems.
    The July 1998 Aging Transport Nonstructural Systems Plan includes 
results of the evaluation of five transport category airplanes 
considered representative of the ``aging fleet of transport 
airplanes.'' The FAA found conditions similar to those the NTSB found 
during its investigation of the TWA Flight 800 accident. Those 
conditions included:
     Deterioration of wiring and related components.
     Stiff and cracked wire.
     Contamination of wire bundles with metal shavings, dust, 
and fluids.
     Corrosion on connector pins.
     Improper wire installation and repairs.
    The FAA also found, as had NTSB investigators, that wires contained 
in wire bundles are difficult to inspect.
    The conclusions reached from this evaluation were that:
     Current maintenance practices do not adequately address 
wiring components.
     Wire inspection criteria are too general.
     Unacceptable conditions, such as improper repairs and 
installations, are not described in enough detail in maintenance 
instructions.
     Repair instructions and data are difficult to extract from 
SWPMs.
     The information that maintenance personnel are given for 
wire replacement may not be adequate.
     Current incident/maintenance reporting procedures do not 
allow for easy identification of failures.
    The NTSB agreed with these conclusions.
    The Aging Transport Nonstructural Systems Plan detailed several 
tasks and associated subtasks aimed at correcting these problems, 
including:
     Improving wiring inspection criteria and providing more 
detailed descriptions of undesirable conditions.
     Improving inspector training to ensure that it adequately 
addresses the recognition and repair of aging wiring components.
     Developing new methods for nondestructive testing of 
wiring.
    The NTSB responded to the issues defined in the Aging Transport 
Nonstructural Systems Plan. They concluded that they are important 
safety issues and must be fully addressed through rulemaking or other 
means. Specifically addressed by the NTSB (NTSB Recommendation No. A-
00-108, included in the docket) were the need for:
     Improved training of maintenance personnel to ensure 
adequate recognition and repair of potentially unsafe wiring 
conditions;
     Improved documentation and reporting of potentially unsafe 
electrical wiring conditions; \1\ and
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    \1\ Recommendations for improved documentation and reporting and 
for incorporation of new technology are not addressed by this 
proposed rule. They are, however, part of the FAA's Enhanced 
Airworthiness Program for Airplane Systems (EAPAS). The EAPAS 
report, dated October 15, 2002, can be found in the docket for this 
NPRM. For a discussion of training, see ``ATSRAC Recommendations for 
Rulemaking'' in the same docket.
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     Incorporation of the use of new technology, such as arc-
fault circuit breakers and automated wire test equipment.
    The NTSB also recommended (NTSB Recommendation A-00-106, included 
in the docket) that the FAA review the design specifications for 
aircraft wiring systems of all U.S.-certified aircraft and then:
     Identify which systems are critical to safety; and
     Require revisions, as necessary, to ensure that adequate 
separation is provided for the wiring related to those critical 
systems.
    Finally, the NTSB recommended that the FAA ensure that all part 25 
transport category airplanes, regardless of whether they are operated 
under parts 91, 121, 125, or 135, be included in the review of aging 
transport airplane systems and structures (NTSB Recommendation A-00-
119, contained in the docket).
    The FAA Administrator established a formal advisory committee (the 
Aging Transport Systems Rulemaking Advisory Committee, or ATSRAC) in 
1998. Its purpose was to facilitate actions recommended by the Aging 
Transport Nonstructural Systems Plan (FAA Order 11110.127, Aging 
Transport Systems Rulemaking Advisory Committee, dated Jan. 19, 1999, 
included in the docket). This committee is made up of representatives 
of aircraft manufacturers, transport airplane operators, aerospace and 
industry associations, and governmental agencies.
    In January 1998, the FAA assigned five tasks to ATSRAC. These 
included collecting data on aging wiring systems through airplane 
inspections, reviewing

[[Page 58512]]

airplane manufacturers' service information, reviewing operators' 
maintenance programs, and providing the FAA with recommendations to 
improve the safety of those systems. ATSRAC's work on those tasks 
focused on transport category airplanes.
    The ATSRAC review of data (The ``Aging Systems Task Force Aging 
Transport Systems Task 1 and Task 2 Final Report,'' included in the 
docket) yielded the following wiring-related findings:
     Nine B-727 airplanes inspected; 276 discrepancies found.
     Nine B-737 airplanes inspected; 399 discrepancies found.
     Seven B-747 airplanes inspected; 238 discrepancies found.
     Fourteen DC-8 airplanes inspected; 974 discrepancies 
found.
     Fifteen DC-9 airplanes inspected; 116 discrepancies found.
     Fourteen DC-10 airplanes inspected; 714 discrepancies 
found.
     Three L-1011 airplanes inspected; 247 discrepancies found.
     Ten A-300 airplanes inspected; 408 discrepancies found.
    The results from those five initial tasks showed that problems 
related to wiring systems on aging airplanes were not entirely related 
to degradation over time. Inadequate installation and maintenance 
practices were identified as factors that can lead to what is commonly 
referred to as an ``aging system'' problem. As a result, the scope of 
ATSRAC's work was expanded to include improving the continued 
airworthiness of airplane systems, particularly wiring systems.
    In May 2001, the FAA assigned four new tasks to the committee to 
carry out the ATSRAC recommendations on the first five tasks (66 FR 
29203). These next tasks were to accomplish the following:
     Address the need for new wire system certification 
requirements.
     Propose changes to the standard wiring practices manual.
     Develop a training program for wire systems.
     Develop maintenance criteria for wire systems.
    The results discussed earlier from ATSRAC's review of the eight 
models of large transport category airplanes had heightened concern 
about whether similar conditions existed in small transport category 
airplanes (airplanes with a 6- to 30-passenger seating capacity). As a 
result, in March 2002 (67 FR 9799), the FAA assigned another task to 
ATSRAC--to investigate and develop recommendations to improve the 
safety of electrical wiring systems in transport category airplanes 
certificated for fewer than 30 passengers. In response to this task, 
ATSRAC examined the applicability of their previous recommendations to 
this group of airplanes and identified issues unique to electrical 
wiring systems on small transport category airplanes. ATSRAC's work in 
this area is continuing.
    Another investigative group functioning within ATSRAC, whose wiring 
inspections extended to the laboratory, was the Intrusive Inspection 
Working Group (IIWG).\2\ The IIWG subjected selected wire installations 
on six decommissioned airplanes to an intensive, detailed visual 
inspection, followed by destructive testing and laboratory analysis (an 
intrusive inspection). They studied the results to assess the state of 
wire on aged airplanes as a function of wire type and service history. 
In addition, the results from the visual inspections were compared with 
the nondestructive testing and laboratory analysis to determine the 
efficacy of visual inspections for the detection of age-related 
deterioration.
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    \2\ The IIWG was a separate but parallel group within the Aging 
Systems Task Force (ASTF). The Air Transport Association (ATA) 
formed the ASTF in June 1998 to review the effectiveness of 
maintenance on electrical wiring systems and assess the condition of 
those systems on aircraft with type certificates (TC) older than 20 
years. When ATSRAC was formed in 1998, it continued the work started 
under the ASTF.
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    The findings from the IIWG were documented in the ``Transport 
Aircraft Intrusive Inspection Project (An Analysis of the Wire 
Installations of Six Decommissioned Aircraft) Final Report,'' issued on 
December 29, 2000 (from now on referred to as ``Intrusive Inspection 
Report''). A copy is included in the docket. The findings showed that 
wire-related failures have multiple causes. These include:
     Localized heat damage.
     Breaches in wire insulation.
     Wire embrittlement.
     Charred wire insulation.
     Missing insulation.
     Chafing.
     Arcing.
     Arc tracking.
     Reduced insulation resistance in certain wires.
     Defective and broken connectors.
     Damage to connector backshells.
    Both the nonintrusive, visual inspections on the airplane and the 
intrusive inspections found most wiring discrepancies were in areas of 
frequent maintenance activity. In addition, fluid contamination and 
dust and dirt accumulations were common in those areas.
    The Intrusive Inspection Report identified several areas that 
required special emphasis. Three areas--the cockpit, electrical power 
centers, and power feeder cables--were considered critical. This is 
because chafing on wiring in these areas, combined with flammable 
materials close by, can result in severe outcomes, such as wire-to-
structure or wire-to-wire shorting and arcing. Since a fire in these 
areas could present a high risk to continued safe flight and landing, 
the IIWG recommended more detailed inspections for those three areas. 
The intent was to ensure potential problems are identified and 
corrected. This effort led to the development of an enhanced zonal 
analysis procedure (EZAP) to assess risk for fire so that maintenance 
programs developed for wire systems in such critical areas would 
require more detailed inspections. An EZAP is a specific wire-focused 
version of the zonal analysis procedure widely used to analyze an 
airplane's physical areas or zones. It's used for developing 
maintenance tasks. One version of an EZAP is described in proposed AC 
120-XX, ``Program to Enhance Transport Category Airplane Electrical 
Wiring Interconnection System Maintenance.''
    ATSRAC made a number of recommendations to the FAA. Those 
recommendations and the FAA's responses to them are included in the 
docket in the document titled ``ATSRAC Recommendations for 
Rulemaking.'' ATSRAC working groups also produced four proposed 
advisory circulars (AC) as guidance for their recommended rulemaking. 
These proposed ACs are on the topics of wiring system maintenance, 
training, standard wiring practices manuals, and the proposed subpart 
H, and will be briefly discussed at the end of this preamble under the 
heading ``Advisory Circulars.''

D. Fuel Tank Safety Rule

    In addition to the activities described earlier, in response to the 
TWA 800 accident, the FAA has developed an extensive program to address 
safety problems associated specifically with fuel tanks. As mentioned 
previously, on May 7, 2001, the FAA issued a final rule entitled, 
``Transport Airplane Fuel Tank System Design Review, Flammability 
Reduction, and Maintenance and Inspection Requirements.'' This 
discussion refers to that final rule as the ``Fuel Tank Safety Rule.'' 
The Fuel Tank Safety Rule was issued to address unforeseen failure 
modes and the lack of specific maintenance procedures that could result 
in degrading the design safety features intended to preclude ignition 
of fuel tank vapors.
    One part of the Fuel Tank Safety Rule, Special Federal Aviation 
Regulation 88,

[[Page 58513]]

(SFAR 88) applies to design approval holders of certain turbine-powered 
transport category airplanes, and any person who modifies those 
airplanes later. SFAR 88 requires these regulated parties to perform 
safety assessments to confirm if the design of the fuel tank system 
precludes the existence of ignition sources in the fuel tank system. 
SFAR 88 also requires development of design changes and maintenance and 
inspection instructions to assure the safety of the fuel tank system.
    Other sections of the Fuel Tank Safety Rule (referred to as the 
``operational rules'') require that operators of those airplanes 
include fuel tank safety maintenance and inspection instructions in 
their existing maintenance or inspection programs. The requirements of 
those sections address two areas:
    (i) The fuel tank systems of the ``baseline'' airplane (as 
originally made by the TC holder); and
    (ii) The ``actual configuration'' of the fuel tank systems of each 
affected airplane (as modified or altered after original manufacture).
    As discussed later, one purpose of this rulemaking is to make sure 
that the implementation of this proposal for wiring is aligned with the 
implementation of the Fuel Tank Safety Rule.

E. Existing Wiring Certification Regulations

    Traditionally, wire has not been looked upon as having the same 
importance to safety as the rest of the systems for which it provides 
the electrical interconnection. Whereas a particular piece of 
electrical equipment may be the focus of intense scrutiny regarding its 
design, installation, and maintenance, the wires that provide the 
electrical interconnection to that equipment have not received the same 
amount of attention, except for the wiring on engines. Additionally, in 
the past, system safety assessments usually addressed only the effect 
of a wire failure on the system itself. The safety assessments have not 
usually identified the effect of wire failures on other systems or on 
the airplane.
    Existing regulations fall short of providing specific wiring-
related requirements that we now recognize should be included. For 
example, current rules do not adequately address requirements for wires 
in system separation, safety assessments, component selection, 
component identification, protection in cargo and baggage compartments, 
and accessibility for inspection, maintenance, and repair.
    This quote from FAA Wiring Policy ANM-01-04 supports the need for 
more specific wiring information: ``The FAA expects the applicant to 
provide engineering drawings instead of merely statements such as 
`install in accordance with industry standard practices,' or `install 
in accordance with AC 43.13 [``Acceptable Methods, Techniques, and 
Practices--Aircraft Inspection and Repair''].' The FAA considers such 
statements inadequate because the standard practices cannot define the 
location or routing of the wiring to the level needed to ensure that 
new/modified wiring does not invalidate previous certification findings 
for existing airplane systems.''

III. General Discussion of the Proposal

A. Nature of the Problem

    Electrical wiring systems perform roles essential to the safety of 
the entire airplane. They distribute power throughout the airplane, 
transmit signals for control, and send data. Over time, as more 
sophisticated computerized systems have been introduced into airplane 
controls, their electrical wires, cables, and associated components 
have become increasingly important to safe flight.
    Historically, manufacturers have been required to provide 
maintenance-related information for airplane systems. However, there 
has never been a requirement for maintenance information specifically 
addressing wiring systems. Since January 28, 1981, design approval 
holders have been required to provide ICA for the airplane. ICA must be 
prepared in accordance with Appendix H to part 25. In developing ICA, 
the applicant must include certain information. This includes a 
description of the airplane and its systems, servicing information, and 
maintenance instructions, including the frequency and extent of 
inspections necessary to provide for the continued airworthiness of the 
airplane. Currently, Sec.  25.1529 includes a requirement for an FAA-
approved Airworthiness Limitations section in the ICA. This section 
must list those mandatory inspections, inspection intervals, 
replacement times, and related procedures approved under Sec. Sec.  
25.571 and 25.981. There are no requirements for specific information 
related to wiring.
    Airplanes must be continually maintained and inspected, and the 
information contained in the ICA is used as a basis for developing a 
maintenance program. Yet the examinations of large transport airplanes 
discussed earlier revealed many anomalies in electrical wiring systems 
and their components, as well as contamination by dirt and debris.
    Section 43.13(b) requires anyone performing maintenance or 
alteration to do the work in such a manner and use materials of such a 
quality that the condition of the aircraft, airframe, aircraft engine, 
propeller, or appliance worked on will be at least equal to its 
original or properly altered condition (with regard to aerodynamic 
function, structural strength, resistance to vibration and 
deterioration, and other qualities affecting airworthiness). Anyone 
performing maintenance must use methods, techniques, and practices 
prescribed in the current manufacturer's maintenance manual or ICA 
prepared by the manufacturer, or methods, techniques, and practices 
referred to in Sec.  43.13(a) as acceptable to the Administrator. 
However, current practice has shown that, when wiring is inspected as 
part of the maintenance program or following alterations, it is not 
always cleaned appropriately for the inspection being performed. 
Generally, neither FAA inspectors nor airline maintenance workers have 
been fully aware of the vulnerable and critical condition of wire and 
fuel tank systems. Little focus has been placed on the importance of 
cleaning electrical wiring during maintenance or alteration. The result 
has been to hasten the aging of wiring.
    Extensive research by the FAA, in partnership with the aviation 
industry and other government agencies, has shown that electrical 
wiring on transport category airplanes is subject to a breakdown of 
physical and functional properties. This is not just a function of 
time, but also because of many stresses on the wiring. These stressors 
include chafing, vibration, contamination, and temperature variation, 
all of which can cause cumulative damage. Each airplane maintenance 
procedure or modification, whether performed on the wiring system 
itself or on surrounding components, introduces possibilities for 
unintentional damage, changes to the previously approved wire design, 
or contamination of the wiring systems by fluids, foreign objects, and 
debris. As the aviation industry matures, there are more older 
airplanes in service, and the wiring in those airplanes has had more 
years of exposure to all these factors. Electrical wiring system 
malfunctions resulting from inadequate design, alteration, maintenance, 
inspection, and repair practices can cause incidents and accidents 
involving smoke, fire, and/or loss of function.
    Wire contamination is a major concern, especially in older 
airplanes,

[[Page 58514]]

and it occurs in many ways. Dust, dirt, and lint from airplane carpets 
and seats, lavatory waste products, hydraulic fluid, engine oil, 
corrosion prevention compounds, and galley spills all collect over 
time. Liquids can corrode connectors and other wiring components and 
degrade wire insulation. In addition, electrical current flow in the 
wiring attracts dust, dirt, and lint, and they are deposited on the 
wiring system and surrounding airplane structure by cabin airflow. 
Leakage of fluid lines and spills make the wiring grimy, so more dust, 
dirt, and lint are attracted to them.
    To fully understand why wiring system contamination is a major 
problem and a potential fire hazard that could prevent the safe 
operation of an airplane, it is necessary to understand the ``fire 
triangle'' of combustion. The fire triangle symbolizes three elements--
oxygen, heat or ignition source, and fuel. All three are necessary for 
fire to occur.
    In an airplane, oxygen, the first element of the triangle, is 
always present, because the heating and air-conditioning system must 
provide a suitable environment for passengers. Wiring can act as an 
ignition source (second element), especially if damage, such as cracked 
insulation or chafing, causes a short to ground or to another 
conductor, or if it causes arcing. Fuel for fire (third element) can be 
present in the form of dust, dirt, lint, hydraulic fluid, engine oil, 
engine fuel, and corrosion prevention compound. Eliminating or 
mitigating any of these elements will help remove the fire threat.
    For obvious reasons, oxygen cannot be eliminated from an airplane. 
Wiring systems provide critical functions, so they cannot be eliminated 
either. But their ability to act as a fire ignition source can be 
mitigated by proper design, maintenance, and repair. The easiest 
element to alleviate is fuel for fire. The improved maintenance 
requirements in this proposal, as well as the more rigorous design 
standards, are intended to address the fuel and ignition elements of 
the fire triangle of combustion.
    This NPRM also addresses the requirement that certain operators 
incorporate ICA for their fuel tank systems into their maintenance or 
inspection programs, to ensure the continued safe operation of those 
design features that minimize the potential for an ignition source in 
the fuel tank system. Although there are existing regulations that 
require these ICA, the FAA believes, based on lessons learned from SFAR 
88 and industry comments, that the existing operational rules need to 
address several issues that have arisen since they were adopted. Also, 
because there are elements in the fuel tank system that include wiring, 
those ICA could conflict with the requirements for electrical systems 
in this proposal. Additionally, the FAA believes that the compliance 
times for the regulations for those two systems, wiring systems and 
fuel tank systems, should be aligned.

B. Relationship of This Proposal to Other Aging Aircraft Initiatives

    The FAA, as part of a broader review and realignment of its Aging 
Airplane Program, has determined that certain compliance dates in 
existing rules and pending proposals could be better aligned, so that 
operators can comply more efficiently with the requirements during 
scheduled maintenance. Compliance dates could also impact our ability 
to schedule oversight programs efficiently. In addition, based on our 
review, we have determined that certain substantive changes are needed 
to improve the cost-effectiveness of these rules and proposals. 
Therefore, we have decided to revise these requirements and proposals 
and align the compliance schedules as practically as possible. Notice 
of these changes and a description of our Aging Airplane Program review 
appeared in the Federal Register on July 30, 2004 (69 FR 45936). The 
actions affected by these revisions are this proposal and three others:
     Transport Airplane Fuel Tank System Design Review, 
Flammability Reduction, and Maintenance and Inspection Requirements 
Special Federal Aviation Regulation (Fuel Tank Safety Rule) (final 
rule).
     Aging Airplane Safety (interim final rule).
     Widespread Fatigue Damage (pending proposal).
    To prevent any conflicts within this proposal, which affects fuel 
tank wiring issues, changes to the operational requirements of the Fuel 
Tank Safety Rule requiring the incorporation of fuel tank system 
maintenance and inspection tasks are proposed as part of this 
rulemaking.

C. Alternatives to Rulemaking

    Before proposing new rulemaking, the FAA must consider alternative 
ways to solve the safety issues under consideration. Following is a 
brief discussion of two of the alternatives we considered during 
deliberations on this rulemaking proposal.
    No new regulatory action. The FAA believes that the result of no 
action would be continued incidents and accidents resulting from wiring 
system failures. We would continue to address these situations 
``reactively'' on a case-by-case basis (as they occur) by issuing 
airworthiness directives. This is unacceptable from a safety 
standpoint. Improved certification regulations, inspection and 
maintenance programs, and ICA for wiring systems are needed to address 
the potential for similar problems arising on existing and future 
designs, and to ensure their long-term safety.
    Rely on voluntary compliance with the intent of the rule by 
affected parties. Some in industry have suggested simply issuing ACs to 
give guidance on the changes that need to be made. Issuing ACs would 
depend on voluntary compliance, and would not be enforceable. While 
certain members of the industry would proceed with voluntary programs, 
others would not. The use of ACs alone would ensure neither consistent 
results nor the achievement of the safety objectives of this proposal 
for the current and future fleet. Previous voluntary safety 
assessments, such as those relating to the thrust reverser and cargo 
door reviews, have been difficult to complete in a timely manner 
because they lacked enforceability. The proposed rules provide an 
enforceable means to require timely completion of the actions 
identified as necessary to address aging electrical wiring systems.

IV. Overview of Proposal

    The FAA proposes several rule changes that collectively provide a 
more proactive management of wiring systems. These changes would 
require development and implementation of ICA for wiring systems and 
subsequent incorporation of those ICA into the operators' maintenance 
or inspection program. We are also proposing changes in the 
certification rules to require, during design and installation of 
airplane systems, more attention to conditions that could compromise 
wire safety and accessibility.
    The result of these changes to the maintenance and certification 
programs would be to remove, as far as possible, sources of ignition 
and fuel for fire from the wiring systems. In addition, a new part 25 
subpart dedicated to wiring systems would be created. The current part 
25 regulations for wire would be moved into this new subpart and 
combined with new regulations. An alignment of the compliance times for 
incorporation of the wire and fuel tank ICA would also occur to enable 
a more comprehensive treatment of those ICA and accomplishment of the 
maintenance instructions at time intervals consistent

[[Page 58515]]

with typical airplane maintenance checks.
    The FAA believes that traditional ways of addressing wiring are no 
longer enough. Because wire damage or degradation can be the result of 
successive and interactive factors introduced over time, the approach 
to ensuring wiring safety must be analytical, multilayered, and 
proactive, rather than reactive. An analytical approach means assessing 
logically the possibilities for fire occurring. A multilayered approach 
means addressing multiple layers of stressors, like chafing, vibration, 
temperature change, and modification that act on wiring in succession 
or concurrently and can cause cumulative damage to an electrical 
system. A proactive approach means addressing conditions affecting safe 
flight that we know can happen--before they happen. Causes of wire 
degradation must be addressed separately and collectively, and analyzed 
in relation to the entire airplane. Based on the findings and research 
described earlier in this document, the FAA has determined that air 
carriers, operators, TC holders, supplemental type certificate (STC) 
holders, repair stations, and certificated maintenance personnel need 
to place more emphasis on wiring and fuel tank systems when performing 
maintenance and alterations. Currently, other than the visual 
inspections required by maintenance or inspection programs, maintenance 
is not normally performed on these systems unless an obvious 
discrepancy is identified. This proposal is designed to heighten 
awareness of the criticality of wiring systems and to change the 
current approach to maintaining and modifying them. Maintenance 
personnel need to be aware that current industry practice for 
maintenance and inspection of these systems is inadequate and must be 
improved, as provided by this proposal.
    The changes proposed in this NPRM were derived from the 
maintenance, inspection, design, and alteration best practices 
developed through extensive research by ATSRAC and other groups, 
including the White House Commission on Aviation Safety and 
Security,\3\ the National Science and Technology Council Committee on 
Technology Wire System Safety Interagency Working Group,\4\ the IIWG, 
and safety reviews required in accordance with SFAR 88.
---------------------------------------------------------------------------

    \3\ ``Final Report to President Clinton, February 12, 1997,'' a 
copy of which is in the docket.
    \4\ ``Review of Federal Programs for Wire System Safety,'' 
November 2000, in the docket.
---------------------------------------------------------------------------

    The following table summarizes the proposed regulatory changes that 
are discussed in detail in this section.

               Summary of Proposed Rulemaking in This NPRM
------------------------------------------------------------------------
                                 Description of
   Affected part of 14 CFR          proposal             Applies to
------------------------------------------------------------------------
1...........................  Adds the
                               abbreviation
                               ``EWIS''.
25..........................  Harmonization rules.  Applicants for type,
                                                     amended, and
                                                     supplemental type
                                                     certificates
25..........................  New subpart H         Applicants for type,
                               containing: New and   amended, and
                               revised wire-         supplemental type
                               related               certificates
                               certification
                               requirements
                               including
                               requirements to
                               develop ICA for
                               electrical wiring
                               interconnection
                               systems.
25..........................  New subpart I         Type certificate
                               containing: New       holders for large
                               requirements to       transport category
                               develop ICA for       airplanes and
                               electrical wiring     certain applicants
                               interconnection       for type, amended
                               systems in            and supplemental
                               accordance with       type certificates
                               proposed Sec.
                               25.1539 and the
                               revised Appendix H
                               for the current
                               specified fleet.
Parts 121/129...............  Requirement to        U.S. certificate
                               incorporate new       holders and foreign
                               EWIS ICA into         persons operating
                               maintenance program   U.S. registered
                               (included in new      large transport
                               subparts for          category airplanes
                               Continued
                               Airworthiness).
Parts 91/121/125/129........  New subparts (L, Y,   U.S. certificate
                               M, and B              holders and foreign
                               respectively) for     persons operating
                               Continued             U.S. registered
                               Airworthiness         large transport
                               containing parts      category airplanes.
                               121/129 EWIS ICA
                               requirements
                               (above) and:
                               Requirement
                               to incorporate fuel
                               tank ICA into
                               maintenance program.
                              
                               Redesignation of
                               other existing
                               requirements into
                               these new subparts.
------------------------------------------------------------------------

    Currently, part 25 does not have a separate subpart governing 
wiring. Certification rules that apply to wiring appear throughout the 
regulations, under the headings ``Design and Construction,'' 
``Powerplant,'' and ``Equipment.'' In some of these rules, the term 
``wiring'' is not specifically used.
    The discussion of proposed changes to part 25 is broken into four 
parts:
     Part 25 Subpart H--Electrical Wiring Interconnection 
Systems (EWIS).
     Part 25 Subpart I--Continued Airworthiness.
     Other Proposed Changes to Part 25.
     Part 25 Electrical System Harmonization Rules.
    ATSRAC recommended placing part 25 wiring-related regulations into 
one section. This change would increase the visibility of these 
regulations and facilitate a comprehensive process for the design and 
certification of wire systems. ATSRAC reviewed the current part 25 to 
identify each regulation that related to wiring, either directly or 
indirectly. Each wire-related regulation was then reviewed to determine 
if it should be moved (in whole or in part) into the proposed new 
subpart. As a result of ATSRAC's recommendations, this NPRM would 
change some existing wire requirements, add new ones, and compile all 
of them into a new subpart: subpart H of part 25.
    No single regulation was moved in its entirety to the new subpart, 
but applicable portions of regulations were moved. Some regulations 
easily lent themselves to division into wire and non-wire portions, 
while others did not. In some cases it was difficult to remove the 
wire-related portion and maintain the continuity of the existing 
regulation. In those cases, the regulation was not moved to subpart H. 
Instead, the current regulation remained in place and a new subpart H 
regulation was created to state the importance of wiring systems to the 
safe design of the system that is the subject of the existing 
regulation. Portions of some current regulations that were moved to the 
new subpart were divided and distributed among

[[Page 58516]]

several new subpart H sections to follow the logical structure of the 
new subpart. Accordingly, there is not always a one-to-one 
correspondence between the existing regulations and the new subpart H 
regulations. A table showing the correlation between proposed new 
regulations and the existing regulations can be found in APPENDIX B. 
The table in APPENDIX C compares the existing regulations to the 
proposed new ones. The APPENDIX D table shows which of the current 
wire-related rules must be changed to accommodate the new subpart and 
which will remain the same.
    Adoption of the proposed new and revised requirements and advisory 
material would help prevent future occurrences of the types of 
incidents and accidents described in this NPRM. The creation of a new 
part 25 subpart for all existing, revised, and new wire system 
certification requirements would strengthen the role of properly 
designed, installed, and maintained wire systems in increasing the 
safety of flight. It would also provide the regulatory tools to help 
ensure this outcome and locate all applicable regulations in a single 
place that is easy to reference and use.
    Certain vintage airplanes type certificated before 1958, the 
beginning of the jet age, would be excluded from the requirements of 
this proposal. They are named in paragraph (f) of Sec.  25.1805 and in 
the final paragraph of each of the proposed fuel tank and EWIS 
operating rules. There are no known reciprocating-powered transport 
category airplanes currently in scheduled passenger service, and the 
few remaining in cargo service would be excluded. Compliance is not 
required for these specific older airplanes because their advanced age 
or small numbers would likely make compliance economically impractical.

V. Section-by-Section Discussion of Proposed Rules

    The FAA proposes to add the abbreviation for electrical wiring 
interconnection systems (EWIS) to 14 CFR part 1--Definitions and 
Abbreviations. The purpose of this addition is to ensure the use of a 
common term for EWIS throughout the regulations. More detailed analysis 
of the other proposed changes and additions is outlined below.

A. Part 25 Subpart H--Electrical Wiring Interconnection Systems (EWIS)

    The proposed subpart H consists of relocated, revised, and new 
regulations about EWIS. Unless we say otherwise, our purpose in moving 
requirements to subpart H is to ensure their application to EWIS. We do 
not intend to change their legal effect in any other way.
Section 25.1701 Definition
    Proposed Sec.  25.1701 would define what constitutes an EWIS for 
the purposes of complying with the proposed subpart H requirements and 
other EWIS-related requirements of parts 25, 121, and 129.
    Current regulations do not provide a definition of a wiring system. 
Without this definition, the proposed rules could be inconsistently 
applied to various wire-related components. To completely address the 
safety issues associated with wiring systems, requirements must address 
not only the wiring itself, but also components and devices that are 
required to adequately install and identify each wire. Various 
components and devices needed to route and identify wires are critical 
in ensuring that a proper electrical interconnection is made and 
maintained.
    For the purposes of this NPRM, the term ``wire'' means bare and/or 
insulated wire used