[Federal Register Volume 71, Number 77 (Friday, April 21, 2006)]
[Proposed Rules]
[Pages 20574-20593]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 06-3758]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
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 

  Federal Register / Vol. 71, No. 77 / Friday, April 21, 2006 / 
Proposed Rules  

[[Page 20574]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25, 121, 129

[Docket No. FAA-2005-21693; Notice No. 05-11]
RIN 2120-AI32


Damage Tolerance Data for Repairs and Alterations

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This action would require holders of design approvals to make 
available to operators damage tolerance data for repairs and 
alterations to fatigue critical airplane structure. This proposal is 
needed to support operator compliance with the requirement to include 
damage tolerance inspections and procedures in their maintenance 
programs, and to enable operators to take into account the possible 
adverse effects of repairs and alterations on fatigue critical 
structure. The intended effect of this proposal is to ensure the 
continued airworthiness of fatigue critical airplane structure by 
requiring design approval holders to support operator compliance with 
specified damage tolerance requirements.

DATES: Send your comments by July 20, 2006.

ADDRESSES: You may send comments [Identified by Docket Number FAA-2005-
21693] using any of the following methods:
     DOT Docket Web site: Go to http://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to http://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 20590-0003.
     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 
http://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 
http://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: Greg Schneider, ANM-115, Airframe and 
Cabin Safety, Federal Aviation Administration, 1601 Lind Avenue SW., 
Renton, Washington 98055-4056, telephone: (425-227-2116); facsimile 
(425-227-1232), e-mail [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites interested persons to participate in this 
rulemaking by sending written comments, data, or views. We also invite 
comments about 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 for 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 http://dms.dot.gov.
    Before acting on this proposal, we will consider all comments we 
receive by 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 because 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.

Proprietary or Confidential Business Information

    Do not file in the docket information that you consider to be 
proprietary or confidential business information. Send or deliver this 
information directly to the person identified in the FOR FURTHER 
INFORMATION CONTACT section of this document. You must mark the 
information that you consider proprietary or confidential. If you send 
the information on a disk or CD-ROM, mark the outside of the disk or 
CD-ROM and identify electronically within the disk or CD-ROM the 
specific information that is proprietary or confidential.
    Under 14 CFR 11.35(b), when we are aware of proprietary information 
filed with a comment, we do not place it in the docket. We hold it in a 
separate file to which the public does not have access, and place a 
note in the docket that we have received it. If we receive a request to 
examine or copy this information, we treat it as any other request 
under the Freedom of Information Act (5 U.S.C. 552). We process such a 
request under the DOT procedures found in 49 CFR part 7.

[[Page 20575]]

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 (http://dms.dot.gov/search);
    (2) Visiting the FAA's Regulations and Policies Web page at http://www.faa.gov/regulations_policies/; or
    (3) Accessing the Government Printing Office's Web page at http://www.gpoaccess.gov/fr/index.html.
    You can also get a copy by sending 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.

Authority for This Rulemaking

    The FAA's authority to issue rules about 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 
requires DAHs to support compliance with damage tolerance requirements 
that are necessary for continued airworthiness of transport category 
airplanes.

Table of Contents

I. Executive Summary
II. Background
III. Evolution of Damage Tolerance Requirements
IV. What Is Damage Tolerance?
V. Application of Damage Tolerance
VI. Damage Tolerance Requirements
    A. Requirements of Sec.  25.571 for Establishing Inspections or 
Other Procedures
    B. Damage Tolerance Applied to Pre-Amendment 25-45 Airplanes
    C. Damage Tolerance Applied to Amendment 25-45 (and later) 
Airplanes
    D. Damage Tolerance Applied to Repairs and Alterations
    E. Damage Tolerance Requirements of the Aging Airplane Safety 
Final Rule
VII. Statement of the Problem
VIII. Requirements for Design Approval Holders
    A. Ongoing Responsibility of Design Approval Holders for 
Continued Airworthiness
    B. Need for Design Approval Holder Requirements To Support 
Compliance With the Aging Airplane Safety Final Rule
    C. Alternatives to This Proposal
    D. ``Retroactivity'' of Design Approval Holder Requirements
IX. Proposed Regulatory Changes
    A. Applicability
    B. Lists of Fatigue Critical Structure for Baseline Structure 
and Alterations
    C. Damage Tolerance Evaluations and Damage Tolerance Inspections
    D. Repair Evaluation Guidelines
    E. Damage Tolerance Data Implementation Schedule
    F. Compliance Plan
X. New Subparts for Airworthiness Operational Rules
XI. FAA Advisory Committee Tasking: Guidance Material
XII. Paperwork Reduction Act
XIII. Regulatory Evaluation/Analysis
XIV. The Amendments

I. Executive Summary

    Fatigue cracking has been a major aviation safety concern for many 
years. Unless detected and repaired, fatigue cracks can grow to the 
point of catastrophic failure. Since 1978 the FAA has required new 
types of airplanes to meet damage tolerance \1\ (DT) requirements to 
ensure their continued airworthiness. Industry has also used this 
method successfully to develop inspection programs for older airplanes. 
Since the 1980s, the FAA has mandated that operators of most large 
transport airplanes carry out these programs.
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    \1\ Damage tolerance (DT) is a method used to evaluate the crack 
growth and residual strength characteristics of structure. Based on 
the results, inspections or other procedures are established as 
necessary to prevent catastrophic failures due to fatigue. Most 
commonly, the maintenance actions developed are directed inspections 
for fatigue cracking.
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    While these programs have been effective, industry has not carried 
out DT methods comprehensively. In particular, while these programs 
apply to the airplane ``baseline'' structure (the airplane structure as 
originally manufactured), they often do not apply to repairs and 
alterations. This is important because airplanes are subject to many 
repairs and alterations throughout their operational lives. If fatigue 
cracking occurs in a repaired or altered area, the results can be just 
as catastrophic as if it occurs in the baseline structure.
    The FAA adopted the Aging Airplane Safety final rule (AASFR) \2\ in 
early 2005, which, among other things, requires airline operators of 
certain large transport category airplanes \3\ to implement DT based 
inspection programs for airplane structure; that is, structure 
susceptible to fatigue cracking that could contribute to a catastrophic 
failure. In this proposal, we refer to this structure as ``fatigue 
critical structure.'' Most importantly for this rulemaking, the AASFR 
requires these inspection programs to ``take into account the adverse 
effects repairs, alterations, and modifications \4\ may have on fatigue 
cracking and the inspection of this airplane structure.''
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    \2\ 70 FR 5518, February 2, 2005.
    \3\ The rule applies to turbine powered airplane models with a 
maximum type certificated passenger seating capacity of 30 or more, 
or a maximum payload capacity of 7,500 pounds or more.
    \4\ Throughout this proposal, reference is made to 
``alterations.'' We consider this term to be synonymous with the 
term ``modification.'' An ``alteration'' is a design change that is 
made to an airplane; however, various segments of industry have also 
defined these changes as ``modifications.'' We use the term 
``alteration'' in the proposed rule to be all-inclusive of any 
design change.
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    With the AASFR, we now have in place the regulatory means to 
provide for comprehensive implementation of DT methods on all large 
transport airplanes used by air carriers. To carry out these 
requirements fully, however, we find it necessary to place 
corresponding requirements on the holders of FAA design approvals for 
these airplanes. Otherwise, the operators may not be able to obtain the 
data and documents they need to comply with the AASFR. As the owners of 
the data for these airplanes, the design approval holders \5\ (DAHs) 
are in the best position to identify the fatigue critical structure and 
the methods and frequency of inspections that may be needed. Therefore, 
the FAA proposes to require DAHs to develop and make available to 
operators the data and documents they need to support compliance with 
the DT requirements of the AASFR.
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    \5\ For purposes of this proposal, design approval holders 
(DAHs) are holders of type certificates (TCs) or supplemental type 
certificates (STCs) issued under 14 CFR part 21.
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    Specifically, today's proposal would require DAHs to develop and 
make available the following four types of documents to operators, 
which we describe in more detail in the discussion section of this 
proposal:
    (1) Lists of fatigue critical structure (to aid operators in 
identifying repairs and

[[Page 20576]]

alterations that need to be addressed for DT).
    (2) Damage tolerance inspections to provide operators with the 
necessary inspection times and methods for the following--
     Repair data published by type certificate (TC) holders; 
\6\
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    \6\ Published repair data are generally applicable instructions 
for accomplishing repairs, such as those contained in structural 
repair manuals (SRMs) and service bulletins. These data are approved 
for general application to a particular airplane model or airplane 
configuration.
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     TC holder's future repair data not published for general 
use; \7\
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    \7\ This may include repairs that are developed for individual 
airplanes at the request of an operator. These repairs are often 
complex or unique to a particular airplane or group of airplanes 
experiencing similar damage conditions.
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     Repair data developed by supplemental type certificate 
(STC) holders; and
     Alteration data developed by TC and STC holders.
    (3) Damage tolerance evaluation guidelines for all other repairs 
(to enable operators to develop the necessary damage tolerance 
inspections).
    (4) Implementation schedules (to define the necessary timing for 
performing damage tolerance evaluations and developing damage tolerance 
inspections, and for incorporating the DT data into their maintenance 
programs).
    This proposed rule transfers the responsibility of developing DT 
based data from operators to DAHs and, therefore, has minimal to no 
costs. The aviation industry as a whole would also benefit because DAHs 
could amortize their development costs for DT data over a larger fleet.

II. Background

    Structural fatigue cracking of aging airplanes has been a major 
aviation safety concern for many years. If not detected and repaired, 
fatigue cracking can eventually lead to catastrophic structural failure 
and loss of the airplane. Since the late 1970s, the FAA has issued 
numerous airworthiness directives \8\ (ADs) and other regulations to 
reduce the likelihood of fatigue cracking and to ensure its timely 
detection and correction. Most recently, on February 2, 2005, the FAA 
published the Aging Airplane Safety final rule (AASFR, 70 FR 5518). 
This rule addresses airworthiness safety concerns associated with 
structural fatigue cracking on turbine powered transport category 
airplanes having a passenger seating capacity of 30 or more or a 
maximum payload of 7,500 pounds or more.
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    \8\ The FAA issues airworthiness directives (ADs) to address 
unsafe conditions that may exist or develop on particular types of 
aircraft. See 14 CFR part 39.
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    The airplanes affected by this rulemaking are normally operated by 
air carriers (airlines). Domestic air carriers operate these airplanes 
under the regulations contained in 14 CFR part 121. Foreign airlines 
operating United States registered airplanes operate under 14 CFR part 
129.\9\ The AASFR includes a requirement for these air carriers to 
incorporate supplemental inspections of fatigue critical structure, 
referred to as damage tolerance inspections, into their maintenance 
programs by December 20, 2010. The damage tolerance inspections are 
necessary to preclude catastrophic failure resulting from fatigue 
cracking. The damage tolerance inspections must take into account the 
adverse effects \10\ that repairs and alterations may have on the 
fatigue life \11\ or inspectability \12\ of fatigue critical structure.
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    \9\ Under international law, the FAA can regulate the 
airworthiness of an airplane operated by a foreign operator only if 
the airplane is U.S.-registered.
    \10\ The term ``take into account the adverse effects,'' means a 
DT evaluation is performed to address any degradation in the fatigue 
life or inspectability of fatigue critical structure that may result 
from a repair or alteration. Degradation in fatigue life (earlier 
occurrence of critical fatigue cracking) may result from an increase 
in loading, while degradation of inspectability may result from 
physical changes made to the structure. The DT evaluation would also 
address the fatigue life and inspectability of any fatigue critical 
structure that may be added to an airplane by a repair or 
alteration. The evaluation would be performed within a time frame 
that ensures the continued airworthiness of affected or added 
fatigue critical structure.
    \11\ The term ``fatigue life,'' means the life span, in terms of 
airplane flight cycles or hours, that structure is expected to 
achieve in service without the presence of critical fatigue 
cracking. Critical fatigue cracking refers to cracking that could 
contribute to a structural failure. Repairs and alterations may 
increase or change the load distribution acting on structure, 
resulting in the earlier onset of such cracking.
    \12\ The term ``inspectability'' means the ability to inspect 
fatigue critical structure. In certain cases, as a result of 
physical changes made to this structure by repairs or alterations, 
the DT inspections established for this structure may no longer be 
an effective means for detecting fatigue cracking.
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    Before publishing the final rule, we published an interim final 
rule \13\ and asked for public comments, which we responded to in the 
February 2005 AASFR. We received comments from airplane operators, 
stating they would have difficulty complying with the supplemental 
inspection requirements of the AASFR without support from the design 
approval holders (DAHs). As the owners of the design data for the 
affected airplanes, the DAHs are in the best position to identify the 
fatigue critical structure and the maintenance actions (e.g., 
inspections, modifications) necessary to avoid failures due to fatigue 
cracking. The commenters expressed concern that operators had to rely 
on voluntary efforts by DAHs to provide data operators needed to meet 
the compliance deadline in the AASFR. After reviewing these comments, 
we determined the proper course of action was to require DAHs to 
develop data necessary to support operator compliance.
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    \13\ 67 FR 72726, December 6, 2002.
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    We informed the public of our intent to propose DAH requirements in 
the July 30, 2004 publication of the ``Fuel Tank Safety Compliance 
Extension (Final rule) and Aging Airplane Program Update (Request for 
comments)'' \14\ (Aging Program Update). In the Aging Program Update, 
the FAA requested comments about requiring DAHs to support an 
operator's compliance with several safety rules. Generally, operators 
support this concept, while manufacturers oppose it.
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    \14\ 69 FR 45936, July 30, 2004.
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    On July 12, 2005, the FAA issued a Policy Statement \15\ that 
explains our criteria for adopting DAH requirements in any future 
rulemaking. At the same time we published a disposition of comments 
addressing the comments received on the Aging Program Update. As we 
explain more fully later in this preamble, we have concluded that DAH 
requirements may be necessary when the safety objective for continuing 
airworthiness of aging airplanes can only be fully achieved if the DAHs 
provide operators with certain necessary information in a timely 
manner. Today's proposal supports this determination.
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    \15\ 70 FR 40166, July 12, 2005.
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III. Evolution of Damage Tolerance Requirements

    Throughout the history of the transport airplane airworthiness 
standards, various technical approaches have been employed to address 
structural fatigue. The original Civil Aviation Regulations (CAR) used 
a ``fatigue strength'' approach, which was based on achieving a design 
where fatigue cracking was not likely to occur within the operational 
life of the airplane.
    One of the first significant changes in the standard for airplane 
structure occurred in March 1956 when the fatigue evaluation 
requirements contained in CAR 4b.270 were revised to add ``fail-safe 
strength'' as an option to the ``fatigue strength'' approach. This was 
largely motivated by the realization that precluding the occurrence of 
fatigue cracking might not always be possible and, therefore, as an 
option, the

[[Page 20577]]

structure may be designed to survive an obviously detectable structural 
failure caused by fatigue cracking.
    The fail-safe approach assumed that cracking could occur and was 
based on maintaining a specified minimum strength after a ``fatigue 
failure or obvious partial failure'' had occurred. The success of the 
fail-safe approach was dependent both on the structure retaining the 
specified minimum strength with the fatigue damage present and on the 
damage being found during normal maintenance. As applied, the fail-safe 
approach emphasized structural redundancy, as opposed to fatigue 
resistance, while detectability of damage through inspections was 
generally assumed and not evaluated. The fail-safe option was the 
predominant approach chosen for the majority of large transport 
category airplanes certified in the 1960s and 1970s.
    As these airplanes accumulated more and more usage, however, there 
was increasing concern about the ability of the airframe to meet long-
term fail-safe requirements. The FAA recognized that the capability of 
a redundant design to survive a ``fatigue failure or obvious partial 
failure'' of an element could decrease with time since all elements 
could be subject to fatigue and would eventually crack. Additionally, 
we realized in many cases failures that were assumed to be obvious 
during certification were not readily apparent in practice. These 
concerns, coupled with findings during service, resulted in the 
decision to remove the fail-safe approach for structures from the 
airworthiness standards and adopt damage tolerance as the preferred 
approach for addressing fatigue. This was accomplished in 1978 with 
Amendment 25-45 to 14 CFR 25.571.

IV. What Is Damage Tolerance?

    Damage tolerance (DT) as applied to civil aircraft is a method used 
to evaluate the crack growth and residual strength characteristics of a 
structure. Based on the results, inspections or other procedures are 
established, as necessary, to prevent catastrophic failures due to 
fatigue. Damage tolerance can and has been applied to existing designs 
as well as to new designs.

V. Application of Damage Tolerance

    The first step in applying DT methods is to identify fatigue 
critical structure. This generally includes all structure commonly 
referred to as ``primary structure'' such as the wing, empennage, 
control surfaces and their systems, the fuselage, engine mounting, 
landing gear and their related primary attachments. Once identified, 
this structure is subject to an evaluation \16\ that includes 
identification and quantification of--
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    \16\ The term ``damage tolerance evaluation (DTE)'' as used in 
this rule means a process that leads to a determination of 
maintenance actions necessary to detect and remove fatigue cracking 
that could contribute to a catastrophic failure if left undetected. 
As applied to repairs and alterations, a damage tolerance evaluation 
includes the evaluation of both the repair or alteration and of the 
fatigue critical structure affected by the repair or alteration. The 
evaluation may include analysis, tests, or specialized processes 
developed by a TC holder that operators could use to establish 
damage tolerance inspections for existing and future repairs (e.g., 
Repair Assessment Guidelines).
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     Site--the potential areas where fatigue cracks could 
start;
     Scenario--how the cracking will proceed;
     Detectable crack size--what can be found reliably 
(probability of detection) with the inspection method planned;
     Critical crack size--the crack size that reduces the 
strength of the structure down to the minimum level that we want to 
assure with the assumed crack(s) present; and
     Duration--the time it will take the crack(s) to grow from 
``detectable crack size'' to ``critical crack size.''
     Inspection threshold--the time in airplane hours/cycles 
when inspections are initiated to detect a crack.
    Once these elements are defined and quantified, decisions can be 
made about required maintenance actions. In many cases an in-service 
directed inspection for fatigue cracking may be reliable and practical. 
However, there may be cases where the results of the evaluation show 
that inspections are neither reliable nor practical. When this is the 
case, replacement or modification of the structure may be the best 
solution.\17\
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    \17\ For additional information on applying DT methods, see 
Advisory Circular (AC) 25.571-1C.
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VI. Damage Tolerance Requirements

A. Requirements of Sec.  25.571 for Establishing Inspections or Other 
Procedures

    Under 14 CFR 21.17, the version of the airworthiness standards that 
applies to a type certificate (TC) is the version in effect on the date 
of application for the TC. For any given TC, this is referred to as the 
``certification basis'' of the airplane. Since these standards have 
been revised several times, different types of airplanes may have 
complied with different versions of these standards.
    The current DT requirements of 14 CFR 25.571 include--
     Evaluation of the airplane structure to identify structure 
that is susceptible to fatigue cracking;
     Performance of a damage tolerance evaluation of the 
fatigue critical structure; and,
     Establishment of necessary inspections and procedures.

B. Damage Tolerance Applied to Pre-Amendment 25-45 Airplanes

    On May 6, 1981, we issued Advisory Circular (AC) 91-56 to provide 
guidance to TC holders on the development of Supplemental Inspection 
Documents (SIDs) for pre-Amendment 25-45 airplanes. Type certificate 
holders voluntarily performed damage tolerance evaluations of the 
baseline structure \18\ of their airplane designs.\19\ Based on these 
evaluations, DT data (e.g., inspections) were published in SIDs that 
were mandated by airworthiness directive (AD), starting in the early 
1980s.
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    \18\ Structure designed under the original TC or amended TC for 
that airplane model.
    \19\ The affected airplanes are the Airbus Model A300, British 
Aerospace Model BAC 1-11, Boeing Model 707, 720, 727, 737, 747, 
McDonnell Douglas Model DC-8, DC-9/MD-80, DC-10, Fokker Model F28, 
and Lockheed Model L-1011.
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    The SIDs did not provide a comprehensive means to ensure repairs 
and alterations were evaluated for DT. As a result, the FAA and 
industry recognized that coverage for these airplanes relative to 
potential fatigue of repairs and alterations was incomplete. In part to 
address this problem, the B-727 \20\ and 737-100/200 \21\ SID ADs were 
superseded to require damage tolerance evaluations of all repairs and 
alterations made to structures covered by the SID. However, repairs and 
alterations are not adequately addressed by SID ADs that have been 
issued for the other affected airplane models.
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    \20\ AD 98-11-03 R1 [64 FR 989 No. 4 01/07/99].
    \21\ AD 98-11-04 R1 [64 FR 987 No. 4 01/07/99].
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C. Damage Tolerance Applied to Amendment 25-45 (and Later) Airplanes

    Amendment 25-45 amended Sec.  25.571 to require DT and fatigue 
evaluation of structure for transport airplane type designs.\22\ The 
resulting inspections or other procedures had to be included in the 
maintenance manual as required by Sec.  25.1529.
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    \22\ ``Type design'' generally includes the engineering data 
necessary to define the configuration and design features of an 
aviation product (airplane, engine, or propeller) that is shown to 
comply with the applicable airworthiness standards. See 14 CFR 
21.31.
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    The fatigue strength approach was retained as a default option to 
be used only if the DT approach was shown to be impractical for certain 
areas of the airplane (e.g., landing gear). Airplanes certificated to 
the Amendment 25-45 requirements include--
     Bombardier model CL-600;
     SAAB 340; and

[[Page 20578]]

     Boeing models 757 and 767 airplanes.
    Amendment 25-54 revised Sec.  25.571 and Sec.  25.1529 to mandate 
that the damage tolerance inspections and procedures required by Sec.  
25.571 be included in the newly created Airworthiness Limitations 
section of the Instructions for Continued Airworthiness (ICA) required 
by Sec.  25.1529. Section 25.1529 requires the applicant for a TC to 
prepare ICA according to appendix H to part 25.
    Airplanes certificated to Amendment 25-54 or later requirements 
include--
     Airbus models A300-600, A310, A318, A319, A320, A321;
     Boeing models B717, B737-900, 777, MD-11, MD-90;
     Empresa Brasiliera de Aeronautica (Embraer) models EMB 
120, 135, 145, 170;
     Aerospatiale ATR 42/72;
     BAE (Operations) Limited AVRO/BAE 146;
     Construcciones Aeronautics, S.A. CN 235;
     Bombardier DHC 8;
     BAE (Operations) Limited JTSRM 4101;
     SAAB Aircraft, A.B. SAAB 340; and
     AvCraft Aerospace GMBH DO 328.
    In 1998, we again revised the DT requirements of Sec.  25.571 in 
Amendment 25-96 to prescribe how inspection thresholds should be 
established for certain types of structure.\23\ This change required, 
in part, that these inspection thresholds be established based on crack 
growth analyses and tests, assuming the structure contained an initial 
flaw of the maximum probable size that could exist because of 
manufacturing- or service-induced damage.
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    \23\ The inspection ``threshold'' is the time, usually measured 
in flight hours or flight cycles, when the first DT inspection must 
be performed.
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D. Damage Tolerance Applied to Repairs and Alterations

    On April 25, 2000, the FAA published a final rule entitled ``Repair 
Assessment for Pressurized Fuselages.'' \24\ This rule adopted four new 
operating rules \25\ applicable to the twelve large transport category 
airplane models that had been certified to the pre-amendment 25-45 
fail-safe standards. That final rule prohibits operation of these 
airplanes beyond a specified implementation time, unless FAA-approved 
DT based repair assessment guidelines (RAG), which only apply to 
fuselage skin, door skin, and bulkhead webs, are incorporated in the 
operator's operations specifications or approved inspection program. 
Generally, these guidelines, most of which were developed by the TC 
holders for the affected models,\26\ provide a streamlined approach for 
operators to assess the DT of repairs. Based on this assessment, 
operators determine whether their existing inspection programs are 
adequate, or whether additional inspections or replacement of the 
repair are necessary.\27\
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    \24\ 65 FR 24108, April 25, 2000.
    \25\ Sec.  91.410 (Amdt. 91-264); Sec.  121.370 (Amdt. 121-275); 
Sec.  125.248 (Amdt. 25-33); and Sec.  129.32 (Amdt. 129-28).
    \26\ Airbus Model A300, British Aerospace Model BAC 1-11, Boeing 
Model 707, 720, 727, 737, 747, McDonnell Douglas Model DC-8, DC-9/
MD-80, DC-10, Fokker Model F28, and Lockheed Model L-1011.
    \27\ For more information on methods of compliance with this 
rule, see AC 120-73, ``Damage Tolerance Assessment of Repairs to 
Pressurized Fuselages,'' dated December 14, 2000.
---------------------------------------------------------------------------

    In accordance with 14 CFR 21.101, certain amended TCs and 
supplemental type certificates (STCs), whose original type 
certification basis did not require DT, may require damage tolerance 
inspections (Amendment 25-45 or later) for new or significantly 
modified structure.\28\ However, structure that was not significantly 
altered on these airplanes would not have to comply with these 
requirements. In addition, for alterations that were not considered 
significant, in some cases SIDs were not developed for the altered 
structure, even though the DAH had developed a SID for the original 
airplane model. As a result, in many cases, alterations to these 
airplanes were not assessed for DT.
---------------------------------------------------------------------------

    \28\ See AC 21.101-1, ``Establishing the Certification Basis of 
Changed Aeronautical Products. A copy can be downloaded from http://www.airweb.faa.gov/rgl.
---------------------------------------------------------------------------

    For airplanes certified to comply with Amendment 25-45 or later 
amendments, the DT requirement applies to fatigue critical structure, 
which may include certain baseline structure, repairs, and alterations. 
Nevertheless, for repairs and alterations to this structure TC holders 
and others have not always complied with the requirement to develop DT 
data. Some of the circumstances that resulted in a shortfall of DT data 
for repairs and alterations are summarized below.
    In some cases, TC holders' damage tolerance evaluations of baseline 
structure were not completed at the time of type certification. This 
was permitted because we recognized that the fatigue problems that 
inspections are intended to detect would not occur until the airplanes 
had operated for many years. However, because operators needed 
structural repair manuals \29\ (SRMs) when they first placed the 
airplanes into service, the TC holders provided SRMs for which damage 
tolerance evaluations also had not been performed. The FAA erroneously 
approved these SRMs for compliance to the damage tolerance requirements 
of Sec.  25.571.
---------------------------------------------------------------------------

    \29\ Various regulations, including 14 CFR 121.379(b), require 
that operators obtain FAA approval of ``major repairs'' before 
approving airplanes for return to service following such repairs. As 
a source of pre-approved repairs, the structural repair manual (SRM) 
provides the means for operators to make timely repairs to airplanes 
without risk of disruption of operations while awaiting the required 
approval. While the part 25 airworthiness standards do not require 
TC holders to develop SRMs, it has been a common practice for many 
years.
---------------------------------------------------------------------------

    In many cases there are similarities between structural elements of 
pre-Amendment 25-45 and Amendment 25-45 and later airplanes. If SRM 
repairs for a pre-Amendment 25-45 airplane were applicable to the new 
airplane structure, in some cases the FAA approved them without 
consideration of the requirement for DT. Under bilateral aviation 
safety agreements,\30\ other national aviation authorities granted 
similar approvals.
---------------------------------------------------------------------------

    \30\ Under these agreements, the ``importing state'' (the civil 
aviation authority with oversight of the airplane operator) agrees 
to accept the compliance findings of the exporting state (the civil 
aviation authority with oversight of the airplane manufacturer).
---------------------------------------------------------------------------

    Many airplanes that were certified to comply with the DT 
requirements of Amendment 25-45 or later contain repairs and 
alterations that have not been adequately evaluated for DT. Because 
some TC holders did not develop DT data for the baseline structure at 
the time of type certification (and in some cases for several years 
thereafter), in some cases repairs and alterations developed by them 
and published in service bulletins did not give adequate consideration 
to DT. For the same reason, STC applicants were unable to evaluate the 
effects of their alterations on the DT of the baseline structure. 
Designers of repairs had the same difficulty. In some cases, STC 
applicants and designers of alterations and repairs were unfamiliar 
with the requirements and methods for DT. Finally, in some cases, air 
carriers improperly classified repairs and alterations that affect 
fatigue critical structure as ``minor'' and damage tolerance 
evaluations were not conducted. This proposed rule would correct the 
shortfall of DT data as described in these three circumstances.
    Table 1 below provides a summary of the regulatory requirements for 
DT based inspections and procedures that were in place before the 
adoption of the AASFR. The table addresses airplanes that are subject 
to the AASFR. It shows areas of the affected airplanes that are

[[Page 20579]]

addressed by these requirements. The shaded areas in the table 
represent the structural areas for which, prior to Sec.  121.370a, 
there were no regulatory requirements to develop DT data and for which 
almost none are in existence. The DAHs would need to develop DT data to 
support operator compliance with the Sec.  121.370a of the AASFR.

                                                     Table 1
----------------------------------------------------------------------------------------------------------------
         Airplane models          Regulatory actions prior to Sec.   121.370a that require damage tolerance data
---------------------------------                                   development
                                 -------------------------------------------------------------------------------
                                                          Repairs to
  Sec.   25.571 Amendment level                         fuselage & door     Repairs to all       Alterations/
                                  Baseline structure    skin, bulkhead        other areas        modifications
                                                             webs
----------------------------------------------------------------------------------------------------------------
25-45 or later
  737-900, 757, 767, 777, MD11,   Certification       Certification       Certification       Certification
   ATR42, ATR72, F100, A320,       Basis: Sec.         Basis: Sec.         Basis: Sec.         Basis: Sec.
   A321, A318, A319, A300-600,     25.571.             25.571.             25.571.             25.571.
   A310, A340, A330, EMB 135,     --Amdt 25-45 and    --Repaired          --Repaired          --Altered
   EMB 145, SAAB 340, SAAB 2000,   later amendments    airplane            airplane            structure must
   CL-600, DHC-8, DO-328,          require damage      structure must      structure must      meet type
   BAE146, BAE Jetstream 4100.     tolerance (DT)      meet structure      meet structure      certification
                                   inspections.        type requirements.  type requirements.  requirements.
Pre 25-45
  727, 737-100/200..............  SID AD's..........  Sec.   121.370      SID AD's..........  SID AD's.
                                                       (Repair            --ADs require       --ADs require
                                                       Assessment Rule)    repairs made to     alterations made
                                                       and SID ADs.        SID principal       to SID PSEs to be
                                                                           structural          assessed for DT.
                                                                           elements (PSEs)
                                                                           to be assessed
                                                                           for DT.
Pre 25-45
  A300, 707, 720, 747, BAC 1-11,  SID AD's..........  Sec.   121.370....  Sec.   121.370a...  Sec.   121.370a.
   F-28, L-1011, DC-8, DC-9, MD-
   80, DC-10.
Pre 25-45
  L-188, DHC-7..................  SID AD............  Sec.   121.370a...  Sec.   121.370a...  Sec.   121.370a.
Pre 25-45
  F.27, L-382...................  DT data have been   Sec.   121.370a...  Sec.   121.370a...  Sec.   121.370a.
                                   developed.
Pre 25-45
  737-300/400/500...............  A SID has been      Sec.   121.370....  Sec.   121.370a...  Sec.   121.370a.
                                   developed.
                                  --AD is pending...
Pre 25-45
  737-600/700/800...............  A SID will be       Sec.   121.370....  Sec.   121.370a...  Sec.   121.370a.
                                   developed.
                                  --An AD will need
                                   to be issued.
----------------------------------------------------------------------------------------------------------------

E. Damage Tolerance Requirements of the Aging Airplane Safety Final 
Rule

    In adopting the Aging Aircraft Safety Act (AASA) of 1991, Congress 
required the FAA to ``prescribe regulations that ensure the continuing 
airworthiness of aging aircraft.'' \31\ The AASA states, in part, that 
an air carrier must show ``that maintenance of the aircraft's 
structure, skin, and other age-sensitive parts and components have been 
adequate and timely enough to ensure the highest degree of safety.'' To 
comply with this requirement, the AASFR includes supplemental 
inspection requirements that address the continued airworthiness of 
fatigue critical structure.
---------------------------------------------------------------------------

    \31\ 49 U.S.C. 44717(a).
---------------------------------------------------------------------------

    These regulations apply to all fatigue critical structure, which 
includes the baseline structure of the airplane, repairs and 
alterations that affect fatigue critical baseline structure, and 
alterations that contain fatigue critical structure. Listed below are 
examples of alterations that are included.
     Passenger-to-Freighter Conversions.
     Operating Weight Increases.
     Re-engining and Hushkits.
     Winglets.
     Auxiliary Wing Tip Fuel Tanks.
     Auxiliary Fuel Tanks Installed in the Fuselage.
     External Door Installation in a Pressurized Fuselage.
    The damage tolerance inspections and procedures required by the 
AASFR are based on the same methodology used to comply with 14 CFR 
25.571, at Amendment 25-45 and later amendments. The AASFR, in effect, 
requires compliance with the DT airworthiness standard by all affected 
airplanes, regardless of original certification basis, past AD action, 
or other operating rules.

VII. Statement of the Problem

    Without additional rulemaking, operators run the risk of not having 
the necessary DT data in time to support compliance with the 
supplemental inspection requirements of the AASFR, which has a final 
compliance date of December 20, 2010. DAHs may not voluntarily commit 
the resources needed to develop DT data within a time frame that would 
allow operators to revise programs as necessary to comply with the 
rule. We believe a regulatory approach that includes not just 
operational requirements, but corresponding DAH requirements, would 
result in a more uniform and timely response to the safety issues.
    For pre-Amendment 25-45 airplanes, as stated in the preamble to the 
AASFR, the DT data contained in FAA-approved SIDs and RAG are an 
acceptable means of compliance with the AASFR for those structural 
areas addressed by the SIDs and RAG. Therefore, to support operator

[[Page 20580]]

compliance with the AASFR adequately, DT data will need to be developed 
for fatigue critical structure in the following areas, unless 
previously accomplished:
     Existing repairs not addressed by RAG.
     Alterations, including those documented in TC holders' 
service bulletins and in STCs.
     New repairs, including those documented in TC holders' 
SRMs and service bulletins.
    For Amendment 25-45 (and later) airplanes, to support operator 
compliance with the AASFR, DT data may need to be developed for 
existing and new repairs and alterations.

VIII. Requirements for Design Approval Holders

    The FAA believes the proposed requirements are not a significant 
shift in the responsibilities of DAHs for the continued airworthiness 
of airplanes. Airplane operators always have the ultimate 
responsibility for maintaining their airplanes in a condition that 
allows for their continued safe operation. The DAH requirements would 
support this responsibility by making documents and data available to 
the operators that are necessary to meet their airworthiness 
obligation. Such actions include performing assessments, developing 
design changes, revising ICAs, and making available necessary 
documentation to affected persons. We believe this requirement is 
necessary to facilitate compliance by air carriers with operating 
rules. DAHs, in this proposal, would only be responsible for their 
repairs and alterations, and for the development of guidelines 
applicable only to their type design structure.

A. Ongoing Responsibility of Design Approval Holders for Continued 
Airworthiness

    Several recent safety regulations necessitated action by air 
carriers and other operators but did not require DAHs to develop and 
provide the necessary data and documents to facilitate the operators' 
compliance. As noted earlier, on July 12, 2005, we issued policy PS-
ANM110-7-12-2005, ``Safety--A Shared Responsibility--New Direction for 
Addressing Airworthiness Issues for Transport Airplanes.'' The policy 
states, in part, ``Based on our evaluation of more effective regulatory 
approaches for certain types of safety initiatives and the comments 
received from the Aging Airplane Program Update (July 30, 2004), the 
FAA has concluded that we need to adopt a regulatory approach 
recognizing the shared responsibility between design approval holders 
(DAH) and operators. When we decide that general rulemaking is needed 
to address an airworthiness issue, and believe the safety objective can 
only be fully achieved if the DAHs provide operators with the necessary 
information in a timely manner, we will propose requirements for the 
affected DAHs to provide that information by a certain date.''
    We believe the safety objectives contained in this proposal can 
only be reliably achieved and acceptable to the FAA if the DAHs provide 
the parts 121 and 129 operators with the DT data for repairs and 
alterations to fatigue critical structure. Our determination that DAH 
requirements are necessary to support the initiatives contained in this 
proposal is based on several factors:
     Developing DT data is complex. Operators do not have 
access to the necessary type design data needed for the timely and 
efficient development of the required DT data.
     FAA-approved DT data need to be available in a timely 
manner. Due to the complexity of these data, we need to ensure that the 
DAHs submit them for approval on schedule. This will allow the FAA 
Oversight Office having approval authority to ensure the data are 
acceptable, are available on time, and can be readily implemented by 
the affected operators. Additionally, accurate and timely information 
is necessary to ensure the operators are able to obtain the data in 
enough time to meet the December 20, 2010 compliance date of the AASFR.
     The proposals in this NPRM affect a large number of 
different types of transport category airplanes. Because the safety 
issues addressed by this proposal are common to many airplanes, we need 
to ensure that technical requirements are met consistently and the 
processes of compliance are consistent. This will ensure that the 
proposed safety enhancements are implemented in a standardized manner.
    Based on the above reasons and the stated safety objectives of FAA 
policy PS-ANM110-7-12-2005, we are proposing to implement DAH 
requirements applicable to the development of DT data to support 
compliance to the AASFR with respect to repairs and alterations.
    Operators are often dependent on action by a DAH before they can 
implement new safety rules. Ongoing difficulty reported by operators in 
attempting to meet these rules has convinced us that corresponding DAH 
responsibilities may be warranted under certain circumstances to enable 
operators to meet regulatory deadlines.
    When DAHs fail to provide the required data in a timely manner, 
operators may be forced to incur the costs associated with obtaining 
the expertise to develop the data. Some examples of programs in which 
some DAHs did not develop and make available the necessary information 
in a timely manner include--
     Thrust reversers, where it took 10 years to develop some 
service information for AD-related items;
     Class D to Class C Cargo Conversions, where one holder of 
a TC did not develop the necessary alterations in time to support 
operator compliance and where several operators were unable to obtain 
timely technical support and alteration parts from holders of an STC;
     The Reinforced Flight Deck Door Program, where most 
operators had substantially less than the one-year compliance time 
originally anticipated because of delays in developing and certifying 
the new designs;
     Repair Assessment Rule, where an operator had to develop 
data for FAA approval to meet the rule's compliance date; and
     SRMs, where operators are still awaiting DAH action to 
ensure repairs are damage tolerant, even though the DAH committed to 
completing this activity by 1993. (In reference to the bulleted items 
ADA had this question: Did FAA also contribute in any way to these 
delays?
    In addition, DAHs have committed in the past to providing data to 
the FAA to support the certification basis of an airplane. In some 
instances, the DAH has missed the due date given for this by several 
years.
    We intend to require TC holders, manufacturers, and others to take 
actions when necessary to support the continued airworthiness and to 
improve the safety of transport category airplanes. We believe this 
regulation is necessary to facilitate compliance by air carriers with 
operating rules that require the use of new safety features.
    To address this problem, we propose to amend subpart A of part 25 
to expand its coverage and to add a new subpart I to establish 
requirements for certain design approval holders. As contemplated in 
``FAA Policy Statement: Safety--A Shared Responsibility--New Direction 
for Addressing Airworthiness Issues for Transport Airplanes'' the FAA 
proposes to add provisions to a new subpart I requiring actions by DAHs 
that will allow operators to comply with our rules.

[[Page 20581]]

    Part 25 currently sets airworthiness standards for the issuance of 
TCs and changes to those certificates for transport category airplanes. 
It does not list the specific responsibilities of manufacturers to 
ensure continued airworthiness of these airplanes once the certificate 
is issued. Therefore, we propose to revise Sec.  25.1 by adding 
paragraph (c) to make clear that part 25 creates such responsibilities 
for holders of existing TCs and STCs for transport category airplanes 
and applicants for approval of design changes to those certificates.
    This proposal would establish a new subpart I, Continued 
Airworthiness and Safety Improvements, where we would locate rules 
imposing ongoing responsibilities on DAHs. In the past, this type of 
requirement took the form of a Special Federal Aviation Regulation 
(SFAR). These regulations are difficult to locate because they are 
scattered throughout Title 14. Placing all these types of requirements 
in a single subpart of part 25, which contains the airworthiness 
standards for transport category airplanes, would provide ready access 
to critical rules.
    To ensure the effectiveness of this change, we would add Sec.  25.3 
to require compliance to a new Subpart I by DAHs, which may require 
design changes and other actions by TC and STC holders.
    In preliminary discussions with foreign aviation authorities, 
regarding harmonization of our airworthiness rules, they expressed 
concern about adopting parallel requirements in their counterparts to 
part 25. They suggested that it may be more appropriate to place them 
in part 21 or elsewhere. Therefore, we specifically request comments 
from the public, including foreign authorities, on the appropriate 
place for these airworthiness requirements for TC holders currently 
proposed in subpart I.
    We reserve additional sections in this proposed subpart to include 
other future airworthiness requirements such as aging airplane rules, 
several of which are under development. Some of these proposals include 
similar language establishing the general airworthiness 
responsibilities of DAHs. Once any proposal establishing these broad 
responsibilities becomes a final rule, we will delete the duplicative 
requirements from the other proposals and retain only that language 
pertinent to any specific new safety regulations (such as fuel-tank 
flammability reduction).
    For safety reasons, we are requiring that any application for a 
type design change not degrade the level of safety that this rule 
proposes to achieve. Currently, when reviewing an application for such 
a change, we employ the governing standards in part 21, specifically 
Sec.  21.101. That section generally requires compliance with standards 
in effect on the date of application but contains exceptions that may 
allow applicants to show compliance with earlier standards. For 
example, if a change is not considered significant, the applicant may 
be allowed to show compliance with standards that applied to the 
original TC. With the adoption of subpart I rules, we must ensure that 
safety improvements that result from DAH compliance with these 
requirements are not undone by later modifications. Therefore, even 
when we determine under Sec.  21.101 that applicants need not comply 
with the latest airworthiness standards, they will be required to 
demonstrate that the change would not degrade the level of safety 
provided by the TC holder's compliance with the subpart I requirements.

B. Need for Design Approval Holder Requirements To Support Compliance 
With the Aging Airplane Safety Final Rule

    Based on public comments received on the interim final rule to the 
AASFR, as well as comments provided by the Air Transport Association 
(ATA) in a February 28, 2003 public meeting, the FAA concluded that 
compliance with the AASFR would require a DT assessment for a large 
number of repairs and alterations made to transport category airplanes. 
The ATA expressed concern that industry will not have the resources to 
handle a large portion of DT assessments. They said Boeing has 
indicated that there are about 3,100 U.S. registered airplanes for 
which they might have to provide support for DT assessments. The ATA 
also said that Boeing might be required to provide DT analysis for 
142,600 \32\ repairs installed on these airplanes. The ATA estimated 
that about 3,300 \33\ STCs may require damage tolerance evaluation. 
Based on current industry practice of performing damage tolerance 
evaluations of individual repairs, the FAA agrees with the ATA that, 
without DAH support, industry will likely not have the resources needed 
to evaluate the repairs that will be required to be assessed for 
compliance with the AASFR.
---------------------------------------------------------------------------

    \32\ This estimate includes repairs installed on all airplane 
models subject to the DT requirements of the AASFR, which includes 
those airplanes certificated to the DT requirements of Sec.  25.571 
at Amendment 25-45 or later amendments. The type certification basis 
of airplanes certificated at amendment 25-45 or later amendments, 
requires that repairs and alterations made to these airplanes meet 
the DT requirements of Sec.  25.571. Therefore, the percentage of 
repairs estimated by the ATA that apply to airplanes certificated at 
amendment 25-45 or later amendments is about 40%. The ATA estimate 
is based on 3.5 repairs being installed per year on each Boeing 
model airplane.
    \33\ The percentage of alterations that apply to airplane models 
type certificated at amendment 25-45 or later amendments is about 
40%. The certification basis for these airplanes requires that all 
alterations meet the DT requirements of Sec.  25.571.
---------------------------------------------------------------------------

    The current practice of conducting evaluations of individual 
repairs will require an excessive amount of industry time and 
resources. This process would typically involve, for example, data 
collection for each repair, documentation of repair data, and submittal 
of documentation from operators to the DAH. The DAH would, at the 
request of an operator, review the repair data and determine if damage 
tolerance inspections would be required for the repair and any fatigue 
critical structure affected by the repair. This determination by the 
DAH can be a complex task, depending on the repair configurations, and 
the fatigue critical structure that it may affect. Therefore, to 
support operator compliance, DT guidance that provides a streamlined 
approach for assessing repairs will need to be made available.
    The DAHs possess the requisite technical expertise, proprietary 
data, and procedures to develop the required DT guidance. While some 
air carriers have extensive engineering departments that may be able to 
develop the DT data required to comply with the AASFR, they would still 
be dependent on the TC holder to provide detail data for the fatigue 
critical structure to perform the evaluation. For smaller airlines that 
do not have extensive engineering capabilities, reliance on the TC 
holder is all the more necessary for compliance with the rule. Airlines 
in general are unable to generate DT based service information (as the 
TC holder typically does) and, most significantly for this rulemaking, 
would be unable to develop the guidance required to assess the 
thousands of existing repairs.
    Although the involvement of DAHs is necessary, we also recognize 
that it would be unreasonable to require them to assume responsibility 
for the DT of repairs and alterations they did not develop. However, as 
discussed later, while the DAHs would only be responsible for providing 
specific DT data for repairs and alterations they developed, they are 
required to make available guidelines on how to assess the effects of 
other repairs on their baseline structure.

C. Alternatives to This Proposal

    The FAA considered three alternatives to this proposed rule. These 
were to--
    (1) Not mandate DAH requirements;

[[Page 20582]]

    (2) Rescind Sec. Sec.  121.370a and 129.16; and
    (3) Rescind approval of SRMs and other published service 
information that do not contain the necessary damage tolerance 
inspection data.
    We concluded that Alternative 1 is not a viable option. As 
discussed in section IX of this preamble, if we adopt this alternative, 
the operators may not be able to comply with the requirement to 
incorporate damage tolerance inspections and procedures by December 20, 
2010. The reason is the DAH may not voluntarily develop the DT data 
required for compliance.
    Under Alternative 2, the FAA recognizes that many repairs and 
alterations made to fatigue critical structure would not have 
supplemental inspections necessary to maintain the continued 
airworthiness of affected airplanes.
    Alternative 3 would place an unacceptable burden on operators. 
Future major repairs or alterations to affected airplanes would not be 
possible without FAA approval. As operators routinely use these 
documents to support their operations, it is possible that airplanes 
may be taken out of service for extensive periods until the DT data for 
a particular repair or alteration are FAA approved.
    The FAA has concluded that these alternatives may not preclude the 
installation of repairs or alterations that could contribute to a 
catastrophic failure. As noted in the AASFR, the AASA specified that an 
air carrier must demonstrate to the Administrator ``that maintenance of 
the aircraft's structure, skin, and other age-sensitive parts and 
components have been adequate and timely enough to ensure the highest 
degree of safety.''

D. ``Retroactivity'' of Design Approval Holder Requirements

    In the past, and particularly in comments to the Aging Airplane 
Program Update, DAH requirements have been referred to as 
``retroactive.'' They are considered ``retroactive'' in the sense that 
they impose requirements on holders of existing design approvals. But 
they are not ``retroactive'' in the legal sense that they impose legal 
consequences in the past.\34\ On the contrary, all of the proposed DAH 
requirements are only prospective in effect. In each case they would 
require DAHs to take actions in the future. For example, in this 
proposal, DAHs would be required to develop DT data and submit them for 
FAA approval before a specified future compliance time.
---------------------------------------------------------------------------

    \34\ In Bowen v. Georgetown University Hospital, 488 U.S. 204 
(1988), the Supreme Court invalidated a 1984 Social Security 
Administration regulation on the grounds that it was not authorized 
to issue such a ``retroactive'' regulation. That regulation changed 
a Medicare reimbursement schedule, effective as of 1981. The effect 
was to require hospitals to refund fees they had been entitled to 
when the fees were paid.
---------------------------------------------------------------------------

    This proposal would not change the certification basis of any 
airplane, nor would it invalidate any previous FAA approval. This 
proposal would not change any past or current airworthiness standards, 
including Sec.  25.571; although it would require future applicants for 
design changes to pre-Amendment 25-45 airplanes to meet additional 
requirements. This proposal would not invalidate the approval of any 
previously installed repair or alteration. But it would require DAHs to 
develop and make available DT data for use by operators to inspect or 
replace such repairs and alterations in the future.
    In this sense, this proposal is similar to many ADs. We have 
identified a safety problem (fatigue cracking) with existing airplanes 
that, unless addressed, may result in accidents in the future. To 
prevent those accidents, we have adopted the AASFR to require operators 
to implement programs to detect and fix the problem. And, to enable the 
operators to comply with the AASFR, we are now proposing requirements 
for DAHs to make the necessary data available to the operators.

IX. Proposed Regulatory Changes

    As discussed earlier, the AASFR requires operators to take into 
account the effects repairs and alterations may have on fatigue 
critical structure. This proposal would require DAHs to take several 
different actions to support operators' compliance with the AASFR with 
respect to repairs and alterations. Table 2 summarizes the proposed 
regulatory changes.

                                       Table 2.--Summary of Proposed Rules
----------------------------------------------------------------------------------------------------------------
                 14 CFR                           Description of proposal                    Applies to
----------------------------------------------------------------------------------------------------------------
25.1....................................  Expands applicability to current         Applicants for TCs, and
                                           holders of TCs and STCs.                 changes to those TCs for
                                                                                    transport category
                                                                                    airplanes.
25.3....................................  New Sec.   25.3 to make reference to     .............................
                                           the proposed subpart I.
Subpart I 25.1801.......................  Defines the intent of the subpart......  TCs, and design changes to
                                                                                    those TCs for transport
                                                                                    category airplanes.
25.1823.................................  Requires a list of fatigue critical      Holders of a TC for the
                                           baseline structure, DT data for          affected airplane model(s).
                                           repairs to baseline structure, and
                                           repair evaluation guidelines.
25.1825.................................  Requires a list of fatigue critical      Holders of a TC for the
                                           alteration structure, DT data for        affected airplane model(s).
                                           alterations and repairs to those
                                           alterations.
25.1827.................................  Requires a list of fatigue critical      Holders of an STC for the
                                           alteration structure, DT data for        affected airplane models.
                                           alterations and repairs to those
                                           alterations.
25.1829.................................  Requires Compliance Plans for each       Holders of a TC and an STC.
                                           section.
----------------------------------------------------------------------------------------------------------------

A. Applicability

    Today's proposal would apply to current and future holders of TCs, 
holders of STCs, and future applicants for changes to TCs. This rule 
would apply to transport category, turbine powered airplane models with 
an original TC issued after January 1, 1958. Specifically, with certain 
exceptions, this proposal would apply to those airplanes, that, as a 
result of the original certification, or later increase in capacity, 
have a maximum type certificated passenger seating capacity of 30 or 
more or a maximum payload capacity of 7,500 pounds or more. There are a 
number of these airplanes that are not operated under 14 CFR parts 121 
or 129 and, therefore, are not subject to the AASFR. Proposed Sec.  
25.1823(h) would exclude those airplanes because the purpose of this 
rule is to require DAHs to support operators of airplanes under 14 CFR 
parts 121 or 129. We specifically request comments on whether there are 
other airplanes of this size that are not operated under 14 CFR parts 
121 or 129 and that should be excluded from this rule.

[[Page 20583]]

    As discussed earlier, Sec.  25.571 has required new TCs to meet DT 
requirements since 1978, but for a variety of reasons, these 
requirements have not been met for many repairs and alterations. 
Therefore, to ensure that repair and alteration data for future TCs 
will meet these requirements, today's proposal would apply to DAHs for 
future TCs, as well as existing TCs. This proposal is different in this 
respect from other DAH requirements currently being considered by the 
FAA, which would not apply to TCs for which application is made in the 
future. This is because these rulemaking initiatives would adopt a 
change to the airworthiness standards in 14 CFR part 25 to impose a 
similar requirement on those future applicants.
    Today's proposal, if adopted, would apply to both domestic and 
foreign DAHs. This rule would be different from most type certification 
programs for new TCs, where foreign applicants typically work with 
their responsible certification authority and the FAA relies upon that 
authority's findings of compliance per the conditions of bilateral 
airworthiness agreements. Presently, no other certification authority 
has adopted requirements addressing DT for repairs and alterations for 
existing TCs.
    Accordingly, the FAA will retain the authority to make all the 
necessary compliance determinations and, where appropriate, may request 
certain compliance determinations by the appropriate foreign 
authorities, using procedures developed under the bilateral agreements. 
The compliance planning provisions of this proposed rule are equally 
important for domestic and foreign DAHs and applicants, and we will 
work with the foreign authorities to ensure that their DAHs and 
applicants perform the planning necessary to comply with those 
requirements.

B. Lists of Fatigue Critical Structure for Baseline Structure and 
Alterations

    The first step in evaluating the DT of repairs or alterations is 
for TC and STC holders to determine which ones affect fatigue critical 
structure.\35\ This can only be done once the fatigue critical 
structure that may be repaired or altered is identified. Therefore, for 
each airplane model subject to today's proposal, a list of fatigue 
critical structure for the following three areas would be required:
---------------------------------------------------------------------------

    \35\ This proposal would define ``Fatigue critical structure'' 
as ``airplane structure that is susceptible to fatigue cracking that 
could contribute to a catastrophic failure, as determined by Sec.  
25.571.'' This proposal would also define ``affects'' to mean, 
``fatigue critical structure has been physically repaired, altered, 
or modified, or the structural loads acting on fatigue critical 
structure have been increased or redistributed.'' Because of 
industry's extensive experience in showing compliance with the 
damage tolerance requirements of Sec.  25.571, these key terms 
should be readily understood and applied.
---------------------------------------------------------------------------

     Baseline structure.
     Alterations developed by TC holders that affect any 
fatigue critical baseline structure.
     Alterations developed by STC holders that affect any 
fatigue critical baseline structure.
    In most cases, TC holders have already performed the technical 
analyses necessary to produce the list for baseline structure, either 
in developing SIDs (for pre-Amendment 25-45 airplanes) or in showing 
compliance with Sec.  25.571 (for Amendment 25-45 and later airplanes). 
To ensure the list includes the full range of structural designs that 
operators and STC holders need to know about, TC holders would be 
required to address all of their current and out of production model 
variations and derivatives. TC holders would also be required to 
identify all post-production alterations they developed (typically 
documented in service bulletins) that affect fatigue critical baseline 
structure. For these alterations, the TC holder would determine whether 
the alterations themselves contain fatigue critical structure. For 
example, installation of a large cargo door would clearly affect 
fatigue critical baseline structure, but the door installation also may 
contain fatigue critical structure, such as door webs, frames, hinge 
installations, and door attachment structure installed on the baseline 
structure.
    Today's proposal would require TC holders to submit the list of 
fatigue critical structure for both the baseline airplane and 
alterations no later than 90 days after the effective date of the rule, 
for review and approval by the FAA Oversight Office. Upon approval, 
they would have to make the list available to operators required to 
comply with the supplemental inspection requirements of the AASFR and 
to STC holders required to comply with this rule.
    STC holders would also be required to identify their alterations 
that affect fatigue critical baseline structure. For these alterations, 
the STC holder would then determine whether the alterations themselves 
contain fatigue critical structure. STC holders would have to submit 
the list of fatigue critical alteration structure no later than 270 
days after the effective date of the rule, for review and approval by 
the FAA Oversight Office, and upon approval, make the list available to 
affected operators. The six-month difference between the STC and TC 
holder submittal dates is intended to allow STC holders time to obtain 
and review the list of fatigue critical baseline structure developed by 
the TC holder. STC holders may need this list to determine if any of 
their alterations approved under an STC affect this structure.
    Throughout this proposal, the term ``make available'' is used in 
the same sense that it is currently used in 14 CFR 21.50, which 
requires DAHs to make ICAs available to operators and others required 
to comply with them. We do not intend by this proposal to alter or 
interfere with the existing commercial relationships between DAHs and 
these other persons. We anticipate that DAHs would be allowed 
reasonable compensation for developing all of the required documents, 
which is consistent with current practice.

C. Damage Tolerance Evaluations and Damage Tolerance Inspections

    Because holders of TCs and STCs have not performed damage tolerance 
evaluations for many of their repairs and alterations, damage tolerance 
evaluations must be performed for operators to comply with the AASFR. 
Additionally, unless already accomplished, all future repairs and 
alterations affecting fatigue critical structure identified in the 
lists described above would need to have damage tolerance evaluations 
performed and damage tolerance inspections developed.
    In today's proposal, repair and alteration data developed by TC and 
STC holders are divided into the following six categories:
    (1) Repair data published by TC holders.
    (2) Existing unpublished repair data developed by TC holders.
    (3) Future repair data developed by TC holders.
    (4) Alteration data developed by TC holders.
    (5) Alteration data developed by STC holders.
    (6) Repair data developed by STC holders.
    For repairs identified in category 2, TC holders would have to 
develop repair evaluation guidelines that provide a process operators 
could use to establish new or confirm the acceptability of existing 
damage tolerance inspections for those repairs. These guidelines will 
be discussed later in this section of the preamble. For the other 
categories of repair and alteration data, today's proposal would 
require TC and STC holders to develop damage tolerance inspections.

[[Page 20584]]

    Repair data published by TC holders: TC holders publish repair data 
in SRMs, service bulletins, and other forms of data transmittal. They 
develop data for general application to a particular airplane model or 
airplane configuration. Since operators use these data for most 
repairs, providing damage tolerance inspections in these documents 
would enable them to comply with the AASFR for most existing and future 
repairs.
    For their published repair data that is current \36\ as of the 
effective date of this proposed rule, and for all later published 
repair data, the TC holder would be required to review the data and 
identify each repair that affects fatigue critical structure. For each 
such repair, unless previously accomplished, the TC holder would be 
required to perform damage tolerance evaluations and develop any 
necessary changes to the repair or damage tolerance inspections. If the 
DTE concludes that damage tolerance based supplemental structural 
inspections are not necessary for a repair or for fatigue critical 
baseline structure affected by a repair, the DTI would contain a 
statement to that effect. For repair data published by the TC holder, 
today's proposal would require the TC holder to submit DT data \37\ by 
June 30, 2009 for review and approval by the FAA Oversight Office, or 
its properly authorized designees.\38\ And, upon approval, make the 
damage tolerance inspections available to operators required to comply 
with the DT requirements of the AASFR.
---------------------------------------------------------------------------

    \36\ By current, we mean repair data that is currently made 
available to operators by TC holders. We recognized that in some 
cases, TC holders will no longer have data for repairs they 
developed many years ago, and, therefore, would not be able to 
perform damage tolerance evaluations of those repairs. For these 
repairs, the TC holder would be required to develop repair 
evaluation guidelines that provide operators with a process for 
establishing DT data (see footnote 37). The repair evaluation 
guidelines are discussed later in this preamble.
    \37\ The term DT data as used in this rule means any DTE 
documentation and DTI that an operator may incorporate into their 
maintenance program for compliance with the AASFR.
    \38\ The term ``properly authorized designees'' is used 
throughout this proposal to refer to DERs who are fully trained in 
DT principles and who are specifically authorized by their 
supervising aircraft certification offices (ACOs) to make the 
referenced compliance findings. In many cases, we expect the initial 
compliance findings would be made by the ACOs themselves, and only 
later findings would be delegated.
---------------------------------------------------------------------------

    Existing unpublished repair data developed by TC holders: This 
category consists of repairs that are typically developed for 
individual airplanes at the request of an operator. These repairs are 
often unique to a particular airplane or to a small group of airplanes 
experiencing similar damage conditions and, therefore, are typically 
not published for general application. Because of the significant 
number of these repairs that TC holders have developed, it would be 
very time consuming and costly for them to research and identify all 
the repair data that may affect fatigue critical structure. Today's 
proposal would not specifically \39\ require TC holders to develop 
damage tolerance inspections for these repairs. To address these 
repairs, TC holders would be required by today's proposal to develop 
repair evaluation guidelines, as discussed later in this preamble.
---------------------------------------------------------------------------

    \39\ The process developed by the TC holder for the repair 
evaluation guidelines may, however, recommend that operators submit 
such repairs to the TC holder for a DTE. This may be the case if the 
TC holder determines there are not a large number of such repairs on 
that airplane model fleet.
---------------------------------------------------------------------------

    Future unpublished repair data developed by a TC holder: While this 
category consists of the same types of repairs as the previous 
category, these repairs will be developed after the effective date of 
this proposed rule when TC holders will be fully aware of operators' 
needs for DT data. Therefore, we are proposing that TC holders be 
required to develop DT data for these repairs. However, these repairs 
are frequently developed for airplanes that are undergoing maintenance 
and must be repaired before they can be returned to service. Because 
requiring damage tolerance evaluations under these circumstances would 
significantly delay the airplanes' return to service, we are proposing 
that the DT data be developed according to an approved implementation 
schedule, as discussed later in this preamble.
    Alteration data developed by TC holders: These data include 
alterations specified in service bulletins or other service 
information. TC holders would be required to evaluate their alteration 
data to determine whether the alteration affects fatigue critical 
structure. If so, the TC holder would be required to develop a list of 
fatigue critical structure of the alteration, perform damage tolerance 
evaluations, and develop damage tolerance based inspections, if 
necessary. For existing alterations, TC holders would be required to 
submit these data by June 30, 2009 for FAA approval. For future 
alterations, the DT data would be required before we approve the 
alteration data.
    Alteration and repair data developed by STC holders: Similarly, STC 
holders would be required to determine whether their alterations affect 
fatigue critical structure (as identified in the list made available by 
the TC holder), develop lists of fatigue critical structure of their 
alterations, perform damage tolerance evaluations, and develop damage 
tolerance inspections. In addition to alterations, some STC holders 
have developed repairs that are applicable to their alterations. STC 
holders would be required to perform damage tolerance evaluations and 
develop damage tolerance based inspections, if necessary, for those 
repairs that affect any fatigue critical structure. For existing 
alterations, STC holders would be required to submit these data by June 
30, 2009 for FAA approval. For future alterations, the DT data would be 
required before we approve the alteration data.

D. Repair Evaluation Guidelines

    Today's proposal would require TC holders to develop guidelines 
that would provide processes that operators could use for establishing 
DT data for repairs that affect fatigue critical structure. The 
guidelines must include the following items:
     A process for conducting surveys of affected airplanes to 
identify and document all existing repairs that affect fatigue critical 
baseline structure.
     A process for establishing DT data for repairs and for 
fatigue critical baseline structure affected by the repairs.
     A DT data implementation schedule for repairs covered by 
the guidelines.
    The DT data implementation schedule is discussed later as a 
separate topic as it applies to repairs addressed by the guidelines and 
future unpublished repairs for which the TC holders must develop damage 
tolerance inspections.
    For operators to be able to determine effectively which existing 
repairs need damage tolerance evaluations performed, they would need a 
process to identify and document those repairs. Today's proposal would 
require TC holders to develop a survey process that operators can use 
for identification and documentation of repairs for the affected 
airplanes. Using the lists of fatigue critical structure developed by 
TC and STC holders, this process would provide operators with a means 
for determining which existing repairs affect fatigue critical 
structure. The process would also provide instructions for documenting 
those repairs by listing or describing the repair information \40\ that 
will be necessary to establish DT data for the repair.
---------------------------------------------------------------------------

    \40\ Examples of repair information include location, 
dimensions, materials, fastener configuration, physical changes made 
to fatigue critical structure, and proximity of repairs or 
alterations to other repairs.

---------------------------------------------------------------------------

[[Page 20585]]

    Today's proposal would also require the TC holder to develop a 
process that operators can use for establishing DT data. The process 
most commonly used today by operators to obtain DT data is time 
consuming and resource intensive. The process required by today's 
proposal would provide operators with various methods for obtaining DT 
data for repairs. Possible methods for obtaining the required DT data 
may include--
     Using existing FAA approved data. These may include TC 
holder developed service information such as SRMs, service bulletins, 
and Repair Assessment Guideline (RAG) documents developed for 
compliance to Sec.  121.370.
     Making direct requests for support from the TC holder for 
repairs. If the TC holder determines that the existing service 
information does not provide operators with the needed DT data, the 
process may recommend that the operator directly solicit DT data from a 
TC holder. In this case, the TC holder would evaluate the operator's 
request and make available damage tolerance inspections for a specific 
repair or alteration or group of repairs and alterations as needed. If 
the processes developed for the repair evaluation guidelines direct the 
operator to obtain assistance from the TC holder, the TC holder would 
be required to provide such assistance. This assistance must be 
provided in a manner that would support the DT data implementation 
schedule.
     Using repair evaluation procedures. These procedures would 
enable operators to establish damage tolerance inspections without 
having to contact the TC holder for direct support. These procedures 
may be similar in concept to the RAG documents.

E. Damage Tolerance Data Implementation Schedule

    Today's proposal would require the TC holder to develop an 
implementation schedule that addresses the timing of key tasks required 
by this proposal. The DT data implementation schedule would specify 
appropriate timing for the following tasks:
     Conducting airplane surveys to identify and document 
repairs and alterations that affect fatigue critical structure.
     Performing damage tolerance evaluations and developing 
damage tolerance inspections for existing repairs that affect fatigue 
critical structure.
     Performing damage tolerance evaluations and developing 
damage tolerance inspections for unpublished future repairs that affect 
fatigue critical structure.
     Revising maintenance programs to incorporate damage 
tolerance inspections.
    In establishing the timing of these tasks, TC holders would need to 
determine if the available industry resources are sufficient to perform 
the tasks within the proposed time. If not, the processes or timing 
developed for the tasks may need to be reassessed to provide schedules 
that make the most efficient use of resources, while ensuring the 
continued airworthiness of the affected airplanes.
    For future unpublished repair data, the implementation schedule may 
define a process that allows an airplane to return to service before 
all necessary DT data are submitted for FAA approval. This process may 
involve an initial approval of repair data to allow an airplane to 
return to service and subsequent submittal and approval of the DT data. 
The details of the timing of when data are to be submitted and approved 
would be included in the implementation schedule. A phased process may 
be necessary to minimize the burden placed on TC holder resources and 
to reduce unnecessary down time of airplanes.
    A similar process is described in AC 25.1529-1. A modified version 
of the process defined in AC 25.1529-1 has been approved by the FAA and 
is currently being used in industry. ARAC has established a process 
that is similar to the modified version of the process defined in AC 
25.1529-1. This process has been incorporated into a proposed advisory 
circular and may be incorporated into the DT data implementation 
schedule for future repairs that is required by today's proposal.
    For implementation schedules required for existing repairs, the TC 
holder would submit implementation schedules as part of the repair 
evaluation guidelines to the FAA Oversight Office, for review and 
approval by December 30, 2009. This proposal would mandate that future 
repair data be submitted to the FAA Oversight Office for review and 
approval, according to the implementation schedule approved as part of 
the Repair Evaluation Guidelines.

F. Compliance Plan

    The FAA intends to establish the requirements for a compliance plan 
to ensure that affected DAHs and the FAA have a common understanding 
and agreement of what is necessary to achieve compliance with this 
proposed rule. The plan would also ensure that the DAHs produce the DT 
data in a timely manner that is acceptable in content and format. 
Integral to the compliance plan will be the inclusion of procedures to 
allow the FAA to monitor progress toward compliance. These aspects of 
the plan will help ensure that the expected outcomes will be acceptable 
and on time for incorporation by the affected operators into their 
maintenance programs as required by the AASFR. The affected DAHs would 
be required to submit a compliance plan that addresses the following:
     The proposed schedule for meeting the compliance dates, 
including all major milestones.
     A proposed means of compliance with the requirements to 
develop and make available DT data.
     Any planned alternatives to guidance provided in FAA 
advisory material.
     A draft of all required compliance items not less than 60 
days before the stated compliance dates.
     A process for continuous assessment of service information 
for the affected transport category airplane fleet that includes:

--Effectiveness of the damage tolerance inspections and repair 
evaluation guidelines; and
--Development of new or revised DT data.

     Distribution of approved DT data.
    The compliance plan is based substantially on ``The FAA and 
Industry Guide to Product Certification,'' which describes a process 
for developing project-specific certification plans for type 
certification programs. This guide \41\ recognizes the importance of 
ongoing communication and cooperation between applicants and the FAA. 
Today's proposal, while regulatory in nature, is intended to encourage 
the establishment of the same type of relationship in the process of 
complying with DAH requirements.
---------------------------------------------------------------------------

    \41\ This Guide is available at http://www.faa.gov/certification/aircraft.
---------------------------------------------------------------------------

    We will issue an AC to include guidance for a compliance plan. FAA 
advisory material, while not mandatory, describes one means, but not 
the only means, of compliance. Similar to the process used in the type 
certification, applicants may propose acceptable alternatives to the 
means of compliance described in advisory circulars. When an applicant 
chooses to comply by an alternative means, it should identify the 
alternative as early as possible to provide an opportunity to resolve 
any issues that may arise that could lead to delays in the compliance 
schedule.

[[Page 20586]]

    One of the sections in the proposed compliance plan requires a 
detailed explanation of how the proposed means of compliance would meet 
the requirements of the section if the proposed means of compliance 
differs from that described in FAA advisory material. This part of the 
compliance plan would enable the FAA Oversight Office to identify and 
resolve any issues that may arise with the proposal of the DAH without 
jeopardizing the ability of the applicant or DAH to comply by the 
compliance time.
    Today's proposal would require TC holders and applicants for TCs to 
correct a deficient plan, or deficiencies in implementing the plan, in 
a manner identified by the FAA Oversight Office. Before the FAA 
formally notifies a TC holder or TC applicant of deficiencies, we 
intend to establish a mutual understanding of the deficiencies and a 
way to correct them. Therefore, the notification referred to in this 
paragraph should document the corrective action. The TC holder or 
applicant will then have 30 days to implement the corrective action.
    The ability of an operator to comply with the AASFR is dependent on 
TC holders, certain STC holders, and applicants complying on time with 
the approved compliance plan requirements. The FAA will carefully 
monitor compliance and take appropriate action if necessary to help 
ensure timely compliance. Failure to comply by the specified dates 
would constitute a violation of the requirements and may subject the 
violator to certificate action to amend, suspend, or revoke the 
affected certificate (49 U.S.C. 44709). It may also subject the 
violator to a civil penalty of not more than $25,000 per day, per 
certificate until the violator complies with these requirements (49 
U.S.C. 46301).
    For those persons applying after the effective date of the rule for 
STCs or amendments to TCs, the affected persons would not have to 
address DT for repairs and alterations until a compliance plan defining 
the certification basis for the overall STC or amended TC is needed. 
The proposal also specifies compliance dates for submitting compliance 
plans for evaluating design changes and developing service information 
for maintenance actions that must be performed. The compliance dates 
for the affected persons are as follows:
     Holders of TCs--no later than 90 days after the effective 
date of the rule.
     Holders of STCs--no later than 180 days after the 
effective date of the rule.
     Applicants for STCs and amendments to TCs if the 
certificate was not issued before the effective date of the final 
rule--before the certification of STC or amended TC.

X. New Subparts for Airworthiness Operational Rules

    As we discussed earlier in this preamble, today's proposal would 
create a new subpart I, Continued Airworthiness and Safety 
Improvements, in part 25. This new subpart would provide a common 
location for rules that impose ongoing responsibilities on DAHs. In 
addition, the FAA proposes to create new subparts for airworthiness-
related operational rules to provide a common location for these rules. 
The FAA believes creating new subparts where these rules could be 
located will enhance the reader's ability to readily identify rules 
pertinent to continued airworthiness. In addition, we believe this will 
ensure easy visibility of these requirements.
    These new subparts would contain certain rules from other proposals 
(e.g., Enhanced Airworthiness Program for Airplane Systems/Fuel Tank 
Safety (EAPAS/FTS)) and other existing and future rules related to the 
support of continued airworthiness. In particular, these new subparts 
would contain rules that address aging airplane issues. Unless stated 
otherwise in the specific aging airplane proposal, our purpose in 
moving requirements to these new subparts is to ensure easy visibility 
of those requirements applicable to the continued airworthiness of the 
airplane. We do not intend to change the legal effect of the 
requirements in any other way. In the context of today's proposal, the 
most significant effect of the proposed reorganization of the 
operational airworthiness requirements is to redesignate sections of 
the AASFR and place those sections in the new subparts. The affected 
sections include the supplemental inspection requirements, currently 
codified as Sec. Sec.  121.370a and 129.16; the repair assessment for 
pressurized fuselages requirements, currently codified as Sec. Sec.  
121.370 and 129.32; and the aging airplane inspections and records 
reviews requirements, currently codified as Sec. Sec.  121.368 and 
129.33. This proposal would redesignate
     Sec. Sec.  121.370a and 129.16 as Sec.  121.1109 and Sec.  
129.109, respectively, and place them in new subparts AA and B, 
respectively.
     Sec. Sec.  121.370 and 129.32 as Sec.  121.1107 and Sec.  
129.107, respectively, and place them in new subparts AA and B, 
respectively.
     Sec. Sec.  121.368 and 129.33 as Sec. Sec.  121.1105 and 
129.105, respectively, and place them in new subparts AA and B, 
respectively.
    Some of the other planned aging airplane proposals include similar 
language that establishes the new operational subparts, redesignates 
certain sections of these rules, and establishes requirements common to 
each of the aging airplane proposals. In addition, certain of the 
proposals include new requirements specific to that rule. Today's 
proposal, however, does not include any new operational requirements. 
Once any one of the aging airplane proposals becomes a final rule, we 
will remove the duplicative requirements (i.e., requirements that 
establish the new subparts and redesignate sections of certain 
operational rules) from the other aging airplane proposals.

XI. FAA Advisory Committee Tasking: Guidance Material

    The FAA tasked the Aviation Rulemaking Advisory Committee (ARAC) 
\42\ to help with the development of a process that operators can use 
for establishing DT data for repairs. The goal of this task was to have 
the ARAC develop guidance materials that would support industry 
compliance with the AASFR, as it applies to repairs affecting fatigue 
critical structure. The ARAC has developed guidelines and 
implementation schedules for existing and future repairs. These 
guidelines and implementation schedules are provided in proposed draft 
AC 120-XX, which the FAA has published with today's proposal. This AC 
will provide DAHs guidance for producing the DT data that would be 
necessary for compliance with this proposed rule. In addition, it will 
provide operators with a recommended process for incorporating DT data 
into their maintenance programs, after the data are approved by the FAA 
and made available to them.\43\ We request comments on this draft AC.
---------------------------------------------------------------------------

    \42\ 69 FR 26641, May 13, 2004.
    \43\ The means of incorporating the DT data into an air 
carrier's FAA-approved maintenance program is subject to approval by 
the certificate holder's Principal Maintenance Inspector (PMI) or 
other cognizant airworthiness inspector.
---------------------------------------------------------------------------

XII. Paperwork Reduction Act

    Information collection requirements in the AASFR have been 
previously approved by the Office of Management and Budget (OMB) under 
the provisions of the Paperwork Reduction Act of 1995 (44 U.S.C. 
3507(d)) and have been assigned OMB Control Numbers: 2120-0020 and 
2120-0008. Part 129 record requirements can be found in

[[Page 20587]]

International Civil Aviation Organization Annexes.
    The FAA reviewed data associated with compliance to the AASFR and 
data associated with this proposal. We have determined that this rule 
is a transfer of responsibility only and there is no additional 
paperwork burden on the public. The paperwork burden for compliance 
with the AASFR will be reduced as a result of today's proposal due to a 
reduction in the numbers of repairs and alterations that will need an 
individual damage tolerance assessment. This is because this proposal 
will require design approval holders to develop a streamlined approach 
for assessing repairs.
    Under the Paperwork Reduction Act of 1995, (5 CFR 
1320.8(b)(2)(vi)), an agency may not conduct or sponsor, and a person 
is not required to respond to, a collection of information unless it 
displays a currently valid OMB control number.

XIII. Regulatory Evaluation/Analysis

Regulatory Evaluation, Regulatory Flexibility Analysis, International 
Trade Impact Assessment, and Unfunded Mandates Assessment

    Proposed changes to Federal regulations must undergo several 
economic analyses. First, Executive Order 12866 directs that each 
Federal agency shall propose or adopt a regulation only upon a reasoned 
determination that the benefits of the intended regulation justify its 
costs. Second, the Regulatory Flexibility Act of 1980 requires agencies 
to analyze the economic impact of regulatory changes on small entities. 
Third, the Trade Agreements Act (19 U.S.C. 2531-2533) prohibits 
agencies from setting standards that create unnecessary obstacles to 
the foreign commerce of the United States. In developing U.S. 
standards, this Trade Act requires agencies to consider international 
standards and, where appropriate, to be the basis of U.S. standards. 
Fourth, the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4) 
requires agencies to prepare a written assessment of the costs, 
benefits, and other effects of proposed or final rules that include a 
Federal mandate likely to result in the expenditure by State, local, or 
tribal governments, in the aggregate, or by the private sector, of $100 
million or more annually (adjusted for inflation).
    The Department of Transportation Order DOT 2100.5 prescribes 
policies and procedures for simplification, analysis, and review of 
regulations. If the expected cost impact is so minimal that a proposal 
does not warrant a full evaluation, this order permits a statement to 
that effect. The basis for the minimal impact must be included in the 
preamble, if a full regulatory evaluation of the cost and benefits is 
not prepared. Such a determination has been made for this rule. The 
reasoning for that determination follows.
    The recently published Aging Airplane Safety final rule (AASFR) 
\44\ requires airline operators of certain large transport category 
airplanes to implement damage tolerance (DT) based inspections and 
procedures for airplane structure susceptible to fatigue cracking that 
could contribute to catastrophic failure. This proposed rule is a 
counterpart to the AASFR. This proposed rule transfers the 
responsibility of developing DT data and documents from operators to 
Design Approval Holders (DAHs) and, therefore, has minimal to no costs. 
Additionally, the DAH requirements do not preclude DAHs from recouping 
their costs by seeking reasonable compensation from the operators for 
the proposal's required DT data and documents.
---------------------------------------------------------------------------

    \44\ 70 FR 5518, February 2, 2005.
---------------------------------------------------------------------------

    The purpose of this proposal is to ensure that operators have the 
necessary data and documents to support timely compliance with the 
requirements of Sec. Sec.  121.370(a) and 129.16 of the AASFR. Timely 
operator compliance improves the safety of the fleet.
    Existing certification and operational rules already require 
operators to implement the DT inspections and procedures this proposal 
would require DAHs to develop. Amendment 25-45 (or later) airplanes, 
affected by this proposal, are required by Sec.  25.571 to incorporate 
damage tolerance inspections to the baseline structure, repairs, and 
alterations. On pre-Amendment 25-45 airplanes, DT inspection and 
procedures for the baseline structure are required by airworthiness 
directive (AD). In addition, damage tolerance inspections for repairs, 
alterations and modifications to affected Boeing 727 and 737-100/200 
are also required by AD. Damage tolerance inspections for repairs to 
the pressurized fuselage \45\ for certain pre-Amendment 25-45, 
airplanes \46\ are required by Sec.  121.370. By December 2010, damage 
tolerance inspections for the baseline structure and repairs, 
alterations, and modifications for the remaining pre-Amendment 25-45 
affected airplanes will be required by Sec. Sec.  121.370a and 129.16. 
Despite these requirements, in many cases, DT data and documents have 
not yet been developed for many repairs and alterations made to the 
affected airplanes.
---------------------------------------------------------------------------

    \45\ Fuselage, door skins, and bulkhead webs.
    \46\ A-300 (excluding the -600 model), 707/720, 727, 737-300/
400/500/600/700/800, 747, BAC 1-11, F-28, L-1011, DC-8, DC-9/MD-80, 
DC-10.
---------------------------------------------------------------------------

    The following table shows a summary of the regulatory requirements 
for DT inspection programs. The shaded areas in the table represent 
regulatory gaps filled by the AASFR (Sec.  121.370a) requirements to 
develop DT inspections and procedures for fatigue critical airplane 
structural areas.

----------------------------------------------------------------------------------------------------------------
                                                      Airplane damage tolerance requirements
                                 -------------------------------------------------------------------------------
                                                          Repairs to
 Amendment level airplane models                        fuselage & door     Repairs to all       Alterations/
                                  Baseline structure    skin, bulkhead        other areas        modifications
                                                             webs
----------------------------------------------------------------------------------------------------------------
25-45 or later
  737-900, 757, 767, 777, MD11,   Certification       Certification       Certification       Certification
   ATR42, ATR72, F100, A320,       Basis: Sec.         Basis: Sec.         Basis: Sec.         Basis: Sec.
   A321, A318, A319, A300-600,     25.571.             25.571.             25.571.             25.571.
   A310, A340, A330, EMB 135,     --Amdt 25-45 and    --Amdt 25-45 and    --Amdt 25-45 and    --Amdt 25-45 and
   EMB 145, SAAB 340, SAAB 2000,   later amendments    later amendments    later amendments    later amendments
   CL-600, DHC-8, DO-328,          require damage      require damage      require damage      require damage
   BAE146, BAE Jetstream 4100.     tolerance (DT)      tolerance (DT)      tolerance (DT)      tolerance (DT)
                                   inspections.        inspections.        inspections.        inspections.

[[Page 20588]]

 
Pre 25-45
  727, 737-100/200..............  SID \47\ ADs......  Sec.   121.370      SID ADs...........  SID ADs.
                                                       (Repair
                                                       Assessment Rule)
                                                       and SID ADs.
Pre 25-45
  A300, 707, 720, 747, BAC 1-11,  SID ADs...........  Sec.   121.370....  121.370a..........  121.370a.
   F-28, L-1011, DC-8, DC-9, MD-
   80, DC-10.
Pre 25-45
  L-188, DHC-7..................  SID ADs...........  121.370a..........  121.370a..........  121.370a
Pre 25-45
  F27, L-382....................  DT data has been    121.370a..........  121.370a..........  121.370a.
                                   developed.
Pre 25-45
  737-300/400/500...............  A SID has been      Sec.   121.370....  121.370a..........  121.370a.
                                   developed.
                                  --AD is pending...
Pre 25-45
  737-600/700/800...............  A SID will be       Sec.   121.370....  121.370a..........  121.370a.
                                   developed.
                                  --An AD will need
                                   to be issued.
----------------------------------------------------------------------------------------------------------------

    In summation, this proposed rule would transfer the responsibility 
from the existing requirements for developing DT based inspections and 
procedures from part 121 operators to DAHs. This would result in a 
decrease of the societal cost of compliance because the DAHs, with 
their greater expertise and access to design data, are in the best 
position to identify fatigue critical structure and methods and 
frequency of inspections operators need to comply with the AASFR. DAHs 
can develop these data with greater efficiency than individual 
operators and these costs would be amortized over a larger fleet. This 
proposed rule would ensure that the required data are developed in a 
timely manner to minimize the possibility for disruption of airline 
operations when the AASFR compliance deadline is reached.
---------------------------------------------------------------------------

    \47\ Supplemental Inspection Document.
---------------------------------------------------------------------------

    The FAA has, therefore, determined this rulemaking action is not a 
``significant regulatory action'' as defined in section 3(f) of 
Executive Order 12866, and is not ``significant'' as defined in DOT's 
Regulatory Policies and Procedures. In addition, the FAA has determined 
that this rulemaking action: (1) Would not have a significant economic 
impact on a substantial number of small entities; (2) would not affect 
international trade; and (3) would not impose an unfunded mandate on 
state, local, or tribal governments, or on the private sector. We 
solicit comments regarding these findings.

Regulatory Flexibility Analysis

    The Regulatory Flexibility Act of 1980 (RFA) establishes ``as a 
principle of regulatory issuance that agencies shall endeavor, 
consistent with the objective of the rule and of applicable statutes, 
to fit regulatory and informational requirements to the scale of the 
business, organizations, and governmental jurisdictions subject to 
regulation.'' To achieve that principle, the RFA requires agencies to 
solicit and consider flexible regulatory proposals and to explain the 
rationale for their actions. The RFA covers a wide-range of small 
entities, including small businesses, not-for-profit organizations and 
small governmental jurisdictions.
    Agencies must perform a review to determine whether a proposed or 
final rule will have a significant economic impact on a substantial 
number of small entities. If the agency determines that it will, the 
agency must prepare a regulatory flexibility analysis as described in 
the Act.
    However, if an agency determines that a proposed or final rule is 
not expected to have a significant economic impact on a substantial 
number of small entities, section 605(b) of the 1980 RFA provides that 
the head of the agency may so certify and a regulatory flexibility 
analysis is not required. The FAA believes the proposed rule would not 
have a significant economic impact on a substantial number of small 
entities.
    The FAA recently adopted the Aging Airplane Safety final rule 
(AASFR),\48\ which, among other things, requires airline operators of 
certain large transport category airplanes \49\ to implement damage 
tolerance (DT) based inspections and procedures for airplane structure.
---------------------------------------------------------------------------

    \48\ 70 FR 5518, February 2, 2005.
    \49\ The rule applies to turbine powered airplane models with a 
maximum type certificated passenger capacity of 30 or more, or a 
maximum payload capacity of 7,500 pounds or more.
---------------------------------------------------------------------------

    This proposed rule is a counterpart to the AASFR. By the effective 
date of this proposal, DT inspection programs, required by this 
proposal, will already be required by AD, certification or operational 
regulations for all part 121 airplanes affected by this proposal. The 
proposed rule would transfer the requirement to develop AASFR DT based 
inspections and procedures from part 121 operators to design approval 
holders (DAHs). A significant number of part 121 operators are small 
entities. By transferring the responsibility from part 121 operators to 
DAHs, this proposal would relieve small-entity part 121 operators of 
what could be a significant cost.
    DAHs include manufacturers of part 25 airplanes and supplemental 
type certificate (STC) holders for repairs and alterations made to 
these airplanes.
    The current United States part 25 airplane manufacturers include: 
Boeing, Cessna Aircraft, Gulfstream Aerospace, Learjet (owned by 
Bombardier), Lockheed Martin, McDonnell Douglas (a wholly owned 
subsidiary of The Boeing Company), and Raytheon Aircraft. These 
manufacturers would incur Type Certificate (TC) and Amended TC costs. 
Because all U.S. transport-aircraft category manufacturers have more 
than 1,500 employees, none are considered small entities.
    STC holders include manufacturers and operators of part 25 
airplanes, some of which are small-entities. Since the

[[Page 20589]]

DAH requirements do not preclude them from seeking reasonable 
compensation from the operators for the proposal's required DT data and 
documents, small-entities STC holders, with less than 1,500 employees, 
should be able to recoup their costs.
    Therefore, the FAA certifies that this proposed rule would not have 
a significant economic impact on a substantial number of small 
entities. We request comments on this finding.

International Trade Impact Assessment

    The Trade Agreement Act of 1979 prohibits Federal agencies from 
establishing any standards or engaging in related activities that 
create unnecessary obstacles to the foreign commerce of the United 
States. Legitimate domestic objectives, such as safety, are not 
considered unnecessary obstacles. The statute also requires 
consideration of international standards and, where appropriate, that 
they be the basis for U.S. standards.
    The FAA has assessed the potential effect of this proposed rule and 
determined that it would impose the same costs on domestic and 
international entities and thus have a neutral trade impact.

Unfunded Mandate Assessment

    The Unfunded Mandate Reform Act of 1995 (the Act) is intended, 
among other things, to curb the practice of imposing unfunded Federal 
mandates on State, local, and tribal governments. Title II of the Act 
requires each Federal agency to prepare a written statement assessing 
the effects of any Federal mandate in a proposed or final agency rule 
that may result in an expenditure of $100 million or more (adjusted 
annually for inflation) in any one year by State, local, and tribal 
governments, in the aggregate, or by the private sector; such a mandate 
is deemed to be a ``significant regulatory action.'' The FAA currently 
uses an inflation-adjusted value of $120.7 million in lieu of $100 
million.
    This proposal does not contain such a mandate. The requirements of 
Title II do not apply.

List of Subjects

14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

14 CFR Part 121

    Air carriers, Aircraft, Airmen, Alcohol abuse, Aviation safety, 
Charter flights, Drug abuse, Drug testing, Reporting and recordkeeping 
requirements, Safety, Transportation.

14 CFR Part 129

    Air carriers, Aircraft, Aviation safety, Reporting and 
recordkeeping requirements, Security measures, Smoking.

XIV. The Proposed Amendments

    In consideration of the foregoing, the Federal Aviation 
Administration proposes to amend Chapter I of Title 14, Code of Federal 
Regulations part 25 as follows:

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

    1. The authority citation for part 25 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702 and 44704.

    2. Amend Sec.  25.1 by adding a new paragraph (c) to read as 
follows:


Sec.  25.1  Applicability.

* * * * *
    (c) This part also establishes requirements for holders of type 
certificates and supplemental type certificates to take actions 
necessary to support the continued airworthiness of transport category 
airplanes.
    3. Add a new section Sec.  25.3 to read as follows:


Sec.  25.3  Design approval holder requirements.

    Subpart I of this part contains requirements that apply to--
    (a) Holders of type certificates and supplemental type 
certificates; and
    (b) Applicants for type certificates and changes to those 
certificates.
    4. Amend part 25 by adding a new subpart I to read as follows:
Subpart I--Continued Airworthiness
Sec.
25.1801 Purpose and definition.

Supplemental Structural Inspections

25.1823 Holders of type certificates--Repairs.
25.1825 Holders of type certificates--Alterations and repairs to 
alterations.
25.1827 Holders of and applicants for a supplemental type 
certificate--Alterations and repairs to alterations.
25.1829 Compliance plan.

Subpart I--Continued Airworthiness


Sec.  25.1801  Purpose and definition.

    (a) This subpart establishes requirements for support of the 
continued airworthiness of transport category airplanes. These 
requirements may include performing assessments, developing design 
changes, developing revisions to Instructions for Continued 
Airworthiness, and making necessary documentation available to affected 
persons. This subpart applies to the following persons as specified in 
each section of this subpart:
    (1) Holders of type certificates and supplemental type 
certificates.
    (2) Applicants for type certificates and changes to those 
certificates (including services bulletins describing design changes). 
Applicants for changes to type certificates must comply with the 
requirements of this subpart in addition to the airworthiness 
requirements determined applicable under Sec.  21.101 of this 
subchapter.
    (b) For purposes of this subpart, the FAA Oversight Office is the 
aircraft certification office or office of the Transport Airplane 
Directorate with oversight responsibility for the relevant type 
certificate or supplemental type certificate, as determined by the 
Administrator.

Supplemental Structural Inspections


Sec.  25.1823  Holders of type certificates--Repairs.

    (a) Applicability. Except as specified in paragraph (h) of this 
section, this section applies to transport category, turbine powered 
airplane models with a type certificate issued after January 1, 1958, 
that as a result of original type certification or later increase in 
capacity have--
    (1) A maximum type certificated passenger seating capacity of 30 or 
more; or
    (2) A maximum payload capacity of 7,500 pounds or more.
    (b) Definitions. The following definitions apply to this section 
and Sec. Sec.  25.1825, 25.1827, and 25.1829 of this subpart:
    Affects means structure has been physically repaired, altered, or 
modified, or the structural loads acting on the structure have been 
increased or redistributed.
    Baseline structure means structure that is designed under the 
original type certificate or amended type certificate for that airplane 
model.
    Damage Tolerance Evaluation (DTE) means a process that leads to a 
determination of maintenance actions necessary to detect or preclude 
fatigue cracking that could contribute to a catastrophic failure. As 
applied to repairs and alterations, DTE includes the evaluation both of 
the repair or alteration and of the fatigue critical structure affected 
by the repair or alteration.
    Damage Tolerance Inspection (DTI) means inspections and other 
procedures developed as a result of a DTE. These include the location 
of the airplane

[[Page 20590]]

structure to be inspected, the inspection method, the threshold and 
interval associated with those inspections, and corrective maintenance 
actions. In some cases the corrective actions may include replacement 
of structure. If the DTE concludes that damage tolerance based 
supplemental structural inspections are not necessary for a repair or 
alteration that affects fatigue critical structure, the DTI would 
contain a statement to that effect.
    DT Data means DTE documentation and DTI.
    DT data implementation schedule consists of documentation that 
establishes the timing for accomplishing the necessary actions for 
developing DT data for repairs and alterations, and for incorporating 
those data into an operator's continuing airworthiness maintenance 
program.
    DTE documentation means data that identifies the evaluated fatigue 
critical structure, the basic assumptions applied in a DTE, and the 
results of a DTE.
    Fatigue critical structure means airplane structure that is 
susceptible to fatigue cracking that could contribute to a catastrophic 
failure, as determined in accordance with Sec.  25.571 of this part. 
Such structure may be part of the baseline structure or part of an 
alteration.
    Published repair data means generally applicable instructions for 
accomplishing repairs, such as those provided in structural repair 
manuals and service bulletins.
    (c) List of fatigue critical baseline structure. For airplanes 
specified in paragraph (a) of this section, the holder of a type 
certificate must:
    (1) Identify fatigue critical baseline structure for all airplane 
model variations and derivatives approved under the type certificate.
    (2) Develop and submit to the FAA Oversight Office for review and 
approval, a list of the structure identified in (c)(1) and, upon 
approval, make the list available to persons required to comply with 
Sec.  25.1827 of this part and Sec. Sec.  121.1109 and 129.109 of this 
chapter.
    (d) Existing and future published repair data. For repair data 
published by a holder of a type certificate that is current as of 
[effective date of the final rule] and for all later published repair 
data, the holder of a type certificate must:
    (1) Review the repair data, and identify each repair specified in 
the data that affects fatigue critical baseline structure identified in 
paragraph (c)(1).
    (2) Perform a DTE and develop DTI for each repair identified in 
paragraph (d)(1), unless previously accomplished.
    (3) Submit the DT data to the FAA Oversight Office or its properly 
authorized designees for review and approval.
    (4) Upon approval, make the DTI available to persons required to 
comply with Sec. Sec.  121.1109 and 129.109 of this chapter.
    (e) Future repair data not published. For repair data developed by 
a holder of a type certificate that is approved after [effective date 
of the final rule] and is not published, the type certificate holder 
must accomplish the following for repairs specified in the repair data 
that affect fatigue critical baseline structure:
    (1) Perform a DTE and develop DTI in accordance with the approved 
DT data implementation schedule developed for compliance with paragraph 
(f)(1)(iii) of this section.
    (2) Submit the DT data in accordance with the implementation 
schedule for review and approval by the FAA Oversight Office or its 
properly authorized designees.
    (3) Upon approval, make the approved DTI available to persons 
required to comply with Sec. Sec.  121.1109 and 129.109 of this 
chapter.
    (f) Repair Evaluation Guidelines. The holder of a type certificate 
for each airplane model subject to this section must--
    (1) Develop repair evaluation guidelines for operators' use that 
include--
    (i) A process for conducting surveys of affected airplanes that 
will enable identification and documentation of all existing repairs 
that affect fatigue critical baseline structure identified in paragraph 
(c)(1) of this section and Sec.  25.1825(b)(2) of this part;
    (ii) A process for establishing DT data for repairs identified in 
paragraph (f)(1)(i);
    (iii) A DT data implementation schedule for repairs covered by the 
repair evaluation guidelines.
    (2) Submit the repair evaluation guidelines to the FAA Oversight 
Office for review and approval. (3)Upon approval, make the guidelines 
available to persons required to comply with Sec.  25.1827 of this part 
and Sec. Sec.  121.1109 and 129.109 of this chapter.
    (4) If the guidelines direct the operator to obtain assistance from 
the holder of a type certificate, provide such assistance in accordance 
with the DT data implementation schedule.
    (g) Compliance times. Holders of type certificates must submit the 
following to the FAA Oversight Office or its properly authorized 
designees for review and approval by the specified compliance time:
    (1) The list of fatigue critical baseline structure required by 
paragraph (c)(2) of this section must be submitted no later than 90 
days after [the effective date of the rule].
    (2) For published repair data that is current as of [the effective 
date of the rule], the DT data required by paragraph (d)(3) of this 
section must be submitted by June 30, 2009.
    (3) For repair data published after [the effective date of the 
rule], the DT data required by paragraph (d)(3) of this section must be 
submitted before FAA approval of the repair data.
    (4) The repair evaluation guidelines required by paragraph (f)(1) 
of this section must be submitted by December 30, 2009.
    (h) Exceptions. The requirements of this section do not apply to 
the following ransport category airplane models:
    (1) Convair CV-240, 340, 440, if modified to include turbine 
engines.
    (2) Vickers Armstrong Viscount, TCDS No. A-814.
    (3) Douglas DC-3, if modified to include turbine engines, TCDS No. 
A-618.
    (4) Bombardier CL-44, TCDS No. 1A20.
    (5) Mitsubishi YS-11, TCDS No. A1PC.
    (6) British Aerospace BAC 1-11, TCDS No. A5EU.
    (7) Concorde, TCDS No. A45EU.
    (8) deHavilland D.H. 106 Comet 4C, TCDS No. 7A10.
    (9) VFW-Vereinigte Flugtechnische Werk VFW-614, TCDS No. A39EU.
    (10) Illyushin Aviation IL 96T, TCDS No. A54NM.
    (11) Bristol Aircraft Britannia 305, TCDS No. 7A2.
    (12) Handley Page Herald Type 300, TCDS No. A21N.
    (13) Avions Marcel Dassault--Breguet Aviation Mercure 100C, TCDS 
No. A40EU.
    (14) Airbus Caravelle, TCDS No. 7A6.


Sec.  25.1825  Holders of type certificates--Alterations and repairs to 
alterations.

    (a) Applicability. This section applies to transport category 
airplanes subject to Sec.  25.1823 of this part.
    (b) Fatigue critical alteration structure. For each existing 
alteration, developed by the holder of a type certificate, the holder 
of a type certificate must:
    (1) Review existing alteration data and identify all alterations 
that affect fatigue critical baseline structure identified in Sec.  
25.1823(c)(1) of this part.
    (2) For each alteration identified in paragraph (b)(1) of this 
section, identify any fatigue critical alteration structure.

[[Page 20591]]

    (3) Develop and submit to the FAA Oversight Office for review and 
approval a list of the structure identified in paragraph (b)(2) of this 
section.
    (4) Upon approval, make the list required in paragraph (b)(2) of 
this section available to persons required to comply with Sec. Sec.  
121.1109 and 129.109 of this chapter.
    (c) DT Data For Alterations. For each existing and future 
alteration developed by a holder of a type certificate, that affects 
fatigue critical baseline structure identified in Sec.  25.1823(c)(1) 
of this part, unless previously accomplished, the type certificate 
holder must:
    (1) Perform a DTE and develop DTI for the alteration.
    (2) Submit the DT data developed in accordance with paragraph 
(c)(1) of this section to the FAA Oversight Office or its properly 
authorized designees for review and approval.
    (3) Upon approval, make the DTI available to persons required to 
comply with Sec. Sec.  121.1109 and 129.109 of this chapter.
    (d) DT Data for Repairs Made to Alterations. For existing and 
future repair data developed by a holder of a type certificate, the 
type certificate holder must:
    (1) Review the repair data, and identify each repair that affects 
any fatigue critical alteration structure identified in paragraph 
(b)(2) of this section.
    (2) For each repair identified in (d)(1) of this section, unless 
previously accomplished, perform a DTE and develop DTI.
    (3) Submit the DT data developed in accordance with paragraph 
(d)(2) of this section to the FAA Oversight Office or its properly 
authorized designees for review and approval;
    (4) Upon approval, make the DTI available to persons required to 
comply with Sec. Sec.  121.1109 and 129.109 of this chapter.
    (e) Compliance times. Holders of type certificates must submit the 
following to the FAA Oversight Office or its properly authorized 
designees for review and approval by the specified compliance time:
    (1) The list of fatigue critical alteration structure required by 
paragraph (b)(2) of this section must be submitted no later than 90 
days after [the effective date of the rule].
    (2) For alteration data developed and approved before [the 
effective date of the rule], the DT data required by paragraph (c)(2) 
of this section must be submitted by June 30, 2009.
    (3) For alteration data approved on or after [the effective date of 
the rule], DT data required by paragraph (c)(2) of this section must be 
submitted before initial approval of the alteration data.
    (4) For repair data developed and approved before [the effective 
date of the rule], the DT data required by paragraph (d)(3) of this 
section must be submitted by June 30, 2009.
    (5) For repair data developed and approved after [the effective 
date of the rule], the DT data required by paragraph (d)(3) of this 
section, must be submitted within 12 months after initial approval of 
the repair data and before making the DT data available to persons 
required to comply with Sec. Sec.  121.1109 and 129.109 of this 
chapter.


Sec.  25.1827  Holders of and applicants for a supplemental type 
certificate--Alterations and repairs to alterations.

    (a) Applicability. This section applies to transport category 
airplanes subject to Sec.  25.1823 of this part.
    (b) Fatigue critical alteration structure. For each existing 
alteration developed by the holder of a supplemental type certificate, 
the STC holder must:
    (1) Review existing alteration data and identify all alterations 
that affect fatigue critical baseline structure identified in Sec.  
25.1823(c)(1) of this part.
    (2) For each alteration identified in paragraph (b)(1) of this 
section, identify any fatigue critical alteration structure.
    (3) Develop and submit to the FAA Oversight Office or its properly 
authorized designees for review and approval a list of the structure 
identified in paragraph (b)(2) of this section.
    (4) Upon approval, make the list required in paragraph (b)(2) of 
this section available to persons required to comply with Sec. Sec.  
121.1109 and 129.109 of this chapter.
    (c) DT Data for Alterations. For each existing and future 
alteration developed by the holder of a supplemental type certificate 
that affects fatigue critical baseline structure identified in Sec.  
25.1823(c)(1) of this part, unless previously accomplished, the holder 
of a supplemental type certificate must:
    (1) Perform a DTE and develop DTI for the alteration.
    (2) Submit the DT data developed in accordance with paragraph 
(c)(1) of this section to the FAA Oversight Office or its properly 
authorized designees for review and approval.
    (3) Upon approval, make the DTI available to persons required to 
comply with Sec. Sec.  121.1109 and 129.109 of this chapter.
    (d) DT data for repairs made to alterations. For existing and 
future repair data developed by a holder of a supplemental type 
certificate holder, the supplemental type certificate holder must:
    (1) Review the repair data, and identify each repair that affects 
any fatigue critical alteration structure identified in paragraph 
(b)(2) of this section.
    (2) For each repair identified in paragraph (d)(1) of this section, 
unless previously accomplished, perform a DTE and develop DTI.
    (3) Submit the DT data developed in accordance with paragraph 
(d)(2) of this section to the FAA Oversight Office or its properly 
authorized designees for review and approval;
    (4) Upon approval, make the DTI available to persons required to 
comply with Sec. Sec.  121.1109 and 129.109 of this chapter.
    (e) Compliance times. Holders of supplemental type certificates 
must submit the following to the FAA Oversight Office or its properly 
authorized designees for review and approval by the specified 
compliance time:
    (1) The list of fatigue critical alteration structure required by 
paragraph (b)(3) of this section must be submitted no later than 270 
days after [the effective date of the rule].
    (2) For alteration data developed and approved before [the 
effective date of the rule], the DT data required by paragraph (c)(2) 
of this section must be submitted by June 30, 2009.
    (3) For alteration data developed after [the effective date of the 
rule], the DT data required by paragraph (c)(2) of this section must be 
submitted before approval of the alteration data and before making it 
available to persons required to comply with Sec. Sec.  121.1109 and 
129.109 of this chapter.
    (4) For repair data developed and approved before [the effective 
date of the rule], the DT data required by paragraph (d)(3) of this 
section must be submitted by June 30, 2009.
    (5) For repair data developed and approved after [the effective 
date of the rule], the DT data required by paragraph (d)(3) of this 
section, must be submitted within 12 months after initial approval of 
the repair data and before making the DT data available to persons 
required to comply with Sec. Sec.  121.1109 and 129.109 of this 
chapter.


Sec.  25.1829  Compliance plan.

    (a) Compliance plan. Each person identified in Sec. Sec.  25.1823, 
25.1825, and 25.1827 of this subpart must submit a compliance plan 
consisting of the following:
    (1) A project schedule identifying all major milestones for meeting 
the compliance times specified in Sec. Sec.  25.1823(d) and (f), 
25.1825(c) and (d),

[[Page 20592]]

and 25.1827(c) and (d) of this subpart, as applicable.
    (2) A proposed means of compliance with Sec. Sec.  25.1823, 
25.1825, and 25.1827 of this subpart, as applicable.
    (3) If the proposed means of compliance differs from that described 
in FAA guidance, an explanation of how the alternative means of 
compliance will be shown to comply with Sec. Sec.  25.1823, 25.1825, 
and 25.1827 of this subpart.
    (4) A plan for submitting a draft of all compliance items required 
by this section for review by the FAA Oversight Office not less than 60 
days before the applicable compliance date.
    (5) A process for continually assessing service information related 
to structural fatigue damage.
    (b) Compliance dates for compliance plans. The following persons 
must submit the compliance plan described in paragraph (a) of this 
section to the FAA Oversight Office for approval on the following 
schedule--
    (1) For holders of type certificates, no later than 90 days after 
[the effective date of the rule].
    (2) For holders of supplemental type certificates no later than 180 
days after [the effective date of the rule].
    (3) For applicants for changes to type certificates no later than 
December 30, 2007 or 90 days after the date of application, whichever 
occurs later.
    (c) Compliance Plan Deficiencies. Each affected person must 
implement the compliance plan as approved in compliance with paragraph 
(a) of this section. If either paragraph (c)(1) or (2) of this section 
applies, the affected person must submit a corrected plan to the FAA 
oversight office and implement the corrected plan within 30 days after:
    (1) The FAA oversight office notifies the affected person of 
deficiencies in the proposed compliance plan and how to correct them; 
or
    (2) The FAA oversight office notifies the affected person of 
deficiencies in the person's implementation of the plan and how to 
correct them.

PART 121--OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL 
OPERATIONS

    5. The authority citation for part 121 continues to read:

    Authority: 49 U.S.C. 106(g), 40113, 40119, 41706, 44101, 44701-
44702, 44705, 44709-44711, 44713, 44716-44717, 44722, 44901, 44903-
44904, 44912, 45101-45105, 46105, 46301.

    6. Amend Sec.  121.1 by adding a new paragraph (g) to read as 
follows:
* * * * *
    (g) This part also establishes requirements for operators to take 
actions to support the continued airworthiness of each airplane.
    7. Amend part 121 by adding subpart AA, consisting of Sec. Sec.  
121.1101, 121.1103, 121.1111, 121.1113, and 121.1115, to read as 
follows:
Subpart AA--Continued Airworthiness and Safety Improvements
Sec.
121.1101 Purpose and definition.
121.1103 [Reserved]
121.1111 [Reserved]
121.1113 [Reserved]
121.1115 [Reserved]

Subpart AA--Continued Airworthiness and Safety Improvements


Sec.  121.1101  Purpose and definition.

    (a) This subpart requires persons holding an air carrier or 
operating certificate under part 119 of this chapter to support the 
continued airworthiness of each airplane. These requirements may 
include, but are not limited to, revising the maintenance program, 
incorporating design changes, and incorporating revisions to 
Instructions for Continued Airworthiness.
    (b) For purposes of this subpart, the ``FAA Oversight Office'' is 
the aircraft certification office or office of the Transport Airplane 
Directorate with oversight responsibility for the relevant type 
certificate or supplemental type certificate, as determined by the 
Administrator.


Sec.  121.1103  [Reserved]


Sec.  121.1111  [Reserved]


Sec.  121.1113  [Reserved]


Sec.  121.1115  [Reserved]


Sec.  121.368  [Redesignated]

    8. Redesignate Sec.  121.368 as Sec.  121.1105.


Sec.  121.368  [Added and Reserved]

    9. A new Sec.  121.368 is added and reserved.


Sec.  121.370  [Redesignated]

    10. Redesignate Sec.  121.370 as Sec.  121.1107.


Sec.  121.370  [Added and Reserved]

    11. A new Sec.  121.370 is added and reserved.


Sec.  121.370a  [Redesignated]

    12. Redesignate Sec.  121.370a as Sec.  121.1109.


Sec.  121.370a  [Added and Reserved]

    13. A new Sec.  121.370a is added and reserved.

PART 129--OPERATIONS: FOREIGN AIR CARRIERS AND FOREIGN OPERATORS OF 
U.S.-REGISTERED AIRCRAFT ENGAGED IN COMMON CARRIAGE

    14. The authority citation for part 129 continues to read as 
follows:

    Authority: 49 U.S.C. 1372, 49113, 440119, 44101, 44701-44702, 
447-5, 44709-44711, 44713, 44716-44717, 44722, 44901-44904, 44906, 
44912, 44105, Pub. L. 107-71 sec. 104.

    15. Amend Sec.  129.1 by revising paragraph (b), and adding a new 
paragraph (d) to read as follows:


Sec.  129.1  Applicability and definition.

* * * * *
    (b) Operations of U.S.-registered aircraft solely outside the 
United States. In addition to the operations specified under paragraph 
(a) of this section, Sec. Sec.  129.14 and 129.20 and subpart B of this 
part also apply to U.S.-registered aircraft operated solely outside the 
United States in common carriage by a foreign person or foreign air 
carrier.
* * * * *
    (d) This part also establishes requirements for an operator to take 
actions to support the continued airworthiness of each airplane.
* * * * *
    16. Amend part 129 by designating existing Sec. Sec.  129.1 through 
Sec.  129.33 as subpart A and by adding the heading to read as follows:

Subpart A--General

    17. Amend part 129 to adding subpart B to read as follows:
Subpart B--Continued Airworthiness and Safety Improvements
Sec.
129.101 Purpose and definition.
129.103-129.115 [Reserved]
129.117 [Reserved]

Subpart B--Continued Airworthiness and Safety Improvements


Sec.  129.101  Purpose and definition.

    (a) This subpart requires a foreign person or foreign air carrier 
operating a U.S.-registered airplane in common carriage to support the 
continued airworthiness of each airplane. These requirements may 
include, but are not limited to, revising the maintenance program, 
incorporating design changes, and incorporating revisions to 
Instructions for Continued Airworthiness.
    (b) For purposes of this subpart, the ``FAA Oversight Office'' is 
the aircraft certification office or office of the Transport Airplane 
Directorate with

[[Page 20593]]

oversight responsibility for the relevant type certificate or 
supplemental type certificate, as determined by the Administrator.


Sec.  129.103-129.115  [Reserved]


Sec.  129.117  [Reserved]

    18. Redesignate Sec.  129.16 as new Sec.  129.109.


Sec.  129.16  [Added and Reserved]

    19. A new Sec.  129.16 is added and reserved.


Sec.  129.32  [Redesignated]

    20. Redesignate Sec.  129.32 as new Sec.  129.107.


Sec.  129.32  [Added and Reserved]

    21. A new Sec.  129.32 is added and reserved.


Sec.  129.33  [Redesignated]

    22. Redesignate Sec.  129.33 as new Sec.  129.105.


Sec.  129.33  [Added and Reserved]

    23. A new Sec.  129.33 is added and reserved.

    Issued in Washington, DC, on April 13, 2006.
James J. Ballough,
Director, Flight Standards Service, Aviation Safety.
Dorenda D. Baker,
Acting Director, Aircraft Certification Service, Aviation Safety.
[FR Doc. 06-3758 Filed 4-20-06; 8:45 am]
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