**\[4910-13\]**

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Parts 26, 121, 129**

**Docket No. FAA-2005-21693; Amendment Nos. 26-1, 121-337, 129-44**

**RIN 2120-AI32**

## Damage Tolerance Data for Repairs and Alterations

**AGENCY:** Federal Aviation Administration (FAA), DOT.

**ACTION:** Final rule.

**SUMMARY:** This final rule requires holders of design approvals to
make available to operators damage tolerance data for repairs and
alterations to fatigue critical airplane structure. This rule will
support operator compliance with the Aging Airplane Safety final rule
with respect to the requirement to incorporate into the maintenance
program, a means for addressing the adverse effects repairs and
alterations may have on fatigue critical structure. The intent of this
final rule 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:** These amendments become effective \[insert date 30 days after
date of publication in the [Federal Register]{.underline}\].

**FOR FURTHER INFORMATION CONTACT:** If you have technical questions
about this action, contact Greg Schneider, ANM-115, Airframe and Cabin
Safety, Federal Aviation Administration, 1601 Lind Avenue SW, Renton
Washington, 98057-3356, telephone: (425-227-2116); facsimile
(425-227-1232); e-mail <greg.schneider@faa.gov>. Direct any legal
questions to Doug Anderson, ANM-7, Office of Regional Counsel, Federal
Aviation Administration, 1601 Lind Avenue SW, Renton, WA 98057-3356;
telephone (425) 227-2166; facsimile (425) 227-1007; e-mail
Douglas.Anderson@faa.gov.

**SUPPLEMENTARY INFORMATION**:

**Authority for this Rulemaking**

The FAA's authority to issue rules regarding aviation safety is found in
Title 49 of the United States Code. Subtitle I, Section 106 describes
the authority of the FAA Administrator. Subtitle VII, Aviation Programs,
describes in more detail the scope of the agency's authority.

This rulemaking is promulgated under the authority described in Subtitle
VII, Part A, Subpart III, Section 44701, "General requirements." Under
that section, the FAA is charged with promoting safe flight of civil
aircraft in air commerce by prescribing minimum standards required in
the interest of safety for the design and performance of aircraft;
regulations and minimum standards in the interest of safety for
inspecting, servicing, and overhauling aircraft; and regulations for
other practices, methods, and procedures the Administrator finds
necessary for safety in air commerce. This regulation is within the
scope of that authority because it prescribes---

-   New safety standards for the design of transport category airplanes,
    and

-   New requirements necessary for safety for the design, production,
    operation, and maintenance of those airplanes, and for other
    practices, methods, and procedures relating to those airplanes.

**Table of Contents**

I. Executive Summary

II\. Background

A.  Summary of the NPRM

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1.  The Proposed Rule

2.  Related Activities

B. Differences Between the NPRM and the Final Rule

1\. New Part 26 for Design Approval Holders' Airworthiness Requirements

2\. New Subparts for Airworthiness Operational Rules

3\. Minor Conforming Changes to the Aging Airplane Safety Final Rule

4\. Other Miscellaneous Changes

C. Summary of Comments

III\. Discussion of the Final Rule

A.  Overview

> 1\. Final Rule
>
> 2\. Guidance Material

B.  Airplane Applicability and Exceptions

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1.  Airplane Certification Amendment Level

2.  Parts 91, 125, and 135 Operations

3.  Exception of Airplanes not Operating in the U.S. Under Part 121 or
    129

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C.  Fatigue Critical Structure (FCS)

D.  Damage Tolerance Evaluation (DTE)

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E.  Damage Tolerance Inspections (DTIs)

F.  DT Data for Repairs

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1.  Published Repair Data

2.  Effects of Multiple Repairs

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G.  Repair Evaluation Guidelines (REGs)

H.  DT Data for Alterations

I.  Required Documentation

J.  Proprietary Data

K.  Compliance Plan

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1.  Process for Continuous Assessment of Service Information

2.  Timing of FAA Approval

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L.  Harmonization

> 1\. Foreign Authority Approval of Required Data

M.  Enforcement

N.  Industry and FAA Resources

O.  Compliance Dates

P.  Costs and Benefits

### IV. Final Regulatory Evaluation, Regulatory Flexibility Determination, International Trade Impact Assessment, and Unfunded Mandates Assessment

V. 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.

While these programs have been largely 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.[^2] This omission 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 had occurred in
the baseline structure.

The FAA adopted the Aging Airplane Safety final rule (AASFR)[^3] in
early 2005. Among other things, the AASFR requires airline operators of
certain large transport category airplanes[^4] 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 final rule, we refer to this structure as "fatigue
critical structure." Most importantly for this rule, the AASFR requires
these inspection programs to "take into account the adverse effects
repairs, alterations, and modifications may have on fatigue cracking and
the inspection of this airplane structure."

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, it is 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, this final rule requires DAHs
to develop and make available to operators the data and documents they
need to support compliance with the DT requirements of the AASFR.

Specifically, this final rule requires DAHs to develop and make
available the following four types of documents to operators:

(1) Lists of fatigue critical structure (to aid operators in identifying
    repairs and alterations that need to be addressed for DT).

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(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]

    -   TC holder's future repair data not published for general
        use.[^7]

    -   Repair data developed by supplemental type certificate (STC)
        holders.

    -   Alteration data developed by TC and STC holders.

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(3) Damage tolerance evaluation guidelines for all other repairs (to
    enable operators to obtain 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 the
    operator's maintenance program).

This final rule transfers the responsibility for developing DT-based
data from operators to DAHs and, therefore, has minimal to no societal
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**

**A. Summary of the NPRM**

**1. The Proposed Rule**

On April 21, 2006, the FAA published in the [Federal
Register]{.underline} the Notice of proposed rulemaking (NPRM) entitled,
Damage Tolerance Data for Repairs and Alterations (DAH DT Data
NPRM),[^8] which is the basis of this final rule.

In the DAH DT Data NPRM, the FAA proposed to require DAHs to develop and
make available to operators certain damage tolerance (DT) data that
address the adverse effects repairs, alterations, and modifications may
have on fatigue critical structure. These data are necessary to support
operator compliance with the Aging Airplane Safety Final Rule
(AASFR).[^9] Specifically, we proposed to require DAHs to develop and
make available to operators the following: (1) Lists of fatigue critical
structure for baseline and alteration structure; (2) Damage tolerance
inspections (DTIs) for existing published repair and alteration data;
(3) DTIs for future repair and alteration data; (4) Repair evaluation
guidelines (REGs) that include a process for conducting airplane
surveys, a process for establishing DT Data, and implementation
schedules for the above actions. In addition, we proposed to require
DAHs to develop a compliance plan for meeting these four requirements
and to obtain FAA approval of the plan.

The NPRM contains the background and rationale for this rulemaking and,
except where we have made revisions in this final rule, you should refer
to it for that information.

**2.** **Related Activities**

In July 2004, we published the Fuel Tank Safety Compliance Extension
(Final Rule) and Aging Airplane Program Update (Request for
Comments),[^10] where we informed the public of our intent to propose
DAH airworthiness requirements to support certain operational rules. We
requested comments on our proposal.

In December 2002, we published the Aging Airplane Safety Interim final
rule; request for comments.[^11] In February 2005, we adopted the AASFR
in which we responded to the comments from the interim rule and made
some changes to that rule. The February 2005 AASFR requires affected
operators to include certain damage tolerance inspections and procedures
in their maintenance programs by December 20, 2010. Today's final rule
is directly related to the AASFR in that it provides a means for
operators to get the data and documents they need to comply with the
AASFR.

In July 2005, we published a disposition of comments document,[^12] in
which we responded to comments to the July 2004 action. Also in July
2005, we published a policy statement, Safety -- A Shared Responsibility
-- New Direction for Addressing Airworthiness Issues for Transport
Airplanes,[^13] that explains our criteria for adopting DAH requirements
like those described in this final rule.

On April 21, 2006,[^14] along with the NPRM for this rulemaking, we
published a Notice of availability (NOA) and request for comments on
draft AC 120-XX[^15] (Damage Tolerance Inspections for Repairs). This AC
included guidance related to repairs, which the Aviation Rulemaking
Advisory Committee's (ARAC) Airworthiness Assurance Working Group
(AAWG)[^16] developed.

On July 7, 2006, we published a notice[^17] that granted industry a
90-day extension to comment on the NPRM; and on February 27, 2007, we
published a NOA[^18] and request for comments on revised AC 120-XX,[^19]
which includes guidance from the AAWG on both repairs and alterations.

**B. Differences Between the NPRM and the Final Rule**

**1. New Part 26 for Design Approval Holders' Airworthiness
Requirements**

In the NPRM (and other Aging Airplane Program rules), we placed the DAH
airworthiness requirements in part 25, subpart I. As we explained in the
recently adopted Enhanced Airworthiness Program for Airplane
Systems/Fuel Tank Safety final rule (EAPAS/FTS),[^20] we have placed
these requirements in new part 26, and we have moved the enabling
regulations into part 21.[^21] We determined that this was the best
course of action because it keeps part 25 as strictly airworthiness
standards for transport category airplanes, thus maintaining
harmonization and compatibility among the United States, Canada, and the
European Union regulatory systems. Providing references to part 26 in
part 21 clarifies how the part 26 requirements will address existing and
future design approvals.

In creating new part 26, we renumbered the proposed sections of part 25,
subpart I and we incorporated the changes discussed in this preamble. A
table of this renumbering is shown below.

**Table 1**

**Relationship of Proposed Part 25 Subpart I to Part 26 Final Rules**

  ----------------------------------- -----------------------------------
  **Part 26 Final Rules**             **Proposed Part 25**

  Subpart E--- Aging Airplane         **Subpart I---Continued
  Safety---Damage Tolerance Data for  Airworthiness**
  Repairs and Alterations             

  § 26.5 Applicability table          New[^22]

  § 26.41 Definitions                 New[^23]

  § 26.43 Holders of and applicants   § 25.1823 Holders of type
  for type certificates---Repairs     certificates---Repairs

  § 26.45 Holders of type             § 25.1825 Holders of type
  certificates---Alterations and      certificates---Alterations and
  repairs to alterations              repairs to alterations

  § 26.47 Holders of and applicants   § 25.1827 Holders of and applicants
  for a supplemental type             for a supplemental type
  certificate---Alterations and       certificate---Alterations and
  repairs to alterations              repairs to alterations

  § 26.49 Compliance Plan             § 25.1829 Compliance Plan
  ----------------------------------- -----------------------------------

**2. New Subparts for Airworthiness Operational Rules**

We discussed in the preamble to the proposed rule that we would
establish new subparts for airworthiness-related operational rules.
Since there were several other aging airplane proposals (e.g., EAPAS)
published around the same time, each proposal contained language that
established the new subparts and redesignated certain sections of those
rules. We said when any one of those proposals became a final rule, we
would remove the duplicative provisions that established the new
subparts and redesignated sections from the other aging airplane rules.
In the DAH DT Data proposal, we included regulatory text to add subparts
AA and B (Continued Airworthiness and Safety Improvements) to include
the airworthiness requirements from parts 121 and 129, respectively. We
also included regulatory language to redesignate the section numbers in
parts 121 and 129 that were moved to the new subparts. However, since
the EAPAS final rule was the first to be codified, that final rule
adopted subparts AA and B and redesignated appropriate sections of parts
121 and 129. Therefore, we have removed the duplicative regulatory text
from this final rule.

To aid understanding of our discussion about the DAH DT Data rule as it
relates to the AASFR, we have indicated below the prior and redesignated
sections of parts 121 and 129 of the AASFR that include DT-related
requirements.

[Prior Sections]{.underline} [Redesignated Sections]{.underline}

§ 121.370a § 121.1109

§ 129.16 § 129.109

**3. Minor Conforming Changes to the Aging Airplane Safety Final Rule**

During the rulemaking process for the DAH DT Data rule, the FAA
determined that minor changes to the AASFR were needed to ensure clarity
of the two rules. The original wording in §§ 121.370a and 129.16
(redesignated as §§ 121.1109 and 129.109, respectively) required that
changes to the certificate holder's maintenance program (i.e., inclusion
of DT-based inspections and procedures and any revisions to them) be
approved by the Aircraft Certification Office (ACO)[^24] or office of
the Transport Airplane Directorate with oversight responsibility for the
relevant type certificate or supplemental type certificate, as
determined by the Administrator.

Although the ACO will approve the documentation that the DAH DT Data
final rule requires DAHs to submit to the FAA, the DT inspections and
procedures resulting from this documentation, which certificate holders
must incorporate into their maintenance programs, should be approved by
their Principal Maintenance Inspector (PMI). Therefore, we revised §§
121.1109 and 129.109 to state that it is the PMI's responsibility to
review and approve changes to a certificate holder's maintenance
program.

Also, we believe the requirements in current §§ 121.1109(c)(1) and
129.109(b)(1) that address DT relative to baseline structure and
repairs, alterations, and modifications would be clearer if they were in
separate paragraphs. Therefore, we revised §§ 121.1109 and 129.109 to
include requirements related to baseline structure in § 121.1109(c)(1)
and § 129.109(b)(1) and those related to repairs, alterations, and
modifications in § 121.1109(c)(2) and § 129.109(b)(2). We also made
minor wording changes for clarity and consistency with the new part 26
requirements and Advisory Circular (AC) 120-XX,[^25] which describes an
acceptable means of compliance with the DAH DT Data final rule.

**4. Other Miscellaneous Changes**

Based on comments to the proposed rule, we have revised the final rule
as summarized below and discussed in more detail under the Discussion of
the Final Rule heading.

We extended the compliance times for DAHs to develop the required lists
of fatigue critical structure. For TC holders, we extended the
compliance date for them to submit their lists of fatigue critical
baseline structure to the FAA Oversight Office for review and approval
from 90 to 180 days after the effective date of the final rule. We also
added a provision that makes it clear to future TC holders that the
lists of fatigue critical baseline structure must be submitted as part
of the type certification process.

In the NPRM, we proposed TC holders submit their lists of fatigue
critical alteration structure to the FAA Oversight Office for review and
approval 90 days after the effective date of the final rule. We proposed
270 days for STC holders. In the final rule, we extended the compliance
date to 360 days after the effective date of the final rule for both TC
holders and STC holders to submit these lists.

The NPRM included a requirement for TC and STC holders to develop a
process to enable operators to "establish" damage tolerance inspections
(DTIs) for repairs and alterations to fatigue critical baseline
structure (FCBS). This final rule replaces the term "establish" with
"obtain." We made this change because the term "obtain" better reflects
the intent of the rule and is meant to be all inclusive. That is, the
operator may "obtain" a DTI by establishing it themselves, or by
receiving the DTI directly from a TC holder, STC holder, or a third
party.

Section 25.1823(f)(1)(iii) (adopted as § 26.43(e)(1)(iii)) proposed an
implementation schedule for repairs covered by the repair evaluation
guidelines (REGs). To clarify this proposed requirement, we revised it
in the final rule to specify that the implementation schedule must
identify the times when actions must be taken as specific numbers of
flight cycles, flight hours, or both.

We revised proposed § 25.1823(f)(3) (adopted as § 26.43(e)(3)) to remove
the reference to § 25.1827. That reference would have required TC
holders to make their REGs available to STC holders. We made this change
because TC holders do not need to provide REGs to STC holders. However,
they must provide their lists of fatigue critical structure (FCS) to STC
holders.

As discussed in more detail later in this preamble, based on comments
submitted to other DAH airworthiness rules, we removed some provisions
of the compliance plan in proposed § 25.1829 (adopted as § 26.49).
Specifically, we removed the proposed requirements in § 25.1829(a)(3)
for DAHs to identify the intended means of compliance that differ from
those described in FAA advisory materials. Similarly, we removed the
requirement in proposed § 25.1829(c) that would have authorized the FAA
Oversight Office to identify deficiencies in a compliance plan or the
DAH's implementation of the plan and to require specified corrective
actions to remedy those deficiencies. We do not believe removal of these
requirements will adversely affect our ability to facilitate DAH
compliance.

In § 25.1829(5), we proposed a requirement for including in the
compliance plan a process for continuous assessment of service
information related to structural fatigue damage. As discussed later in
this preamble, we have determined that existing regulations should
enable us to determine whether the objectives of this DAH DT Data final
rule are being met. Therefore, we have removed this provision from this
final rule.

In addition to the changes discussed above, we made minor changes to
clarify the definitions of damage tolerance inspections and published
repair data in proposed § 25.1823 (the definitions are now in § 26.41).
We also made other minor changes to clarify the requirements in proposed
§§ 25.1823 (adopted as § 26.43), 25.1825 (adopted as § 26.45), 25.1827
(adopted as § 26.47), and 25.1829 (adopted as § 26.49).

**C. Summary of Comments**

The FAA received multiple comments from 17 commenters, including the Air
Transport Association (ATA) and a collective group of certain industry
representatives who are members of the AAWG.[^26] In the following
discussion of the comments received to the proposed rule, we will refer
to the comments received from those industry representatives of the AAWG
as the "AAWG industry representatives." Also, several of the AAWG and
the ATA member organizations sent separate comments on behalf of their
organizations, with some specifically expressing support for the
comments submitted by the AAWG industry representatives and the ATA. The
comments to the proposed rule covered an array of topics and contained a
range of responses, which we discuss more fully below under the
Discussion of the Final Rule heading. In general, commenters supported
the intent of the rule and the guidance material. They also requested
some changes and clarifications.

Many of the comments to the proposed rule concerned issues specific to
the Widespread Fatigue Damage (WFD)[^27] proposal. The FAA intends to
address the WFD-related comments in a separate action, so we will not
address them here.

We also received several comments about the DAH airworthiness
requirements. We addressed many of the same or similar comments and
issues in the July 2005 disposition of comments document to the Fuel
Tank Safety Compliance Extension (Final Rule) and Aging Airplane Program
Update (Request for Comments). In addition, we explained in detail the
need for these requirements in our July 2005 policy statement. As a
result, we will not revisit those comments and issues here.

**III. Discussion of the Final Rule**

**A. Overview**

**1. Final Rule**

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 the adoption of Amendment
25-45[^28] in 1978, the FAA has required new types of airplanes to meet
damage tolerance (DT) requirements to ensure their continued
airworthiness. Industry has also used this method successfully to
develop inspection programs for older airplanes, such as Supplemental
Structural Inspection Programs (SSIP). Since the 1980s, the FAA has
mandated that operators of most large transport airplanes carry out
these programs.

Although these programs have been effective for baseline structure (the
airplane structure as originally manufactured), industry has not
comprehensively implemented DT methods for repairs and alterations. For
airplanes certified to Amendment 25-45 and later, repairs and
alterations were not always evaluated for damage tolerance. This
omission 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 had occurred in the baseline structure.

The AASFR requires airline operators of certain large transport category
airplanes[^29] to implement DT-based inspection programs for airplane
structure; that is, structure susceptible to fatigue cracking that could
contribute to a catastrophic failure. In today's DAH DT Data final rule,
we refer to this structure as "fatigue critical structure." Most
importantly for today's DAH DT Data final rule, the AASFR requires the
maintenance program for the airplane include a means to address the
adverse effects repairs and alterations may have on airplane structure.

With the AASFR, we now have in place the regulatory means to provide for
comprehensive implementation of DT methods on all large transport
category airplanes used by air carriers operating under 14 CFR parts 121
and 129. To carry out these requirements fully, however, we must 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 owner of
the design data for these airplanes, the DAH is in the best position to
identify the fatigue critical structure and the methods and frequency of
inspections that may be needed.

As indicated in our July 2005 policy statement about the shared
responsibility for addressing airworthiness issues, in cases where
operators must rely on data or documents from DAHs to comply with
operational rules, we will require DAHs to develop that information by a
specified date. This final rule includes such requirements.

Specifically, 14 CFR 26.43, 26.45, and 26.47 require that the TC holders
and STC holders develop certain information that will provide a means
for operators to address the adverse effects of repairs and alterations.
The information required by this final rule includes the following:

-   List of Fatigue Critical Structure (baseline and alteration).

-   Damage tolerance inspections (DTIs) for existing published repair
    data and all future repair data.

-   DTIs for all existing and future alteration data.

-   Repair evaluation guidelines (REGs), which include---

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-   Instructions for conducting airplane surveys;

-   Instructions an operator uses to obtain DTIs; and

-   An implementation schedule that provides timing for the above
    actions.

**2. Guidance Material**

The FAA has issued Advisory Circular (AC) 120-93, Damage Tolerance of
Repairs and Alterations, concurrently with this rule. The AC provides TC
and STC holders with an acceptable method of compliance with this final
rule. The AC, which was developed through a collaborative effort between
the FAA and the Aviation Rulemaking Advisory Committee (ARAC), supports
operator compliance with the AASFR with respect to repairs and
alterations.

As amended by this final rule, § 121.1109(c)(2) of the AASFR requires
operators to incorporate into their maintenance program a "means" for
addressing the adverse effects that repairs and alterations may have on
fatigue critical structure. This AC provides guidance that TC holders,
STC holders, and operators can use in developing a means for addressing
repairs and alterations.

To facilitate operators' timely compliance with the AASFR for repairs,
the guidance material in this AC includes implementation schedules that
specify acceptable time frames for when operators can incorporate
required DT data into their maintenance programs. The implementation
schedules allow for a phased-in program where existing repairs on the
older and higher utilization airplanes are assessed first, and the newer
airplanes assessed as they approach their Design Service Goal (DSG).
This approach ensures that DTIs will be available when needed for both
older and newer airplanes.

**B. Airplane Applicability and Exceptions**

This rule applies to transport category, turbine powered airplane models
with an original TC issued after January 1, 1958. With certain
exceptions, this rule applies 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. The final rule differs from
the proposal in that we revised the list of excepted airplanes to
include the Lockheed L-300, deHavilland DHC-7, and Boeing 707/720
airplanes. We included these airplanes on the excepted list because they
are not currently being operated in commercial service in the U.S., and
we do not expect they will be in the future.

1.  **Airplane Certification Amendment Level**

Airbus and United Parcel Service (UPS) expressed concern that the
requirements of this rule duplicate certain requirements of current
regulations.

Airbus said because newer airplanes like the A330/A340 and A380 have a
state-of-the-art damage tolerance assessment for all activities related
to baseline structure, repairs, and alterations, the TC holder's
activities under proposed §§ 25.1823(d) and (e) and 25.1825(c) and (d)
would be \"senseless.\" It said applying the proposed requirements to
its newer model airplanes would offer no additional safety benefit
because they are already inherent in the consistent application of the
damage tolerance requirements in § 25.571. It also said the proposed
activities for these airplane models would create an unnecessary
administrative burden and would require re-approval of already
DT-justified modifications and repairs. Airbus asked the FAA to
reconsider applying proposed §§ 25.1823 and 25.1825 to TC holders as
they relate to airplane models A330/A340/A380 and future Airbus models.
It suggested addressing this issue under proposed § 25.1829 in the
model-specific compliance plans.

UPS said if the proposed rule is adopted, it would force operators to
survey every airplane in their fleet to find repairs and then evaluate
them based on guidelines produced by TC holders. UPS believes airplanes
certified to comply with Amendment 25-54 or later already have DT data
developed for fatigue critical structure, which includes certain
baseline structure, as well as all repairs and alterations. UPS
suggested the FAA make the proposed surveys applicable only to airplanes
certified prior to Amendment 25-54. To accomplish this, it said, the FAA
should revise proposed § 25.1823 (a) to limit the applicability to
airplanes type certified to pre-Amendment 25-54 requirements.

As discussed in the NPRM, the FAA has identified several airplane models
certified to Amendment 25-45 or later (including airplane models
certified to Amendment 25-54) for which published repair data have not
been evaluated for DT. Therefore, unless accomplished previously, a
damage tolerance evaluation (DTE) needs to be accomplished for all
airplanes, regardless of the certification level. For those airplanes
certified to Amendment 25-45 or later that have had a DTE completed for
all published repair and alteration data, the compliance plan required
by § 26.49 (proposed as § 25.1829) should contain a statement to that
effect, and the TC holder will need to substantiate this statement with
previously approved data from their certification effort to show
compliance with this rule. TC holders who have already substantiated
compliance with DT requirements should not find compliance with this
rule burdensome.

Regarding UPS's comment, if the TC holder can substantiate compliance
for its repairs and alterations, it is still likely that operators have
installed repairs and alterations that were not designed by the TC
holder on many airplanes. It is also likely that many of these repairs
and alterations were not assessed for damage tolerance. Therefore, a
survey will still be necessary to identify those repairs and alterations
and to determine if DT data are available to support operator compliance
with the AASFR.

Bombardier noted that the proposed rule would apply only to DAHs for
airplanes currently operated under parts 121 or 129. It said this would
not change the requirement to maintain damage tolerance for all
airplanes originally certified as damage tolerant under § 25.571
(Amendment 45 or later). It said it presumes these airplanes will
continue to be regulated under § 25.1529, using AC 25.1529-1 as guidance
(and under Canadian Air Regulations & Airworthiness Manual 511.34 for
Canadian DAHs). Bombardier asserted that the four DAH deliverables
required by proposed § 25.1823 (lists of fatigue critical baseline
structure, damage tolerance inspections, damage tolerance evaluation
guidelines, and implementation schedules) are already required under §
25.1529 (with guidance provided in AC 25.1529-1) and could constitute
compliance with the proposed rule.

We agree that TC holders and others designing repairs and alterations
for airplanes certificated to Amendment 25-45 or later amendments will
continue to be required to comply with § 25.1529, regardless of the
types of operations conducted. For airplanes subject to this DAH DT Data
rule, DAHs and operators should use the guidance in AC 120-93 instead of
AC 25.1529-1 for repairs. Because this rule is entirely consistent with
§§ 25.571 and 25.1529, DTIs that comply with this rule will also comply
with those sections. To the extent such data have been developed
previously, their compliance will be simplified.

**2. Parts 91, 125, and 135 Operations**

Transport Canada and Mr. Thomas A. Knott expressed concern that the
proposed rule only applies to airplanes operated under parts 121 and
129. Mr. Knott also stated that it leaves out airplanes operated under
parts 91, 125, and 135. Transport Canada expressed concern that the DAH
DT Data proposal and the AASFR do not apply to airplanes operated under
part 125 and would allow airplanes such as the B727 and B747 to operate
as passenger-carrying airplanes under part 125 without having to meet DT
or the aging airplane safety requirements.

As we discussed earlier in this preamble, the purpose of this rule is to
support parts 121 and 129 operators' compliance with the AASFR. For the
reasons discussed in the preamble to the AASFR, we limited applicability
of the DT requirements (supplemental inspections) in that rule to
certain large transport airplanes that are typically operated under
parts 121 or 129. For the affected airplanes that are operated under
parts 91, 125, or 135, their utilization is much lower and the risks
associated with fatigue damage that the AASFR is intended to address is,
therefore, also much lower. Because of this, we determined it would not
be cost-effective to impose the AASFR's supplemental inspection
requirements on parts 91, 125, or 135 operators.

**3. Exception of Airplanes not Operating in the U.S. Under Part 121 or
129**

Viking Air Limited said it owns seven de Havilland heritage aircraft,
including the DHC-5 Buffalo and DHC-7. Viking Air Limited said there are
about 23 DHC-5s in confirmed operation, and the DHC-7 has about 66 in
confirmed operation. Many of those in confirmed operation are used in
military operations and are not subject to part 121 or 129. According to
the FAA Registry, no DHC-5 aircraft are presently registered in the U.S.
Therefore, Viking proposed that the DHC-5 be added as an exception under
proposed § 25.1823(h). Viking Air Limited also said that for the DHC-7,
there presently are the following safety measures in place: Canadian
Airworthiness Directive CF-94-19R1 that mandates a Supplemental
Inspection Program; CF- 2005-36 that imposes a Structural Life Limit;
and CF-98-03 that mandates the Corrosion Prevention and Control Program.
With these actions, the DHC-7, the commenter stated, has already met the
intentions of aging aircraft initiative for structures.

The FAA researched its data bases and found that the DHC-5 does not have
a type certificate issued by the U. S. Therefore, there is no need for
an exception for the DHC-5 Buffalo. Furthermore, we have determined that
there are no DHC-7 airplanes currently operated under part 121 or
U.S.-registered DHC-7 airplanes operated under part 129. For the reasons
discussed earlier in this preamble, we added the DHC-7, as well as the
Lockheed L-300 and the Boeing 707/720, to the list of excepted airplanes
in § 26.43(g) of this final rule.

**C. Fatigue Critical Structure (FCS)**

This final rule requires TC and STC holders to evaluate their designs
for baseline and alteration structure to identify FCS. They must also
develop lists of FCS and make the lists available to operators.

This final rule defines fatigue critical structure as airplane structure
that is susceptible to fatigue cracking that could contribute to a
catastrophic failure, as determined under § 25.571. This is structure
that may need special maintenance actions to manage the threat of
fatigue. This would be the case for structure that has the potential to
develop fatigue cracks that, without intervention, could lead to a
catastrophic failure. The fatigue evaluations are performed to determine
if special actions are needed and if so, to provide the data needed to
define the maintenance action requirements. Fatigue critical structure
may be part of the baseline structure or part of an alteration to the
baseline structure. As explained in the NPRM,[^30] by referencing §
25.571 in the sentence noted below, we intended to rely on the many
precedents established in finding compliance with this section.

> Because of industry's extensive experience in showing compliance with
> the damage tolerance requirements of § 25.571, these key terms \[e.g.,
> fatigue critical structure\] should be readily understood and applied.

To clarify how the criteria of § 25.571 apply within the context of this
rule, we revised the definition of "fatigue critical structure" by
adding the following language: "Fatigue critical structure includes
structure, which, if repaired or altered, could be susceptible to
fatigue cracking and contribute to a catastrophic failure."

Airbus, the ATA, and UPS, asked for a more detailed definition of
fatigue critical structure. They expressed concern that, as proposed,
the definition is open to varying interpretations, so it may not be
applied consistently across industry or across different airplane
models. UPS added that some STC holders do not have experience in
complying with § 25.571. It asserted, the definition must be clear so
that it can be interpreted and applied in the same manner across the
industry.

The ATA and UPS said the methodology for identifying fatigue critical
structure should include quantitative criteria for assessing the
criticality of structural elements, based on a comparison of their
operational loads to their design limit loads or ultimate loads; and it
should account for load type and single- and multiple-load paths. Also,
the ATA said, the methodology should define what "could contribute"
means as stated in the definition of fatigue critical structure. It
recommended possibly using criteria similar to that in § 25.1309 to
clarify the definition.

The term "fatigue critical structure," as explained in the proposed
rule, is intended to identify the same kind of structure for which
applicants must perform fatigue evaluations to comply with §
25.571.[^31] These evaluations have been required for new type
certificates since the adoption of Amendment 25-45 in 1978.
Furthermore,\
AC 25-571-1C, published in 1998, provides many examples of the types of
structural elements that should be evaluated. Therefore, we believe
there is little, if any, room for differing interpretations of this
term.

We believe many of the commenters' concerns result from differences in
the way industry has used the term "principal structural elements"
(PSEs). This term, as used in § 25.571 and AC 25.571, is synonymous with
the term "fatigue critical structure." That is, a PSE is structure that
needs to be evaluated to determine if special maintenance actions are
needed to manage fatigue. And if such actions are needed, they must be
defined. The meaning of PSE in § 25.571 contrasts significantly with its
usage in certain industry practices that have evolved over the years.

For some TC and STC holders, a PSE is considered to be a specific,
localized area within fatigue critical structure where special, directed
inspections are required by an Airworthiness Directive (AD) or
airworthiness limitations. For example, all longitudinal skin splices in
a pressurized fuselage should be considered fatigue critical structure
if they are not immune to fatigue cracking which could lead to a
catastrophic failure. However, it may be reasonable to manage fatigue in
these splices by only performing a special directed inspection on the
most highly stressed area, which may only constitute a small percentage
of the at-risk structure.

Some TC and STC holders have identified the PSE as being limited to this
localized area. While this narrow usage of the term might be acceptable
within the context of specific supplemental inspection documents (SID)
or Airworthiness Limitations Sections (ALS), it could and has led to
confusion and inappropriate actions when taken out of context. For this
reason, we have chosen not to use the term "principal structural
element" in this rule.

The purpose of requiring identification and listing of fatigue critical
structure under this rule is to provide operators with a tool that will
help in the evaluation of existing and future repairs and alterations.
In this context, fatigue critical structure (FCS) is any structure that,
if repaired or altered, could be susceptible to fatigue cracking and
contribute to a catastrophic failure.

In the case of the longitudinal skin splices discussed above, we would
expect that the FCS listed by the TC holder would include much more
structure than just, for example, the localized area that is being
inspected to gauge the fatigue state of all the splices. A hypothetical
repair applied to even the lowest stress area of the splices could
potentially make it more critical than the highest stressed area without
a repair by increasing and redistributing structural loads. The result
would be a repair needing its own special directed inspection to prevent
potentially catastrophic failure. The only way to cover this contingency
would be to perform a DTE.

As discussed above, we revised the proposed definition of FCS to clarify
how the criteria of § 25.571 apply in the context of this rule. As we
stated in the NPRM, [^32] we intend for this rule to apply to future
type certificate holders, as well as current holders. Because the list
of FCS required by this rule may be more extensive than the structure
identified as airworthiness limitations items currently developed by TC
applicants, we added provisions to § 26.43 paragraphs (a) and (e) to
make it clear that the list of FCS must be submitted as part of the type
certification process. This requirement will help ensure that, new TC
holders are properly addressing DT requirements in developing structural
repair manuals (SRMs) and other service documents for use by operators.
It will also assist operators in ensuring that a DTE is performed for
all repairs and alterations to structure identified as FCS, as required
by the AASFR, from the beginning of an airplane's operational life.

Regarding the concern that STC holders may not have experience in
complying with § 25.571, current and earlier versions of AC 25.571-1C
provide guidance on identifying PSEs that is also applicable to
identification of FCS under this rule. Also, one reason this rule
requires a compliance plan is to ensure that TC holders, STC holders,
and the FAA have a common understanding of the rule's requirements,
including acceptable compliance methods.

Regarding suggestions to use quantitative methods or methodologies used
to comply with § 25.1309, our intent is to use the same method to
identify FCS that is required by § 25.571. Paragraph (a) of § 25.571
states that an evaluation must be conducted for "each part of structure
that could contribute to a catastrophic failure." Therefore, the
applicant must determine which parts of structure could contribute to a
catastrophic failure when damaged as a result of fatigue cracking.
Applying a probabilistic approach to determine if and when a part will
contribute to a catastrophic failure has not been industry practice in
complying with § 25.571. TC holders are required under § 25.571 to
perform a damage tolerance evaluation on structure to determine when
fatigue cracking may occur. At that point an inspection is performed to
determine if cracking has occurred. A probabilistic approach would raise
many implementation questions because fatigue cracking in metallic
structure is a certainty and detection is imperative in order to prevent
catastrophic failure of airplane structure. Probabilistic approaches
would not be consistent with our objective of facilitating timely
compliance.

**D. Damage Tolerance Evaluation (DTE)**

This rule requires TC holders and STC holders to review their repair and
alteration data and determine if a DTE is needed. Unless previously
accomplished, a DTE must be performed on all repairs and alterations
that affect fatigue critical structure. A DTE is 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, a DTE includes the evaluation of the
repair or alteration and the fatigue critical baseline structure
affected by the repair or alteration. Acceptable methods for performing
DTEs are described in AC 25.571-1C.

The maintenance actions developed as a result of a DTE may include
inspections, time limits for removal and replacement of repairs,
modification of the repair, alteration to improve its fatigue
characteristics, or in some cases modification of the affected FCS. The
type of maintenance action that is appropriate depends upon the type of
structure affected and the type of fatigue anticipated. For example, for
fatigue cracks that grow at a predictable rate and that can be detected
by inspections, a repetitive inspection program would be acceptable. For
cracks in locations that cannot be inspected and for cracking that may
grow too rapidly to be detected reliably, replacement or modification
may be necessary.

Section 26.43(c) requires TC holders to perform a DTE of those repairs
specified in their published repair data that affect fatigue critical
structure. Similarly, §§ 26.45(c) and 26.47(c) require TC and STC
holders to perform a DTE on their FAA-approved alteration data. In
addition to the published repair and alteration data, this final rule
requires that all future repair and alteration data receive a DTE to
determine if inspections or other actions are necessary to ensure the
airworthiness of the repair or alteration. This rule also requires TC
holders to develop Repair Evaluation Guidelines (REGs) that will enable
operators to survey their airplanes to identify repairs that affect
fatigue critical baseline structure (FCBS) and to obtain any necessary
damage tolerance inspections (DTI) for those repairs. If the REG directs
the operator to obtain assistance from the TC holder for developing the
DTI, the TC holder must make such assistance available.

As discussed below, based on comments to the NPRM, we revised the
proposed requirements in §§ 25.1825(c) and 25.1827(c) (adopted as §§
26.45(c)(1) and 26.47(c)(1), respectively)) to clarify that a DTE must
be performed and the DTI developed for the alteration and the FCBS that
is affected by the alteration.

Boeing and AAWG industry representatives asked that the regulatory text
in proposed §§ 25.1825 and 25.1827 be revised to clarify that both
alteration and baseline structure need to be assessed. They state that
the description of the work proposed in these sections of the NPRM may
be interpreted to mean that DTIs only need to be developed for the
alteration that happens to affect FCBS. However, AAWG industry
representatives do not believe this is the interpretation the FAA
intends. AAWG industry representatives recommended that the language in
both §§ 25.1825 and 25.1827 be changed to clearly say that the following
three components must be addressed for alterations:

1\. Identification of alterations that affect baseline fatigue critical
structure.

2\. Identification of the structural design details of the alteration
that require DTE.

> 3\. Identification of the affected design details of the baseline
> fatigue critical structure that require a re-evaluation of their DTE.

The commenters are correct in that we did not intend for the development
of DTIs to be limited to the alteration structure. When a DTE is
performed for an alteration, the DTE must be applied to both the
alteration and the FCBS that is affected by the alteration. Therefore,
the DTI developed (as determined by the DTE) for an alteration would
apply to the alteration structure and to the FCBS that is affected by
the alteration. As stated above, we revised §§ 25.1825(c) and 25.1827(c)
(adopted as §§ 26.45(c)(1) and 26.47(c)(1), respectively) to clarify
that for the alteration and the FCBS that is affected by the alteration
a DTE must be performed and the DTI developed.

The FAA does not believe that §§ 25.1825(c) and 25.1827(c) (adopted as
§§ 26.45(c) and 26.47(c), respectively) need to be revised to clarify
that alterations that affect FCBS need to be assessed, or to provide
clarification on which structural design details of an alteration would
require a DTE. Sections 25.1825(c)(1) (adopted as § 26.45(c)(1)) and
25.1827(c)(1) (adopted as § 26.47(c)(1)) already specify that a DTE must
be performed for alterations that affect FCBS. In addition, the
structure of the alteration that requires development of a DTI will be
identified as part of a DTE performed on the alteration. The DTI may
need to be developed for fatigue critical alteration structure or for
other alteration structure that may affect the FCBS. We expect that this
identification would be part of the DTE of the alteration.

Regarding the commenters' position that the proposed rule needs to be
revised to clarify the design details of the affected FCBS that will
need a re-evaluation of their DTE, the DTE of an alteration will include
an evaluation of the FCS that is affected by the alteration. Therefore,
in performing the evaluation of the affected FCBS, it must be determined
if new or revised DTIs need to be developed for this structure. Such a
determination is made as part of a DTE.

Mr. Thomas A. Knott, P.E., said the proposed rule "is fine," except it
does not address repairs and modifications done under part 43. He said
there are many alterations and repairs that were not approved under an
STC or developed by TC holders.

The FAA acknowledges that there are existing repairs and alterations
that were developed and installed under 14 CFR part 43 without
involvement by DAHs. This final rule takes into account these types of
repairs. The guidelines the DAHs are required to develop will describe
procedures for operators to follow in developing DTIs for repairs. For
alterations affecting FCS for which no DAH is responsible, the AASFR
requires operators either to develop the DT data themselves or contract
for their development. Because there is no DAH for these alterations,
they may be especially problematic if the installers failed to consider
the fatigue characteristics of the alterations or their effects on the
baseline structure. Both repairs and alterations will be identified and
assessed as part of surveys conducted to support compliance with the
AASFR.

**E. Damage Tolerance Inspections (DTIs)**

A DTI is defined in this final rule as inspections developed as a result
of a DTE. The DTI includes the location of the airplane structure to be
inspected, the inspection method, inspection procedures that include
acceptance and rejection criteria, and the thresholds and intervals
associated with those inspections. The DTI may also specify a time limit
when the repair or alteration needs to be replaced. As discussed below,
this definition reflects minor changes from the one in the proposed
rule.

Boeing asked that the FAA revise the definition of DTI. It said the
phrase "and corrective maintenance actions" could be confused with a
requirement to provide repair instructions or other corrective measures
for a condition found during an inspection. It said, historically, the
only instructions provided are how to accomplish the inspection
contained in the DTI and what action should be taken if the inspection
could not be accomplished. Therefore, Boeing requested that the phrase
"and corrective maintenance actions" be removed from the definition and
replaced with the phrase, "or a time limit when the repair needs to be
replaced, or both."

We agree and have revised the definition in the final rule as requested.
The purpose of this rule is to support operators' implementation of
damage tolerance inspection programs, as required by the AASFR.
Operators already have access to information on corrective actions in
the form of SRMs and other documents that may be necessary if the
inspections reveal fatigue cracks. Therefore, it is not necessary to
include the phrase "and corrective maintenance actions" in the
definition of DTI.

Bombardier asked, with respect to inspections of repairs, that we
clarify the phrase "the location of the airplane structure to be
inspected" used in the DTI definition. Bombardier said it understands
this phrase to mean that the DTI should clearly define which regions of
the repair and underlying structure should be inspected and the NDT
(non-destructive testing) method to be used in carrying out the
inspection. It said the DTI should be clearly linked to the repair data,
which will of itself define the repair location.

The FAA agrees that the DTI should clearly define the areas of the
repair and underlying structure that should be inspected and the
inspection method to be applied. The DTI will be applicable to specific
repair data that will define the repair location. This approach is the
same as that currently used by TC holders in developing SRMs to comply
with § 25.571, Amendment 25-45 and later.

**F. DT Data for Repairs**

**1. Published Repair Data**

This final rule requires TC holders to review their published repair
data and determine if DT data exist for the repairs or if the DT data
need to be developed. This final rule defines published repair data as
instructions for accomplishing repairs, which are published for general
use in SRMs and service bulletins (or equivalent types of documents). As
discussed below, we made minor revisions to the proposed definition.

Boeing requested that we revise the definition of "published repair
data" to make it clearer. It recommended the following revised version
of the proposed definition:

> Published repair data means applicable instructions for accomplishing
> repairs, which are published for general use in structural repair
> manuals and service bulletins (or equivalent types of documents).

The FAA agrees with the recommended revision to the definition of
"published repair data," and we have revised the definition,
accordingly, with a minor change in wording.

Bombardier said a list of Structural Significant Items (primary
structure) is provided in the SRMs for Bombardier Regional Aircraft. It
urged the FAA to consider rulemaking to require the SRM to be an
approved document. The SRM, Bombardier commented, can then incorporate
all of the instructions for continuing airworthiness required by the
NPRM and described previously in AC 25.1529. It said this approach has
been used by Bombardier and Transport Canada for SRMs and component
maintenance manuals (CMMs) applicable to aircraft and components
certified as damage tolerant to § 25.571 (Amendment 25-45) and later.

As explained in the NPRM, SRMs, while not required documents, are FAA
approved. Their purpose is to provide operators with readily available
sources of approved repair data. Because the operational rules require
that major repairs be accomplished according to FAA-approved data, an
SRM that has not been FAA approved would not serve operators' needs. The
SRM, if assessed for damage tolerance under § 25.571 (Amendment 25-45 or
later Amendment), should include the necessary instructions to ensure a
particular repair meets the criteria in AC 25.1529.

**2. Effects of Multiple Repairs**

Mr. Glenn Davis commented that DT data should address the effects of
multiple repairs in close proximity on older aircraft, and future
inspections should be based on a "worst case scenario of the
'combination effect' of the multiple repairs." He said the FAA might
consider requiring a time limit for individual or multiple repairs when
the repaired structure would have to be replaced, unless the applicant
or operator can confirm through a rational fatigue analysis, using an
acceptable fatigue model, that the repaired structure does not need to
be replaced. Mr. Davis said such a requirement could be applied to high
stress areas in older aircraft such as pressure bulkheads, door
apertures, attach fitting support structure for wings, and stabilizers.

The FAA agrees with Mr. Davis's comment that the DT data, specifically
the DTE, should take into account the close proximity of repairs. AC
25.571-1C provides guidance on determining the effects of multiple
repairs that are in close proximity. In addition, the repair assessment
guideline (RAG) documents developed in support of § 121.370
(redesignated as § 121.1107)[^33] address the effects of these types of
repairs on the pressure vessel. The FAA believes that existing guidance
in AC 25-571-1C, along with guidance developed in AC 120-93, as part of
this final rule, adequately addresses this issue.

**G. Repair Evaluation Guidelines (REGs)**

This final rule requires TC holders to develop REGs that include
processes operators could use to support compliance with §§ 121.1109 and
129.109 for repairs that affect FCBS. The guidelines must include---

-   A process for conducting surveys of affected airplanes to identify
    and document all existing repairs that affect FCBS;

-   A process that will enable operators to obtain DTIs for repairs that
    affect FCBS and for the FCBS affected by the repairs; and

-   An implementation schedule that provides the timing for conducting
    airplane surveys and for developing and incorporating DTIs into the
    operator's maintenance program.

TC holders must submit the REGs to the FAA Oversight Office for review
and approval and then make them available to affected operators.

As discussed below, we made several minor revisions to the proposed REG
requirements.

In § 25.1823(f)(1)(iii) and (f)(4) (adopted as § 26.43(e)(1)(iii) and
(e)(4)), we removed the term \"DT data\" from the phrase \"DT data
implementation schedule." We made this change because the term "DT data
implementation schedule" may be misunderstood to mean the actual timing
of DT inspections (thresholds and inspection intervals). It was only
intended to refer to the timing of major process related events (i.e.,
survey, development of DTIs, and incorporation of the DTI into the
maintenance program).

We revised proposed § 25.1823(f)(1)(iii) (adopted as
§ 26.43(e)(1)(iii))to make it clear that the implementation schedule
must identify the times when actions must be taken as specific numbers
of flight cycles, flight hours, or both. In developing its
recommendation regarding implementation schedules, the AAWG proposed an
approach that would have referenced the design service goal (DSG) for
determining the timing of various actions and would have allowed for
variability in DSGs for different airplanes of the same model, depending
upon actual flight lengths and other factors.

We agree with the AAWG that it is appropriate to allow reference to DSGs
in the implementation schedule to allow for industry resources to be
allocated for compliance when they are needed. For example, the AAWG
recommended that certain actions be taken when an airplane reaches ¾
DSG, before which fatigue cracking is less likely to have occurred.
However, allowing variability in DSG for different airplanes of the same
model would introduce a level of complexity and uncertainty to the
requirements of the operational rules that would jeopardize their
enforceability. Therefore, this rule requires that DSGs be stated as
"hard numbers."

We revised § 25.1823(f)(3) (adopted as § 26.43(e)(3)) to remove the
requirement that TC holders must make REGs available to STC holders. As
adopted, this paragraph only requires the TC holder to make the REGs
available to specified operators. We made this change because if STC
holders have access to the TC holder's list of FCS, they will not need
their REGs.

We also revised § 25.1823(f)(4) (adopted as § 26.43(e)(4)). The proposed
paragraph reads as follows: "If the guidelines direct the operator to
obtain assistance from the holder of a type certificate, provide such
assistance in accordance with..." We revised this paragraph in the final
rule to replace the words "provide such assistance" with the words "make
such assistance available.\" This change makes it clear that, as with
other requirements for TC holders to support operators, this rule is not
intended to require TC holders to provide this support without
compensation.

Boeing said proposed § 25.1823(f)(3) specifies that the TC holder will
make available the guideline documents to various entities. Boeing
believes this proposed requirement is in error and the reference to
proposed § 25.1827 should be removed from § 25.1823. Section 25.1827 is
applicable to holders of and applicants for an STC. In reading § 25.1827
and draft AC 120-XX,[^34] Boeing said there is no need for third parties
to have access to the guidelines developed as part of § 25.1823.
According to § 25.1827 and AC 120-XX, the only data required by an STC
holder is the list of fatigue critical structure, as stipulated in §
25.1823(c)(2). In light of this, Boeing said, the reference to § 25.1827
should be deleted from proposed § 25.1823.

We agree that STC holders do not need the guidelines to comply with this
final rule as long as they have access to the TC holder's list of FCS.
We have revised the final rule as discussed above.

Boeing commented that proposed § 25.1823(f)(4) appears to be using
incorrect terminology. It said the wording in § 25.1823(f)(4) could
circumvent the current business practices and established relationships
between the TC holder and the operator. Boeing requested that paragraph
(f)(4) be changed as follows:

> If the guidelines direct the operator to obtain assistance from the
> holder of a type certificate, the holder of the type certificate will
> make available such assistance in accordance with the DT data
> implementation schedule.

It was not our intent to require TC holders to provide assistance to
operators without compensation. As indicated above, we have revised the
final rule as the commenter requested.

UPS expressed concern about the effectiveness of the proposed REGs. The
proposed rule, it said, assumes that practical, cost effective REGs are
achievable. However, the proposed procedure will be significantly more
complex than the current Repair Assessment Guideline (RAG) documents,
which only survey fuselage skin. UPS said the current repair assessment
of pressurized fuselage skin results in removal and replacement of some
repairs due to the inability to accurately determine the exact repair
details. Fuselage skin repairs are relatively easy to assess because
almost all damage is cut out and one side of the repair is accessible
for detailed measurements. For other structure (e.g., stringers, ribs,
spars, frames, shear clips, bathtub fitting) the ability to determine
hidden repair details may not be possible without removing the repair.
Consequently, the proposed survey method of documenting and establishing
DTIs on existing repairs could result in a higher than necessary repair
replacement frequency. To minimize the impact of the DTE of repairs, UPS
believes it is vital that the FCS be properly identified.

In response to UPS's concerns about the effectiveness of the proposed
REGs, the airplane repair survey process was patterned after existing
RAG documents to minimize the impact of the DTE of repairs. AC 120-93
provides guidance for performing surveys to identify repairs that may
affect FCS.

Regarding UPS's comment that certain structure may be difficult to
inspect without having to remove the repair, operators should work with
the TC holder in the Structural Task Group (STG) meetings to ensure an
efficient process is developed for assessing repairs to minimize the
unnecessary removal of repairs. The DTE will determine what actions are
necessary to ensure the continued airworthiness of the affected FCBS.
Performing DTIs on these airplanes should be no more difficult than
performing them on airplanes for which repair data already have DTIs for
compliance with the airplane's certification basis. We agree that it is
vital that FCS be properly identified. As discussed previously, this
final rule requires TC holders to apply the same analytical methods to
create this list that they have applied for many years in complying with
§ 25.571.

**H. DT Data for Alterations**

This final rule requires TC holders to perform DTEs, and develop DTI, if
necessary, for their alterations that affect FCBS. For existing
alterations, TC holders must submit the DT data for FAA approval by June
30, 2009. For future alterations, the DT data are required before we
approve the alteration data.

Similarly, STC holders must perform DTEs and develop DTIs for their
alterations that affect FCBS. In addition to alterations, some STC
holders must perform DTEs and develop DTIs, if necessary, for repairs
developed by them that affect any FCS. For existing alterations, STC
holders must submit the DT data for FAA approval by June 30, 2009. For
future alterations, the DT data are required before we approve the
alteration data.

The sections of the proposal that relate to alterations, (§§ 25.1825 and
25.1827 (adopted as §§ 25.45 and 25.47, respectively)) were revised as
discussed below to make them clearer. As proposed, these sections may be
misinterpreted to mean that the TC and STC holders need to perform a DTE
of their alterations as installed on individual airplanes, addressing
variations in the configurations of these airplanes. Our intent,
however, is that they perform a DTE only of their alteration design
data.

These sections may also be misinterpreted to mean that DTIs only need to
be developed for the FCS of the alteration. In addition, as stated in
the definition of damage tolerance evaluation in proposed § 25.1823(b),
we intended that the DTE would also apply to the FCBS that is affected
by the alteration and that the resulting DTI would also address the
affected baseline structure. To clarify these requirements, the final
rule specifies that TC and STC holders must, for each alteration
affecting FCBS, identify and develop DTIs for both the FCBS that is
affected by the alteration and the fatigue critical alteration
structure. Other than some additional minor wording changes, there are
no other changes to the sections of the final rule pertaining to
alterations.

The ATA commented that the FAA should limit the number of DTEs necessary
for alterations. Proposed § 25.1825(c) and § 25.1827(c) require TC
holders to perform a DTE of each existing and future alteration and
submit DT data for the existing alterations to the FAA. These provisions
would apply to an impracticable number of alterations, according to the
commenter. The ATA recommended, therefore, that the FAA clarify\
§§ 25.1825(c) and 25.1827(c) to stipulate that "each alteration" applies
to each certificate or approval of an alteration rather than each
installation.

The FAA agrees that it would be impracticable for TC or STC holders to
perform a DTE for alterations as installed on individual airplanes,
which may contain alterations and repairs that would affect the DTE of
which the TC or STC holder is unaware. It was not the FAA's intent to
require TC and STC holders to develop DT data for the actual
installation of their developed design changes (alterations), but rather
to require them to perform a DTE of the design changes affecting FCBS
that are specified in their FAA-approved alteration data. This DTE must,
however, address the range of airplane configurations on which the TC or
STC holder showed the alteration is eligible for installation. We
revised §§ 25.1825(c) and 25.1827(c) (adopted as §§ 26.45(c) and
26.47(c), respectively) to clarify that the DAHs are only responsible
for performing DTE of their alteration data, and not of the alterations
as actually installed.

**I. Required Documentation**

The ATA said the FAA should define the documents required of DAHs as
specifically as possible, and the product should be delivered to the FAA
for certification or approval in a form ready for direct installation or
incorporation as required by the associated operating rule. The ATA said
adherence to this recommendation should be facilitated by the
participation of Structural Task Groups (STG) in the development of the
DTI and REG. The ATA recommended that the FAA use consistent terminology
in the final rule and in AC 120-XX,[^35] so they clearly describe the
documentation and data DAHs must make available to operators. It said
draft AC 120-XX states that DAHs would provide operators with a
model-specific "compliance document." The NPRM, however, does not
discuss the "compliance document" referenced in the draft AC. Similar to
the ATA comment, Horizon Air asked that the rule define the specific
type of required data that DAHs must make available to operators.

We agree with the ATA that this final rule should clearly identify the
required data and documents. This final rule requires DAHs to develop
and make available to operators lists of fatigue critical structure,
damage tolerance inspections for their alterations and repair data
(supported by DTE documentation submitted to the FAA), repair evaluation
guidelines, and implementation schedules.

Based on the Aviation Rulemaking Advisory Committee's (ARAC)
recommendations, the FAA developed AC 120-93 to facilitate DAH
compliance with this rule and operator compliance with the AASFR. This
AC describes a compliance document that would either contain or
reference these required documents. Because the compliance dates for
these documents differ, the DAH would not make the compliance document,
as a whole, available until the last of these documents is approved.

As described in the AC, this compliance document would support an
operator's development of an Operator's Implementation Plan (OIP). The
OIP would provide the means for addressing the adverse effects of
repairs and alterations. Once this OIP is approved by the operator's
principal maintenance inspector (PMI), the operator would comply with
the AASFR by incorporating the OIP into its maintenance program and
implementing the OIP by performing surveys of its airplanes, obtaining
necessary damage tolerance inspections and procedures, and performing
those inspections and procedures, all in accordance with the approved
implementation schedule contained in the OIP.

STGs, working under the auspices of the ARAC's Airworthiness Assurance
Working Group (AAWG), may be convened to assist TC holders in developing
airplane model-specific DT data. This rule and AC 120-93 reflect
consistent terminology. The DT data to be developed and made available
are described in §§ 26.43, 26.45, and 26.47 of this final rule, as well
as in AC 120-93.

**J. Proprietary Data**

The ATA said the FAA should work with DAHs to establish a narrow and
clear definition of proprietary data. DAHs have expressed concerns that
the proposed requirements could lead to the disclosure of proprietary
data (e.g., DT documentation). Conversely, operators are concerned that
restrictive disclosure policies could result in REGs and DTIs that are
too general to be used without costly and time-consuming consultation
with the DAH. The ATA recommended that the FAA coordinate with DAHs to
support a goal for documents that must be "made available" under the
proposal that would allow operators to comply autonomously with the DT
requirements without consulting with the DAH more than absolutely
necessary. ATA said the FAA can support this recommendation further by
providing guidelines to DAHs and STGs to ensure that claims of
proprietary data are not overstated.

For many years, the FAA has required DAHs to disclose to affected
persons information they might otherwise consider proprietary. For
example, since 1981, DAHs have been required to provide Instructions for
Continued Airworthiness, including DT data, which DAHs may have
considered proprietary. However, because we have determined that this
information is essential to maintaining the airplanes in an airworthy
condition, we have required DAHs to make it available as a condition for
obtaining and retaining their certificates. Regarding the usefulness of
the documents developed by the DAHs, because we expect these documents
will be developed by DAHs in collaboration with the affected operators,
we anticipate that the operators will ensure they are useful for their
intended purposes. FAA technical specialists will also be monitoring
development of these documents for this purpose.

**K. Compliance Plan**

This final rule includes requirements for a compliance plan to ensure
that affected TC and STC holders produce DT data in a timely manner that
are acceptable in content and format. Integral to the compliance plan
are procedures to allow the FAA to monitor progress toward compliance.
The affected TC and STC holders must submit to the FAA Oversight Office
on the compliance dates specified in the rule a compliance plan that
addresses---

-   The project 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; and

-   A plan to submit to the FAA Oversight Office, not less than 60 days
    before the stated compliance dates, a draft of the required
    compliance items.

Based on comments submitted to other DAH airworthiness rules, the FAA
has determined that we can remove some provisions of proposed § 25.1829
(adopted as\
§ 26.49) without adversely affecting our ability to facilitate DAH
compliance. Specifically, in § 25.1829(a)(3), we proposed a requirement
for DAHs to identify the intended means of compliance that differ from
those described in FAA advisory materials. While this is still a
desirable element of any compliance plan, we have concluded that an
explicit requirement is unnecessary. As with normal type certification
planning, we expect that DAHs will identify these differences and fully
discuss them with the FAA Oversight Office early in the compliance
period to ensure that these differences will ultimately not jeopardize
full and timely compliance.

Similarly, § 25.1829(c) contains provisions that would have authorized
the FAA Oversight Office to identify deficiencies in a compliance plan
or the DAH's implementation of the plan and to require specified
corrective actions to remedy those deficiencies. While we anticipate
that this process will still occur in the event of potential
non-compliance, we have concluded that it is unnecessary to adopt
explicit requirements to correct deficiencies.

Ultimately, DAHs are responsible for submitting compliant documents by
the dates specified in §§ 26.43, 26.45, and 26.47 of this final rule.
Section 26.49 retains the requirements to submit a compliance plan and
to implement the approved plan. If the FAA Oversight Office determines
that the DAH is at risk of not submitting compliant documents by the
compliance dates because of deficiencies in either the compliance plan
or the DAH's implementation of the plan, the FAA Oversight Office will
document the deficiencies and request DAH corrective action. Failure to
implement proper corrective action under these circumstances, while not
constituting a separate violation, will be considered in determining
appropriate enforcement action if the DAH ultimately fails to meet the
requirements of this section.

We also added an exception for future TC applicants in § 26.49(a) to
make it clear that these applicants are not required to submit a
separate compliance plan for the applicable requirements of this final
rule. These compliance issues should be addressed as part of the normal
certification plan submitted for any type certificate project.

Section 25.1829(5) included a proposed requirement to include in the
compliance plan a process for continually assessing service information
related to structural fatigue damage. We have reconsidered this proposed
requirement and concluded that existing regulations[^36] that require
both DAHs and operators to report structural defects should be adequate
to enable us to determine whether the objectives of this final rule are
being met. Therefore, we removed this provision from the final rule.

**1. Process for Continuous Assessment of Service Information**

Bombardier, in its comment on the compliance plan, referred to the
proposed requirement that the compliance plan must address a process for
continuous assessment of service information. Bombardier said feedback
from operators on the effectiveness and findings resulting from DT-based
inspections of baseline structure, as well as repairs and alterations,
may not be adequate to enable them to meet this requirement.

As discussed above, we have removed this provision from this final rule
since existing regulations will enable us to determine if the objectives
of this final rule are being met.

**2. Timing of FAA Approval**

Airbus expressed concern that the FAA may not have sufficient resources
to handle approval of compliance plans in a timely manner. Therefore, it
recommends a thorough review of FAA resources needed for this activity
before committing to the proposed compliance date.

FedEx said it understands that the compliance documents must be approved
by the FAA Aircraft Certification Office (ACO) before they are made
available to operators, but the proposed rule does not state when the
documents would be made available to operators. FedEx said the rule
should include a date by which the FAA would approve the DT data that TC
and STC holders provide, as well as a date by which the approved data
will be made available to operators.

The ATA said the FAA should commit to a schedule for approving the DT
data from DAHs and implementation plans from operators. It requested
that the FAA give an estimate of when industry can expect the FAA to
approve the DT documents and implementation plans, taking into account
the volume of the submissions.

We are not including time frames in the regulation for our review and
approval of the compliance plans and compliance documents. Expectations
for FAA personnel have been defined in FAA Order 8110.26, which directs
the Aircraft Certification Service and Flight Standards Service in their
roles and responsibilities for implementing these initiatives. The Order
includes expected times for reviewing and approving DAH compliance
plans, plans to correct deficiencies, and draft and final compliance
data and documents. To facilitate implementation, we will also train
affected personnel in their roles and responsibilities and provide
familiarization with requirements of the regulations and associated
guidance. However, our ability to approve documents, and the timing of
our approvals, ultimately depends on the quality of the documents
submitted by the DAHs and their responsiveness if we identify
deficiencies.

**L. Harmonization**

The AAWG industry representatives, ATA, Boeing, Embraer, and Horizon Air
commented that the FAA should harmonize the DT Data rule with EASA and
other national airworthiness authorities. If the rule is not harmonized,
the AAWG industry representatives expressed concern that the FAA's
retention of authority to make all necessary compliance determinations
for foreign DAHs will establish "a substantial precedent that could
create a significant challenge to all future certification programs."
The AAWG industry representatives said the stated requirements advocate
"a procedure that could permit unilateral and potentially arbitrary
certification activities at the whim of any regulatory authority."

Boeing and the ATA said the lack of harmonization will cause unnecessary
conflicts and complexities between the FAA's and foreign authorities'
requirements. Boeing said while it is aware that EASA is pursuing a
similar proposal, EASA may not adopt the same requirements as the FAA.
Also, Boeing said, having to comply with different requirements in the
same time frame would cause added complications and difficulties with
meeting aggressive schedules, and it would result in unnecessary,
additional work for the FAA.

Both Boeing and the ATA believe harmonization is a standard of
excellence that has been achieved over many years of hard work and this
rule should not interfere with that achievement.

We agree with the commenters that harmonization of this rule with other
national authorities is an important objective. We fully expect to
coordinate with EASA and other authorities on findings of compliance.
EASA and Transport Canada Civil Aviation (TCCA) have participated in the
AAWG's development of the AC that will support compliance with this
final rule. As a follow-on to this activity, EASA has proposed the
formation of a European Aging Aircraft Working Group and has requested
participation by the FAA. The FAA plans to support this activity with
representatives from both the Aircraft Certification Service and the
Flight Standards Service. There is general agreement among the
authorities on the need to address DT for repairs and alterations and on
the approach adopted in this rule.

The AAWG industry representatives commented that there is the potential
for creating substantial negative impact in the industry with respect to
airplane certification sales and transfers between US and foreign
entities because the proposal has not been harmonized with EASA.
According to the AAWG industry representatives, the economics of this
impact has not been accounted for in the regulatory evaluation;
therefore, the FAA should assure that the final rule is harmonized to
the extent possible with EASA because of the potential economic issue
for all parties. The AAWG industry representatives also said it appears
that the long-term intention of EASA is to harmonize with the US
requirements by 2008 or 2009. And it said that the implementation time
scales are different between the two authorities' approaches.

This rule will not have the negative effects suggested by the commenter.
In fact, by requiring DAHs to develop and make available the data
necessary to comply with the AASFR, this rule will facilitate compliance
for all airplanes, which is a prerequisite for transferability. All
authorities recognize that harmonization of this rule is important in
that common requirements will allow expeditious transfer of airplanes
across borders, and we are working towards that objective.

**1.** **Foreign Authority Approval of Required Data**

Airbus commented that the NPRM preamble indicates that the FAA cannot
accept foreign authority approval for documents under Bilateral
Agreements because these foreign authorities have not yet adopted a
similar rule. It said the Joint Aviation Authorities (JAA) issued and
applied Notice of Proposed Amendment (NPA 20-10) (the European Aviation
Safety Agency (EASA) updated NPA 20-10 to NPA 05/2006), which addresses
the same airworthiness issues and incorporates similar technical
guidance. Moreover, evaluation of repairs, alterations, and
modifications to DT requirements is state-of-the-art and is approved
under the EASA regulatory system on a daily basis.

Airbus also said it will be at a disadvantage by having to deal
unilaterally with the FAA without the support and involvement of EASA.
Also, it said it would have to coordinate with the FAA's international
branch along with several other non-U.S. TC holders. However, U.S. TC
holders will have a dedicated FAA certification office to work with and
may be able to use their authorized designees to perform compliance
related activities.

According to Airbus, obtaining support from the FAA is especially
important for proposed §§ 25.1823(d) and 25.1825(c) and (d) for
alteration and repair approvals. Therefore, Airbus requested that the
FAA include EASA in the approval process, such that in the near future
the FAA could accept the majority of the activities performed by EASA
under the Bilateral Agreement. In addition, Airbus requested that the
FAA give non-U.S. TC and STC holders the same level of priority and the
same allocation of FAA resources as U.S. TC and STC holders. This,
Airbus said, would help mitigate delays in reaction and approval time.

Horizon Air said the proposed rule states that data will be submitted to
the FAA Oversight Office or its properly authorized designees. In
defining "authorized designees," reference is made only to Designated
Engineering Representatives (DERs) specifically authorized by their
supervising ACO.

Horizon Air also said that currently because of the Bilateral Agreement
between Transport Canada and the FAA, it is able to incorporate DTE and
DTI documentation for Bombardier and deHavilland airplanes directly into
its maintenance program. Under the new rule, it appears it would be
required to submit the developed repair data to the ACO before being
able to implement it. Therefore, Horizon Air requested that Foreign
Authorities, specifically Transport Canada, or their designees be
included under Bilateral Agreements.

We recognize the important role other national authorities are likely to
play in implementation of this rule. In addition to the on-going efforts
to harmonize these requirements, we have been working closely with the
other national authorities to define appropriate roles,
responsibilities, and relationships among all affected authorities. As
discussed in the NPRM, the compliance planning provisions are equally
important for foreign TC holders, and we expect to have mutually
agreeable arrangements with their authorities on how compliance planning
will be overseen. We expect these other authorities to play a major role
in reviewing their TC holders' compliance plans and other required
documents, which will enable us to provide timely approvals for all
affected TC and STC holders, assuming the submitted documents comply
with the applicable requirements.

**M. Enforcement**

Bombardier and UPS expressed concerns about enforcement. Bombardier
asked what mechanism the FAA would use to impose civil penalties on
non-U.S. DAHs. UPS said the proposed rule does not state how the FAA
would handle a DAH that does not complete the damage tolerance
assessment tasks on time. It is also concerned whether the FAA can
effectively enforce the intent of these types of provisions.

The compliance planning provisions of this rule are intended to
facilitate timely compliance and avoid the need of enforcement for
non-compliance. However, under 49 U.S.C. 46301, the FAA has authority to
take civil penalty action without regard to nationality of the
respondent. The FAA's general enforcement policies, which are set forth
in 14 CFR part 13 and Order 2150.3, will apply to the DAH requirements.
These general policies provide wide discretion for us to impose
administrative action, civil penalties (up to \$25,000 per violation per
day) or action against a TC or STC holder's certificate (including
suspension or revocation).

If a TC or STC holder is found to be non-compliant, we will consider the
circumstances of non-compliance before determining an appropriate course
of action. For example, deliberate violations will be treated more
severely than inadvertent non-compliance. Any enforcement action the FAA
may choose to take will be in consideration of the circumstances of the
violation and defined on a case-by-case basis.

**N. Industry and FAA Resources**

UPS commented that DT analysis depends on complex methodology and data.
Because of this, there are very few DERs in the industry that have FAA
DTE approval authority. UPS suggested it is highly unlikely that this
methodology and relevant data can be streamlined into an approach that
is useful and effective. It suggested the FAA establish an initiative to
authorize additional structures DERs with DTE approval authority.

ABX expressed concern that both industry and the FAA have a shortage of
specialists in areas related to the rule. It said FAA ACOs don't have
enough resources to provide the needed support to industry in a timely
manner. It also said the present delegation requirements in the area of
DT are unachievable for non-OEM DERs. Therefore, ABX said the FAA, with
support of the industry, should take the following steps:

-   Create different levels of delegation for DTE. If necessary, keep
    the requirements the same for full authority but allow DERs with
    less than required experience to obtain delegation to show
    compliance in specific areas, using previously FAA-approved
    methodology.

-   Provide training to DERs and/or call for specific college courses
    that can substitute the experience to facilitate the delegation.

-   Develop methodologies for DT analysis in the areas that are
    frequently needed by operators and STC holders.

-   Postpone any rulemakings until the industry has the required tools
    to comply with the rule in the mandated time frame.

Recognizing the limited industry and FAA resources available to perform
and approve DTEs, ARAC has developed guidance material in AC 120-93 that
describes a means of compliance with this rule and the AASFR that allows
the available resources to focus on the highest priority DTEs for
repairs. This AC describes an implementation schedule with a phased-in
approach under which existing repairs on the older and
higher-utilization airplanes are assessed first (highest risk repairs),
with newer airplanes being assessed when they approach their design
service goal (DSG). This approach is similar to that established for
certain RAGs developed for compliance with § 121.370[^37] (redesignated
as § 121.1107)). Therefore, we find the implementation schedule approach
described in AC 120-93 to be a rational one. We believe this approach
will help ensure that adequate industry and FAA resources will be
available to support timely compliance with this final rule and with the
AASFR.

The FAA agrees that there is a need for an increased number of designees
having authorization for DT. To address this potential problem, the FAA
is continuing to hold DER seminars to encourage participation by DERs in
these programs. DERs can work with their FAA Oversight Office to develop
a plan that would support expanding their authorized delegation to
include DT. Due to the complexities associated with DT, particularly
those related to performing DTEs on repairs and alterations, it is
necessary to ensure DER candidates have adequate experience in
performing DT and in analyzing repairs and alterations. The current
process for obtaining DT-delegated functions requires DER applicants to
have at least 1 year of experience in performing DTEs. This experience
is necessary for the FAA to gain a level of confidence that the DER,
once authorized to perform DT on repairs and alterations, will submit DT
data that are appropriate and not subject to a need for extensive review
by the FAA Oversight Office.

For compliance with the AASFR, it is of particular importance that the
DERs have a working knowledge of what is required for showing compliance
with § 25.571 for repairs and alterations. The FAA does not agree with
the commenter's recommendation to allow DER candidates with less than
the required experience to obtain a delegation for DT, or to substitute
the requirement for experience with college courses to facilitate
delegation. Experience is a key element in ensuring the success of the
FAA's delegation program.

Regarding the recommendation that the FAA develop methodologies for DT
analysis in the areas that are frequently needed by operators and STC
holders, we believe the methodologies employed today, which have been
used for several years throughout the aviation industry, are adequate.
Damage-tolerance-based programs such as RAGs developed by TC holders to
support operator compliance with § 121.370 (redesignated as § 121.1107),
provide a streamlined approach operators can use for assessing repairs
common to the airplane pressure boundary. Expansion of these guidelines
to address additional structural areas (e.g., frequently repaired
areas), or development of new RAGs, may support operator compliance with
the AASFR. However, these types of DT-based programs are model specific
and typically require TC holder involvement. Operators should coordinate
with TC holders during STG meetings to determine the need for such
programs and how they should be structured.

We disagree with the recommendation to postpone this rulemaking because
we do not believe industry needs additional time to comply. As we have
discussed, this final rule is needed to support operator compliance with
the AASFR. That rule was adopted in February 2005. Delaying adoption of
the DAH requirements in this rule would adversely affect operators'
ability to meet the compliance time frame in the AASFR. In addition,
methodologies for performing a DTE have been applied for several years
and are readily available. Also, to reduce the resource burden, we
describe in AC 120-93 an implementation schedule that may provide more
time for operators to obtain DTEs for alterations for which there are no
TC or STC holders. This implementation schedule may provide, in part, a
means for addressing the potential adverse effects of alterations.

UPS said some STC holders may not have the resources (either
financially, technically, or both) to comply with the proposal. Further,
it said, the proposal does not address the situation where an STC holder
has gone out of business or has surrendered its STC to the FAA.

The FAA recognizes that there may be some occasions where the DAH is
unwilling or unable to comply with the regulations. There may also be
cases where the DAH no longer exists. As stated in the policy statement,
Safety -- A Shared Responsibility -- New Direction for Addressing
Airworthiness Issues for Transport Category Airplanes, under these
circumstances, the operator is still obligated to comply with the
operational rules. However, the FAA recognizes that such occasions may
significantly complicate the operator's effort to show compliance with
the operational rules. The FAA recommends the affected operators contact
their DAHs early in the compliance process to ensure their intent to
comply. These operators are also encouraged to collaborate with other
operators who may also be impacted by lack of support on a means for
compliance.

**O. Compliance Dates**

As noted before, today's final rule supports the AASFR, which requires
operators to incorporate a means to address the adverse effects of
repairs and alterations into their maintenance program by December 20,
2010. This DAH DT Data final rule includes compliance dates that require
DAHs to make the required DT documents available to operators in enough
time for them to comply with their approved means for addressing repairs
and alterations. The approved means will include implementation
schedules that provide timing for when airplane repair surveys are to be
performed and when DTI or other maintenance actions for repairs and
alterations need to be incorporated into the maintenance program.
Certain of the compliance dates in the DAH DT Data final rule have
changed from those in the proposed rule.

Specifically, in proposed § 25.1823(g)(1), TC holders would have 90 days
after the effective date of the rule to submit their lists of fatigue
critical baseline structure. In proposed § 25.1825(e)(1), they would
have 90 days to submit their lists of fatigue critical alteration
structure. In proposed § 25.1827(e)(1), STC holders would have 270 days
to submit their lists of fatigue critical alteration structure.

In the final rule (§ 26.43(f)(1)), TC holders have 180 days from the
effective date to submit their lists of fatigue critical baseline
structure. TC and STC holders (§§ 26.45(e)(1) and 26.47(e)(1),
respectively) have 360 days from the effective date of the rule to
submit their lists of fatigue critical alteration structure.

The AAWG industry representatives, Boeing, FedEx, and Embraer asked for
an extension of the compliance date in the AASFR and a commensurate
extension of the DAH DT Data rule's compliance date. While several of
the commenters acknowledged the FAA's prior 3-year extension (from 2007
to 2010) to the compliance time for the AASFR, they said if the FAA had
published the DAH DT Data NPRM at the time of that extension, industry
would have had more time to comply with the DAH DT Data final rule.

The AAWG industry representatives asked us to extend the AASFR
compliance date of December 20, 2010 to December 20, 2013. FedEx asked
the FAA to give operators a minimum of 12 months after receiving the
FAA-approved documents to develop their implementation plan to send to
their FAA Flight Standards District Office. Boeing asked us to extend
the AASFR compliance date to August 18, 2013. It said the FAA should
impose incremental compliance times from the effective date of final
rules, rather than impose a fixed date. For the DAH DT Data final rule,
Boeing believes the FAA should allow DAHs 4 years from the effective
date of the rule to submit their documents to the FAA because of the
addition of the DAH requirements and related compliance plan in this
final rule.

Except as discussed previously regarding lists of fatigue critical
structure (FCS), we do not believe an extension of the compliance dates
in either rule is appropriate. As several of the commenters
acknowledged, we previously extended the compliance date for the AASFR
by 3 years to allow ARAC time to develop guidance material operators
could use to support compliance with DT requirements related to repairs
and alterations.

Based on requests from industry, in May 2004, we tasked[^38] ARAC to
develop guidance to support operator compliance with the AASFR. Included
in the tasking notice was a task for ARAC to do the following:

> Oversee the Structural Task Group (STG) activities that will be
> coordinated for each applicable airplane model by the respective type
> certificate holders and parts 121 and 129 certificate holders. These
> STG activities will involve the development of model specific
> approaches for compliance with §§ 121.370a and 129.16 \[redesignated
> as §§ 121.1109 and 121.109, respectively\]...

In addition, the tasking states that the data developed by the TC
holders via STG meetings, using the guidance material developed by ARAC,
should be completed by December 18, 2009. ARAC accepted this tasking,
which it assigned to the AAWG, and agreed to complete it by the
specified date of December 18, 2009.

In the February 2005 AASFR, we extended the December 5, 2007 compliance
date adopted in the Aging Airplane Safety Interim final rule[^39] to
December 20, 2010. This extension was meant to give ARAC time to
complete the tasking and allow operators a full year to implement the
resulting program changes. The AAWG developed a schedule for completion
of the tasking by the agreed-upon date. The compliance dates specified
in this DAH DT Data final rule are fully consistent with these
commitments, and none of the commenters have identified reasons why we
should not expect these commitments to be fulfilled.

Regarding Boeing's comment that this rule imposes additional
requirements for which they need more time, assuming ARAC and the STGs
fulfill their commitments, we anticipate that the products of the
tasking will enable Boeing and other participating TC holders to meet
the requirements of this rule with little additional effort.
Specifically, regarding compliance planning, this type of planning is
normal business practice, regardless of the requirements of this rule,
as evidenced by the AAWG's schedule development discussed earlier.

The ATA, Boeing, UPS, FedEx, and AAWG industry representatives asked
that DAHs be given 180 days from the effective date of the final rule to
submit their lists of fatigue critical baseline structure to the FAA.
The ATA and UPS asked that the FAA allow 360 days from the effective
date of the final rule for STC holders to submit their lists of fatigue
critical alteration structure. Airbus requested an extension of 1 year
from the effective date of the final rule to submit its lists of fatigue
critical baseline structure. The commenters believe it is important to
allow DAHs enough time to develop the lists to ensure they are accurate.

Boeing and AAWG industry representatives indicated that the FAA should
allow additional time to develop the lists because of their importance
to industry and to other rules like the proposed Widespread Fatigue
Damage (WFD) rule. Boeing said more time would enable it to consult with
the STGs on the format and content of the lists. It also said more time
is needed because of the large numbers of airplanes and alterations
involved and the need for internal coordination to ensure consistency.
It estimates that for its airplane models, it would have to produce more
than 40 lists.

The ATA, FedEx, and UPS said if DAHs do not have sufficient time to
develop accurate lists, they may produce overly conservative lists that
include all primary structure. The ATA and FedEx add that such lists
would be of little value to operators and would add costs and
complexities to operator compliance with the AASFR. Also, the ATA said
DAHs may opt to recommend replacement of structural elements rather than
inspections and repairs if they do not have enough time to compile the
lists. Airbus commented that it does not have the resources to complete
the necessary assessments and compile the lists in the proposed time
frames. Airbus said the consequence of not having enough time to develop
accurate lists could be either incomplete lists or extremely long lists.

The FAA believes additional time to establish the lists of fatigue
critical baseline and alteration structures is appropriate, and has
revised the rule as discussed above. The revised time frames, which give
TC holders 180 days to submit their lists of FCBS and TC and STC holders
360 days to submit their lists of fatigue critical alteration structure,
should allow sufficient time to develop the lists. This is particularly
true since the TC holders have been required to identify fatigue
critical structure to comply with the damage tolerance requirements of §
25.571 since 1978. For pre-amendment 25-45 airplanes, the TC holder
analysis that led to the development of the SID documents provide a
useful starting point for developing these lists. As discussed
previously, these activities should already be well underway.

**P. Costs and Benefits**

The AAWG industry representatives and Boeing commented on our statement
in the NPRM that the costs of the proposed rule were accounted for in
the AASFR. The AAWG industry representatives believe that the economics
on which the proposed rule is based are questionable and their basis
cannot be determined. Boeing said the FAA assumed that much of the work
required for compliance with the proposed rule was already completed by
the TC holders on other programs, such as the SID and RAG initiatives.
The commenters added that the costs ascribed to the TC holder in the
proposed rule, in fact, did not exist at the time the original rule was
published for comment, nor do they exist today.

The AAWG industry representatives and Boeing requested that the FAA
revise the basis of the economic evaluation of the proposed rule, and
include accurate estimates of the cost of the development of compliance
data by the TC holders, based on the means of compliance suggested in AC
120-93.

The ATA said the FAA should disclose DAH estimates for the cost of
damage tolerance data and documents. The ATA indicated that it does not
concur with the FAA's assertion that the proposed rule has minimal to no
costs. The ATA recommended that the FAA include DAH estimates for the
cost of these documents in its disposition of comments to the proposal.

UPS said the costs of the proposed rule changes are understated.
Although the regulatory flexibility analysis in the rulemaking states
that this rule would relieve small-entity part 121 operators of what
could be a significant cost, there is nothing in this proposal that
prevents DAHs from passing all their costs on to the operators. Although
this compensation could be reasonable, it will also likely be
significant. UPS suggested that an accurate cost-benefit analysis be
accomplished and evaluated prior to adopting this rulemaking.

The requirements to develop damage tolerance (DT) based data for repairs
and alterations were originally established in the Aging Airplane Safety
Interim final rule (AASIFR). These responsibilities were initially
placed on the operators of part 121 and U.S.-registered part 129
transport category airplanes. The costs and benefits were computed in
the regulatory evaluation for that rulemaking. The regulatory evaluation
for the AASIFR, as well as the regulatory evaluation for the AASFR,
which clarified these requirements, recognized that to comply with the
rule's requirements, operators would have to develop and implement
DT-based inspections and procedures for the affected airplane structure.
This DAH DT Data final rule is a counterpart to the AASFR; it transfers
the responsibility of developing DT-based data from operators to design
approval holders (DAHs). Therefore, it has minimal to no societal costs.

We anticipate that by the compliance date for the AASFR, DT inspection
programs for baseline structure, required by this DAH DT Data final
rule, will already be mandated by AD or certification or operational
regulations for all airplanes affected by this final rule. A significant
number of operators subject to the AASFR are small entities. If each of
the small-entity operators individually took the responsibility for
developing DT-based data, the cost for the data would be significant. By
transferring the responsibility from part 121 operators to DAHs, this
rule will relieve those operators of what could be a significant cost.

While UPS is correct that operators may have to compensate TC holders
for the data they make available, we expect these costs to be
substantially less than if the operators had been required to
individually develop their own data.

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. With STG
participation, we expect that the resulting compliance documents will
minimize costs for operators and facilitate their compliance with the
AASFR. This final rule will 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. AC 120-93 is
largely a product of ARAC and reflects industry's view of the most cost
effective means for developing the data operators must implement under
the AASFR.

**Paperwork Reduction Act**

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. Information collection requirements in the
AASFR previously have been 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
International Civil Aviation Organization Annexes.

The FAA reviewed data associated with compliance to the AASFR and data
associated with this rule. 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 this rule due to a reduction in the
numbers of repairs and alterations that will need an individual damage
tolerance assessment. This is because this rule will require design
approval holders to develop a streamlined approach for assessing
repairs.

**International Compatibility**

### In keeping with U.S. obligations under the Convention on International Civil Aviation, it is FAA policy to comply with International Civil Aviation Organization (ICAO) Standards and Recommended Practices to the maximum extent practicable. The FAA has determined that there are no ICAO Standards and Recommended Practices that correspond to these regulations.

### **IV. *Final Regulatory Evaluation, Regulatory Flexibility Determination, International Trade Impact Assessment, and Unfunded Mandates Assessment***

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 (Public Law 96-354) requires agencies
to analyze the economic impact of regulatory changes on small entities.
Third, the Trade Agreements Act (Public Law 96-39) prohibits agencies
from setting standards that create unnecessary obstacles to the foreign
commerce of the United States. In developing U.S. standards, the Trade
Act requires agencies to consider international standards and, where
appropriate, that they be the basis of U.S. standards. Fourth, the
Unfunded Mandates Reform Act of 1995 (Public Law 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 with base year of
1995). This portion of the preamble summarizes the FAA's analysis of the
economic impacts of this final rule.

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 proposed or final rule
does not warrant a full evaluation, this order permits that a statement
to that effect and the basis for it 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 final rule. The reasoning
for this determination follows.

We begin with a discussion of the AASFR. Then we discuss the existing
certification and operational rules that already require operators to
develop and implement the DT inspections and procedures this final rule
will require.

This rule transfers the responsibility of developing AASFR DT data and
documents from operators to DAHs. A transfer of responsibility from one
entity to another does not increase societal costs; therefore, this rule
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 required DT data and documents.
The recently published AASFR[^40] requires airline operators of certain
large transport category airplanes to implement DT-based inspections and
procedures for airplane structure susceptible to fatigue cracking that
could contribute to catastrophic failure. Damage tolerance data are
essential for operators to implement and conduct DT-based inspections
and procedures.

This final rule is a counterpart to the AASFR to ensure that operators
have the necessary data and documents to support timely compliance with
the requirements of §§ 121.1109 and 129.109. Timely operator compliance
improves the safety of the fleet.

This final rule will require DAHs to develop DT inspections and
procedures for repairs and alterations. Existing operational rules
already require DT inspections and procedures for repairs and
alterations to baseline structure. TC Holders of airplanes certified to
Amendment 25-45 (or later), which are affected by this proposal, are
required by §25.571 to perform a damage tolerance evaluation and
establish, as necessary, damage tolerance inspections or other
procedures. On pre-Amendment 25-45 airplanes, DT inspection and
procedures for the baseline structure are required by airworthiness
directive (AD). Damage tolerance inspections for repairs and alterations
to affected Boeing 727 and 737-100/200 airplanes are also required by
AD. Damage tolerance inspections for repairs to the pressurized
fuselage[^41] for certain pre-Amendment 25-45 airplanes[^42] are
required by § 121.370 (redesignated as § 121.1107). By December 2010,
damage tolerance inspections for the baseline structure and repairs and
alterations will be required by §§121.1109 and 129.109 for airplanes
certificated after January 1, 1958 that have a passenger seating
capacity of 30 or more or a maximum payload capacity of 7500 pounds or
more. 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.

The following table summarizes the regulatory requirements for DT
inspection programs. The shaded areas in the table represent regulatory
gaps filled by the AASFR (§121.1109) requirements to develop DT
inspections and procedures for fatigue critical airplane structural
areas.

+-------------+-------------+-------------+--------------+-----------+
| #####       | # **Airplan |             |              |           |
|             | e Damage To |             |              |           |
|             | lerance Req |             |              |           |
|             | uirements** |             |              |           |
+-------------+-------------+-------------+--------------+-----------+
| #### **[Am  | BASELINE    | REPAIRS     | REPAIRS      | ALT       |
| endment Lev | structure   |             |              | ERATIONS/ |
| el]{.underl |             | to fuselage | to all other | MODI      |
| ine} Airpla |             | & door      | areas        | FICATIONS |
| ne Models** |             | skin,       |              |           |
|             |             | bulkhead    |              |           |
|             |             | webs        |              |           |
+-------------+-------------+-------------+--------------+-----------+
| #           | [Ce         | [Ce         | [C           | [Cert     |
|  **[25-45 o | rtification | rtification | ertification | ification |
| r later]{.u | Basis]{     | Basis]{     | Basis]       | Basis]{.u |
| nderline}** | .underline} | .underline} | {.underline} | nderline} |
|             |             |             |              |           |
| 737-600/7   | § 25.571    | § 25.571    | § 25.571     | § 25.571  |
| 00/800/900, |             |             |              |           |
| 757, 767,   | **-** Amdt  | \- Amdt     | **-** Amdt   | **-**     |
| 777, MD11,  | 25-45 and   | 25-45 and   | 25-45 and    | Amdt      |
| ATR42/72,   | later       | later       | later        | 25-45 and |
| F100, A320, | amendments  | amendments  | amendments   | later     |
| A321, A318, | require     | require     | require      | a         |
| A319,       | damage      | damage      | damage       | mendments |
| A300-600,   | tolerance   | tolerance   | tolerance    | require   |
| A310, A340, | (DT)        | (DT)        | (DT)         | damage    |
| A330,       | inspections | inspections | inspections  | tolerance |
| A380,\      |             |             |              | (DT)      |
| EMB         |             |             |              | in        |
| 135/1       |             |             |              | spections |
| 45/170/190, |             |             |              |           |
| SAAB 340/   |             |             |              |           |
| 2000,\      |             |             |              |           |
| CL-60       |             |             |              |           |
| 0/700/900,\ |             |             |              |           |
| DHC-8, CASA |             |             |              |           |
| C-295,      |             |             |              |           |
| CN-23       |             |             |              |           |
| 5[,]{.mark} |             |             |              |           |
| DO-328, DO  |             |             |              |           |
| 328JET,     |             |             |              |           |
| BAE146,     |             |             |              |           |
| AVRO 146,   |             |             |              |           |
| BAE         |             |             |              |           |
| Jetstream   |             |             |              |           |
| 4100        |             |             |              |           |
+-------------+-------------+-------------+--------------+-----------+
| # **[Pr     | ##          | [§          | ## [SID ADs] | ## [SI    |
| e 25-45]{.u |             | 121.1107]{  | {.underline} | D ADs]{.u |
| nderline}** | ## [SID]{.  | .underline} |              | nderline} |
|             | underline}[ |             |              |           |
| 727,        | ^43] [ADs]{ | [(Repair    |              |           |
| 737-100/200 | .underline} | Assessment  |              |           |
|             |             | Rule) and   |              |           |
|             |             | SID         |              |           |
|             |             | ADs]{       |              |           |
|             |             | .underline} |              |           |
+-------------+-------------+-------------+--------------+-----------+
| **[Pre      | [A SID has  | #           | #            | #         |
| 25-45]{.u   | been        |             |              |           |
| nderline}** | developed]{ | [§          | [§           | [§        |
|             | .underline} | 121.1107]{  | 121.1109]    | 121       |
| # 737-      |             | .underline} | {.underline} | .1109]{.u |
| 300/400/500 | ## AD       |             |              | nderline} |
|             |  is pending | [(Repair    |              |           |
|             |             | Assessment  |              |           |
|             |             | Rule) and   |              |           |
|             |             | SID         |              |           |
|             |             | ADs]{       |              |           |
|             |             | .underline} |              |           |
+-------------+-------------+-------------+--------------+-----------+
| # **[Pr     | ##          | [§          | [§           | [§        |
| e 25-45]{.u |             | 121.1107]{  | 121.1109]    | 121       |
| nderline}** | ##          | .underline} | {.underline} | .1109]{.u |
|             |             |             |              | nderline} |
| A300, 747,  | ##          | [(Repair    |              |           |
| F-28,\      |  [SID ADs]{ | Assessment  |              |           |
| L-          | .underline} | Rule) and   |              |           |
| 1011-1/-2,\ |             | SID         |              |           |
| DC-8, DC-9, |             | ADs]{       |              |           |
| MD-80,      |             | .underline} |              |           |
| DC-10       |             |             |              |           |
+-------------+-------------+-------------+--------------+-----------+
| **[Pre      | [SID        | #           | #            | #         |
| 25-45]{.u   | ADs]{       |             |              |           |
| nderline}** | .underline} | [§          | [§           | [§        |
|             |             | 121.1109]{  | 121.1109]    | 121       |
| #########   |             | .underline} | {.underline} | .1109]{.u |
|  L-188, F27 |             |             |              | nderline} |
+-------------+-------------+-------------+--------------+-----------+
| **[Pre      | [DT data    | #           | #            | #         |
| 25-45]{.u   | have been   |             |              |           |
| nderline}** | developed]{ | [§          | [§           | # [§ 121  |
|             | .underline} | 121.1109]{  | 121.1109]    | .1109]{.u |
| ####        |             | .underline} | {.underline} | nderline} |
| ##### L-382 |             |             |              |           |
|             |             |             |              |           |
| L1011-3     |             |             |              |           |
+-------------+-------------+-------------+--------------+-----------+

In summation, this final rule will transfer the responsibility from the
existing requirements for developing DT based inspections and procedures
from part 121 operators to DAHs. 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 will be amortized
over a larger fleet. This final rule will 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.

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
final rulemaking action: (1) will not have a significant economic impact
on a substantial number of small entities; (2) will not affect
international trade; and (3) will not impose an unfunded mandate on
State, local, or tribal governments, or on the private sector.

### **Regulatory Flexibility Determination**

The Regulatory Flexibility Act of 1980 (Public Law 96-354) (RFA)
establishes "as a principle of regulatory issuance that agencies shall
endeavor, consistent with the objectives of the rule and of applicable
statutes, to fit regulatory and informational requirements to the scale
of the businesses, organizations, and governmental jurisdictions subject
to regulation. To achieve this principle, agencies are required to
solicit and consider flexible regulatory proposals and to explain the
rationale for their actions to assure that such proposals are given
serious consideration." 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 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 RFA.

However, if an agency determines that a rule is not expected to have a
significant economic impact on a substantial number of small entities,
section 605(b) of the RFA provides that the head of the agency may so
certify and a regulatory flexibility analysis is not required. The
certification must include a statement providing the factual basis for
this determination, and the reasoning should be clear.

We did not receive comments from U.S. small entities in the responses to
the proposed rule.

The FAA recently adopted the Aging Airplane Safety Final Rule
(AASFR),[^44] which, among other things, requires airline operators of
certain large transport category airplanes[^45] to implement damage
tolerance (DT) based inspections and procedures for airplane structure.

This final rule is a counterpart to the AASFR. By the effective date of
this rule, DT inspection programs will already be required by AD,
certification or operational regulations for all part 121 airplanes
affected by this proposal. The final rule will transfer the requirement
to develop AASFR DT based data for inspections and procedures from part
121 operators to design approval holders (DAH). A significant number of
part 121 operators are small entities. By transferring the
responsibility from part 121 operators to DAH, this final rule may
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, and Raytheon Aircraft. These manufacturers
will 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 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, as the Acting FAA Administrator, I certify that this rule
will not have a significant economic impact on a substantial number of
small entities.

### **International Trade Impact Assessment**

The Trade Agreements Act of 1979 (Public Law 96-39) 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 final rule and determined that it will impose the same
costs on domestic and international entities and thus has a neutral
trade impact.

### **Unfunded Mandate Assessment**

Title II of the Unfunded Mandates Reform Act of 1995 (Public Law 104-4)
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 with the base year 1995) 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 \$128.1
million in lieu of \$100 million.

This final rule does not contain such a mandate. The requirements of
Title II do not apply.

**Executive Order 13132, Federalism**

The FAA has analyzed this rule under the principles and criteria of
Executive Order 13132, Federalism. We determined that this action will
not have a substantial direct effect on the States, on the relationship
between the national Government and the States, or on the distribution
of power and responsibilities among the various levels of government,
and, therefore, will not have federalism implications.

**Environmental Analysis**

FAA Order 1050.1E identifies FAA actions that are categorically excluded
from preparation of an environmental assessment or environmental impact
statement under the National Environmental Policy Act in the absence of
extraordinary circumstances. The FAA has determined this rulemaking
action qualifies for the categorical exclusion identified in paragraph
312f and involves no extraordinary circumstances.

**Regulations that Significantly Affect Energy Supply, Distribution, or
Use**

The FAA has analyzed this final rule under Executive Order 13211,
Actions Concerning Regulations that Significantly Affect Energy Supply,
Distribution, or Use (May 18, 2001). We have determined that it is not a
"significant energy action" under Executive Order 12866, and it is not
likely to have a significant adverse effect on the supply, distribution,
or use of energy.

**Availability of Rulemaking Documents**

> You can get an electronic copy of rulemaking documents using the
> Internet by---

1.  Searching the Federal eRulemaking Portal
    (http://www.regulations.gov);

```{=html}
<!-- -->
```
1.  Visiting the FAA's Regulations and Policies Web page at
    http://www.faa.gov/regulations_policies/; or

2.  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 amendment number or docket number of this rulemaking.

Anyone is able to search the electronic form of all comments received
into any of our dockets by the name of the individual submitting the
comment (or signing the comment, if submitted on behalf of an
association, business, labor union, etc.). You may review DOT's complete
Privacy Act statement in the Federal Register published on April 11,
2000 (Volume 65, Number 70; Pages 19477-78) or you may visit
[http://DocketsInfo.dot.gov](http://dms.dot.gov/).

Small Business Regulatory Enforcement Fairness Act

The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 1996
requires FAA to comply with small entity requests for information or
advice about compliance with statutes and regulations within its
jurisdiction. If you are a small entity and you have a question
regarding this document, you may contact your local FAA official, or the
person listed under the FOR FURTHER INFORMATION CONTACT heading at the
beginning of the preamble. You can find out more about SBREFA on the
Internet at
http://www.faa.gov/regulations_policies/rulemaking/sbre_act/.

**List of Subjects**

[14 CFR Part 26]{.underline}

Aircraft, Aviation safety, Continued airworthiness

[14 CFR Parts 121, 129]{.underline}

Air carriers, Aircraft, Aviation safety, Reporting and recordkeeping
requirements, Continued airworthiness

####### V. The Amendments

In consideration of the foregoing, the Federal Aviation Administration
amends Chapter I of Title 14, Code of Federal Regulations parts 26, 121,
and 129 as follows:

Part 26---Continued Airworthiness and Safety Improvements for Transport
Category Airplanes

1\. The authority citation for part 26 continues to read as follows:

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

2\. Revise § 26.5 to read as follows:

§ 26.5 Applicability table.

Table 1 of this section provides an overview of the applicability of
this part. It provides guidance in identifying what sections apply to
various types of entities. The specific applicability of each subpart
and section is specified in the regulatory text.

**TABLE 1**

> Applicability of Part 26 Rules

+--------------------+------------------------+-----------------------+
|                    | **Applicable           |                       |
|                    | Sections**             |                       |
+--------------------+------------------------+-----------------------+
|                    | Subpart B (EAPAS/FTS)  | Subpart E             |
|                    |                        |                       |
|                    |                        | Damage Tolerance Data |
+--------------------+------------------------+-----------------------+
| Effective Date of  | December 10, 2007      | \[insert date 30 days |
| Rule               |                        | after date of         |
|                    |                        | publication\]         |
+--------------------+------------------------+-----------------------+
| Existing^1^ TC     | 26.11                  | 26.43, 26.45, 26.49   |
| Holders            |                        |                       |
+--------------------+------------------------+-----------------------+
| Pending^1^ TC      | 26.11                  | 26.43, 26.45          |
| Applicants         |                        |                       |
+--------------------+------------------------+-----------------------+
| Existing^1^ STC    | N/A                    | 26.47, 26.49          |
| Holders            |                        |                       |
+--------------------+------------------------+-----------------------+
| Pending^1^ STC/ATC | 26.11                  | 26.45, 26.47, 26.49   |
| Applicants         |                        |                       |
+--------------------+------------------------+-----------------------+
| Future^2^ STC/ATC  | 26.11                  | 26.45, 26.47, 26.49   |
| Applicants         |                        |                       |
+--------------------+------------------------+-----------------------+
| Manufacturers      | N/A                    | N/A                   |
+--------------------+------------------------+-----------------------+
| Persons seeking    | N/A                    | N/A                   |
| design approval of |                        |                       |
| repairs            |                        |                       |
+--------------------+------------------------+-----------------------+

^1^ As of the effective date of the identified rule.

^2^ Application made after the effective date of the identified rule.

3\. Amend part 26 to add subparts C, D, and E to read as follows:

Subpart C \[Reserved\]

Subpart D \[Reserved\]

Subpart E---Aging Airplane Safety---Damage Tolerance Data for Repairs
and Alterations

§ 26.41 Definitions.

§ 26.43 Holders of and applicants for type certificates---Repairs.

§ 26.45 Holders of type certificates---Alterations and repairs to
alterations.

§ 26.47 Holders of and applicants for a supplemental type
certificate--Alterations and repairs to alterations.

§ 26.49 Compliance plan.

SUBPART C \[Reserved\]

SUBPART D \[Reserved\]

SUBPART E\--AGING AIRPLANE SAFETY---DAMAGE TOLERANCE DATA FOR REPAIRS
AND ALTERATIONS

§ 26.41 Definitions.

[Affects (or Affected)]{.underline} means structure has been physically
repaired, altered, or modified, or the structural loads acting on the
structure have been increased or redistributed.

[Baseline structure]{.underline} means structure that is designed under
the original type certificate or amended type certificate for that
airplane model.

[Damage Tolerance Evaluation (DTE)]{.underline} 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, a 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]{.underline} (DTI) means the inspection
developed as a result of a DTE. A DTI includes the areas to be
inspected, the inspection method, the inspection procedures, including
acceptance and rejection criteria, the threshold, and any repeat
intervals associated with those inspections. The DTI may specify a time
limit when a repair or alteration needs to be replaced or modified. If
the DTE concludes that DT-based supplemental structural inspections are
not necessary, the DTI contains a statement to that effect.

[DT data]{.underline} mean DTE documentation and the DTI.

[DTE documentation]{.underline} means data that identify the evaluated
fatigue critical structure, the basic assumptions applied in a DTE, and
the results of a DTE.

[Fatigue critical structure]{.underline} means airplane structure that
is susceptible to fatigue cracking that could contribute to a
catastrophic failure, as determined in accordance with § 25.571 of this
chapter. Fatigue critical structure includes structure, which, if
repaired or altered, could be susceptible to fatigue cracking and
contribute to a catastrophic failure. Such structure may be part of the
baseline structure or part of an alteration.

[Implementation schedule]{.underline} 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. The documentation must identify times when actions must be
taken as specific numbers of airplane flight hours, flight cycles, or
both.

[Published repair data]{.underline} mean instructions for accomplishing
repairs, which are published for general use in structural repair
manuals and service bulletins (or equivalent types of documents).

§ 26.43 Holders of and applicants for type certificates---Repairs.

\(a\) [Applicability]{.underline}. Except as specified in paragraph (g)
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.

\(b\) [List of fatigue critical baseline structure]{.underline}. For
airplanes specified in paragraph (a) of this section, the holder of or
applicant for a type certificate must---

\(1\) Identify fatigue critical baseline structure for all airplane
model variations and derivatives approved under the type certificate;
and

\(2\) Develop and submit to the FAA Oversight Office for review and
approval, a list of the structure identified under paragraph (b)(1) of
this section and, upon approval, make the list available to persons
required to comply with § 26.47 and §§ 121.1109 and 129.109 of this
chapter.

\(c\) [Existing and future published repair data]{.underline}*.* For
repair data published by a holder of a type certificate that is current
as of \[insert date 30 days after date of publication in the [Federal
Register]{.underline}\] 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 under
paragraph (b)(1) of this section;

\(2\) Perform a DTE and develop the DTI for each repair identified under
paragraph (c)(1) of this section, unless previously accomplished;

\(3\) Submit the DT data to the FAA Oversight Office or its properly
authorized designees for review and approval; and

\(4\) Upon approval, make the DTI available to persons required to
comply with §§ 121.1109 and 129.109 of this chapter.

\(d\) [Future repair data not published]{.underline}*.* For repair data
developed by a holder of a type certificate that are approved after
\[insert date 30 days after date of publication in the [Federal
Register]{.underline}\] and are 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 the DTI.

(2) Submit the DT data required in paragraph (d)(1) of this section 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 §§ 121.1109 and 129.109 of this chapter.

\(e\) [Repair Evaluation Guidelines]{.underline}. 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 under
        paragraph (b)(1) of this section and § 26.45(b)(2);

    ii.  A process that will enable operators to obtain the DTI for
        repairs identified under paragraph (e)(1)(i) of this section;
        and

    iii. An implementation schedule for repairs covered by the repair
         evaluation guidelines. The implementation schedule must
         identify times when actions must be taken as specific numbers
         of airplane flight hours, flight cycles, or both.

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 §§ 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, make such assistance available in
accordance with the implementation schedule.

(f) [Compliance times]{.underline}. 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 identified list of fatigue critical baseline structure
required by paragraph (b)(2) of this section must be submitted no later
than 180 days after \[insert date 30 days after date of publication in
the [Federal Register]{.underline}\] or before issuance of the type
certificate, whichever occurs later.

(2) For published repair data that are current as of \[insert date 30
    days after date of publication in the [Federal
    Register]{.underline}\], the DT data required by paragraph (c)(3) of
    this section must be submitted by June 30, 2009.

(3) For repair data published after \[insert date 30 days after date of
    publication in the [Federal Register]{.underline}\], the DT data
    required by paragraph (c)(3) of this section must be submitted
    before FAA approval of the repair data.

(4) For unpublished repair data developed after \[insert date 30 days
    after date of publication in the [Federal Register]{.underline}\],
    the DT data required by paragraph (d)(1) of this section must be
    submitted within 12 months of the airplane's return to service or in
    accordance with a schedule approved by the FAA Oversight Office.

(5) The repair evaluation guidelines required by paragraph (e)(1) of
    this section must be submitted by December 30, 2009.

\(g\) [Exceptions]{.underline}*.* The requirements of this section do
not apply to the following transport 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) deHavilland DHC-7, TCDS No. A20EA

(10) VFW-Vereinigte Flugtechnische Werk VFW-614, TCDS No. A39EU

(11) Illyushin Aviation IL 96T, TCDS No. A54NM

(12) Bristol Aircraft Britannia 305, TCDS No. 7A2

(13) Handley Page Herald Type 300, TCDS No. A21N

(14) Avions Marcel Dassault - Breguet Aviation Mercure 100C, TCDS No.
     A40EU

(15) Airbus Caravelle, TCDS No. 7A6

(16) Lockheed L-300, TCDS No. A2S0

(17) Boeing 707-100/-200, TCDS No. 4A21

(18) Boeing 707-300/-400, TCDS No. 4A26

(19) Boeing 720, TCDS No. 4A28

§ 26.45 Holders of type certificates---Alterations and repairs to
alterations.

a.  [Applicability]{.underline}. This section applies to transport
    category airplanes subject to\
    § 26.43.

b.  [Fatigue critical alteration structure]{.underline}. For existing
    and future alteration data developed by the holder of a type
    certificate, the holder must---

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1.  Review existing alteration data and identify all alterations that
    affect fatigue critical baseline structure identified under §
    26.43(b)(1);

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(2) For each alteration identified under paragraph (b)(1) of this
    section, identify any fatigue critical alteration structure;

(3) Develop and submit to the FAA Oversight Office for review and
    approval a list of the structure identified under paragraph (b)(2)
    of this section; and

(4) Upon approval, make the list required in paragraph (b)(3) of this
    section available to persons required to comply with §§ 121.1109 and
    129.109 of this chapter.

\(c\) [DT Data]{.underline}*.* For existing and future alteration data
developed by the holder of a type certificate that affect fatigue
critical baseline structure identified under\
§ 26.43(b)(1), unless previously accomplished, the holder must---

\(1\) Perform a DTE and develop the DTI for the alteration and fatigue
critical baseline structure that is affected by the alteration;

\(2\) Submit the DT data developed in accordance with paragraph~~s~~
(c)(1) of this section to the FAA Oversight Office or its properly
authorized designees for review and approval; and

\(3\) Upon approval, make the DTI available to persons required to
comply with\
§§ 121.1109 and 129.109 of this chapter.

(d) [DT Data for Repairs Made to Alterations]{.underline}*.* For
    existing and future repair data developed by a holder of a type
    certificate, the type certificate holder must---

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(1) Review the repair data, and identify each repair that affects any
    fatigue critical alteration structure identified under paragraph
    (b)(2) of this section;

(2) For each repair identified under 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; and

(4) Upon approval, make the DTI available to persons required to comply
    with §§ 121.1109 and 129.109 of this chapter.

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(e) [Compliance times]{.underline}. 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 identified under
paragraph (b)(3) of this section must be submitted no later than 360
days after \[insert date 30 days after date of publication in the
[Federal Register]{.underline}\].

\(2\) For alteration data developed and approved before \[insert date 30
days after date of publication in the [Federal Register]{.underline}\],
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 \[insert date 30 days
after date of publication in the [Federal Register]{.underline}\], 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 \[insert date 30
days after date of publication in the [Federal Register]{.underline}\],
the DT data required by paragraph (d)(2) of this section must be
submitted by June 30, 2009.

\(5\) For repair data developed and approved after \[insert date 30 days
after date of publication in the [Federal Register]{.underline}\], the
DT data required by paragraph (d)(2) 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 §§
121.1109 and 129.109 of this chapter.

§ 26.47 Holders of and applicants for a supplemental type
certificate--Alterations and repairs to alterations.

\(a\) [Applicability]{.underline}. This section applies to transport
category airplanes subject to § 26.43.

\(b\) [Fatigue critical alteration structure]{.underline}. For existing
structural alteration data approved under a supplemental type
certificate, the holder of the supplemental type certificate must---

\(1\) Review the alteration data and identify all alterations that
affect fatigue critical baseline structure identified under §
26.43(b)(1);

\(2\) For each alteration identified under paragraph (b)(1) of this
section, identify any fatigue critical alteration structure;

> \(3\) Develop and submit to the FAA Oversight Office for review and
> approval a list of the structure identified under paragraph (b)(2) of
> this section; and

\(4\) Upon approval, make the list required by paragraph (b)(3) of this
section available to persons required to comply with §§ 121.1109 and
129.109 of this chapter.

\(c\) [DT Data]{.underline}*.* For existing and future alteration data
developed by the holder of a supplemental type certificate that affect
fatigue critical baseline structure identified under § 26.43(b)(1),
unless previously accomplished, the holder of a supplemental type
certificate must---

\(1\) Perform a DTE and develop the DTI for the alteration and fatigue
critical baseline structure that is affected by 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; and

\(3\) Upon approval, make the DTI available to persons required to
comply with\
§§ 121.1109 and 129.109 of this chapter.

(d) [DT data for repairs made to alterations]{.underline}*.* For
    existing and future repair data developed by the holder of a
    supplemental type certificate, the holder of a supplemental type
    certificate must---

    1.  Review the repair data, and identify each repair that affects
        any fatigue critical alteration structure identified under
        paragraph (b)(2) of this section;

    2.  For each repair identified under paragraph (d)(1) of this
        section, unless previously accomplished, perform a DTE and
        develop the 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; and

    4.  Upon approval, make the DTI available to persons required to
        comply with\
        §§ 121.1109 and 129.109 of this chapter.

(e) [Compliance times]{.underline}. 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 360
days after \[insert date 30 days after date of publication in the
[Federal Register]{.underline}\].

\(2\) For alteration data developed and approved before \[insert date 30
days after date of publication in the [Federal Register]{.underline}\],
the DT data required by paragraph (c)(2) of this section must be
submitted by June 30, 2009.

\(3\) For alteration data developed after \[insert date 30 days after
date of publication in the [Federal Register]{.underline}\], 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\
§§ 121.1109 and 129.109 of this chapter.

\(4\) For repair data developed and approved before \[insert date 30
days after date of publication in the [Federal Register]{.underline}\],
the DT data required by paragraph (d)(2) of this section must be
submitted by June 30, 2009.

\(5\) For repair data developed and approved after \[insert date 30 days
after date of publication in the [Federal Register]{.underline}\], the
DT data required by paragraph (d)(2) 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 §§
121.1109 and 129.109 of this chapter.

**§ 26.49 Compliance plan.**

\(a\) [Compliance plan]{.underline}*.* Except for applicants for type
certificates and supplemental type certificates whose applications are
submitted after \[insert date 30 days after date of publication in the
[Federal Register]{.underline}\], each person identified in §§ 26.43,
26.45, and 26.47, must submit a compliance plan consisting of the
following:

1.  A project schedule identifying all major milestones for meeting the
    compliance times specified in §§ 26.43(f), 26.45(e), and 26.47(e),
    as applicable.

2.  A proposed means of compliance with §§ 26.43, 26.45, and 26.47, as
    applicable.

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(3) A plan for submitting a draft of all compliance items required by
    this subpart for review by the FAA Oversight Office not less than 60
    days before the applicable compliance date.

\(b\) [Compliance dates for compliance plans]{.underline}. 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
    \[insert date 30 days after date of publication in the [Federal
    Register]{.underline}\].

\(2\) For holders of supplemental type certificates no later than 180
days after \[insert date 30 days after date of publication in the
[Federal Register]{.underline}\].

(3) For applicants for changes to type certificates whose application
    are submitted before \[insert date 30 days after date of publication
    in the [Federal Register]{.underline}\], no later than 180 days
    after \[insert date 30 days after date of publication in the
    [Federal Register]{.underline}\].

\(c\) [Compliance Plan Implementation]{.underline}*.* Each affected
person must implement the compliance plan as approved in compliance with
paragraph (a) of this section.

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

4\. The authority citation for part 121 continues to read as follows:

**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.

5\. Amend § 121.1109 to revise paragraph (c) to read as follows:

**§ 121.1109 Supplemental inspections.**

\* \* \* \* \*

\(c\) [General requirements]{.underline}*.* After December 20, 2010, a
certificate holder may not operate an airplane under this part unless
the following requirements have been met:

\(1\) [Baseline Structure]{.underline}. The certificate holder's
maintenance program for the airplane includes FAA-approved
damage-tolerance-based inspections and procedures for airplane structure
susceptible to fatigue cracking that could contribute to a catastrophic
failure. For the purpose of this section, this structure is termed
"fatigue critical structure."

\(2\) [Adverse effects of repairs, alterations, and
modifications]{.underline}. The maintenance program for the airplane
includes a means for addressing the adverse effects repairs,
alterations, and modifications may have on fatigue critical structure
and on inspections required by paragraph (c)(1) of this section. The
means for addressing these adverse effects must be approved by the FAA
Oversight Office.

\(3\) [Changes to maintenance program]{.underline}. The changes made to
the maintenance program required by paragraphs (c)(1) and (c)(2) of this
section, and any later revisions to these changes, must be submitted to
the Principal Maintenance Inspector for review and approval.

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

6\. 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.

7\. Amend 129.109 by revising paragraph (b) to read as follows:

**§ 129.109 Supplemental inspections for U.S.-registered aircraft.**

**\* \* \* \* \***

\(b\) [General requirements]{.underline}*.* After December 20, 2010, a
certificate holder may not operate an airplane under this part unless
the following requirements have been met:

\(1\) [Baseline Structure]{.underline}. The certificate holder's
maintenance program for the airplane includes FAA-approved
damage-tolerance-based inspections and procedures for airplane structure
susceptible to fatigue cracking that could contribute to a catastrophic
failure. For the purpose of this section, this structure is termed
"fatigue critical structure."

\(2\) [Adverse effects of repairs, alterations, and
modifications]{.underline}. The maintenance program for the airplane
includes a means for addressing the adverse effects repairs,
alterations, and modifications may have on fatigue critical structure
and on inspections required by paragraph (b)(1) of this section. The
means for addressing these adverse effects must be approved by the FAA
Oversight Office.

\(3\) [Changes to maintenance program]{.underline}. The changes made to
the maintenance program required by paragraph (b)(1) and (b)(2) of this
section, and any later revisions to these changes, must be submitted to
the Principal Maintenance Inspector for review and approval.

Robert A. Sturgell

Acting Administrator

[^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.

[^2]:  Various segments of industry use the term "modification" to
    define a design change. We consider this term to be synonymous with
    the term "alteration." We use both terms in this rule to mean a
    design change that is made to an airplane.

[^3]: 70 FR 5518; February 2, 2005

[^4]: 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.

[^5]: For purposes of this rule, design approval holders (DAHs) are
    holders of type certificates (TCs) or supplemental type certificates
    (STCs) issued under 14 CFR part 21.

[^6]: Published repair data are instructions for accomplishing repairs,
    which are published for general use in structural repair manuals
    (SRMs) and service bulletins. These data are approved for general
    application to a particular airplane model or airplane
    configuration.

[^7]: This includes 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.

[^8]: 71 FR 20574

[^9]: AASFR: 70 FR 5518; February 2, 2005. See also 70 FR 23935; May 6,
    2005: Aging Airplane Safety; Correcting Amendment.

[^10]: 69 FR 45936; July 30, 2004

[^11]: 67 FR 72726; December 6, 2002

[^12]: 70 FR 40168; July 12, 2005: Fuel Tank Safety Compliance Extension
    (Final Rule) and Aging Airplane Program Update (Request for
    Comments)

[^13]: 70 FR 40166, July 12, 2005 (PS-ANM110-7-12-2005)

[^14]: 71 FR 20750

[^15]: Issued as AC 120-93

[^16]: AAWG Member Organizations: Boeing Commercial Airplanes, Federal
    Express (FedEx), Airbus, Air Transport Association (ATA), American
    Airlines, British Airways, Continental Airlines, Japan Airlines,
    Northwest Airlines, United Airlines, United Parcel Service (UPS),
    Airborne Express, US Airways, Federal Aviation Administration (FAA),
    and European Aviation Safety Agency (EASA).

[^17]: 71 FR 38541

[^18]: 72 FR 8834

[^19]: Issued as AC 120-93

[^20]: 72 FR 63364; November 8, 2007

[^21]: Certification Procedures for Products and Parts

[^22]: This section, which includes an applicability table for part 26,
    was adopted as part of the EAPAS final rule.

[^23]: These definitions were proposed in § 25.1823(b).

[^24]: The regulatory text in this rule refers to the ACO or office of
    the Transport Airplane Directorate with oversight responsibility for
    the relevant type certificate or supplemental type certificate as
    the FAA Oversight Office.

[^25]: Issued as AC 120-93

[^26]: AAWG industry representatives (a collective group of commenters
    who are members of the AAWG): Boeing Commercial Airplanes, Federal
    Express (FedEx), Airbus, American Airlines, British Airways,
    Continental Airlines, Japan Airlines, Northwest Airlines, United
    Airlines, United Parcel Service (UPS), Airborne Express, US Airways.

[^27]: 71 FR 19928; April 18, 2006

[^28]: 43 FR 46242; October 5, 1978

[^29]: 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.

[^30]: 71 FR 20583

[^31]: § 25.571(a): "An evaluation of the strength, detail design, and
    fabrication must show that catastrophic failure due to
    fatigue,...will be avoided throughout the operational life of the
    airplane. This evaluation must be conducted ....for each part of the
    structure which could contribute to a catastrophic failure (such as
    wing, empennage, control surfaces, fuselage, engine mounts, and
    their related primary attachments)..."

[^32]: 71 FR at 20583

[^33]: Repair Assessment for Pressurized Fuselages final rule (65 FR
    24108; April 25, 2000)

[^34]: Issued as AC 120-93

[^35]: Issued as AC 120-93

[^36]: 14 CFR §§ 21.3 and 121.703

[^37]: Special maintenance program requirements

[^38]: 69 FR 26641; May 13, 2004

[^39]: 67 FR 72726; December 6, 2002

[^40]: 70 FR 5518, February 2, 2005

[^41]: Fuselage, door skins, and bulkhead webs.

[^42]: 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, and DC-10.

[^43]: Supplemental Inspection Document.

[^44]: 70 FR 5518, February 2, 2005

[^45]: 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.