[Federal Register Volume 65, Number 80 (Tuesday, April 25, 2000)]
[Rules and Regulations]
[Pages 24108-24127]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-10220]



[[Page 24108]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 91, 121, 125, and 129

[Docket No. 29104; Amendment Nos. 91-264, 121-275, 125-33 & 129-28]
RIN 2120-AF81


Repair Assessment for Pressurized Fuselages

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: This action requires operators of certain transport category 
airplanes to incorporate repair assessment guidelines for the fuselage 
pressure boundary into their FAA-approved maintenance or inspection 
program. This action is the result of concern for the continued 
operational safety of airplanes that are approaching or have exceeded 
their design service goal. The purpose of the repair assessment 
guidelines is to establish a damage-tolerance based supplement 
inspection program for repairs to detect damage, which may develop in a 
repaired area, before that damage degrades the load carrying capability 
of the structure below the levels required by the applicable 
airworthiness standards.

EFFECTIVE DATE: May 25, 2000.

FOR FURTHER INFORMATION CONTACT: Brent Bandley, Los Angeles Aircraft 
Certification Office, Airframe Branch, ANM-120L, Transport Airplane 
Directorate, Federal Aviation Administration, 3960 Paramount Boulevard, 
Lakewood, California 90712-4137, telephone (562) 627-5237, fax (562) 
627-5210.

SUPPLEMENTARY INFORMATION:

Availability of Final Rules

    An electronic copy of this document may be downloaded using a modem 
and suitable communications software from the FAA regulations section 
of the FedWorld electronic bulletin board service (telephone: 703-321-
3339), or the Government Printing Office's (GPO's) electronic bulletin 
board service (telephone: (202) 512-1661).
    Internet users may reach the FAA's web page at http://www.faa.gov/avr/arm/nprm/nprm.htm or the (GPO) Federal Register web page at http://www.access.gpo.gov/nara for access to recently published rulemaking 
documents.
    Any person may obtain a copy of this document by submitting a 
request to the Federal Aviation Administration, Office of Rulemaking, 
ARM-1, 800 Independence Avenue SW., Washington, DC 20591, or by calling 
(202) 267-9680. Communications must identify the amendment or docket 
number of this final rule.
    Persons interested in being placed on a mailing list for future 
rulemaking documents should request from the above office a copy of 
Advisory Circular No. 11-2A, ``Notice of Proposed Rulemaking 
Distribution System,'' which describes the application procedure.

Small Business Regulatory Enforcement Fairness Act

    The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 
1996, requires the FAA to comply with small entity requests for 
information or advice about compliance with statutes and regulations 
within our jurisdiction. Therefore, any small entity that has a 
question regarding this document may contact their local FAA official 
Internet users can find additional information on SBREFA on the FAA's 
web page at http://faa.gov/avr/arm/sbrefa/htm and may send electronic 
inquires to the following Internet address: [email protected].

Background

    On December 22, 1998, the FAA issued Notice of Proposed Rulemaking 
(NPRM) 97-16, which was published in the Federal Register on January 2, 
1998 (98 FR 126). That NPRM proposed to prohibit the operation of 
certain transport category airplanes (operated under 14 CFR parts 91, 
121, 125, and 129) beyond a specified time, unless the operator of the 
airplane incorporated FAA-approved ``repair assessment guidelines'' 
into its approved maintenance inspection program. The FAA provided a 
period of 90 days for the public to submit input on the proposed rule. 
On April 3, 1998 (63 FR 16452), the FAA reopened the period for public 
comment for an additional 90 days. (A discussion of the comments 
received in response to the NPRM appears below.)
    The repair assessment guidelines, which are to be approved by the 
FAA for each airplane model affected by this rule, contain:

     A methodology for assessing the types of repairs 
expected to be found in the fuselage pressure boundary (fuselage 
skins, bulkhead webs, and door skin), and
     Methods to determine the damage-tolerance 
characteristics of the surveyed repairs.

    Each of the guidelines contains repetitive repair inspection 
intervals that are based on residual strength, crack growth, and 
inspectability evaluations, and are closely compatible with typical 
operator maintenance practices (i.e., C-checks, D-Checks, etc.).
    In addition to this final rule, the FAA has developed an associated 
advisory circular (AC), ``Repair Assessment of pressurized Fuselages.'' 
The AC provides guidance for operators of the affected transport 
category airplanes on how to incorporate FAA-approved repair assessment 
guidelines into their FAA-approved maintenanced or inspection program 
as a means to comply with this final rule. Availability of the AC will 
be announced in Federal Register in the near future.

Issues Prompting This Rulemaking Activity

    In April 1988, a high-cycle transport airplane enroute from Hilo to 
Honolulu, Hawaii, suffered major structural damage to its pressurized 
fuselage during flight. This accident was attributed in part to the age 
of the airplane involved. The economic benefit of operating certain 
older technology airplanes has resulted in the operation of many such 
airplanes beyond their previously projected retirement age. Because of 
the problems revealed by the accident in Hawaii and the continued 
operation of older airplanes, both the FAA and industry generally 
agreed that increased attention needed to be focused on the aging fleet 
and on maintaining its continued operational safety.
    In June 1988, the FAA sponsored a conference on aging airplanes. As 
a result of that conference, the FAA established a task force in August 
1988 as a sub-group of the FAA's Research, Engineering, the Development 
Advisory Committee, representing the interests of the aircraft 
operators, aircraft manufacturers, regulatory authorities, and other 
aviation representatives. The task force, then known as the 
Airworthiness Assurance Task Force (AATF), set forth five major 
elements of a program for each airplane model in the aging transport 
fleet that would serve to keep the aging fleet safe:

     Select service bulletins describing modificaitons and 
inspections necessary to maintain structural integrity;
     Develop inspection and prevention programs to address 
corrosion;
     Develop generic structural maintenance program 
guidelines for aging airplanes;
     Review and update the Supplemental Structural 
Inspection Documents (SSID) which describe inspection programs to 
detect fatigue cracking, and
     Assess damage-tolerance of structural repairs.

    By Federal Register notice, dated November 30, 1992 (57 FR 56627), 
the

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AATF was placed under the auspices of the Aviation Rulemaking Advisory 
Committee (ARAC) and renamed as the Airworthiness Assurance Working 
Group (AAWG). Structures Task Groups, sponsored by the AAWG, were 
assigned the task of developing the five elements into workable 
programs. The AAWG completed work on the first four of the elements 
lists above at the time Notice 97-16 was issued. Issuance of this final 
rule completes the fifth element.
    This final rule addresses the specific task assigned to the AAWG 
relevant to the fifth element, which was to develop recommendations 
concerning whether new or revised requirements and compliance methods 
for structural repair assessments of existing repairs should be 
initiated and mandated for the following airplanes.

     Airbus Model A300 (excluding the -600 series);
     British Aerospace Model BAC 1-11;
     Boeing Models 707/720, 727, 737, and 747;
     McDonnell Douglas Models DC-8, DC-9/MD-80, and DC-10;
     Fokker Model F-28;and
     Lockheed Model L-1011.

Related Regulatory Activity

    In addition to these initiatives, there are other on-going 
activities associated with FAA's Aging Aircraft Program.
    The Aging Aircraft Safety Act of 1991 (Public Law 49 U.S.C. 44717) 
instructed the FAA Administrator to prescribe regulations that will 
ensure the continuing airworthiness of aging aircraft through 
inspections and reviews of the maintenance record of each aircraft an 
air carrier uses in air transportation. In response, the FAA published 
Notice 93-14 (58 FR 51944, October 5, 1993)). Among other things, that 
notice proposed to require operators to.

     Certify aging airplane maintenance actions;
     Establish a framework for imposing operational limits 
on certain airplanes; and
     Perform additional maintenance actions, such as 
inspections or parts replacements, in order to continue operating 
the airplane.

    The FAA subsequently withdraw Notice 94-14, and issued a new Notice 
99-02 (64 FR 16298, April 2, 1999). The new notice proposes to require 
that all airplanes operating under parts 121, 129, and 135 undergo 
records reviews and inspection after their 14th year in service to 
ensure that the maintenance of these airplanes' age-sensitive parts and 
components has been adequate and timely. The proposed new rule also 
would prohibit operation of these airplanes after specified deadlines, 
unless damage-tolerance-based inspections and procedures are included 
in their maintenance or inspection program. The period or public 
comment on the proposal ended on August 2, 1999, and the FAA 
anticipates regulatory action in the near future.
    In addition, the FAA has found that some operators do not have a 
programmatic approach to corrosion prevention and control programs 
(CPCP). In its accident investigation report (NTSB/AAR-89/03) on the 
Hawaii accident, the NTSB recommended that the FAA mandate a 
comprehensive and systematic CPCP. Therefore, the FAA is considering 
rulemaking to mandate CPCP's for all airplanes used in air 
transportation. As part of that deliberation, the FAA is considering 
the CPCP's recommended by the AATF and previously mandated by the FAA 
through airworthiness directives (AD); all of the airplanes affected by 
this proposal currently are subject to those AD's.

The Concern Posed by Older Repairs

    The basic structure of the large jet transports that are affected 
by this final rule was required at the time of original certification 
to meet the applicable regulatory standards for fatigue or fail-safe 
strength. Repairs and modifications to this structure also were 
required to meet these same standards. The early fatigue or fail-safe 
requirements, however, did not provide for timely inspection of 
critical structure so that damaged or failed components could be 
dependably identified and repaired or replaced before a hazardous 
condition developed.
    By amendment 25-45 (43 FR 46242, October 5, 1978), the FAA amended 
Sec. 25.571 (``Damage-tolerance and fatigue evaluation of structure'') 
by introducing a new certification requirement called ``damaged-
tolerance'' to assure the continued structural integrity of transport 
category airplanes certificated after that time. Additionally, for 
existing designs, guidance material based on that amendment was 
published in 1981 as Advisory Circular (AC 91-56), ``Supplemental 
Structural Inspection Program for Large Transport Category Airplanes.''
    Damage-tolerance is a structural design and inspection methodology 
used to maintain safety, considering the possibility of metal fatigue 
or other structural damage (i.e., safety is maintained by adequate 
structural inspection until the damage is repaired). The underlying 
principle for damage-tolerance is that the initiation and growth of 
structural fatigue damage can be anticipated with sufficient precision 
to allow inspection programs to safely detect damage before it reaches 
a critical size. A damage-tolerance evaluation entails.

     The prediction of sites where fatigue cracks are most 
likely to initiate in the airplane structure;
     The prediction of the crack growth under repeated 
airplane structural loading;
     The prediction of the size of the damage at which 
strength limits are exceeded; and
     An analysis of the potential opportunities for 
inspection of the damage as it progress.

    Information from the evaluation is used to establish an inspection 
program for structure, which, if rigorously followed, will be able to 
detect cracking that may develop before it precipitates a major 
structural failure. The evidence to date is that, when all critical 
structure is included, the damage-tolerance concept and the 
supplemental inspection programs that are based on it provide the best 
assurance of continued structural integrity that currently is 
available.
    In order to apply the damage tolerance concept to existing 
transport airplanes, the FAA issued a series of AD's, beginning in 
1984, that require operators to comply with supplemental structure 
inspection programs resulting from the concept's application to 
existing airplanes. Nearly all of the airplane models affected by this 
final rule currently are subject to such AD's. Generally, those AD's 
require that operators incorporate Supplemental Structural Inspection 
Documents (SSID) into their maintenance programs for the affected 
airplanes. These documents were derived from damage-tolerance 
assessments of the originally-certificate type designs for these 
airplanes. For this reason, the majority of AD's written for the SSID 
program did not attempt to address issues relating to the damage-
tolerance of repairs that had been made to the airplanes. The objective 
of this final rule is to provide that same level of assurance for areas 
of the structure that have been repaired.
    Repairs are a concern on older airplanes because of the possibility 
that they may develop, cause, or obscure metal fatigue, corrosion, or 
other damage during service. This damage might occur within the repair 
itself or in the adjacent structure, and might ultimately lead to 
structural failure. The damage-tolerance evaluation of a repair would 
be used in an assessment program to establish an appropriate inspection 
program, or a replacement schedule if the necessary inspection program 
is too demanding or not possible. The objective of the repair

[[Page 24110]]

assessment is to assure the continued structural integrity of the 
repaired and adjacent structure based on damage-tolerance principles.
    In general, repairs present a more challenging problem to solve 
than the original structure because each repair is unique and tailored 
in design to correct particular damage to the original structure. 
Whereas the performance of the original structure may be predicted from 
tests and from experience on other airplanes in service, the behavior 
of a repair and its effect on the fatigue characteristics of the 
original structure are generally not known to the same extent as for 
the basic unrepaired structure.
    The available service record and surveys of out-of-service and in-
service airplanes have indicated that existing repairs generally 
perform well. Although the cause of an airplane accident has never been 
attributed to properly applied repairs using the original repair data, 
repairs may be of concern as time-in-service increases for the 
following reasons:
    1. As airplane age, both the number and age of the existing repairs 
increase. Along with this increase is the possibility of unforeseen 
repair interaction, autogenous failure, or other damage occurring in 
the repaired area. The continued operational safety of these airplanes 
depends primarily on a satisfactory maintenance program (inspections 
conducted at the right time, in the right place, using the most 
appropriate technique). To develop this program, a damage-tolerance 
evaluation of repairs to flight critical structure is essential. The 
longer an airplane is in service, the more important this evaluation 
and a subsequent inspection program become.
    2. The practice of damage-tolerance methodology has evolved 
gradually over the last 20 or more years. Some repair described in the 
airplane manufacturers' Structural Repair Manuals (SRM) were not 
designed to current standards. Repairs accomplished in accordance with 
the information contained in the early versions of the SRM's may 
require additional inspections if evaluated using the current 
methodology.
    3. Because a regulatory requirement for damage-tolerance was not 
applied to airplane designs type certificated before 1978, the damage-
tolerance characteristics of repairs may vary widely and are largely 
unknown.

Development of ``Repair Assessment Guidelines''

    To address the ARAC assignment relative to repairs, the AAWG tasked 
the manufacturers to develop ``repair assessment guidelines (RAG)'' 
requiring specific maintenance programs to maintain the damage-
tolerance integrity of the basic airframe. The following criteria were 
developed to assist the manufacturers in the development of the 
guidance material:

     Repairs that do not conform to SRM standards must be 
reviewed and may require further action.
     Repairs must be reviewed where the repair has been 
installed in accordance with SRM data that have been superseded or 
rendered inactive by new damage-tolerant designs.
     Repairs that are in close proximity to other repairs or 
modifications require review to determine their impact on the 
continued airworthiness of the airplane.
     Repairs that exhibit structural distress should be 
replaced before flight.

    To identify the scope of the overall program, fleet data were 
required. This resulted in the development of a five-step program to 
develop factual data for the development of the rule. The five-step 
AAWG program consisted of:
    Step 1. Development of model specific RAG's using AAWG repair 
criteria.
    Step 2. Completion of a survey of a number of operators' airplanes 
to assess fuselage skin repairs and to validate the approach of the 
manufacturer's RAG.
    Step 3. Determination of the need for and the development of a 
worldwide survey.
    Step 4. Collection and assessment of results to determine further 
necessary actions.
    Step 5. Development of specific manufacturer/operator/FAA actions.
    Early in the development of this task, each manufacturer began to 
prepare model-specific RAG's. When sufficiently developed, these draft 
guidelines were shared with the operators to get feedback on 
acceptability and suggestions for improvement. The operators stressed 
the need for commonality in approach and ease of use of the guidelines. 
They also expressed the need for guidelines that could be used on the 
shop floor without engineering assistance and without extensive 
training.
    Meanwhile, the AAWG conducted two separate surveys of existing 
repairs on airplanes to collect necessary data. The first survey was 
conducted in March 1992 on certain large transport category airplanes 
being held in storage. Teams comprised of engineering representatives 
from various organizations, including FAA's Aircraft Certification and 
Flight Standards offices, operators, and manufacturers, surveyed 356 
external fuselage skin repairs on 30 airplanes of 6 types. Using repair 
classification criteria developed by the individual airplane 
manufacturers, the teams concluded that the general quality of the 
repairs appeared good. Forty percent of the repairs were adequate, 
requiring no supplemental inspections, and sixty percent needed a more 
comprehensive damage-tolerance based assessment, with the possibility 
that supplemental inspections might be needed. Some determining factors 
on the need for further assessment were the size of the repair and its 
proximity to other repairs. While the survey sample size was very small 
compared to the total population of transport airplanes type 
certificated prior to 1978, it provided objective information on the 
quality and damage-tolerance characteristics of existing airplane 
repairs.
    In 1994, the AAWG requested that the manufacturers conduct a second 
survey on airplane repairs to validate the 1992 results and to provide 
additional information relative to the estimated cost of the assessment 
program. The manufacturers were requested to visit airplanes that were 
operating their products and to conduct surveys on airplanes that were 
currently undergoing heavy maintenance. An additional 35 airplanes were 
surveyed in which 695 repairs were evaluated. This survey was expanded 
to include all areas of the airframe. The evaluation revealed 
substantially similar results to the 1992 results: forty percent of the 
repairs were classified as adequate, and sixty percent of the repairs 
required consideration for additional supplemental inspection during 
service. In addition, only a small number of repairs (less than 10 
percent) were found on portions of the airframe other than the external 
fuselage skin.
    The AAWG proposed that the repair assessment be initially limited 
to the fuselage pressure boundary; if necessary, future rulemaking 
would address the remaining primary structure. This limitation was 
based on two considerations:
    First, the fuselage is more sensitive to structural fatigue than 
other airplane structure because its normal operating loads are closer 
to its limit design loads. Stresses in a fuselage are primarily 
governed by the pressure relief valve settings of the environmental 
control system, and these are less variable from flight to flight than 
the gust or maneuver loads that typically determine the design stresses 
in other structure.
    Second, the fuselage is more prone to damage from ground service 
equipment than other structure and requires repair more often. The 
result of the second survey described above supports the

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conclusion that repairs to the fuselage are far more frequent than to 
any other structure.

Determining Which Airplanes Should Be Affected

    This final rule and the repair assessment guidelines apply to 11 
large transport category airplane models. (In the original ARAC task, 
the Boeing Models 707 and 720 were counted as one model. This final 
rule addresses the 707 and 720 models separately due to their different 
flight cycle implementation times.) The reason for this limitation is 
that the original tasking to the ARAC limited the scope of the work to 
the 11 oldest models of large transport category airplanes then in 
regular service. This tasking identified those airplanes for which the 
great concern exists as to the status of primary structure repairs. 
Derivatives of the original airplane models are covered to the extent 
that the structure has not been upgraded to meet damage-tolerance 
requirements.
    Those transport category airplanes that have been certificated to 
regulatory standards that include the requirements for damage-tolerance 
structure under Sec. 25.571 are not included in this rulemaking action. 
These later requirements make it incumbent on the operating certificate 
holder to return the structure to the original certification basis by 
installing only those repair that meet the airplane's damage-tolerance 
certification basis. The AAWG, in its final report on this subject, did 
recommend continued monitoring of repairs on the newer airplanes, with 
the possibility of additional rulemaking if conditions warrant. (A copy 
of the AAWG's final report is included in the public docket for this 
rulemaking).
    It was from this activity that the AAWG and manufacturers 
recognized not only the need for a RAG document for each affected 
model, but a SRM updated to include the results of a damage-tolerance 
assessment.

Considerations in Developing and Mandating Repair Assessment 
Guidelines

    In considering the establishment of RAG's, the AAWG recognized that 
the guidelines would add to existing repair approval data and, in some 
cases, may even appear to be in conflict with that data. All repairs 
assessed under the requirements of this final rule should have been 
previously approved by the FAA using an FAA using an FAA-approved SRM, 
an FAA-approved Service Bulletin, or a repair scheme approved by either 
an FAA Designated Engineering Representative or an SFAR 36 
authorization holder. To avoid the appearance of conflicts between FAA 
approved data sources, the manufacturers have agreed to update the 
affected SRM's, as well as repairs identified in Service Bulletins, to 
determine requirements for supplemental inspections, if not already 
addressed.
    Another consideration was that structural modifications and repairs 
mandated by AD's do not always contain instructions for future 
supplemental inspection requirements. The manufacturers have agreed to 
evaluate the need for post modification inspections for these mandated 
modifications and repairs. A list of Service Bulletins that are the 
subject of AD's will be contained in the model-specific RAG documents, 
with required post-modification/repair inspection programs, as 
appropriate. A list of other structural Service Bulletins will be 
provided in the model-specific RAG document, with associated inspection 
thresholds and repeat intervals. The manufacturers have agreed to 
complete their review of Service Bulletins related to skin repairs in 
conjunction with the initial SRM updates.
    These agreements notwithstanding, there is still a possibility that 
the requirements in the RAG document will not agree with those in an 
AD, especially if the AD was written to address a modification to the 
airplane made by someone other than the original manufacturer. Federal 
Aviation Regulations require that compliance be shown with both the AD 
and this final rule. Such dual compliance can be avoided in the longer 
term by working with the manufacturer, if that is the source of 
difficulty, or by securing an Alternative Method of Compliance (AMOC) 
to the AD. In the short term, compliance with the earlier threshold, 
shorter repeat inspection interval or more stringent rework/replace 
schedule would always constitute compliance with the less stringent 
requirement. Thus, the operator would not be faced with an unresolvable 
conflict.
    Another consideration, and one that the AATF originally 
recommended, was that the use of RAG's be mandated by an AD. The FAA 
concluded that an unsafe condition necessitating AD action had not been 
established for repairs, and this position is supported by both repair 
surveys. However, the FAA also considered, and the AAWG agreed, that 
the long term concern with repairs on older airplanes, as described 
earlier, does warrant regulatory action, and this final rule addresses 
that concern.
    The AAWG also recognized that the concerns discussed above for the 
safety of existing repairs also would apply to the long-term safety of 
future repairs to these airplanes. Therefore, the AAWG considered that 
new repairs also should be subject to damage-tolerance assessments. It 
is expected that most new repairs will be installed in accordance with 
an FAA-approved SRM that has been updated to include this damage-
tolerance assessment. However, in the event that a new repair is 
installed for which no such assessment has been made or is available, 
the repair assessment guidelines prepared to meet the requirements of 
this final rule should be used. The intent of this final rule is that 
all repairs to the fuselage pressure boundary will be evaluated for 
damage-tolerance, and that any resulting inspection schedule will be 
specified and the work accomplished, regardless of when, where, or by 
whom the repair was installed.

Development of Repair Assessment Methodology

    The next step in the AAGW's program for this task was to develop a 
repair assessment methodology that is effective in evaluating the 
continued airworthiness of existing repairs for the fuselage pressure 
boundary on affected transport category airplane models. Older airplane 
models may have many structural repairs, so the efficiency of the 
assessment procedure is an important consideration. In the past, 
evaluation of repairs for damage-tolerance would require direct 
assistance from the manufacturer. The size of an assessment task 
conducted in that way would be unmanageable considering that:

     Each repair design is different,
     Each airplane model is different,
     Each area of the airplane is subjected to a different 
loading environemnt, and
     The number of engineers qualified to perform a damage-
tolerance assessment is small.

    Therefore, a new approach was developed.
    Since repair assessment results will depend on the model-specific 
structure and loading environment, the manufacturers were tasked to 
create an assessment methodology for the types of repairs expected to 
be found on each affected airplane model. Since the records on most of 
these repairs are not readily available, locating the repairs 
necessitates surveying the structure of each airplane. A survey form 
was created that may be used to record key repair design features 
needed to accomplish a repair assessment. Airline

[[Page 24112]]

personnel not trained as damage-tolerance specialists can use the form 
to document the configuration of each observed repair.
    Using the information gathered during the survey as input data, the 
manufacturers have developed simplified methods to determine the 
damage-tolerance characteristics of the surveyed repairs. Although the 
repair assessments should be performed by well-trained personnel 
familiar with the model specific repair assessment guidelines, these 
methods enable an engineer or technician, not trained as a damage-
tolerance specialist, to perform the repair assessment without the 
assistance of the manufacturer.
    From the information gathered during the survey, it is also 
possible to classify repairs into one of three categories:
    Category A: A permanent repair for which the baseline zonal 
inspection (BZI), (typical maintenance inspection intervals assumed to 
be performed by most operators), is adequate to ensure continued 
airworthiness (inspectability) equal to the unrepaired surrounding 
structure.
    Category B: A permanent repair that requires supplemental 
inspections to ensure continued airworthiness.
    Category C: A temporary repair that will need to be reworked or 
replaced prior to an established time limit. Supplemental inspections 
may be necessary to ensure continued airworthiness prior to this limit.
    The airplane manufacturers generated this methodology and are 
preparing model-specific repair assessment guidelines for the 11 aging 
airplane models affected by this final rule. The manufacturers chose to 
produce the model-specific repair assessment guidelines for the older 
models first, and to produce those for the newer models as those 
airplanes get closer in age to the implementation time. (Operators 
should be in contact with the manufacturers to obtain a schedule of 
when the repair assessment guidelines will be prepared for their 
specific airplane models.) Uniformity and similarity of these repair 
assessment procedures between models has been an important factor to 
consider in simplifying operator workload. The manufacturers have spent 
considerable time over the last several years to achieve commonality of 
the repair assessment process.
    The inspection intervals contained in the FAA-approved model 
specific RAG documents are based on residual strength, crack growth, 
and inspectability evaluations. The manufacturers have endeavored to 
make the inspection methods and intervals compatible with typical 
operator maintenance practice. Thus, internal inspections would be 
acceptable at flight cycle limits that are equivalent to D-check 
intervals, while simpler external inspections could be accommodated at 
flight cycle limits that are generally equivalent to C-check intervals. 
If the inspection method and intervals for a given repair are not 
compatible with the operator's maintenance schedule, the repair could 
be replaced with a more damage-tolerant repair.
    These guidelines can also be used for evaluating the damage-
tolerance characteristics of new repair for continued airworthiness.

Related Activity Affecting Structural Repair Manuals

    In order to further facilitate the assessment process, the 
manufacturers have agreed to update model-specific SRM's to reflect 
damage-tolerance repair considerations. Their goal is to complete these 
updates by the first revision cycle of the model-specific SRM after the 
release of the associated RAG document. Consistent with the results of 
the surveys, only fuselage pressure boundary repairs are under 
consideration.
    The general section of each SRM, Chapter 51, will contain brief 
descriptions of damage-tolerance considerations, categories of repairs, 
description of baseline zonal inspections, and the repair assessment 
logic diagram. Chapter 53 of the SRM for pressurized fuselage skin will 
be updated to identify repair categories and related information.
    In updating each SRM, existing location-specific repairs should be 
labeled with appropriate repair category identification (A, B, or C), 
and specific inspection requirements for B and C repairs also should be 
provided, as applicable.
    Structural Repair Manual descriptions of generic repairs also will 
contain repair category considerations regarding size, zone, and 
proximity. Detailed information for determination of inspection 
requirements will be provided in separate RAG documents for each model. 
Repairs that were installed in accordance with a once-current SRM, but 
that have now been superseded by a new damage-tolerant design, will 
require review. Such superseded repairs may be reclassified to Category 
A, B, or C. Category B or C repairs would require additional 
inspections and/or rework.

Repair Assessment Process

    There are two principal techniques that can be used to accomplish 
the repair assessment. The first technique involves a three-stage 
procedure. This technique could be well-suited for operators of small 
fleets. The second technique involves the incorporation of the RAG as 
part of an operator's routine maintenance program. This approach could 
be well-suited for operators of large fleets and would evaluate repairs 
at predetermined planned maintenance visits as part of the maintenance 
program.
    Manufacturers and operators also may develop other techniques, 
which would be acceptable as long as they fulfill the objectives of 
this rule and are FAA approved.
    The first technique generally involves the execution of the 
following three stages:
     Stage 1. Data Collection. This stage specifies what 
structure should be assessed for repairs and collects data for further 
analysis. If a repair is on a structure in an area of concern, the 
analysis continues; otherwise, the repair does not require 
classification per this program. Repair assessment guidelines for each 
model will provide a list of structure for which repair assessments are 
required. Some manufacturers have reduced this list by determining the 
inspection requirements for critical details. If the requirements are 
equal to normal maintenance checks (e.g., BZI checks), those details 
were excluded from this list. Repair details are collected for further 
analysis in State 2. Repairs that do not meet the static strength 
requirements or are in a bad condition are immediately identified, and 
corrective actions must be taken before further flight.
     Stage 2. Repair Categorization. The repair categorization 
is accomplished by using the data gathered in Stage 1 to answer simple 
questions regarding structural characteristics. If the maintenance 
program is at least as rigorous as the BZI identified in the 
manufacturer's model specific RAG, well-designed repairs in good 
condition meeting size and proximity requirements are designed as 
Category A. Simple condition and design criteria questions are provided 
in Stage 2 to define the lower bounds of Category B and Category C 
repairs. The process continues for Category B and C repairs.
     Stage 3. Determination of Structural Maintenance 
Requirements. The supplemental inspection and/or replacement 
requirements for Category B and C repairs are determined in this stage. 
Inspection requirements for the

[[Page 24113]]

repair are determined by calculation or by using predetermined values 
provided by the manufacturer, or other values obtained using an FAA-
approved method. In evaluating the first supplemental inspection, Stage 
3 defines the inspection threshold in flight cycles measured from the 
time of repair installation. If the time of installation of the repair 
is unknown and the airplane has exceeded the assessment implementation 
times or has exceeded the time for first inspection, the first 
inspection should occur by the next C-check interval, or equivalent 
cycle limit after the repair data is gathered (Stage 1).
    An operator may choose to accomplish all three stages at once, or 
just Stage 1. In the latter case, the operator would be required to 
adhere to the schedule specified in the FAA-approved model-specific RAG 
for completion of Stages 2 and 3.
    Incorporating the maintenance requirements for Category B and C 
repairs into an operator's individual airplane maintenance or 
inspection program completes the repair assessment process for the 
first Technique.
    The second technique involves setting up a repair maintenance 
program to evaluate all fuselage pressure boundary repairs at each 
predetermined maintenance visit to confirm that they are permanent. 
This technique requires the operator to choose an inspection method and 
interval in accordance with the FAA-approved RAG. The repairs whose 
inspection requirements are fulfilled by the chosen inspection method 
and interval would be inspected in accordance with the regular FAA-
approved maintenance program. Any repair that is not permanent, or 
whose inspection requirements are not fulfilled by the chosen 
inspection method and interval, would either be: (1) Upgraded to allow 
utilization of the chosen inspection method and interval, or (2) 
individually tracked to account for the repair's unique inspection 
method and interval requirements. This process is then repeated at the 
chosen inspection interval.
    Repairs added between the predetermined maintenance visits, 
including interim repairs installed at remote locations, would be 
required either to have a threshold greater than the length of the 
predetermined maintenance visit or to be tracked individually to 
account for the repair's unique inspection method and interval 
requirements. This would ensure the airworthiness of the structure 
until the next predetermined maintenance visit, at which time the 
repair would be evaluated as part of the repair maintenance program.
    Whichever technique is used, there may be some repairs that cannot 
easily be upgraded to Category A due to cost, downtime, or technical 
reasons. Such repairs will require supplemental inspections, and each 
operator should make provisions for this when incorporating the RAG 
into its maintenance program.

Repair Assessment Implementation Time

    The implementation time for the assessment of existing repairs is 
based on the findings of the repair surveys and fatigue damage 
considerations, described previously. As discussed, the repair survey 
findings indicated that all of repairs reviewed appeared to be in 
generally good structural condition. This tended to validate the 
manufacturer's assumptions in designing both the repair and the basic 
structure. Since the manufacturer had based the design stress levels on 
a chosen Design Service Goal (DSG), it was concluded that the repair 
assessment needed to be implemented sometime before a specific model 
reached its DSG. Based on this logic, the manufacturers and operators 
established an upper boundary for an assessment to be completed, and 
then reduced it to establish an ``implementation time,'' defined as 75% 
of DSG in terms of flight cycles.
    Therefore, under this approach, incorporation of the RAG into an 
airplane's maintenance or inspection program ideally should be 
accomplished before an airplane accumulates 75% of its DSG. After the 
guidelines are incorporated into the maintenance or inspection program, 
operators should begin the assessment process for existing fuselage 
repairs within the flight cycle limit specified in the FAA-approved 
model-specific RAG. There are three ``deadlines'' for beginning the 
repair assessment process, depending on the cycle age of the airplane 
on the effective date of the rule.
    1. Airplane cycle age equal to or less than implementation time on 
the rule effective date: The operator is required to incorporate the 
guidelines into its maintenance or inspection program by the flight 
cycle implementation time, or one year after the effective date of the 
rule, whichever occurs later. The assessment process begins (e.g., 
accomplishment of Stage 1) on or before the flight cycle limit 
specified in the RAG after incorporation of the guidelines. (The flight 
cycle limits are expressed in flight cycle numbers, but are generally, 
equivalent to a D-check.)
    2. Airplane cycle age greater than the implementation time but less 
than the DSG on the rule effective date: The operator is required to 
incorporate the guidelines into its maintenance or inspection program 
within one year of the rule effective date. The assessment process then 
begins (e.g., accomplishment of Stage 1) on or before the flight cycle 
limit specified in the RAG (this flight cycle limit is generally 
equivalent to a D-check), not to exceed another specified flight cycle 
limit (computed by adding the DSG to the flight cycle limit equivalent 
of a C-check) after incorporation of the guidelines.
    3. Airplane cycle age greater than the DSG on the rule effective 
date: The operator is required to incorporate the guidelines in its 
maintenance or inspection program within one year after the effective 
date of the rule. The assessment process would begin (e.g. 
accomplishment of Stage 1) on or before the flight cycle limit 
specified in the RAG (generally equivalent to a C-check) after 
incorporation of the guidelines.
    In each of these three cases, the assessment process will have to 
be completed, the inspections conducted, and any necessary corrective 
action taken, all in accordance with the schedule specified in the FAA-
approved RAG document.

Discussion of the Final Rule

    This final rule is intended to ensure that a comprehensive 
assessment for damage-tolerance be completed for fuselage pressure 
boundary repairs, and that the resulting inspections, modifications, 
and corrective actions (if any) be accomplished in accordance with the 
model-specific RAG. To comply with this, the operator will need to 
consider the following:

Consideration 1

    The means by which the FAA-approved RAG's are incorporated into a 
certificate holder's FAA-approved maintenance or inspection program is 
subject to approval by the certificate holder's Principal Maintenance 
Inspector (PMI) or other cognizant airworthiness inspector.

Consideration 2

    The FAA Aircraft Certification Office (ACO) having cognizance over 
the type certificate of the airplane must approve the RAG.

Consideration 3

    This final rule will not impose any new reporting requirements; 
however, normal reporting required under 14 CFR 121.703 will still 
apply.

[[Page 24114]]

Consideration 4

    This final rule will not impose any new FAA recordkeeping 
requirements. However, as with all maintenance, the current operating 
regulations (e.g., 14 CFR 121.380) already impose recordkeeping 
requirements that will apply to the actions required by this final 
rule. When incorporating the RAG into its approved maintenance program, 
each operator should address the means by which it will comply with 
these recordkeeping requirements. That means of compliance, along with 
the remainder of the program, will be subject to approval by the PMI or 
other cognizant airworthiness inspector.

Consideration 5

    The scope of the assessment is limited to repairs on the fuselage 
pressure boundary (which includes fuselage skin, door skin, and 
pressure webs). A list of Service Bulletins that are the subject of 
AD's will be contained in the model-specific RAG with required post 
modification/repair inspection programs, as required. A list of other 
structural Service Bulletins will be provided in the model-specific RAG 
with associated inspection threshold and repeat intervals.

Consideration 6

    The RAG's provided by the manufacturer do not generally apply to 
structure modified by a Supplemental Type Certificate (STC). However, 
the operator will still be responsible to provide RAG's applicable to 
the entire fuselage external pressure boundary that meets the program 
objectives specified in the advisory circular (AC) associated with this 
final rule (which will be available in the near future). This means 
that the operator should develop, submit, and gain FAA approval of 
guidelines to evaluate repairs to such structure.
    The FAA recognizes that operators usually do not have the resources 
to determine a DSG or to develop RAG's, even for a very simple piece of 
structure. The FAA expects the STC holder to assist the operators in 
preparing the required documents. If the STC holder is out of business, 
or is otherwise unable to provide assistance, the operator will have to 
acquire the FAA-approved guidelines independently. To keep the 
airplanes in service, it is always possible for operators, individually 
or as a group, to hire the necessary expertise to develop and gain 
approval of RAG's and the associated DSG. Ultimately, the operator 
remains responsible for the continued safe operation of the airplane.
    The cost and difficulty of developing guidelines for modified 
structure may be less than that for the basic airplane structure for 
three reasons:
    First, the only modifications made by persons other than the 
manufacturer that are of concern in complying with this final rule are 
those that affect the fuselage pressure boundary. Of those that do 
affect this structure, many are small enough to qualify as Category A 
repairs under the RAG, based solely on their size.
    Second, if the modified structure is identical or very similar to 
the manufacturer's original structure, then only a cursory 
investigation may be necessary. In such cases, the manufacturer's RAG 
may be shown to be applicable with few, if any, changes. If the 
operator determines that a repair to modified structure can be 
evaluated using the manufacturer's model-specific RAG, that determined 
should be documented and submitted to the operator's PMI or other 
cognizant airworthiness inspector for approval. For all other repairs, 
a separate program will need to be developed.
    Third, the modification may have been made so recently that no RAG 
will be needed for many years. Compliance with this final rule could be 
shown by:

     Establishing the DSG for the new modified structure,
     Calculating an implementation time that is equal to 
three quarters of that DSG, and
     Then adding a statement to the operations 
specifications for part 121, 125 and 129 operators that the RAG will 
be incorporated into the maintenance or inspection program by that 
time. For part 91 operators, the inspection program will be revised 
to include the RAG.

    If the modified structure is very similar to the original, then the 
DSG for the modified structure may also be very similar. No RAG would 
be needed until 75% of that goal is reached. For example, in the case 
of a large cargo door, such installations are often made after the 
airplane has reached the end of its useful life as a passenger-carrying 
airplane. For new structure, the clock would start on repair assessment 
at the time of installation. Further, since the DSG is measured in 
cycles, and cargo operation usually entails fewer operational cycles 
than passenger operations, the due date for incorporation of the RAG 
for that structure could be many years away.
    Compliance with this final rule requires that conditions such as 
those described above be properly documented in each operator's FAA-
approved maintenance program; however, the FAA considers that the cost 
of doing so should not be significant. There should be very few 
examples where the STC holder is unavailable, and the operators would 
have to bear the cost of developing a complete RAG document. Guidance 
on how to comply with this aspect of the rule is discussed in the soon-
to-be-released AC associated with this rule.

Consideration 7

    An operator's repair assessment program will have to include 
damage-tolerance assessments for new repairs. Repairs made in 
accordance with the revised version of the SRM would already have a 
damage-tolerance assessment performed; otherwise, the manufacturer's 
RAG could be used for this purpose, or operators may develop other 
methods as long as they achieve the same objectives.

Consideration 8

    Once the airworthiness inspector having oversight responsibilities 
is satisfied that the operator's continued airworthiness maintenance or 
inspection program contains all of the elements of the FAA-approved 
RAG, the airworthiness inspector will approve a maintenance program or 
inspection program revision. This will have the effect of requiring use 
of the approved RAG.
    In summary, based on discussions with representatives of the 
affected industry, recommendations from ARAC, and a review of current 
rules and regulations affecting repair of primary structure, the FAA 
recognizes the need for a repairs assessment program to be incorporated 
into the maintenance program for certain transport category airplanes. 
This final rule accomplishes that.

Discussion of Comments

    The FAA received 16 comments in response to Notice 97-16. Comments 
included airplane manufacturers, airplane operators, non-U.S. aviation 
authorities, and aviation industry representatives and groups. The 
disposition of all comments, grouped by subject, follows.

Support for the Proposal

    Several commenters support the proposed rule.

No Need for the Rule

    One commenter contends that the proposed rule is largely redundant 
and may not even be needed. The commenter points out that, in 1978, 
with amendment 25-45, the FAA amendment Sec. 25.571 to impose damage-
tolerance criteria for design of aircraft structure. Airplanes 
certified after that

[[Page 24115]]

date have damage-tolerance criteria built in to the manufacturers' 
repair philosophies. Airplanes older than that are regulated by FAA-
approved Supplemental Inspection Documents.
    The commenter also points out that, in 1989 (ref. memorandum from 
Manager, Transport Airplane Directorate, ``Policy Regarding Impact of 
Modification and Repairs on the Damage-tolerance Characteristics of 
Transport Category Airplanes,'' dated November 27, 1989), the FAA 
clarified that ``* * * All transport category airplanes having the 
damage-tolerance requirements of Sec. 25.571, amendment 25-45, as their 
certification basis and those with mandated Supplemental Inspection 
Documents [SID] * * * must continue to maintain their damage-tolerance 
characteristics when repaired or modified in any way.'' Industry has 
adhered to this rendering since that time.
    Thus, through the certification rule for new airplanes and through 
the SID programs for older airplanes, the damage-tolerance assessment 
of repairs is already being done. For this reason, commenter does not 
see a need for the proposed rule and implies that it should be 
withdrawn.
    The FAA acknowledges the commenters' observations, but does not 
occur that the rule is unnecessary. As discussed in the preamble to the 
notice (and this final rule), the airplanes certified after amendment 
25-45 must be maintained in accordance with their certification basis 
and, therefore, a damage-tolerance analysis of all repairs is required. 
The 1989 memorandum was issued by the FAA to clarify that operators 
with airplanes subject to the mandated SID programs should continue to 
maintain the damage-tolerance capabilities of the airplanes when 
repaired or modified in any way. However, all operators of the 
airplanes covered by SSID's have not routinely followed this policy. 
This fact was made clear by the adoption of Airworthiness Directive 
(AD) 98-11-03 (Amdt. 39-10530; 63 FR 27455, May 19, 1998) and AD 98-11-
04 (Amdt. 39-10531; 63 FR 27456, May 19, 1988) which revised the SSID 
programs for the Model 727 and 737, respectively. In response to the 
NPRM's for those AD's, numerous commenters (including the ATA) objected 
to proposed requirements that repairs be assessed. In part, these 
objections were based on the argument that operators did not have the 
records to identify, or the methods to assess existing repairs. The 
FAA, as well as the AAWG, in developing the repair assessment program, 
concluded that it is necessary to assess the repairs on all of the 
affected 11 models of (aging) aircraft to ensure that the original 
intent of the SID programs (and related AD's mandating them) is being 
followed.

Manufacturers' Commitments to Providing Documents

    Two commenters suggest that adoption of the rule and implementation 
of the repair assessment program be delayed until the RAG documents, 
revised SRM's, and service bulletins are available from the 
manufacturers to affected operators.
    One of these commenters states that the FAA should not rely on 
verbal commitments from the manufacturers to issue these documents 
sometime in the future. The commenter further states that commitments 
cannot be depended on, especially where manufacturers are operating 
with greatly reduced staffs and resources (i.e., due to takeovers). The 
commenter suggests that, if manufacturers are unable to supply these 
documents in a timely manner, operators may find themselves in 
situations where they are not in compliance with this rule.
    The other commenter points out that the manufacturer has not 
provided any information regarding the SRM update schedule for the 
affected airplanes in this commenter's fleet. The commenter states 
that, being unable to review the SRM beforehand, raises concerns about 
possible conflicts between the model-specific RAG document and the 
corresponding SRM. If the FAA does not delay implementation of the 
rule, this commenter requests that an appropriate ``grace period'' be 
provided after the SRM's are completely updated so that operators will 
have time to incorporate the new changes.
    The FAA acknowledges these commenters' concerns, but does not agree 
that a delay is necessary. This final rule is written such that it 
neither requires the type certificate (TC) holder to develop the 
guidelines, nor depends on this issuance of any documents from the TC 
holder to be enforceable. As stated in the preamble to the notice and 
this final rule, the operator is responsible for providing the RAG 
applicable to the fuselage external pressure boundary of the airplanes 
in its fleet. If the TC holder does not or cannot provide relevant 
service information, the operator may develop, submit, and gain 
approval of its own guidelines to evaluate repairs to such 
structure.The information contained in the soon-to-be-released 
accompanying AC describes one method that may be used by any entity--
operator, TC holder, or otherwise--to develop such guidelines. 
Additionally, it is always possible for operators, individually or as a 
group, to hire the necessary expertise to develop and gain approval of 
RAG's. Ultimately, however, the operator remains responsible for the 
continued safe operation of its airplanes.
    Further, the FAA also does not concur with the commenter's request 
that implementation of the repair assessment program be postponed, or a 
grace period provided, until SRM's are updated to correspond with the 
RAG documents. The purpose of the two documents is different: the 
purpose of the RAG document is to assist in evaluating existing 
repairs; the purpose of the updated SRM is, as is usual, to assist in 
the installation of new repairs. Operators affected by this new rule 
will be required to show how new repairs installed after the effective 
date of the final rule will be handled. The methods described in the 
soon-to-be-released AC associated with this rule also may be used for 
this purpose.
    The FAA has been advised, however, that as of the date of 
publication of this rule, the manufacturers have finalized the RAG's 
applicable to the older airplane models affected by this rule. The 
guidelines for the newer models are nearly complete and certainly will 
be finalized by the time the newer models will require the initial 
inspections.
    Further, the FAA also has been advised that the manufacturers (1) 
have completed updating the pertinent parts of their Structural Repair 
Manuals and (2) are ready to provide necessary training programs.

Airplanes Subject to the Final Rule

    Airbus Models Subject to Rule. One commenter requests that the 
listing of affected models of Airbus airplanes in the proposed rule be 
revised as follows:

     Change references to the Airbus A300 to: ``Airbus A300 
(excluding the -600 series); and
     Clarify paragraph (a)(3) of the proposed Sec. 91.410, 
Sec. 121.370, Sec. 125.248; and Sec. 129.32 to include references to 
the Airbus Model C4-200 and F4-200 models.

    The FAA concurs with the commenter's first request to exclude the 
Airbus A300-600 series from the applicability of the rule, and has 
revised the text of the final rule accordingly. The FAA finds it is 
appropriate to exclude the Airbus A300-600 series from the 
applicability of this rule because this model been certified to 
regulatory standards that include the requirements for damage-tolerant 
structure under Sec. 25.571, as amended by amendment 25-45. As 
explained earlier, such airplanes are not included in this rulemaking 
action. An Airworthiness Limitations Section has been approved

[[Page 24116]]

for the Airbus A300-600 series airplanes, and it is considered a 
damage-tolerant airplane. Based on the Airbus airplanes currently 
certificated in the U.S., the following airplanes in the Model A300-600 
series would be excluded from compliance with this rule:

     A300 Model B4-600 series,
     A300 Model B4-600R series, and
     A300 Model F4-600R series.

    The FAA does not concur with the commenter's second request to add 
references to Airbus A300 Model C4-200 and A300 Model F4-200 model 
airplanes to the applicability of the rule. The C4-200 and F4-200 model 
airplanes currently are not certified in the U.S. and, therefore, 
cannot be made part of the rule's applicability.
    In light of this commenter's requests, the FAA finds that 
additional clarification is appropriate as to specify exactly which 
Airbus A300 airplanes are subject to the requirements of this rule.
    In Sec. 91.410, Sec. 121.270, Sec. 125.248, and Sec. 129.32, the 
FAA delineates the Airbus A300 ``Model B2'' as a separate model, whose 
implementation threshold is 36,000 flights, Based on the airplanes 
currently certified in the U.S. specified in Type Certificate Data 
Sheet (TCDS) A35EU, the ``A300 Model B2'' designation referred to in 
the rule includes:

     Model B2-1A,
     Model B2-1C,
     Model B2K-3C, and
     Model B2-203.

    If any new ``Model B2'' airplanes are certified in the U.S. in the 
future, those airplanes would be required to follow he implementation 
time of 36,000 flights above the window line and 36,000 flights below 
the window line, as outlined in the rule.
    Readers also note that, in Sec. 91.410, Sec. 121.370, Sec. 125.248, 
and Sec. 129.32, the FAA delineates the Airbus A300 ``Model B4-100 
(including Model B4-2C)'' as a separate model whose implementation 
threshold is 30,000 flights above the window line and 36,000 flights 
below the window line. Based on the airplanes currently certificated in 
the U.S. specified in TCDS A35EU, this model designation referred to in 
the rule includes:

     Model B4-103 and
     Model B4-2C.

    If any new ``Model B4-100'' airplanes are certificated in the U.S. 
in the future, those airplanes would be required to follow the 
implementation time of 30,000 flights above the window line and 36,000 
flights below the window line, as outlined in the rule.
    Further, in Sec. 91.410, Sec. 121.370, Sec. 125.248, and 
Sec. 129.32 and FAA, delineates the Airbus A300 ``Model B4-200.'' as a 
separate model whose implementation threshold is 25,000 flights above 
the window line and 34,000 flights below the window line. Based on the 
airplanes currently cerfificated in the U.S. specified in TCDS A35EU, 
this model designation referred to in the rule is the Model B4-203.
    If any new ``Model B-200'' airplanes are certificated in the U.S. 
in the future, those airplanes would be required to follow the 
implementation time of 25,500 flights above the window line and 34,000 
flights below the window line, as outlined in the rule.
    Fokker Models Subject to Rule. One commenter states that the AAWG 
recommended that only the Fokker F28 Mark 1000 through 4000 airplanes 
were to be affected by this action. The commenter requests that 
proposed paragraph (1) of the affected regulations be revised to 
specify this. The proposal includes reference to the Mark 1000C and 
3000C models, which is incorrect.
    The FAA concurs. The Mark 1000C and 3000C were inadvertently added 
to the applicability of the proposed rule. References to those models 
have been deleted from the final rule.
    Boeing Models Subject to Rule. Another commenter requests 
clarification as to whether the Boeing Model 737-300 is affected by the 
proposed rule. The commenter notes that the Boeing 737 Repair 
Assessment Guidelines appear to address only the -100 and -200 models, 
whereas the proposed rule appears to include the -300.
    The FAA points out that the Boeing 737-300 is included in the 
applicability of the rule, as are all models of the Boeing 737. The 
manufacturers usually produce documents for the older airplanes first 
before they produce documents for the newer model airplanes Boeing has 
advised the FAA that it will produce RAG's for all the models of the 
Boeing 737. Boeing is expected to produce the documents based on how 
soon the fleet leaders for a specific model will reach the mandated 
implementation time. The operators should maintain close contact with 
the manufacturers to obtain a schedule of when the model-specific RAG's 
will be produced.
    General Applicability of the Rule. Another commenter notes that the 
proposed rule did not mention the ``later design'' airplanes, that is, 
airplanes that are certified to Sec. 25.571, amendment 25-45, or later. 
The commenter requests clarification as to whether these airplanes 
would be affected by the proposed rule.
    The FAA concurs with the commenter's observation that the proposal 
did not mention the term ``later design [airplanes].'' The FAA infers 
that the commenter uses this term to refer to airplanes certificated 
after the time that amendment 25-45 became effective. As explained 
previously, damage-tolerance requirements were introduced into the 
airplane design in post-amendment 25-45 airplanes, and the certificate 
holder is required by the amendment to return repaired airplane 
structure to the original certification basis by installing only those 
repairs that meet the airplane's damage-tolerance certification basis. 
In light of the fact that damage-tolerance is ``designed into'' the 
post-amendment 25-45 airplanes, the FAA considers it unnecessary to 
include those airplanes in this rule. This final rule, therefore, 
applies to those airplanes whose certification basis was approved 
before amendment 25-45 became effective, and were not designed with 
requirements for damage-tolerant structure. [The FAA points out, 
however, that the AAWG did recommend continued monitoring of repairs on 
the newer (``later design'') airplanes, and additional rulemaking if 
conditions warrant.]

Areas of Inspection

    One commenter requests that the FAA clarify the proposed rule to 
indicate that the area of inspection termed the ``fuselage pressure 
boundary'' includes not only the fuselage skin and bulkhead web, but 
the door skin as well.
    The FAA concurs. The intent of the repair assessment is to include 
the entire fuselage pressure boundary, which does include, among other 
things, the fuselage, bulkhead webs, and the door skin. (The preamble 
to the proposal, in fact, did refer to assessment of modified structure 
relevant to large cargo doors.) The rule has been revised for clarity 
as suggested by the commenter.

Effective Date of the Rule

    One commenter requests that the effective date of the final rule be 
changed to at least one year after each of the model-specific RAG 
documents is officially approved and published. The commenter further 
requests that an additional grace period be added to allow operators 
the time for preparation work before starting a new complicated program 
like the repair assessment program and time to train their personnel. 
The commenter states that

[[Page 24117]]

none of the model-specific RAG's developed by manufacturers have been 
officially approved yet by the FAA, and it is difficult for the 
operators to review and prepare for implementing the program without 
the actual guideline materials in hand. To justify this request, the 
commenter points out that the FAA previously provided similar extended 
compliance times for incorporating other complex programs such as the 
CPCP and the SSID programs.
    The FAA does not concur that a revision to the effective date of 
the final rule is appropriate. As it is written, the rule does allow a 
``grace period'' of one year after the effective date for operators to 
implement the program. (This is similar to the provisions of the CPCP 
and SSID programs.) The FAA also points out that operators and airlines 
have had the opportunity to work with the manufacturers in the 
development of the guidelines over the past 6 years. The FAA already 
has reviewed the RAG documents for 9 of the 11 models affected by the 
rule and has found that they would satisfy the intent of the rule, the 
FAA will approve these RAG documents when the rule becomes effective. 
However, even if these documents are not approved, the rule places the 
onus on the operators to have guidelines and a program in place. The 
airframe manufacturers are providing the RAG documents as a ``service'' 
to their customers. However, if the manufacturer does not have a RAG 
document available, the operator would still be required to develop 
repair assessment guidelines. Therefore, trying the compliance time of 
the rule in any way with the date of publication of the manufacturers' 
documents is immaterial.
    Another commenter requests that the proposed implementation time be 
increased from 1 year to 18 months to allow manufacturers adequate time 
``to respond to the new rule.'' The commenter is concerned that the 
proposed rule will be implemented sooner than the manufacturers can 
support the operators with inspection thresholds and repeat inspection 
intervals for multiple repair configurations, Service Bulletin repairs, 
and SRM repairs.
    The FAA does not concur that additional calendar time for 
implementation is appropriate. The FAA has reached this conclusion for 
several reasons:
    First, the original notice of this rulemaking provided a 3-month 
period for public comments. The FAA later reopened the comment period 
for an additional 3 months to allow the manufacturers time to 
distribute copies of the RAG's and allow the operators time to review 
those documents and provide comments.
    Second, industry has been aware of the need to assess the damage-
tolerance of repairs since at least 1978, when amendment 25-45 was 
issued to impose damage-tolerance criteria for design of aircraft 
structure. Airplanes certificated after 1978 have damage-tolerance 
criteria built in to the manufacturers' repair philosophies. Airplanes 
certificated before that date are regulated by FAA-approved 
Supplemental Inspection Documents. The FAA then clarified for the 
industry in 1989 that all transport category airplanes having the 
damage-tolerance requirements of Sec. 25.571, amendment 25-45, as their 
certification basis (i.e., post-1978 certificated airplanes) and those 
with mandated Supplemental Inspection Document programs ( i.e., pre-
1978 certificated airplanes) must continue to maintain their damage-
tolerance characteristics when repaired or modified in any way. 
Industry has been aware of this policy since that time. Thus, the 
damage-tolerance assessment of repairs is already being done; it is not 
a new concept. The RAG's have been under development for many years 
and, during that development, the manufacturers of the affected 
airplanes have consulted with operators.
    Similarly, another commenter requests that additional time be 
provided before implementation of the assessment program so that 
regulated aviation community can review, understand, comment on, and 
assimilate the RAG documents. The commenter claims that ``FAA's 
aggressive schedule on the instant rulemaking has resulted in placing a 
lot of pressure on the airframe manufacturers to publish the RAG 
documents as soon as possible.'' The commenter asserts that, because of 
this, the documents are of poor quality, with obvious gaps and numerous 
inconsistencies between them. The commenter maintains that there is a 
``compelling need'' to have these documents reviewed for completion and 
for inconsistencies within and among them prior to starting the clock 
for compliance.
    The FAA does not concur. Numerous operators have participated in 
the development of this rule, and have worked closely with the 
manufacturers in the development of the RAG's. During various working 
group meetings, the FAA raised the issue of inconsistencies between 
documents; however, the operators represented at the meetings did not 
raise any concerns about this. The FAA does not agree that granting 
more time before implementing this rule will result in the timely 
resolution of inconsistencies; as long as the repair assessment 
guidelines meet the intent of the rule, the guidelines are not required 
to be identical.

Implementation Times

    One commenter requests clarification concerning the implementation 
times of the repair assessment for new repairs. The commenter questions 
what implementation period would apply for new repairs, assuming that 
an airplane already has surpassed the flight cycle implementation time 
specified for that model, and assuming that the operator has already 
assessed every applicable repair under the proposed rule.
    The FAA clarifies this issue by noting that the operator is 
required to incorporate an FAA-approved repair assessment program into 
its maintenance or inspection program, and that this program must 
include a provision for addressing new repairs. As stated in the final 
rule, for airplanes that have already exceeded the specified 
implementation time, the maintenance program must be revised to 
incorporate the repair assessment program within a year after the 
effective date of this final rule. Once the program is revised, 
operators are required to comply with it thereafter, under normal 
maintenance rules. Therefore, there is no separate ``implementation 
time'' for new repairs.
    Another commenter requests clarification on the definitions of 
various phases of the repair assessment program described in the Boeing 
Model 727 RAG document, D6-56167. Since this commenter's questions are 
not specifically relevant to this final rulemaking action, they are not 
included in this preamble. However, the FAA has responded directly to 
the commenter and a copy of the detailed response is contained in the 
docket.

Determination of Inspection Intervals

    One commenter questions why the proposed rule holds airplanes with 
mechanical fuselage joints to the same inspection intervals as those 
whose fuselage joints are assembled with adhesives. The commenter 
implies that the inspection intervals should be different for each type 
of these airplanes.
    The FAA does not concur. The final rule does not specify any 
explicit interval for repetitive inspections. Those intervals will be 
developed based on what is determined to be appropriate for the 
particular design features of the airplane. These intervals will be 
specified in the model-specific RAG

[[Page 24118]]

documents and will be subject to approval by the cognizant FAA Aircraft 
Certification Office. The only aspect that all airplanes will be held 
to is that the inspection intervals must ensure that damage is detected 
and corrected before failure of a structural repair could occur.
    Another commenter requests that the FAA issue a determination in 
advance stating that the results of SID inspections could serve as an 
alternative means of compliance with the proposed rule. The commenter 
asserts that it is unclear how to address an apparent conflict where 
damage-tolerance analysis done under a SID program, which is mandated 
by an AD, might render a different inspection schedule from the 
guidelines in the RAG document.
    The FAA does not concur with the commenter's request. The FAA 
understands that the commenter's concern arises from a scenario such as 
the following:

     A repair to a principal structural element (PSE) has 
been accomplished previously.
     The operator has an inspection schedule, as part of its 
SID program, for the repaired PSE based on damage-tolerance 
analyses.
     While assessing the repair of a PSE in accordance with 
the new RAG document, the operator finds that the inspection 
schedule under the RAG is more conservative than the SID (i.e., 
shorter inspection intervals, more frequent inspections).

    The FAA does not consider it either necessary or appropriate to 
issue ``an advance determination'' that SID inspection results could 
serve as an alternative method of compliance to the rule for, in fact, 
they may not. As stated in the preamble to the notice and this final 
rule, there is the potential that there will be some situations where 
requirements of the RAG do not agree with those of an AD (especially if 
the AD were written to address a modification to the airplane made by 
someone other that the original manufacturer). In those cases, the 
Federal Aviation Regulations would require that compliance be shown 
with both the AD and this rule. Such a ``dual compliance'' situation 
can be avoided in the long term by working with the manufacturer, if 
that is the source of difficulty, or by securing approval of an 
alternative method of compliance with the AD. In the short term, 
however, accomplishment of the earlier threshold, the shorter repeat 
inspection interval, or the more stringent rework/replacement schedule 
would always constitute compliance with the less stringent requirement. 
Thus, the operator would not be faced with an unresolvable conflict.

Escalation of Inspection Intervals

    One commenter, an airframe manufacturer, requests that the proposed 
rule be revised to allow a ``less restrictive policy'' with regard to 
escalating the repetitive inspection intervals required by the program. 
This commenter notes that, in approving the RAG documents developed for 
affected airplanes, the FAA stated that it would approve provisions 
allowing for escalation of repeat inspection intervals for an 
individual airplane, but on the condition that each escalation is first 
approved by the FAA airworthiness inspector on a case-by-case basis. In 
approving these documents, the FAA indicated that it would not allow 
(1) any escalation of the inspection threshold or (2) a generally 
applicable escalation of repetitive inspection intervals.
    The commenter maintains that the requirement of gaining prior 
approval by the FAA airworthiness inspector on a case-by-case basis is 
more restrictive than similar requirements currently required by other 
FAA-approved programs, such as the SSID and the CPCP. The SSID program, 
for example, allows the repeat inspection interval for individual 
airplanes to be increased by up to 10% of the normal interval. 
Additionally, the CPCP program allows the repeat inspection interval to 
be increased by up to 10% (but not to exceed 6 months) in order to 
accommodate unanticipated scheduling requirements; the operator needs 
only to notify the cognizant FAA Principal Inspector (PI) in writing of 
any extension made. This commenter suggests that the approach taken by 
these programs appears to be a more reasonable method of addressing the 
escalation of inspection intervals, and asserts that the inspection 
intervals found in the RAG's all could be increased by 10% and still 
provide adequate inspections to maintain safety. The commenter requests 
that the proposed rule be revised to allow the same escalation policy 
provided in for the SSID and CPCP programs be applied to the repair 
assessment program.
    The FAA does not concur with the commenter's request. This position 
is based on experience that the FAA has gained over the years in trying 
to administer the SSID and CPCP programs. In trying to allow for some 
flexibility in those programs to accommodate scheduling and other 
situations, the FAA has found that some affected operators are very 
confused about the process for escalating the repeat inspection 
intervals; the FAA also has found that some affected operators abuse 
the process. The operators themselves pointed this out in the numerous 
meetings that were held during the development of the repair assessment 
program. In September 1997, the Manager of the Transport Airplane 
Directorate issued a memorandum to all cognizant ACO's providing 
guidance for development of the RAG's. That memorandum addressed areas 
of concern regarding inspection intervals and established two policies:

     Inspection thresholds shall be fixed and there should 
be no provisions for escalation of them; and
     Repeat intervals can be escalated up to either 10% or a 
specific time interval specified by the manufacturer, whichever is 
less. Escalation must be approved by the airworthiness inspector on 
a case-by-case basis to accommodate one-time scheduling conflicts.

    One of the purposes of the memorandum was to ensure standardization 
of the application of the program across FAA offices. Further, because 
many operators have various airplane models and multiple TC holders are 
involved, there was a great desire on the part of the operators to have 
the repair assessment program standardized as much as possible and be 
less confusing. As stated previously, operators have been involved in 
many meetings with the FAA and TC holders as the RAG's were being 
developed; therefore, they are aware of the policy regarding escalation 
and have indicated their agreement with that policy.

New Repairs

    One commenter's understanding of the proposed rule is that it would 
allow the use of the RAG document as a tool to evaluate new repairs. 
The commenter does not believe, however, that this is in line with the 
intent of the repair assessment program, which is to serve as a 
``catch-up'' process to ``remedy'' old repairs and not as a design tool 
for new repairs. If it is possible to use the RAG to assess new 
repairs, the commenter foresees a situation where it could be possible 
to install repairs with a bad damage-tolerance capability and, through 
the RAG document, to demonstrate that the repair is still ``safe'' 
during a certain period. The commenter maintains that, if the proposed 
rule were to be revised to require that the general guidelines for 
designing repairs--as defined in the SRM--are followed for the new 
repair installed, then the situation described will certainly not 
occur. The commenter requests that the proposed rule state that the 
damage-tolerance assessment of a ``new repair'' will have to be done 
through the current recommendations found in the relevant part of the 
SRM,

[[Page 24119]]

or the repair assessment will have to be done by a design office (TC 
holder or other) and approved by the FAA following current procedures.
    This commenter justifies this request by stating that all the 
repairs installed on the pressurized shell boundary will have to be 
assessed for their damage-tolerance characteristics. The commenter 
states that, in order to avoid design and installation of ``Category 
C'' repairs (temporary repairs that will need to be reworked or 
replaced prior to an established time limit), operators will need to 
use the repair instructions and methods described in the updated SRM 
guidelines. The commenter maintains that this will compel the 
manufacturer to update its SRM and not to rely only on the RAG document 
to fulfill its obligations to the operators under this final rule. If 
the SRM is used in lieu of the RAG, the approach will be preventive 
instead of curative and this will, in a certain manner, increase the 
level of safety.
    The FAA recognizes the commenter's point, but does not concur that 
a revision to the rule is necessary. Existing regulations [e.g., 14 CFR 
43.13(b)] already require that all repairs restore the airplane to at 
least its original or properly altered condition, and those 
requirements are not affected by this final rule. As discussed 
previously, this rule simply ensures that the durability of repairs is 
assessed, and that necessary inspections and rework are accomplished in 
a timely manner. The TC holders have been devoting resources to update 
their SRM's, but this process has not proceeded as quickly as hoped; 
therefore, as an interim measure, the operators can use the RAG 
document to evaluate their repairs. The FAA considers that use of the 
RAG document to evaluate temporary repairs will not compromise the 
repair assessment program required by this final rule.

Classification of Major/Minor Repairs

    One commenter questions whether any levels of rework or repairs 
resulting from the inspections that would be required under the 
proposed rule would be classified as ``major repairs.'' The commenter 
suggests that this item be clarified.
    The FAA responds by noting that there should be no change regarding 
the classification of either ``major'' or ``minor'' repairs based on 
the requirements of the new rule. Generally, repairs to PSE's meet the 
definition of ``major'' repairs.

Supplemental Type Certificate Holders

    One commenter raises a concern about Supplemental Type Certificate 
(STC) holders and any commitment that they would owe to operators in 
developing the repair assessment program. Under the proposed rule, an 
STC holder could quite easily withhold assistance and the operator 
would have to acquire an FAA-approved RAG independently. The commenter 
requests that the rule be revised to require the TC holder to assist 
the operator in assessing whether a repair to an STC modification can 
be evaluated through the use of the manufacturer's RAG, based on 
similarity. The TC holder's assistance should be required to gain 
approval from the operator's Principal Maintenance Inspector (PMI) or 
other cognizant airworthiness inspector. If the rule is not changed and 
the support of the STC holder is not required, significant additional 
costs could be incurred by the operators.
    The FAA does not concur with the commenter's request that the TC 
holders be required to assist the operators in assessing repairs to STC 
modifications. Under this rule--and operating rules in general--the 
operator is ultimately responsible for maintenance of its fleet. As 
discussed in the NPRM, the operator is required to establish a program 
to assess repairs to modified structure, and may be compelled to 
contract for the necessary expertise to develop that program.

Relationship of Rule to Operation Specifications

    One commenter states that, in a number of places in the preamble to 
the notice, the phrase, ``an operator's operation specification or 
maintenance program'' is used correctly, while in other places only the 
term ``operation specification'' is used, which is incorrect. Small 
operators can be expected to have their maintenance programs 
incorporated into Section D of the airplane's operation specifications. 
However, large operators, especially those permitted reliability-based 
maintenance programs, have only a chapter of their Maintenance Manual 
listed in Section D of the operation specifications. The commenter 
requests that the proposed rule be revised to clarify this.
    The FAA concurs. The FAA has removed the term ``operation 
specification'' and replaced it with ``maintenance program'' in the 
appropriate areas of the text of the final rule.

Adjustment for Pressure Factor

    One commenter expresses concern that the 1.2 adjustment factor for 
the Boeing 747SR touch and go allowance, and the allowance for flights 
with less than 2.0 PSI, were removed from the Boeing 747 RAG document. 
The commenter requests that the rule specifically permit the use of 
these pressure factor allowances in the RAG document.
    The FAA does not concur. The FAA is concerned about tracking 
individual airplanes and their usage in order to comply with such an 
allowance. If the operator submitted a plan on how the airplanes would 
be tracked and how this information would be transferred in the event 
the transfer of such an aircraft, the FAA would consider a proposal 
that could be approved on a case-by-case basis.

Recordkeeping

    Several commenters raised concerns about recordkeeping that could 
necessarily accompany the implementation of the requirements of the 
proposed rule. In the preamble to the notice, the FAA indicated that 
the rule would not impose any new FAA recordkeeping requirements, and 
that the current operating regulations (e.g., 14 CFR 121.380, 
``Maintenance recording requirements'') already impose adequate 
recordkeeping requirements that would apply to the actions required by 
the rule. As discussed below, certain commenters contest that 
statement:
    Transfer of Repair Data. One commenter states that Sec. 121.380 is 
not an adequate regulation either to mandate the transfer of repair 
data from one owner to another, or to ensure the transfer of inspection 
data resulting from the new regulation. The commenter points out that 
Sec. 121.380 requires that data be retained for only certain periods of 
time (usually one year), not the lifetime of the airplane. This poses a 
problem if operators are required to be knowledgeable of all the 
repairs previously performed on every airplane in its fleet. The 
commenter asserts that the proposed rule fails to take into 
consideration that ``over half of the commercial airplanes in the U.S. 
are leased and, therefore, subject to transfer between two U.S. 
operators.'' Those involved in such transfers today are well aware that 
the ability to obtain repair data is dependent on the individual 
recordkeeping standards of the operators--how long or how well the 
operator has kept the data. Moreover, the current regulations do not 
assist in the acquisition of such data.

[[Page 24120]]

The commenter suggests that Sec. 121.380 should be revised to require 
the retention of records for the lifetime of the aircraft or to exempt 
repair data from the current ``one-year destruction'' rule.
    The FAA acknowledges the commenter's observations, but does not 
agree that there is a need either to impose new recordkeeping 
requirements in conjunction with this rulemaking, or to revise 
Sec. 121.380. In every case, when an operator purchases an aircraft, it 
is the operator's responsibility to ensure that the aircraft complies 
with the operational requirements prior to adding it to its 
certificate. If pertinent data are not available at the time of the 
purchase, it normally is the operator's responsibility to go about 
obtaining the necessary information. In the case of this final rule, if 
the repair data are not available, an operator may be required to 
perform an assessment of the aircraft to establish the damage-tolerance 
of the repairs to the fuselage pressure boundary. The operator could 
then retain records of this assessment. Generally, the FAA anticipates 
that availability of necessary repair records will significantly 
enhance the value of affected airplanes because of the degree to which 
such records will simplify airplane transfers. Therefore, it is likely 
that, as a matter of commercial practice, operators will retain those 
records indefinitely.
    Information Actually Retained. One commenter states that, while 
most U.S. operators agree that records covering ``unsuperseded'' 
routine maintenance functions must be maintained, they do not all agree 
that ``non-routine functions resulting from these inspections are 
equally important.'' In short, a record that documents the performance 
of a repair assessment inspection may be kept, but any rework, repairs, 
etc., resulting from that inspection may not. This is especially true 
in cases where operators have totally automated their record systems. 
The commenter suggests that the proposed rule, in actuality, will 
impose new recordkeeping requirements since operators will have to 
maintain repair data resulting from inspections.
    The FAA acknowledges the commenter's comments. However, the FAA 
reiterates that, as stated previously, there are no new recordkeeping 
requirements mandated by this rule. As in any case, operators are 
required to maintain satisfactory evidence that they are in compliance 
with the regulations; this new rule requires nothing in addition to 
this.

New Methods To Retain/Maintain Repair Data

    One commenter states that it has developed an inexpensive software 
program and has a ``U.S. Patented Process'' to track new and old 
repairs completed on aircraft by using digital cameras. The commenter 
suggests that this product would be an excellent way of tracking 
aircraft repairs for the proposed repair assessment program.
    The FAA infers from this comment that the commenter is suggesting 
the rule be revised to require the use of such software to maintain 
repair data. The FAA understands that this software and others like it 
currently are available on the market. Operators could certainly use 
these types of products to simplify the retention of the necessary 
information needed to demonstrate compliance with this rule. However, 
no change to the rule is necessary to indicate this.

Enforceability of Sec. 129.32

    One commenter questions the enforceability of the proposed 
Sec. 129.32 on operators that are not subject to FAA regulations, 
specifically non-U.S. operators. The commenter states that, for 
example, although maintenance program provisions specified in part 129 
may be issued by the FAA and provided by the airplane lessor (in the 
U.S.) to an international lessee, there is ``no way to enforce [the 
lessee's] adherence'' to the requirements of that regulation. The 
commenter asserts that ``there are no recordkeeping enforcement 
provisions for part 129 operators'' and, since ``they do not operate to 
14 CFR, the proposed rule would be meaningless to them.'' The commenter 
fears that this could result in the invalidation of the leased 
airplane's Standard Airworthiness Certificate when it is returned to 
the U.S.
    The FAA does not concur. The rule will be enforceable with regard 
to part 129 foreign air carriers operating U.S.-registered aircraft 
into the U.S. As discussed in the preamble to the notice, the new 
repair assessment program required by Sec. 129.32 will be approved as 
part of the foreign air carrier's operations specifications (the 
maintenance programs will be incorporated into or listed in Section D 
of the operation specifications). In accordance with Sec. 129.11, part 
129 foreign air carriers must conduct their operations in accordance 
with the operations specifications.
    If foreign persons operating U.S.-registered aircraft in common 
carriage or foreign air carriers operating outside the U.S. do not 
maintain the aircraft in accordance with U.S. airworthiness standards, 
or cannot present adequate documentation of such maintenance, then the 
airworthiness certificate will be invalidated. A prudent aircraft owner 
will insist, as a matter of contract, that the repairs and maintenance 
are adequately documented so that, when the lease is terminated or the 
airplane sold, the airplane can retain its airworthiness certificate.

Impact on International Trade

    One commenter raises three issues concerning the International 
Trade Impact Assessment that appeared in the preamble to the notice, 
and the intended effect of the proposed rule on the import and export 
of airplanes:
    First, the commenter questions whether the International Trade 
Impact Assessment took into account the fact that other nations could 
emulate this rulemaking action and establish their own similar repair 
assessment programs. Usually foreign operators maintain considerably 
better records for such things as repairs than do U.S. operators and if 
the proposed rule does not require ``any new recordkeeping 
requirements,'' U.S. operators may be hard-pressed to provide adequate 
data to support the other country's repair assessment program. The 
commenter implies that this may be a hindrance to the export of 
airplanes to those countries.
    Second, the commenter asks that, if an imported airplane has never 
been inspected under a repair assessment program, (1) would its 
baseline inspection suffice, or (2) does the FAA/AAWG assume that the 
airplane's next U.S. part 121 operator would be responsible for 
bringing it up to the standards of the proposed rule prior to 
operation? The commenter notes that there is no FAA checklist of items 
that require action prior to issuance of a Standard Airworthiness 
Certificate, but an airplane being imported must meet the requirements 
of parts 21, 43, and 91 to obtain a Standard Airworthiness Certificate. 
The commenter states that the proposed change to Sec. 91.410 would 
establish deadlines that would preclude the issuance of the certificate 
prior to an airplane being added to a part 121 operator's fleet.
    Third, the commenter considers that the AAWG did not possess the 
necessary expertise that would come from experience in the transfer of 
airplanes, to reach the conclusion that the proposed rule would not 
affect the import or export of airplanes to or from the U.S. The 
commenter implies that the International Trade Impact Assessment

[[Page 24121]]

statement that appeared in the preamble to the notice is incorrect.
    The FAA does not concur with the commenter. The information 
provided in the International Trade Impact Assessment states only that 
the proposed rule would not constitute a ``barrier to international 
trade, including the export of American airplanes to foreign countries 
and the import of foreign airplanes into the United States.'' Despite 
the condition that an airplane is in when imported to the U.S., a part 
121 operator will still be responsible for ensuring compliance with the 
repair assessment requirements--as well as with every other applicable 
regulation--prior to putting the airplane into operation. While this 
may entail additional work on the part of the operator, it does not 
constitute a ``barrier to international trade.'' In fact, it is general 
practice for the importing operator to ensure the airplane is 
compliance with all applicable regulations of the importing country.
    Regarding the effect on exports, as indicated previously, the FAA 
anticipates that, as a commercial practice, operators will retain 
repair assessment records to facilitate future transfers. Assuming that 
foreign civil aviation authorities adopt requirements similar to this 
final rule, these records would also be sufficient to meet those 
requirements.
    As for the qualifications of the AAWG, the FAA points out that the 
AAWG is comprised of representatives from the aviation industry both in 
the U.S. and foreign countries; this includes manfuacturers, airlines, 
leasing companies, industry associations, unions, and non-U.S. civil 
aviation authorities. These representatives are some of the most 
experienced individuals in aviation worldwide who possess far-reaching 
expertise in numerous relevant areas. Their qualifications are 
incomparable and, as demonstrated in their work at part of AAWG, their 
knowledge and capabilities are considerable.

Proposed Regulatory Evaluation

    One commenter states that the proposal grossly underestimates the 
cost impact it will have on operators. The commenter states that one 
operator, who manages a fleet of about 10 percent of the affected U.S. 
fleet, has assessed the potential impact of the proposed program on its 
staffing requirements as follows:

     If only 12 repairs per airplane require assessment 
under the program, the total number of repairs for a fleet of 356 
airplanes will be 4,272.
     Approximately 4 engineering hours (at $55 per hour) 
would be required for each initial assessment. Based on this figure, 
the total number of work hours could be as many as 17,088, costing 
over $900,000.
     If half the number of repairs would require evaluation 
beyond the scope of existing manufacturers' documents, engineering 
support would be twice the level of the ordinary initial assessment 
and, thus, an additional cost of $900,000 could be expected.
     Repetitive inspections resulting from the program will 
add another $2.3 million in costs and over 10,000 hours of out-of-
service time.

    The total estimated cost for this single operator is at least $4.1 
million, and the loss of service of three airplanes out of the fleet 
for the remainder of their operational lives. If the airlines elects to 
replace the lost capacity, additional costs on the order of $300 
million will be incurred. While one carrier may elect not to replace 
lost capacity and allow the lost traffic to go to competitors, the 
industry as a whole cannot take this strategy. If all operators opted 
not to add capacity, load factors would have to grow. At over 70%, load 
factors are already at an all-time high, and production is at its 
limits. As a result, there would be a severe degradation in service to 
the public, as more travelers would be forced into second and third 
choices involving indirect routing and higher fares. The implied total 
U.S. cost would then be at least $40 million, and potentially as much 
as $3 billion more to replace lost capacity.
    The commenter avers that cost analysis indicated by FAA fails to 
recognize that the extensive repair analyses and additional repetitive 
inspections on airplanes will force many airplanes to be pulled out of 
normal rotations to complete the required work; the resulting out-of-
service time will wreak havoc on airline schedules. The commenter 
points out that the potential impact on system capacity has not been 
addressed by the FAA and should be adequately treated prior to adopting 
the proposed rule. Moreover, the commenter states that the FAA does not 
address the potential redundancy of the requirements with regard to 
existing Supplemental Structural Inspection Program and airworthiness 
directives that also result in damage-tolerance evaluation of 
structural repairs. The commenter requests that the FAA initiate and 
complete a more formal cost-benefit evaluation of the proposed action, 
and make it available to the public for review and comment, prior to 
taking final action.
    The FAA does not concur with the commenter's conclusions concerning 
the economic impact of this rule, or the need to provide additional 
time for public comment on the cost-benefit evaluation. A summary of 
the final economic evaluation appears in the Regulatory Evaluation 
Summary section of this document. The summary provides details of the 
FAA's final determination as to the economic impact and cost-benefit of 
this final rule. The full final economic evaluation can be found in the 
public docket. The FAA's response to specific points brought up by the 
commenter in its arguments is as follows.
    The commenter used the figure of 4 engineering hours as the number 
of hours necessary to carry out each initial assessment. According to 
the commenter, this figure was based on one operator's estimate. The 
FAA used a figure of 1 engineering hour for an initial assessment; this 
figure was based on estimates provided by members of the AAWG group 
associated with this rule, who had arrived at the figure from the input 
from several operators and others in pertinent aviation fields. The FAA 
considers the 1 hour figure more feasible due to the fact it represents 
data obtained from a wider range of entities affected by this rule.
    The commenter estimated that repetitive inspections would add 
another $2.3 million in costs and over 10,000 hours of out-of-service 
time. The FAA does not consider those figures to be appropriate. With 
regard to the $2.3 million, the commenter made no mention of using 
discounted values; therefore, the FAA assumes that the $2.3 million 
figure is represented in current values/prices. However, the 
inspections are to take place in the future--and they would need to be 
discounted to present values. This would substantially reduce their 
magnitude in present value.
    With regard to the 10,000 hours of out-of-service time, the 
commenter made no mention of accomplishing the inspections required by 
the rule during a regularly-scheduled C- or D-check. The use of the C- 
and D-check. The use of the C- and D-checks to carry out inspections 
would significantly reduce or effectively eliminate the out-of-service 
time.
    In its proposed economic evaluation, the FAA carried out cost 
estimates for operators by using 1 hour for the accomplishment of the 
initial assessments, and 2 hours for carrying out supplemental 
inspections. The assessments and inspections also were assumed to take 
place during C- or D-checks. The cost estimates thus derived were 
subsequently discounted to present day values--since the assessments 
and inspections would not

[[Page 24122]]

take place today but at some years in the future.
    The commenter considers the rule to be largely redundant and not 
needed because the current certification regulations for new airplanes, 
and the Supplemental Structural Inspection Programs (SSIP) for older 
airplanes, already accomplish the intent of a damage-tolerance 
assessment of repairs that would be required by the rule. The FAA does 
not concur with the commenter's assumption and has explained, in both 
the preamble to the notice as well as this preamble, the reasons why 
this rule is essential. To reiterate: The Supplemental Structural 
Inspection Programs for existing airplanes, including nearly all of the 
airplane models affected by this new rule, were mandated by 
Airworthiness Directives (AD) beginning in 1984. The majority of those 
AD's did not attempt to address issues relating to the damage tolerance 
of repairs that had been made to the airplanes; therefore, one of the 
objectives of this new rule is to provide that same level of assurance 
for areas of the structure that have been repaired.
    The practice of damage-tolerance methodology has evolved gradually 
over the last 20-plus years. Because a regulatory requirement for 
damage-tolerance was not applied to airplane designs type certificated 
before 1978, the damage-tolerance characteristics of repairs that 
currently exist on airplanes may vary widely and are largely unknown. 
Further, some repair designs contained in the airplane manufacturers' 
Structural Repair Manuals (SRM) were not designed to current standards, 
and repairs accomplished in accordance with those SRM's may require 
additional inspections if evaluated using current methodologies. This 
new rule will ensure that those inspections are accomplishments and 
that repairs are brought up to standards, if necessary.

Terminology Changes in Final Rule

    The FAA has revised certain terminology that appeared in the 
proposed introductory text of Sec. 91.410 and Sec. 125.248.The 
provisions of those sections, as they appeared in the proposal, 
included the phrase ``No certificate holder may operate * * *'' 
However, in this final rule, that phrase has been replaced with ``No 
person may operate * * *'' in order to conform with the terminology 
used throughout parts 91 and 125.
    Additionally, the FAA has replaced this same terminology in the 
next of Sec. 129.32 with ``No foreign air carrier or foreign persons a 
U.S.-registered airplane may operate * * *'' This change has been made 
in order to correctly reflect the operators who are affected by this 
section of the regulations.
    The FAA also has revised certain other wording in the introductory 
text of Secs. 121.370, 125.248, and 129.32. The proposed text in each 
of those sections stated that none of the affected airplanes could be 
operated beyond the specified time(s) ``* * * unless its operation 
specifications have been revised to reference repair assessment 
guidelines * * *'' This text in the final rule has been revised to 
state ``* * * unless operations specifications have been issued to 
reference repair assessment guidelines * * *'' This change is necessary 
to corrently reflect the interface of this rule with the operations 
specifications process.
    Additionally, in the proposal, the introductory text for each of 
the proposed regulations indicated that approval of the repair 
assessment guidelines could be granted only by the FAA Aircraft 
Certification Office (ACO) having cognizance over the type certificate 
for the affected airplane. The FAA has revised this text in the final 
rule to indicate that there are FAA offices other than ACO's that have 
cognizance over type certificates and, therefore, those office may 
approve the repair assessment guidelines.

Paperwork Reduction Act

    In accordance with the Paperwork Reduction Act of 1995 [44 U.S.C. 
3507(d)], the FAA has determined that there are no requirements for 
information collection associated with this final rule.

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 
determined that there are no ICAO Standards and Recommended Practices 
that correspond to these regulations.

Regulatory Evaluation Summary

    Changes to Federal regulations must undergo several economic 
analyses. First, Executive Order 12866 directs that each Federal agency 
shall propose or adopt a regulation only upon a reasoned determination 
that the benefits of the intended regulation justify its costs. Second, 
the Regulatory Flexibility Act of 1980 requires agencies to analyze the 
economic impact of regulatory changes on small entities. Third, the 
Office of Management and Budget (OMB) directs agencies to assess the 
effect of regulatory changes on international trade. And fourth, the 
Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4) requires agencies 
to prepare a written assessment of the costs, benefits, and other 
effects of proposed or final rules that include a Federal mandate 
likely to result in the expenditure by State, local, or tribal 
governments, in the aggregate, or by private sector, or $100 million or 
more annually (adjusted for inflation).
    In conducting these analyzes, the FAA has determined that this rule 
is not ``a significant regulatory action'' as defined under section 
3(f) of Executive Order 12866 and, therefore is not subject to review 
by the Office of Management and Budget. The rule is not considered 
significant under the regulatory policies and procedures of the 
Department of Transportation (44 FR 11034, February 26, 1979). This 
rule will not have a significant impact on a substantial number of 
small entities and will not constitute a barrier to international 
trade.
    These analyses, available in the docket, are summarized below.

Costs to Manufacturers

    This section presents the FAA's estimate of costs to the four 
manufacturers of the airplane models affected by the rule. The FAA has 
conservatively included estimates of costs to non-U.S. manufacturers 
(i.e., Airbus Industrie, British Aerospace, and Fokker Aircraft B.V.), 
although only those costs to U.S. manufacturers are required to be 
estimated. Manufacturers will incur one-time, ``set-up'' costs to:
    1. Revise their SRM and to develop RAG's to reflect damage-tolerant 
repair considerations:
    2. Publish the revised SRM and the RAG's; and
    3. Train their engineers, personnel of the operator, and the FAA to 
conduct repair assessments.
    Manufacturers also will incur continuing program maintenance costs 
of:

     Maintenance of records for the program,
     Additional training and subsequent revisions to the 
SRM, and
     Assessments of unusual repairs that are not described 
in the published guidelines.

    The total one-time, set-up costs are estimated to be $10.8 million 
in the year 2000. Total annual, recurring costs for the years 2001 
through 2022 are estimated to be $28.7 million, or about $1.3 million 
per year. The total non-discounted costs of the rule to affected 
manufacturers are estimated to be $39.5 million over the years 2000 
through

[[Page 24123]]

2022, or $25.2 million discounted to present value at 7 percent.
    The estimates are based on an effective date of 2000. The FAA 
assumes that the manufacturers' costs of setting up their repair 
assessment programs would be incurred in the year 2000, and that annual 
costs would be incurred each year beginning in 2001 through 2022. The 
setting-up costs include the cost of revising Structural Repair Manuals 
and developing repair assessment guidelines for some models, the cost 
of publishing these documents, and the cost of training. Costs are 
expressed in constant dollars.

Costs to Operators

    Operators will incur costs to

     Train inspectors,
     Integrate the repair assessment program into the 
maintenance program for each affected model,
     Conduct repair assessments and supplemental 
inspections, and
     Maintain records of assessments and inspections.

    Because repair assessments and supplemental inspections are assumed 
to be conducted during regularly scheduled C- and D-checks, the FAA has 
not attributed any downtime costs. The FAA estimates that it takes 
between 25 and 30 people, working three shifts per day, 10 to 14 days 
to conduct a C-check. The FAA also estimates that it takes between 30 
and 40 people, working three shifts per day, three to seven weeks to 
conduct a D-check. The relatively brief time to conduct a repair 
assessment or a supplemental inspection check could be incorporated 
into a C- or D-check without additional loss of service.
     Fleet Data and Noise Restrictions: The FAA used Airclaims 
fleet data to estimate operators' costs to conduct repair assessments 
and inspections. Airplane-specific cumulative and current annual flight 
cycles and flight hours for all U.S.-registered airplanes affected by 
the program were used to predict each airplane's ``threshold'' date 
(i.e., the date on which the proposed flight cycle implementation time 
is reached). The analysis includes affected U.S.-registered airplanes 
that are operated by foreign entities. The threshold, or flight 
implementation time, is 75 percent of the original equipment 
manufacturer's design service goal. Information received from several 
of the affected manufacturers confirmed the accuracy of the database.
    Noise restrictions on airplanes also have an impact on the estimate 
of the number or airplanes affected by the rule. Because of noise 
restrictions, as of January 1, 2000, Stage 1 and Stage 2 airplanes will 
not longer be allowed to operate in the continental United States; and 
the FAA assumes that U.S. operators will either retire or sell to 
foreign entities those models that are exclusively State 1 or Stage 2 
airplanes. This relates to airplanes such as the BAC 1-11 and Fokker F-
28.
    The database of airplanes used for this analysis includes data that 
are effective as of January 1, 1999. To carry out calculations, the FAA 
assumed that airplanes in that database that still had Stage 2 hush 
kits would not be equipped with Stage 3 hush kits by the end of 1999. 
These airplanes were, thus, not included in the calculations. The FAA 
recognizes that an underestimate of the number of airplanes with Stage 
2 hush kits may thus occur; however, the FAA believes that number to be 
small and indeterminate. This estimate includes both N-registered 
airplanes operated by airlines as well as by non-airline entities, but 
does not include any additional airplanes that might be imported. It 
also does not include future production (i.e. ``new'') airplanes that 
may reach the threshold before 2022, the estimate of which would be 
highly tenuous and whose present value costs will be low or zero.
     Repair Assessment and Supplemental Inspection Costs: The 
activities involved in the entire repair assessment program can be 
classified into three basic stages. The first stage requires that a 
certificate holder (i.e., an operator) incorporate a repair assessment 
program into this maintenance or inspection program by the time that an 
airplane, for that particular model, reaches its flight cycle 
implementation time (e.g., the threshold) or within one year from the 
effective date of the rule--whichever occurs later. The actual outcome 
between these two possibilities is affected by the actual number of 
flight cycles in relationship to the design service goal of the 
airplane at the effective date of the rule.
    The second stage involves repair assessments. This work is to be 
conducted, for individual airplanes, within the D-check or C-check 
flight cycle interval after the first stage. The D-check interval is 
used for airplanes whose flight cycles will not have exceeded their 
design service goal by the effective date of the rule. The C-check 
interval is used for those airplanes that will have exceeded their 
design service goal by the effective date of the rule. In this second 
stage, the previous repairs to the fuselages of the affected airplanes 
are assessed, by operators' maintenance personnel, to check whether 
they meet the damage-tolerance criteria. If they do, additional work is 
not required. If they do not, these repairs are to be repaired again 
and brought up to the expected quality.
    During the third stage, these repairs are to be inspected at the C-
check interval of that particular airplane model.
    With regard to specific chronology, given an expected effective 
date of the rule of 2000 and the requirements in the rule, the repair 
assessment will be conducted at the next heavy maintenance D-check 
after January 1, 2001, or after the threshold, whichever occurs later. 
For those airplanes that have exceeded the design service goal, by the 
effective date of the rule. The repair assessment will be conducted at 
the next C-check after January 2001.
    The AAWG estimated the number of repairs for airplanes, in each 
affected airplane model, that would require assessment at the 
appropriate date, and the number of those repairs that would require 
supplemental inspections. The AAWG also estimated that it would take 1 
hour to assess a repair and 2 hours to inspect a repair. For 
supplemental inspections, the AAWG estimated that \1/2\ of the repairs 
would require inspections during every C-check, while the other half 
would require inspections during every fourth children-check. 
Manufacturers and operators provided information on the average number 
of flight hours between C-checks and D-checks, by affected model. The 
AAWG estimated that affected airplanes would continue to be operated 
for 10 years beyond the dates of their repair assessments.
    The FAA has estimated operator compliance costs for repair 
assessment and supplemental inspections through the year 2022 to the 
$17.4 million, or $6.0 million discounted to present value.
     Training Costs: Operators of affected U.S.-registered 
airplanes will incur costs in order to train their maintenance 
personnel to assess and inspect repairs. Moreover, it is expected that, 
rather than train their own maintenance personnel, operators with only 
a few affected airplanes will likely contract out assessments and 
inspections with other operators whose maintenance personnel have been 
trained to conduct these activities.
    The FAA assumes that training costs for operators' maintenance 
personnel would be incurred in 2000. Moreover, in order to account for 
turnover among maintenance personnel trained for repair assessment, the 
FAA estimates that operators would incur annual training costs, equal 
to 5 percent of the 2000 training costs, for each year from

[[Page 24124]]

2001 through 2022. Operators' costs for training are described in more 
detail in the full regulatory evaluation.
    The FAA estimates that total training costs over the years 2000 
through 2022 will be $869,842, or $643,279 discounted to present value.
     Administrative Costs of the Repair Assessment Program: The 
rule will require each affected operator to integrate a repair 
assessment program into either its maintenance program (for affected 
airplanes operated under part 121 or 129) or its inspection program 
(for affected airplanes operated under part 91 or 125) by the time the 
threshold is reached or within one year from the effective date of the 
proposed rule, whichever is later. The repair assessment program can 
include such information as:

     The scope of the assessment;
     Relevant Airworthiness Directives (AD) and Service 
Bulletins (SB);
     The means to identify, assess, and inspect repairs; and
     Procedures to maintain records for each airplane's 
repair survey, assessments, and supplemental inspections.

    Costs to operators for program administration are estimated to 
total $0.7 million, or $0.3 million discounted to present value.
    Based on estimates of manufacturers, operators, the AAWG, and the 
FAA, over the years 2000 through 2022, operators of airplanes affected 
by the proposed rule are expected to incur total costs of $19.0 
million, or $6.9 million discounted to present value. Repair 
assessments and supplemental inspection costs account for about 92 
percent of total costs and 86 percent of present value costs.

Costs to the FAA

    The rule requires FAA approval of repair assessment programs. 
Aircraft Certification Offices (ACO) will review repair assessment 
guidelines for airline and non-airline operators. The FAA Principal 
Maintenance Inspectors (PMI) will review the maintenance programs for 
their assigned airlines to ensure implementation and compliance with 
the repair assessment program. In addition, PMI's and other FAA 
inspectors also will be trained to conduct repair assessments and 
supplemental inspections. It is estimated that the total cost to the 
FAA will be $548,353, or $344,695 discounted to present value.

Total Costs of the Rule

    Total costs of the rule to manufacturers, operators, and the FAA 
are estimated to be $59.1 million over the years 2000 through 2022, or 
$32.5 million in present value.

Benefits

    Based on available data, no accidents have been caused by the 
failure of structural repairs to airplanes of the models affected by 
the rule. Nevertheless, these airplanes being operated beyond their 
design service objective and the FAA has determined that the repair 
assessment program is needed to maintain the continued airworthiness of 
these aging airplanes. The FAA is unable to determine the number of 
accidents that would be prevented by this rule. However, only one 
serious accident needs to be avoided in order to offset the total cost 
of the rule. Based on International Aircraft Price Guide [Summer 1994: 
Airclaims Limited: London, England], the FAA estimated that the 
weighted average value of an affected airplane is $10.8 million, in 
constant dollars. Using a conservative load factor of 63 percent for 
passenger airplanes and accounting for those airplanes that are 
operated in cargo service, the weighted average number of occupants is 
103. Using $2.7 million as the statistical value of a fatality avoided, 
the average cost of an accident to an affected airplane resulting in 
the loss of the airplane and half of its occupants, would be $150.9 
million, including $1 million for accident investigation. If this 
accident occurred halfway between the first and last year of repair 
assessments in this analysis (i.e., between 2001 and 2022), the present 
value of benefits is estimated to be $46.8 million.

Benefits Compared to Costs

    The benefits of the rule are estimated at $46.8 million, at present 
value, while the costs of the rule are estimated at $32.5 million at 
present value. The FAA, therefore, has determined that if the rule 
prevents one ``average'' accident, the repair assessment program will 
be cost-beneficial.

Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) of 1980, 5 U.S.C. 601-612, 
directs the FAA to fit regulatory requirements to the scale of the 
business, organizations, and governmental jurisdictions subject to the 
regulation. We are required to determine whether a proposed or final 
action will have a ``significant economic impact on a substantial 
number of small entities'' as defined in the Act. If we find that the 
action will have a significant impact, we must do a ``regulatory 
flexibility analysis.''
    This final rule will affect manufacturers and operators of 
airplanes, in the specified parts of the CFR. For both manufacturers 
and operators, a small entity is currently defined as one with 1,500 or 
fewer employees. None of the airplane manufacturers that are affected 
by this final rule have employee levels that fall below this employment 
threshold. Consequently, the FAA certifies that the final rule will not 
have a significant economic impact on a substantial number of 
manufacturers of airplanes.
    Some operators, however, do have employee levels that fall below 
the employment threshold. Consequently, calculations were carried out 
to assess whether the rule will have a significant impact on a 
substantial number of these operators. These calculations showed that 
the annualized cost of the rule is very small in comparison to annual 
revenues of the affected entities--considerably smaller than 1 percent 
of their revenues. Consequently, the rule will not have a significant 
impact on small operators.

International Trade Impact Assessment

    The provisions of this rule will have little or no impact on trade 
for U.S. firms doing business in foreign countries and foreign firms 
doing business in the United States.

Executive Order 13132, Federalism

    The FAA has analyzed this final 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. Therefore, the FAA has determined that this rule does not 
have federalism implications.

Unfunded Mandates Analysis

    Title II of the Unfunded Mandates Reform Act of 1995 (the Act), 
codified as 2 U.S.C. 1501-1571, requires each Federal agency, to the 
extent permitted by law, to prepare a written assessment of the effects 
of any Federal mandate in a proposed or final agency rule that may 
result in the expenditure by State, local, and tribal governments, in 
the aggregate, or by the private sector, of $100 million or more 
(adjusted annually for inflation) in any one year. Section 204(a) of 
the Act, 2 U.S.C. 1534(a), requires the Federal agency to develop an 
effective process to permit timely input by elected officers (or their 
designees) of State, local, and tribal governments on a proposed 
``significant intergovernmental mandate.'' A ``significant 
intergovernmental

[[Page 24125]]

mandate'' under the Act is any provision in a Federal agency regulation 
that would impose an enforceable duty upon State, local, and tribal 
governments, in the aggregate, of $100 million (adjusted annually for 
inflation) in any one year. Section 203 of the Act, 2 U.S.C. 1533, 
which supplements section 204(a), provides that before establishing any 
regulatory requirements that might significantly or uniquely affect 
small governments, the agency shall have developed a plan that, among 
other things, provides for notice to potentially affected small 
governments, if any, and for a meaningful and timely opportunity to 
provide input in the development of regulatory proposals.
    This rule does not contain a Federal intergovernmental or private 
sector mandate that exceeds $100 million in any one year.

Environmental Analysis

    FAA Order 1050.1D defines FAA actions that may be categorically 
excluded from preparation of a National Environmental Policy Act (NEPA) 
environmental assessment or environmental impact statement. In 
accordance with FAA Order 1050.1D, appendix 4, paragraph 4(j), this 
rulemaking action qualifies for a categorical exclusion.

Regulations Affecting Intrastate Aviation in Alaska

    Section 1205 of the FAA Reauthorization Act of 1996 (110 Stat. 
3213) requires the Administrator, when modifying regulations in Title 
14 of the CFR in a manner affecting intrastate aviation in Alaska, to 
consider the extent to which Alaska is not served by transportation 
modes other than aviation, and to establish such regulatory 
distinctions as he or she considers appropriate. Because this amendment 
applies to the operation of certain transport category airplanes under 
parts 91, 121, 125, and 129 of Title 14, it could affect intrastate 
aviation in Alaska. Because no comments were received regarding this 
regulation affecting intrastate aviation in Alaska, the FAA will apply 
the rule in the same way that it is being applied nationally.

Energy Impact

    The energy impact of the rule has been assessed in accordance with 
the Energy Policy and Conservation Act (EPCA) Pub. L. 94-163, as 
amended (43 U.S.C. 6362) and FAA Order 1053.1. It has been determined 
that the final rule is not a major regulatory action under the 
provisions of the EPCA.

List of Subjects

14 CFR Part 91

    Aircraft, Aviation safety, Federal Aviation Administration, 
Reporting and recordkeeping requirements.

14 CFR Part 121

    Air carriers, Aircraft, Aviation Safety, Federal Aviation 
Administration, Reporting and recordkeeping requirements, Safety, 
Transportation.

14 CFR Part 125

    Aircraft, Aviation safety, Federal Aviation Administration, 
Reporting and recordkeeping requirements.

14 CFR Part 129

    Air carriers, Aircraft, Aviation Safety, Federal Aviation 
Administration, Reporting and recordkeeping requirements.

The Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration amends parts 91, 121, 125, and 129 of Title 14, Code of 
Federal Regulations as follows:

PART 91--GENERAL OPERATING AND FLIGHT RULES

    1. The authority citation for part 91 continues to read:

    Authority: 49 U.S.C. 106(g), 40103, 40113, 40120, 44101, 44111, 
44701, 44709, 44711, 44712, 44715, 44716, 44717, 44722, 46306, 
46315, 46316, 46502, 46504, 46506-46507, 47122, 47508, 47528-47531.


    2. Add a new Sec. 91.410 to read as follows:


Sec. 91.410  Repair assessment for pressurized fuselages.

    No person may operate an Airbus Model A300 (excluding the -600 
series), British Aerospace Model BAC 1-11, Boeing Model, 707, 720, 727, 
737 or 747, McDonnell Douglas Model DC-8, DC-9/MD-80 or DC-10, Fokker 
Model F28, or Lockheed Model L-1011 airplane beyond applicable flight 
cycle implementation time specified below, or May 25, 2001, whichever 
occurs later, unless repair assessment guidelines applicable to the 
fuselage pressure boundary (fuselage skin, door skin, and bulkhead 
webs) that have been approved by the FAA Aircraft Certification Office 
(ACO), or office of the Transport Airplane Directorate, having 
cognizance over the type certificate for the affected airplane are 
incorporated within its inspection program:
    (a) For the Airbus Model A300 (excluding the -600 series), the 
flight cycle implementation time is:
    (1) Model B2: 36,000 flights.
    (2) Model B4-100 (including Model B4-2C): 30,000 flights above the 
window line, and 36,000 flights below the window line.
    (3) Model B4-200: 25,000 flights above the window line, and 34,000 
flights below the window line.
    (b) For all models of the British Aerospace BAC 1-11, the flight 
cycle implementation time is 60,000 flights.
    (c) For all models of the Boeing 707, the flight cycle 
implementation time is 15,000 flights.
    (d) For all models of the Boeing 720, the flight cycle 
implementation time is 23,000 flights.
    (e) For all models of the Boeing 727, the flight cycle 
implementation time is 45,000 flights.
    (f) For all models of the Boeing 737, the flight cycle 
implementation time is 60,000 flights.
    (g) For all models of the Boeing 747, the flight cycle 
implementation time is 15,000 flights.
    (h) For all models of the McDonnell Douglas DC-8, the flight cycle 
implementation time is 30,000 flights.
    (i) For all models of the McDonnell Douglas DC-9/MD-80, the flight 
cycle implementation time is 60,000 flights.
    (j) For all models of the McDonnell Douglas DC-10, the flight cycle 
implementation time is 30,000 flights.
    (k) For all models of the Lockheed L-1011, the flight cycle 
implementation time is 27,000 flights.
    (l) For the Fokker F-28 Mark 1000, 2000, 3000, and 4000, the flight 
cycle implementation time is 27,000 flights.

PART 121--CERTIFICATION AND OPERATIONS: DOMESTIC, FLAG, AND 
SUPPLEMENTAL AIR CARRIERS AND COMMERCIAL OPERATORS OF LARGE 
AIRCRAFT

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

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


    2. Add a new Sec. 121.370 to read as follows:


Sec. 121.370  Repair assessment for pressurized fuselages.

    No certificate holder may operate an Airbus Model A300 (excluding 
the -600 series), British Aerospace Model BAC 1-11, Boeing Model 707, 
720, 727, 737, or 747, McDonnel Douglas Model DC-8, DC-9/MD-80 or DC-
10, Fokker Model F28, or Lockheed Model L-1011 airplane beyond the 
applicable flight cycle implementation time specified below, or May 25, 
2001, whichever

[[Page 24126]]

occurs later, unless operations specifications have been issued to 
reference repair assessment guidelines applicable to the fuselage 
pressure boundary (fuselage skin, door skin, and bulkhead webs), and 
those guidelines are incorporated in its maintenance program. The 
repair assessment guidelines must be approved by the FAA Aircraft 
Certification Office (ACO), or office of the Transport Airplane 
Directorate, having cognizance over the type certificate for the 
affected airplane.
    (a) For the Airbus Model A300 (excluding the -600 series), the 
flight cycle implementation time is:
    (1) Model B2: 36,000 flights.
    (2) Model B4-100 (including Model B4-2C): 30,000 flights above the 
window line, and 36,000 flights below the window line.
    (3) Model B4-200: 25,000 flights above the window line, and 34,000 
flights below the window line.
    (b) For all models of the British Aerospace BAC 1-11, the flight 
cycle implementation time is 60,000 flights.
    (c) For all models of the Boeing 707, the flight cycle 
implementation time is 15,000 flights.
    (d) For all models of the Boeing 720, the flight cycle 
implementation time is 23,000 flights.
    (e) For all models of the Boeing 727, the flight cycle 
implementation time is 45,000 flights.
    (f) For all models of the Boeing 737, the flight cycle 
implementation time is 60,000 flights.
    (g) For all models of the Boeing 747, the flight cycle 
implementation time is 15,000 flights.
    (h) For all models of the McDonnell Douglas DC-8, the flight cycle 
implementation time is 30,000 flights.
    (i) For all models of the McDonnell Douglas DC-9/MD-80, the flight 
cycle implementation time is 60,000 flights.
    (j) For all models of the McDonnell Douglas DC-10, the flight cycle 
implementation time is 30,000 flights.
    (k) For all models of the Lockheed L-1011, the flight cycle 
implementation time is 27,000 flights.
    (l) For the Fokker F-28 Mark 1000, 2000, 3000, and 4000, the flight 
cycle implementation time is 60,000 flights.

PART 125--CERTIFICATION AND OPERATIONS: AIRPLANES HAVING A SEATING 
CAPACITY OF 20 OR MORE PASSENGERS OR A MAXIMUM PAYLOAD CAPACITY OF 
6,000 POUNDS OR MORE

    1. The authority citation for part 125 continues to read:

    Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44705, 44710-
44711, 44713, 44716-44717, 44722.


    2. Add a new Sec. 125.248 to read as follows:


Sec. 125.248  Repair assessment for pressurized fuselages.

    No person may operate an Airbus Model A300 (exlcuding the -600 
series), British Aerospace Model BAC 1-11, Boeing Model 707, 720, 727, 
737 or 747, McDonnell Douglas Model DC-8, DC-9/MD-80 or DC-10, Fokker 
Model F28, or Lockheed Model L-1011 beyond the applicable flight cycle 
implementation time specified below, or May 25, 2001, whichever occurs 
later, unless operations specifications have been issued to reference 
repair assessment guidelines applicable to the fuselage pressure 
boundary (fuselage skin, door skin, and bulkhead webs), and those 
guidelines are incorporated in its maintenance program. The repair 
assessment guidelines must be approved by the FAA Aircraft 
Certification Office (ACO), or office of the Transport Airplane 
Directorate, having cognizance over the type certificate for the 
affected airplane.
    (a) For the Airbus Model A300 (excluding the -600 series), the 
flight cycle implementation time is:
    (1) Model B2: 36,000 flights.
    (2) Model B4-100 (including Model B4-2C): 30,000 flights above the 
window line, and 36,000 flights below the window line.
    (3) Model B4-200: 25,000 flights above the window line, and 34,000 
flights below the window line.
    (b) For all models of the British Aerospace BAC 1-11, the flight 
cycle implementation time is 60,000 flights.
    (c) For all models of the Boeing 707, the flight cycle 
implementation time is 15,000 flights.
    (d) For all models of the Boeing 720, the flight cycle 
implementation time is 23,000 flights.
    (e) For all models of the Boeing 727, the flight cycle 
implementation time is 45,000 flights.
    (f) For all models of the Boeing 737, the flight cycle 
implementation time is 60,000 flights.
    (g) For all models of the Boeing 747, the flight cycle 
implementation time is 15,000 flights.
    (h) For all models of the McDonnell Douglas DC-8, the flight cycle 
implementation time is 30,000 flights.
    (i) For all models of the McDonnell Douglas DC-9/MD-80, the flight 
cycle implementation time is 60,000 flights.
    (j) For all models of the McDonnell Douglas DC-10, the flight cycle 
implementation time is 30,000 flights.
    (k) For all models of the Lockheed L-1011, the flight cycle 
implementation time is 27,000 flights.
    (l) For the Fokker F-28 Mark, 1000, 2000, 3000, and 4000, the 
flight cycle implementation time is 60,000 flights.

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

    1. The authority citation for part 129 continues to read:

    Authority: 49 U.S.C. 106(g), 40104-40105, 40113, 40119, 44701-
44702, 44712, 44716-44717, 44722, 44901-44904, 44906.


    2. Add a new Sec. 129.32 to read as follows:


Sec. 129.32  Repair assessment for pressurized fuselages.

    No foreign air carrier or foreign persons operating a U.S. 
registered airplane may operate an Airbus Model A300 (excluding -600 
series), British Aerospace Model BAC 1-11, Boeing Model 707, 720, 727, 
737, or 747, McDonnell Douglas Model DC-8, DC-9/MD-80 or DC-10, Fokker 
Model F28, or Lockheed Model L-1011 beyond the applicable flight cycle 
implementation time specified below, or May 25, 2001, whichever occurs 
later, unless operations specifications have been issued to reference 
repair assessment guidelines applicable to the fuselage pressure 
boundary (fuselage skin, door skin, and bulkhead webs), and those 
guidelines are incorporated in its maintenance program. The repair 
assessment guidelines must be approved by the FAA Aircraft 
Certification Office (ACO), or office of the Transport Airplane 
Directorate, having cognizance over the type certificate for the 
affected airplane.
    (a) For the Airbus Model A300 (excluding the -600 series), the 
flight cycle implementation time is:
    (1) Model B2: 36,000 flights.
    (2) Model B4-100 (including Model B4-2C): 30,000 flights above the 
window line, and 36,000 flights below the window line.
    (3) Model B4-200: 25,500 flights above the window line, and 34,000 
flights below the window line.
    (b) For all models of the British Aerospace BAC 1-11, the flight 
cycle implementation time is 60,000 flights.
    (c) For all models of the Boeing 707, the flight cycle 
implementation time is 15,000 flights.
    (d) For all models of the Boeing 720, the flight cycle 
implementation time is 23,000 flights.
    (e) For all models of the Boeing 727, the flight cycle 
implementation time is 45,000 flights.

[[Page 24127]]

    (f) For all models of the Boeing 737, the flight cycle 
implementation time is 60,00 flights.
    (g) For all models of the Boeing 747, the flight cycle 
implementation time is 15,000 flights.
    (h) For all models of the McDonnell Douglas DC-8, the flight cycle 
implementation time is 30,000 flights.
    (i) For all models of the McDonnell Douglas DC-9/MD-80, the flight 
cycle implementation time is 60,000 flights.
    (j) For all models of the McDonnell Douglas DC-10, the flight cycle 
implementation time is 30,000 flights.
    (k) For all models of the Lockheed L-1011, the flight cycle 
implementation time is 27,000 flights.
    (l) For the Fokker F-28 Mark 1000, 2000, 3000, and 4000, the flight 
cycle implementation time is 60,00 flights.

    Issued in Washington, DC, on April 19, 2000.
Jane F. Garvey,
Administrator of Federal Aviation Administration (FAA).
[FR Doc. 00-10220 Filed 4-24-00; 8:45 am]
BILLING CODE 4910-13-M