[Federal Register Volume 63, Number 1 (Friday, January 2, 1998)]
[Proposed Rules]
[Pages 126-136]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-34166]
[[Page 125]]
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Part II
Department of Transportation
_______________________________________________________________________
Federal Aviation Administration
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14 CFR Parts 91, 121, 125, and 129
Repair Assessment for Pressurized Fuselages; Proposed Rule
Proposed Advisory Circular (AC) 120-XX, Repair Assessment of
Pressurized Fuselages; Notice
Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 /
Proposed Rules
[[Page 126]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Parts 91, 121, 125, and 129
[Docket No. 29104; Notice No. 97-16]
RIN 2120-AF81
Repair Assessment for Pressurized Fuselages
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking.
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SUMMARY: This proposed rulemaking would require incorporation of repair
assessment guidelines for the fuselage pressure boundary (fuselage
skins and pressure webs) of certain transport category airplane models
into the FAA-approved maintenance or inspection program of each
operator of those airplanes. 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
supplemental 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.
DATES: Comments must be submitted on or before April 2, 1998.
ADDRESSES: Comments on this document may be mailed in triplicate to:
Federal Aviation Administration, Office of the Chief Counsel,
Attention: Rules Docket (AGC-200), Docket No. 29104, 800 Independence
Avenue SW., Washington, DC 20591; or delivered in triplicate to: Room
915G, 800 Independence Avenue SW., Washington, DC 20591. Comments
delivered must be marked Docket No. 29104. Comments may also be
submitted electronically to: [email protected] Comments may be
examined in Room 915G weekdays, except Federal holidays, between 8:30
a.m. and 5:00 p.m. In addition, the FAA is maintaining an information
docket of comments in the Transport Airplane Directorate (ANM-100),
Federal Aviation Administration, Northwest Mountain Region, 1601 Lind
Avenue SW., Renton, WA 98055-4056. Comments in the information docket
may be examined weekdays, except Federal holidays, between 7:30 a.m.
and 4:00 p.m.
FOR FURTHER INFORMATION CONTACT:
Dorenda Baker, Manager, Aging Aircraft Program, ANM-109, FAA Transport
Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue
SW., Renton, WA 98055-4056; telephone (425) 227-2109, facsimile (425)
227-1100.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in this proposed
rulemaking by submitting such written data, views, or arguments as they
may desire. Comments relating to the environmental, energy, federalism,
or economic impact that might result from adoption of the proposals in
this notice are also invited. Substantive comments should also be
accompanied by cost estimates. Commenters should identify the
regulatory docket or notice number and submit comments in triplicate to
the Rules Docket address specified above. All comments received on or
before the closing date for comments will be considered by the
Administrator before taking action on this proposed rulemaking. The
proposals contained in this notice may be changed in light of the
comments received. All comments received will be available in the Rules
Docket for examination by interested persons, both before and after the
closing date for comments. A report summarizing each substantive public
contact with FAA personnel concerned with this rulemaking will be filed
in the docket. Commenters wishing the FAA to acknowledge receipt of
their comments submitted in response to this notice must include a
self-addressed, stamped postcard on which the following statement is
made: ``Comments to Docket No. 29104. The postcard will be date stamped
and returned to the commenter.
Availability of the NPRM
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), the online Federal Register database through GPO Access
(telephone: 202-512-1661), or the FAA's Aviation Rulemaking Advisory
Committee Bulletin Board service (telephone: 202-267-5948).
Internet users may reach the FAA's web page at http://www.faa.gov
or GPO's Federal Register web page at http://www.access.gpo.gov/
su__docs for access to recently published rulemaking documents.
Any person may obtain a copy of this NPRM by submitting a request
to the Federal Aviation Administration, Office of Rulemaking, ARM-1,
800 Independence Avenue SW., Washington, D.C. 20591, or by calling
(202) 267-9677. Communications must identify the notice number of this
NPRM. Persons interested in being placed on a mailing list for future
rulemaking documents should request from the Office of Public Affairs,
Attention: Public Inquiry Center, APA-230, 800 Independence Ave SW.,
Washington, D.C. 20591, or by calling (202) 267-3484, a copy of
Advisory Circular No. 11-2A, Notice of Proposed Rulemaking Distribution
System, which describes the application procedure.
Background
This proposal, to require the incorporation of repair assessment
guidelines into the maintenance or inspection program for certain
transport category airplanes, follows from commitments made by the FAA
and the aviation community in June 1988 to address the issues
concerning the safety of aging transport airplanes.
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, an aging aircraft task force was
established in August 1988 as a sub-group of the FAA's Research,
Engineering, and 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 keeping the aging fleet safe. For each
airplane model in the aging transport fleet, (1) select service
bulletins describing modifications and inspections necessary to
maintain structural integrity; (2) develop
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inspection and prevention programs to address corrosion; (3) develop
generic structural maintenance program guidelines for aging airplanes;
(4) review and update the Supplemental Structural Inspection Documents
(SSID) which describe inspection programs to detect fatigue cracking;
and (5) assess damage-tolerance of structural repairs. Structures Task
Groups sponsored by the Task Force were assigned the task of developing
these elements into usable programs.
Today the Task Force, which has been reestablished as the
Airworthiness Assurance Working Group (AAWG) of the Aviation Rulemaking
Advisory Committee (ARAC), has completed its work on the first four
elements. This proposed rulemaking addresses the fifth element, the
assessment of repair damage tolerance.
Related Regulatory Activity
In addition to the initiatives previously discussed, there are
other activities associated with FAA's Aging Aircraft Program. These
include FAA's response to the Aging Aircraft Safety Act and future
rulemaking to mandate corrosion prevention and control programs for all
airplanes used in air transportation.
The Aging Aircraft Safety Act of 1991 (Pub. L. 49 U.S.C. 44717)
instructed the Administrator to prescribe regulations that ensure the
continuing airworthiness of aging aircraft through inspections and
reviews of the maintenance records of each aircraft an air carrier uses
in air transportation. In response to the Act, the FAA published notice
93-14 on October 5, 1993 (58 FR 51944). The FAA has reviewed the public
comments to that Notice and anticipates regulatory action in the near
future based on those comments and other considerations.
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
Aloha accident, the NTSB recommended that the FAA mandate a
comprehensive and systematic CPCP. Therefore, the FAA is considering
rulemaking to mandate CPCPS for all airplanes used in air
transportation. As part of that deliberation, the FAA is considering
the corrosion prevention and control programs recommended by the AATF
and adopted by the FAA through Airworthiness Directives (ADs); those
ADs affect all of the airplanes affected by this proposal.
The Aviation Rulemaking Advisory Committee
The ARAC was formally established by the FAA on January 22, 1991
(56 FR 2190), to provide advice and recommendations concerning the full
range of the FAA's safety-related rulemaking activity. This advice was
sought to develop better rules in less overall time using fewer FAA
resources than are currently needed. The committee provides the
opportunity for the FAA to obtain firsthand information and insight
from interested parties regarding proposed new rules or revisions of
existing rules.
There are over 60 member organizations on the committee,
representing a wide range of interests within the aviation community.
Meetings of the committee are open to the public, except as authorized
by section 10(d) of the Federal Advisory Committee Act.
The ARAC establishes working groups to develop proposals to
recommend to the FAA for resolving specific issues. Tasks assigned to
working groups are published in the Federal Register. Although working
group meetings are not generally open to the public, all interested
parties are invited to participate as working group members. Working
groups report directly to the ARAC, and the ARAC must concur with a
working group proposal before that proposal can be presented to the FAA
as an advisory committee recommendation.
The activities of the ARAC will not, however, circumvent the public
rulemaking procedures. After an ARAC recommendation is received and
found acceptable by the FAA, the agency proceeds with the normal public
rulemaking procedures. Any ARAC participation in a rulemaking package
will be fully disclosed in the public docket.
By Federal Register notice dated November 30, 1992 (57 FR 56627),
the AATF was placed under the auspices of the Aviation Rulemaking
Advisory Committee (ARAC) and renamed as the Airworthiness Assurance
Working Group. One of the specific tasks assigned to the AAWG 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 Airbus A300; BAC 1-11;
Boeing 707/720, 727, 737, 747; Douglas DC-8, DC-9/MD-80, DC-10; Fokker
F-28; and Lockheed L-1011 airplanes.
The Concern Posed By Older Repairs
The basic structure of each of the large jet transports that would
be affected by this proposed 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 were
also required to meet these same standards.
These early fatigue or fail-safe requirements 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. In 1978 a new certification
requirement called damage tolerance was introduced to assure the
continued structural integrity of transport category airplanes
certificated after that time. This concept was adopted as an amendment
to Sec. 25.571 by Amendment 25-45 (43 FR 46242), and for existing
designs, guidance material based on this rule 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 trajectories and rates
of 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 progresses. This information is used to establish an inspection
program for the structure that, if rigorously followed, will be able to
detect cracking that may develop before it precipitates a major
structural failure. A damage-tolerant structure is one in which damage
would be detected by reliance on normally performed maintenance and
inspection actions long before it becomes hazardous.
The evidence to date is that when all critical structure is
included, the damage-tolerant concept, and the supplemental inspection
programs that
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are based on it, provide the best assurance of continued structural
integrity that is currently available. In order to apply this concept
to existing transport airplanes, beginning in 1984, the FAA issued a
series of Airworthiness Directives (AD's) requiring compliance with the
first supplemental inspection programs resulting from application of
this concept to existing airplanes. Nearly all of the airplane models
affected by this proposed rule are now covered by such AD's. Generally,
these AD's require that operators incorporate Supplemental Structural
Inspection Documents (SSID's) into their maintenance programs for the
affected airplanes. These documents were derived from damage-tolerance
assessments of the originally certificated type designs for these
airplanes. For this reason, the majority of AD's written for the SID
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 proposed 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
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 they are 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 indicted that existing repairs 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 airplanes age, both the number and age of the existing
repairs increase. Along with this increase in the number of and age of
repairs 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 plus years. Some repairs described in the
airplane manufacturers' Structural Repair Manuals (SRMs) were not
designed to current standards. Repairs accomplished in accordance with
the information contained in the early versions of the SRMs 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 Recommendation
To address the ARAC assignment on repairs, the AAWG tasked the
manufacturers to develop repair assessment guidelines 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 that guidance
material:
Specific repair size limits for which no assessment is
necessary should be selected for each model of airplane.
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 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 further 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:
Development of model specific repair assessment guidelines
using AAWG repair criteria.
Completion of a survey of a number of operators' airplanes
to assess fuselage skin repairs, and to validate the approach of the
manufacturer's repair assessment guidelines.
Determination of the need for and the development of a
world-wide survey.
Collection and assessment of results to determine further
necessary actions.
Development of specific manufacturer/operator/FAA actions.
Early in the development of this task, each manufacturer began to
prepare model specific repair assessment guidelines. 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
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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 airlines operating
their products and to conduct surveys on airplanes in 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 in which 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 (fuselage skins and bulkhead webs);
if necessary, future rulemaking would address the remaining primary
structure. This limitation is 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
conclusion that repairs to the fuselage are far more frequent than to
any other structure.
This proposed rule would only apply to eleven large transport
category airplane models. (In the original ARAC task, the 707 and 720
were counted as one model. This proposed 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 eleven oldest models of
large transport category airplanes then in regular service. This
tasking identified those airplanes for which the greatest concern
exists as to the status of primary structure repairs. Derivatives of
the original airplanes 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 tolerant
structure under Sec. 25.571 of 14 CFR part 25, as amended by Amendment
25-45, are not included. These later requirements make it incumbent on
the operating certificate holder to return the structure to the
original certification basis by installing only those repairs that meet
the airplane's damage-tolerant 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.)
As a result of the AAWG activities, the manufacturers have
recognized the need for, and made a commitment to develop, for each
affected airplane model, a repair assessment guidelines document and a
Structural Repair Manual, updated to include the results of a damage-
tolerance assessment. When referring to these documents and related
actions in this proposed rule, the FAA is referring to actions the
manufacturers have agreed to take.
It was also recognized by the AAWG that repair assessment
guidelines would add to, or in some cases appear to be in conflict
with, existing repair approval data. All repairs assessed under this
proposed rule should have been previously approved by the FAA using an
FAA-approved SRM, an FAA-approved Service Bulletin, or a repair scheme
approved by 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 SRMs, as well as repairs identified in Service Bulletins, to
determine requirements for supplemental inspections, if not already
addressed.
Structural modifications and repairs mandated by Airworthiness
Directives 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
Airworthiness Directives will be contained in the model specific repair
assessment guidelines, with required post modification/repair
inspection programs as required. A list of other structural Service
Bulletins will be provided in the model specific repair assessment
guidelines with associated inspection thresholds and repeat intervals.
The manufacturers have agreed to complete their review of Service
Bulletin related skin repairs in conjunction with the initial SRM
updates.
These agreements notwithstanding, there is still a possibility that
the requirements in the repair assessment guidelines will not agree
with that 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 would require that
compliance be shown with both the AD and this proposed 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.
The AATF originally recommended that the use of repair assessment
guidelines be mandated by Airworthiness Directive. 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 proposed rule
addresses that concern.
The AAWG also recognized that the concerns discussed above for the
safety of existing repairs would also apply to the long-term safety of
future repairs to these airplanes. Therefore, the AAWG considered that
new repairs should also 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 proposal should be used. The intent of this proposed rule is that
all repairs to
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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, or by whom the repair was
installed.
Repair Assessment Guidelines
The next step in the AAWG'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. Considering that each repair design
is different, that each airplane model is different, that each area of
the airplane is subjected to a different loading environment, and that
the number of engineers qualified to perform a damage-tolerance
assessment is small, the size of an assessment task conducted in that
way would be unmanageable. 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 will
necessitate 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 personnel not trained as
damage-tolerance specialists can use the form to document the
configuration of each observed repair.
Using the information from the survey form 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 on the survey form, 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 rewarded or
replaced prior to an established time limit. Supplemental
inspections may be necessary to ensure continued airworthiness prior
to this limit.
This methodology is being generated by the airplane manufacturers.
Model specific repair assessment guidelines will be prepared by the
manufacturers for the eleven aging airplane models. Uniformity and
similarity of these repair assessment procedures between models is
important to simplify operator workload. The manufacturers have spent
considerable time over the last four years to achieve commonality of
the repair assessment process. The inspection intervals contained in
the FAA-approved model specific guidelines documents are based on
residual strength, crack growth, and inspectability evaluations. The
manufacturers are endeavoring to make the inspection methods and
intervals compatible with typical operator maintenance practice. Thus,
internal inspections would be acceptable at ``D-check'' intervals, or
equivalent cycle limit, while simpler external inspections could be
accommodated at multiple ``C-check'' intervals, or equivalent cycle
limit. 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.
The model specific repair assessment guidelines documents are
scheduled to be published no later than July 1, 1997, and will require
approval by the FAA Aircraft Certification Office (ACO) having
cognizance over the type certificate. Once approved, this material can
also be used for evaluating the damage-tolerance characteristics of new
repairs for continued airworthiness.
In order to further facilitate the assessment process, the
manufacturers have agreed to update model specific SRMs to reflect
damage tolerance repair considerations. The goal is to complete these
updates by the first revision cycle of the model specific SRM, after
the release of the associated repair assessment guidelines document.
Consistent with the result of the surveys, only fuselage pressure
boundary repairs are under consideration in this proposal.
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 should also be
provided as applicable.
Structural Repair Manual descriptions of generic repairs will also
contain repair category considerations regarding size, zone, and
proximity. Detailed information for determination of inspection
requirements will be provided in separate repair assessment guidelines
documents for each model. Repairs which were installed in accordance
with a once current SRM, but which have now been superseded by a new
damage-tolerant design, will require review. Such superseded repairs
may be reclassified to Category B or C, requiring additional
inspections and/or rework.
Repair Assessment Process
There are two principle 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 repair
assessment guidelines 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
may develop other techniques, which would be acceptable as long as they
fulfill the objectives of this proposed 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.
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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 Stage 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 repair assessment
guidelines, well designed repairs in good condition meeting size and
proximity requirements are 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 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 will
define 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
repair assessment guidelines 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 would involve 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 would require the operator to choose an inspection
method and interval in accordance with the FAA-approved repair
assessment guidelines. 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 for cost, downtime, or technical
reasons. Such repairs will require supplemental inspections, and each
operator should make provisions for this when incorporating the repair
assessment guidelines 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. The repair survey findings indicated that all repairs
reviewed appeared to be in 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 bound for an assessment to be
completed and then reduced it to establish an ``implementation time,''
defined as 75 percent of DSG in terms of flight cycles.
Therefore, under this approach, incorporation of the repairs
assessment guidelines into an airplane's maintenance or inspection
program ideally should be accomplished before an airplane accumulates
75 percent of 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 repair
assessment guidelines. 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 would be required to incorporate the guidelines in 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 would begin (e.g., accomplishment
of Stage 1) on or before the cycle limit specified in the repair
assessment guidelines (generally equivalent to a ``D'' check) after
incorporation of the guidelines.
2. Airplane Cycle Age greater than the Implementation Time but less
than the DSG on the Rule Effective Date
The operator would be required to incorporate the guidelines in its
maintenance or inspection program within one year of the rule effective
date. The assessment process would begin (e.g., accomplishment of Stage
1) on or before the cycle limit in the repair assessment guidelines
(generally equivalent to a ``D'' check), not to exceed the cycle limit
computed by adding the DSG to the cycle limit equivalent of a ``C''
check (also specified in the repair assessment guidelines) after
incorporation of the guidelines.
3. Airplane Cycle Age greater than the DSG on the Rule Effective Date
The operator would be required to incorporate the guidelines in its
maintenance or inspection program within one year of the rule effective
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date. The assessment process would begin (e.g., accomplishment of Stage
1) on or before the cycle limit specified in the repair assessment
guidelines (equivalent to a ``C'' check) after incorporation of the
guidelines.
In each of these three cases, the assessment process would have to
be completed, the inspections conducted, and any necessary corrective
action taken, all in accordance with the schedule specified in the FAA-
approved repair assessment guidelines.
Discussion of the Proposed Rule
This proposed rule is intended to ensure that a comprehensive
repairs 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 repair assessment guidelines. To
comply with this, the operator would need to consider the following:
1. The means by which the FAA-approved repair assessment guidelines
are incorporated into a certificate holder's FAA-approved maintenance
or inspection program, as would be required by the proposed rule, is
subject to approval by the certificate holder's principal maintenance
inspector (PMI) or other cognizant airworthiness inspector.
2. The repair assessment guidelines must be approved by the FAA
Aircraft Certification Office (ACO) having cognizance over the type
certificate of the airplane.
3. This rule would not impose any new reporting requirements;
however, normal reporting required under 14 CFR 121.703 would still
apply.
4. This rule would 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 would apply to the actions required by this proposed
rule. When incorporating the repair assessment guidelines 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, would be
subject to approval by the cognizant PMI or other cognizant
airworthiness inspector.
5. The scope of the assessment is limited to repairs on the
fuselage pressure boundary (fuselage skins and pressure webs).
a. A list of Service Bulletins that are the subject of AD's will be
contained in the model specific repair assessment guidelines with
required post modification/repair inspection programs, as required.
b. A list of other structural Service Bulletins will be provided in
the model specific repair assessment guidelines with associated
inspection threshold and repeat intervals.
6. The repair assessment guidelines provided by the manufacturer do
not generally apply to structure modified by a Supplemental Type
Certificate (STC). The operator, however, would still be responsible,
under this proposed rule, to provide repair assessment guidelines
applicable to the entire fuselage external pressure boundary that meets
the program objectives specified in Advisory Circular 121-XX. This
means that the operator should develop, submit, and gain FAA approval
of guidelines to evaluate repairs to such structure.
It is recognized that operators do not usually have the resources
to determine a DSG or to develop repair assessment guidelines, 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 would 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 repair assessment
guidelines 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 proposed
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 repair assessment guidelines, 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
repair assessment guidelines 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
repair assessment guidelines, that determination should be documented
and submitted to the operator's PMI or other cognizant airworthiness
inspector for approval. For all other repairs, a separate program would
need to be developed. Third, the modification may have been made so
recently that no repair assessment guidelines would be needed for many
years. Compliance with this proposed 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 that repair
assessment guidelines would be incorporated into the maintenance
program by that time. If the modified structure is very similar to the
original, then the DSG for the modified structure may also be very
similar. No repair assessment guidelines would be needed until 75
percent 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 repair assessment
guidelines for that structure could be many years away.
Compliance with this proposed rule would require that conditions
such as those described above be properly documented in each operator's
FAA-approved maintenance program; however, the cost of doing so should
not be significant. There should be very few examples where the STC
holder is unavailable, and the operators must bear the cost of
developing a complete repair assessment guidelines document. Guidance
on how to comply with this aspect of the proposed rule is also
discussed in the accompanying Advisory Circular 120-XX.
7. An operator's repair assessment program would 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
repair assessment guidelines could be used for this purpose, or
operators may develop other methods as long as they achieve the same
objectives.
8. Once the airworthiness inspector having oversight
responsibilities is
[[Page 133]]
satisfied that the operator's continued airworthiness maintenance or
inspection program contains all of the elements of the FAA-approved
repair assessment guidelines, the airworthiness inspector would approve
an operation specification(s) or inspection program revision. This
would have the effect of requiring use of the approved repair
assessment guidelines.
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.
The proposed rule would prohibit the operation of certain transport
category airplanes operated under 14 CFR parts 91, 121, 125, and 129
beyond a specified compliance time, unless the operator of those
airplanes had incorporated FAA-approved repair assessment guidelines
applicable to the fuselage pressure boundary in its operation
specification(s) or approved inspection program, as applicable.
FAA Advisory Material
In addition to the amendments proposed in this notice, the ARAC has
developed Advisory Circular 120-XX, ``Repair Assessment of Pressurized
Fuselages.'' This AC would provide guidance for operators of the
affected transport category airplanes on how to incorporate FAA-
approved repair assessment guidelines into their FAA-approved
maintenance or inspection program. Public comments concerning the
proposed AC are invited by separate notice published elsewhere in this
issue of the Federal Register.
Regulatory Evaluation
Changes to federal regulations must undergo several economic
analyses. First, Executive Order 12866 directs Federal agencies to
promulgate new regulations or modify existing regulations only if the
potential benefits to society justify its costs. Second, the Regulatory
Flexibility Act of 1980 requires agencies to analyze the economic
impact of regulatory changes on small entities. Finally, the Office of
Management and Budget directs agencies to assess the effects of
regulatory changes on international trade. In conducting these
assessments, the FAA has determined that this proposed rule: (1) Would
generate benefits exceeding its costs and is not ``significant'' as
defined in Executive Order 12866; (2) is not ``significant'' as defined
in DOT's Policies and Procedures; (3) would not have a significant
impact on a substantial number of small entities; and (4) would not
constitute a barrier to international trade. These analyses, available
in the docket, are summarized below.
Regulatory Evaluation Summary
Costs and Benefits
The proposed rule would result in costs to the manufacturers and
operators of the affected airplanes and to the FAA. Costs to
manufacturers would include revising the Structural Repair Manuals,
developing repair assessment guidelines, and developing and conducting
training programs for Original Equipment Manufacturers' Engineers,
airplane operators' inspectors, and the FAA's PMIs or other cognizant
airworthiness inspector. Costs to operators would include inspector
training, integrating the assessment program into the maintenance
program for each airplane model, assessing and subsequently inspecting
repairs, and maintaining records. Cost to the FAA would include PMI/
other cognizant airworthiness inspector training and review/approval of
assessment programs.
The FAA estimates that the total cost to all affected manufacturers
would be $43.3 million over the years 1995 through 2020, or $26.9
million discounted to present value. The equivalent annualized cost
would be $2.3 million. Although this proposed rule would not directly
impose any costs on manufacturers, the FAA recognizes that
manufacturers have incurred, and will continue to incur, costs in order
to develop and provide data to operators that will enable them to
comply with the proposal. The FAA has chosen to attribute these costs
to the proposed rule, beginning in 1995. The total cost to airplane
operators would be $25.5 million over the years 1997 through 2020, or
$10.2 million discounted to present value. The equivalent annualized
cost would be $893,622. The total costs to the FAA would be $516,000,
or $324,358 discounted to present value. The equivalent annualized cost
would be $28,280. The total cost of the proposed rule to all affected
entities would be $69.3 million, or $37.5 million discounted to present
value. The equivalent annualized cost would be $3.2 million.
The cause of an airplane accident has never been attributed to a
properly applied repair to the airplane models that would be affected
by the proposed rule. Nevertheless, airplanes designed and certificated
to older technology are operated beyond their original design service
objectives, and the FAA has determined that the repair assessment
program to ensure the continued airworthiness of these aging airplanes
could prevent structural failure and resulting accidents. The benefits
of the proposed rule, therefore, are based on the avoidance of such
accidents.
The FAA estimates that the prevention of an accident resulting in
the loss of an average affected airplane and half its passengers and
crew would result in present value benefits of $46.8 million, assuming
that the accident would otherwise have occurred midway through the
analysis period. The FAA cannot predict the number of accidents that
would be prevented by this proposed rule. Based on one such prevented
loss, however, the FAA has determined that the proposed rule would be
cost-beneficial.
Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980 (RFA) was enacted by
Congress to ensure that small entities are not unnecessarily and
disproportionately burdened by government regulations. The RFA requires
a Regulatory Flexibility Analysis if the proposed or final rule would
have significant economic impact, either detrimental or beneficial, on
a substantial number of small entities. FAA Order 2100.14A, Regulatory
Flexibility Criteria and Guidance, prescribes standards for complying
with RFA review requirements in FAA rulemaking actions. The Order
defines ``small entities'' in terms of thresholds, ``significant
economic impact'' in terms of annualized cost thresholds, and
``substantial number'' as a number which is not less than eleven and
which is more than one-third of the small entities subject to the
proposed or final rule.
The proposed rule would affect Boeing Commercial Airplane Group,
Douglas Aircraft Company, Lockheed Aeronautical Systems Company,
Airbus, British Aerospace, and Fokker Aircraft B.V. Order 2100.14A
specifies a size threshold for classification as a small manufacturer
as 75 or fewer employees. Since none of these manufacturers has 75 or
fewer employees, the proposed rule would not have a significant
economic impact on a substantial number of small manufacturers.
The proposed rule would also affect operators of certain U.S.-
registered B707/720, B727, B737, B747, DC-8, DC-9/MD80, DC-10, L-1011,
A300, BAC 1-11 and F28 airplanes. Order 2100.14A
[[Page 134]]
specifies a size threshold for classification as a small operator as
ownership of 9 or fewer aircraft. The annualized cost thresholds for
significant impact, expressed in 1995 dollars, are $119,900 for a
scheduled air carrier whose fleet of airplanes have seating capacities
of over 60, $67,000 for other scheduled air carriers, and $4,700 for an
unscheduled operator. The FAA examined the annualized costs of the
proposed rule to ``small'' operators of the current fleet of affected
airplanes and determined that no small operator's annualized cost would
exceed the threshold of $4,700. Therefore, the proposed rule would not
have a significant impact on a substantial number of small operators.
International Trade Impact Assessment
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.
Federalism Implications
The regulations proposed herein will not have substantial direct
effects on the States, or on the relationship between the national
government and the States, or on the distribution of power and
responsibility among the various levels of the government. Therefore,
in accordance with Executive Order 12612, it is determined that this
proposed rule would not have significant federalism implications to
warrant the preparation of a Federalism Assessment.
International Civil Aviation Organization (ICAO) and Joint Aviation
Regulations
In keeping with U.S. obligations under the Convention on
International Civil Aviation, it is FAA policy to comply with ICAO
Standards and Recommended Practices to the maximum extent practicable.
The FAA has determined that this proposed rule would not conflict with
any international agreement of the United States.
Paperwork Reduction Act
There are no new requirements for information collection associated
with this proposed rule that would require approval from the Office of
Management and Budget pursuant to the Paperwork Reduction Act of 1995
(44 U.S.C. 3507(d)).
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
distributions as he or she considers appropriate. Because this proposed
rule would apply to the operation of certain transport category
airplanes under parts 91, 121, 125, and 129 of Title 14, if could, if
adopted, affect intrastate aviation in Alaska. The FAA therefore
specifically requests comments on whether there is justification for
applying the proposed rule differently to intrastate operations in
Alaska.
Conclusion
Because the proposed repair assessment programs are not expected to
result in substantial economic cost, the FAA has determined that this
proposed regulations is not a significant regulatory action under
Executive Order 12866. The FAA has also determined that this proposal
is not significant under DOT Regulatory Policies and Procedures (44 FR
11034, February 25, 1979). In addition, the FAA certifies that this
proposal, if adopted, will not have a significant economic impact,
positive or negative, on a substantial number of small entities under
the criteria of the Regulatory Flexibility Act, since none are
affected. An initial evaluation of this proposal, including a
Regulatory Flexibility Determination and an International Trade Impact
Analysis, has been placed in the docket. A copy may be obtained by
contacting the person identified under the caption FOR FURTHER
INFORMATION CONTACT.
List of Subjects
14 CFR Part 91
Aircraft, Aviation safety, Maintenance, Rebuilding, Pressurized
fuselage repair and alteration.
14 CFR Parts 121, 125, and 129
Air carriers, Aircraft, Aviation safety, Pressurized fuselage
repair assessment, Safety, Transportation.
The Proposed Amendment
In consideration of the foregoing, the Federal Aviation
Administration proposes to amend 14 CFR parts 91, 121, 125, and 129 of
the Federal Aviation 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. A new Sec. 91.410 is added to read as follows:
Sec. 91.410 Repair assessment for pressurized fuselages.
No certificate holder may operate an Airbus Model A300, 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 the applicable flight cycle
implementation time specified in the following paragraphs, or [a date
one year after the effective date of the amendment], whichever occurs
later, unless repair assessment guidelines applicable to the fuselage
pressure boundary (fuselage skin and bulkhead webs) that have been
approved by the FAA Aircraft Certification Office (ACO) having
cognizance over the type certificate for the affected airplane are
incorporated within its inspection program:
(a) For the A300, the flight cycle implementation time is:
(1) Model B2, 36,000 flights.
(2) Model B4-100, 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 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 Douglas DC-8, the flight cycle
implementation time is 30,000 flights.
(i) For all models of the Douglas DC-9/MD-80, the flight cycle
implementation time is 60,000 flights.
(j) For all models of the 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.
[[Page 135]]
(l) For the Fokker F-28 Mark 1000, 1000C, 2000, 3000, 3000C, and
4000, the flight cycle implementation time is 60,000 flights.
PART 121--OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL
OPERATIONS
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. A new Sec. 121.370 is added to read as follows:
Sec. 121.370 Repair assessment for pressurized fuselages.
No certificate holder may operate an Airbus Model A300, British
Aerospace Model BAC 1-11, Boeing Model 707, 720, 727, 737 or 747,
McDonald 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 in the following paragraphs, or [a date
one year after the effective date of the amendment], whichever occurs
later, unless its operation specifications have been revised to
reference repair assessment guidelines applicable to the fuselage
pressure boundary (fuselage 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) having cognizance over the type certificate
for the affected airplane.
(a) For the A300, the flight cycle impelementation time is:
(1) Model B2, 36,000 flights.
(2) Model B4-100, 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 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 Douglas DC-8, the flight cycle
implementation time is 30,000 flights.
(i) For all models of the Douglas DC-9/MD-80, the flight cycle
implementation time is 60,000 flights.
(j) For all models of the 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, 1000C, 2000, 3000, 3000C, 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. A new Sec. 125.248 is added to read as follows:
Sec. 125.248 Repair assessment for pressurized fuselages.
No certificate holder may operate an Airbus Model A300, 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 in the following paragraphs or [a date one year after
the effective date of the amendment], whichever occurs later, unless
its operation specifications have been revised to reference repair
assessment guidelines applicable to the fuselage pressure boundary
(fuselage 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) having cognizance over the type certificate for the affected
airplane.
(a) For the A300, the flight cycle implementation time is:
(1) Model B2, 36,000 flights.
(2) Model B4-100, 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 BAC 1-11, the flight cycle implementation
time is 60,000 times.
(c) For all models of the Boeing 707, the flight cycle
implementation time is 15,000 times.
(d) For all models of the Boeing 720, the flight cycle
implementation time is 23,000 times.
(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 Douglas DC-8, the flight cycle
implementation time is 30,000 flights.
(i) For all models of the Douglas DC-9/MD-80, the flight cycle
implementation time is 60,000 flights.
(j) For all models of the Douglas DC-10, the flight cycle
implementation time is 30,000 flights.
(j) 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, 1000C, 2000, 3000, 3000C, 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. A new Sec. 129.32 is added to read as follows:
Sec. 129.32 Repair assessment for pressurized fuselages.
No certificate holder may operate an Airbus Model A300, 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 in the following paragraphs, or [a date one year after
the effective date of the amendment], whichever occurs later, unless
its operation specifications have been revised to reference repair
assessment guidelines applicable to the fuselage pressure boundary
(fuselage 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) having cognizance over the type certificate for the affected
airplane.
[[Page 136]]
(a) For the A300, the flight cycle implementation time is:
(1) Model B2, 36,000 flights.
(2) Model B4-100, 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 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 Douglas DC-8, the flight cycle
implementation time is 30,000 flights.
(i) For all models of the Douglas DC-9/MD-80, the flight cycle
implementation time is 60,000 flights.
(j) For all models of the 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, 1000C, 2000, 3000, 3000C, and
4000, the flight cycle implementation time is 60,000 flights.
Issued in Washington, D.C. on December 22, 1997.
Thomas E. McSweeney,
Director, Aircraft Certification Service.
[FR Doc. 97-34166 Filed 12-31-97; 8:45 am]
BILLING CODE 4910-13-M
