126 Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules

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.

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 FAAapproved 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: 9–NPRM–

CMTS@faa.dot.gov. 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/suldocs 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
Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules 127

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 failsafe 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 § 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
128 Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules

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 damagetolerance 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-inservice 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 fivestep program to develop factual data for

the development of the rule. The fivestep 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
Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules 129

prior to 1978, it provided objective

information on the quality and damagetolerance 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

§ 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 FAAapproved 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
130 Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules

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 damagetolerance 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 damagetolerance 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 ‘‘Dcheck’’ 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 damagetolerant 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.
Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules 131

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 ‘‘Ccheck’’ 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 FAAapproved 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 FAAapproved 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 FAAapproved 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
132 Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules

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 FAAapproved 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 FAAapproved 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 damagetolerance 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
Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules 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 FAAapproved 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 FAAapproved 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
134 Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules

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 § 91.410 is added to read as

follows:

§ 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.
Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules 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 § 121.370 is added to read

as follows:

§ 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 § 125.248 is added to read

as follows:

§ 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 § 129.32 is added to read as

follows:

§ 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.
136 Federal Register / Vol. 63, No. 1 / Friday, January 2, 1998 / Proposed Rules

(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