[Federal Register Volume 68, Number 127 (Wednesday, July 2, 2003)]
[Proposed Rules]
[Pages 39485-39490]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-16693]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-11-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -200C, -
300, -400, and -500 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), applicable to certain Boeing Model 737 series 
airplanes, that would have required inspections of certain bonded skin 
panels to detect delamination of the skin doublers (tear straps) from 
the skin panels, and follow-on corrective actions if necessary. This 
new action revises the proposed rule by revising certain inspection 
methods and expanding the area of certain inspections. This new action 
also proposes to extend the compliance time for certain inspections. 
The actions specified by this new proposed AD are intended to prevent 
skin doublers from

[[Page 39486]]

delaminating from their skin panels, which could result in fatigue 
cracks in the skin doublers and skin panels and consequent rapid 
decompression of the airplane.

DATES: Comments must be received by July 28, 2003.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-11-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9 a.m. and 3 p.m., Monday through Friday, except Federal 
holidays. Comments may be submitted via fax to (425) 227-1232. Comments 
may also be sent via the Internet using the following address: [email protected]. Comments sent via fax or the Internet must contain 
``Docket No. 98-NM-11-AD'' in the subject line and need not be 
submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Duong Tran, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 917-6452; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this action may be changed in 
light of the comments received.
    Submit comments using the following format:
    [sbull] Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
    [sbull] For each issue, state what specific change to the proposed 
AD is being requested.
    [sbull] Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-11-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 98-NM-11-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to 
certain Boeing Model 737 series airplanes, was published as a 
supplemental notice of proposed rulemaking (NPRM) in the Federal 
Register on August 10, 2000 (65 FR 48937). That original supplemental 
NPRM (hereafter referred to as ``the first supplemental NPRM'') would 
have required inspections of certain bonded skin panels to detect 
delamination of the skin doublers (tear straps) from the skin panels, 
and follow-on corrective actions if necessary. The first supplemental 
NPRM was prompted by reports that certain skin doublers were 
delaminated from their skin panels due to improper processing of 
certain skin panels. That condition, if not corrected, could result in 
fatigue cracks in the skin doublers and skin panels and consequent 
rapid decompression of the airplane.

Explanation of New Service Information

    Since the issuance of the first supplemental NPRM, Boeing has 
issued Service Bulletin 737-53-1179, Revision 2, dated October 25, 
2001. (The first supplemental NPRM refers to Revision 1 of that service 
bulletin, dated September 30, 1999, as the appropriate source of 
service information for the actions proposed in that first supplemental 
NPRM.) Revision 2 of the service bulletin does the following:
    [sbull] Revises the inspection method from close visual to detailed 
visual for the one-time internal inspection for cracks or corrosion of 
bonded skin panels.
    [sbull] Extends the compliance time for the one-time internal 
inspection to 50,000 total flight cycles (or 50,000 flight cycles after 
skin panel replacement, as applicable), or 20,000 flight cycles after 
service bulletin release, whichever is later.
    [sbull] Expands the area of the external inspection from under 
stringer 17 to under all stringers.
    [sbull] Expands the inspection area following a finding of 
delamination to include all fasteners common to the delamination area 
plus two fasteners on each side of the delamination area.
    [sbull] Expands the effectivity to include certain airplanes not 
listed in the effectivity listing of Revision 1 of the service 
bulletin.
    Accomplishment of the actions specified in Revision 2 of the 
service bulletin is intended to adequately address the unsafe 
condition.

Explanation of Changes to Proposal

    We have revised the preamble and body of this second supplemental 
NPRM to identify affected airplane models more specifically.
    We have changed all references to ``detailed visual inspection'' in 
the first supplemental NPRM to ``detailed inspection'' in this second 
supplemental NPRM. Also, for clarification, we have revised the 
definition of a ``general visual inspection'' in this second 
supplemental NPRM.
    In addition, because the language in Note 6 of the first 
supplemental NPRM is regulatory in nature, that note has been 
redesignated as paragraph (g) of this second supplemental NPRM.

Comments

    Due consideration has been given to the comments received in 
response to the first supplemental NPRM. While one commenter supports 
the proposal, certain comments have resulted in changes to the proposal 
that are reflected in this second supplemental NPRM. Certain other 
comments received in response to the original NPRM and first 
supplemental NPRM are no longer relevant to this proposal because of 
the changes in the proposal related to Revision 2 of the service

[[Page 39487]]

bulletin. Certain other comments that are still relevant but that have 
not resulted in any change to the proposal will be addressed in the 
final rule, along with any additional comments received in response to 
this second supplemental NPRM.

Revise References to Inspection Methods and Procedures

    One commenter, the airplane manufacturer, requests that the FAA 
revise certain references to inspection methods and procedures in 
various places in the first supplemental NPRM:
    [sbull] In paragraphs (a)(2)(i) and (b)(2)(i) of the first 
supplemental NPRM, change the method for the inspection for cracks or 
corrosion of bonded ``Zone A'' skin panels from internal general visual 
to internal detailed visual. The procedures in the service bulletin 
describe a detailed visual inspection rather than a general visual 
inspection.
    [sbull] In paragraphs (a)(2)(i), (a)(2)(ii), (b)(2)(i), and 
(b)(2)(ii) of the first supplemental NPRM, clarify the inspection 
requirements for ``Zone A'' and ``Zone B'' skin panels by referring to 
the figures in the service bulletin that define those inspections.
    [sbull] In Note 6 of the first supplemental NPRM, clarify that the 
internal inspections described in that paragraph apply only to ``Zone 
A'' areas, and that accomplishment of those internal inspections is 
acceptable specifically for compliance with paragraph (a)(2)(i) of the 
proposed AD.
    [sbull] For clarification, if the changes above are implemented, 
delete Note 7 of the first supplemental NPRM.
    We concur with the commenter's requests and, accordingly, have made 
the following changes to this second supplemental NPRM:
    [sbull] We have revised paragraphs (a)(2)(i) and (b)(2)(i) of this 
second supplemental NPRM to specify a one-time internal detailed 
inspection to detect cracks or corrosion of ``Zone A'' skin panels.
    [sbull] We have revised paragraphs (a)(2)(i), (a)(2)(ii), 
(b)(2)(i), and (b)(2)(ii) of this second supplemental NPRM to refer to 
the Accomplishment Instructions of Revision 2 of the service bulletin. 
(We find that referring to the Accomplishment Instructions of the 
service bulletin meets the commenter's intent with regard to referring 
to the specific figures.)
    [sbull] We have revised paragraph (g) of this second supplemental 
NPRM (which contains the provisions of Note 6 of the first supplemental 
NPRM) to state that internal detailed inspections of ``Zone A'' skin 
panels that are accomplished before the effective date of the AD per 
previous revisions of the service bulletin are acceptable for 
compliance with paragraph (a)(2)(i) of this AD.
    [sbull] We have not included the contents of Note 7 of the first 
supplemental NPRM in this second supplemental NPRM.

Give Credit for Inspections Accomplished per Existing Programs

    One commenter to the first supplemental NPRM, as well as one 
commenter to the original NPRM, requests that we allow credit for 
visual inspections of areas subject to this proposal if they were 
previously accomplished per an FAA-approved Corrosion Prevention and 
Control Program (CPCP).
    We concur with the commenters' requests. We have previously issued 
AD 90-25-01, amendment 39-6789 (55 FR 49263, November 27, 1990), to 
require the implementation of a CPCP on all Boeing Model 737 series 
airplanes. Inspections accomplished per that CPCP are an acceptable 
method of compliance for certain inspections that would be required by 
this proposed AD, provided that these inspections are accomplished 
within the compliance times specified in this proposed AD. Operators 
must note that this credit applies only for general visual inspections 
of ``Zone A'' skin panels. Accordingly, we have added a new paragraph 
(h) to this second supplemental NPRM to provide this credit.

Allow Repair per Structural Repair Manual

    Two commenters request that any subject area that has been repaired 
previously per the Boeing 737 Structural Repair Manual (SRM) be 
exempted from the inspection requirements of this proposal. One of the 
commenters notes that repair by installation of solid fasteners is 
defined in Chapter 51-00-01, Figure 225, of the SRM, which the 
commenter states is referenced in the proposal. The other commenter 
asks whether we intend to require an alternative method of compliance 
(AMOC) for each fuselage flush or external repair in the inspection 
area. That commenter specifically requests that all repairs per the SRM 
be approved as an AMOC to the proposed AD, and that we allow Boeing 
Designated Engineering Representatives to approve repairs.
    We partially concur with the commenters' requests. We do not find 
it appropriate to give ``blanket'' approval of any repair per the SRM, 
and we note that neither the first supplemental NPRM nor the service 
bulletin refers to the specific section and figure of the SRM referred 
to by the commenter. However, we find that repairs accomplished 
according to specific sections of the SRM referred to in Boeing Service 
Bulletin 737-53-1179, Revision 2, eliminate the need for the proposed 
inspections for the area of the repair only. All other repairs must be 
approved by the FAA or per data meeting the type certification basis of 
the airplane approved by a Boeing Company Designated Engineering 
Representative who has been authorized by the FAA to make such 
findings. Therefore, we have added a new paragraph (f) to this second 
supplemental NPRM (and reordered subsequent paragraphs accordingly) to 
specify that, where the service bulletin refers to specific sections of 
the SRM for repair instructions, repairs per those SRM sections 
eliminate the requirement to do the inspections required by this 
proposed AD for the repaired area only.

Define Method for Determining Configuration

    One commenter requests clarification on what method to use to 
determine the configuration of skin panels as ``Zone A'' or ``Zone B,'' 
as specified in Figure 2, Sheet 4 of 4, in the service bulletin.
    We concur that some clarification may be necessary. As stated 
previously, we have revised paragraphs (a)(2)(i), (a)(2)(ii), 
(b)(2)(i), and (b)(2)(ii) of this second supplemental NPRM to refer to 
the Accomplishment Instructions and Figure 2 of the service bulletin as 
the appropriate reference for determining whether a skin panel is 
``Zone A'' or ``Zone B.'' The criteria for determining the category of 
a skin panel are shown under paragraph 3.A. in the Accomplishment 
Instructions of the service bulletin. We find that these criteria are 
adequate for determining the applicable inspection method for each skin 
panel. No further change to this second supplemental NPRM is necessary 
in this regard.

Give Credit for Actions Accomplished Previously

    One commenter requests clarification that an operator is in 
compliance with the proposed AD if the terminating inspection has been 
done prior to the effective date of the AD.
    We find that no change is necessary to meet the intent of the 
commenter's request. We give credit for actions accomplished before the 
effective date of an AD by means of the phrase ``Compliance: Required 
as indicated, unless accomplished previously,'' which appears in every 
AD.

[[Page 39488]]

Explanation of New Requirements of Proposal

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, this 
second supplemental NPRM would require accomplishment of the actions 
specified in Boeing Service Bulletin 737-53-1179, Revision 2, described 
previously, except as discussed below.

Explanation of Applicability

    The applicability statement of this second supplemental NPRM 
includes Model 737-100, -200, -200C, -300, -400, and -500 series 
airplanes; having line numbers 1 through 2947 inclusive. As explained 
in the first supplemental NPRM, in determining the applicability of 
this proposed AD, we considered the possibility that any airplane 
delivered prior to October 1, 1997, might be equipped with an 
improperly processed skin panel. We have determined that line number 
2947 corresponds to a delivery date of October 1, 1997.

Differences Between Second Supplemental NPRM and Service Bulletin

    Operators also should note that, although the service bulletin 
specifies that the manufacturer may be contacted for disposition of 
certain repair conditions, this second supplemental NPRM would require 
the repair of those conditions to be accomplished in accordance with a 
method approved by the FAA; or in accordance with data meeting the type 
certification basis of the airplane approved by a Boeing Company 
Designated Engineering Representative who has been authorized by the 
Manager, Seattle Aircraft Certification Office, to make such findings.
    Additionally, the service bulletin specifies that certain 
inspections may be accomplished in accordance with ``an equivalent'' 
procedure. However, this second supplemental NPRM would require that 
those inspections be accomplished in accordance with the procedures 
specified in the chapter of the 737 Nondestructive Test Manual 
specified in the service bulletin. An ``equivalent'' procedure may be 
used only if approved as an alternative method of compliance in 
accordance with the provisions of paragraph (i) of this second 
supplemental NPRM.

Conclusion

    Since certain changes expand the scope of the originally proposed 
rule, the FAA has determined that it is necessary to reopen the comment 
period to provide additional opportunity for public comment.

Cost Impact

    There are approximately 2,083 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 863 airplanes of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 10 work hours per airplane to 
accomplish the proposed external general visual and detailed 
inspections, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of these external inspections proposed 
by this AD on U.S. operators is estimated to be $517,800, or $600 per 
airplane, per inspection cycle.
    It would take approximately 360 work hours per airplane to 
accomplish the proposed internal detailed and ultrasonic inspections, 
at an average labor rate of $60 per work hour. Based on these figures, 
the cost impact of this inspection proposed by this AD on U.S. 
operators is estimated to be $18,640,800, or $21,600 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the proposed requirements 
of this AD action, and that no operator would accomplish those actions 
in the future if this proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

Regulatory Impact

    The regulations proposed herein would not have a substantial direct 
effect on the States, on the relationship between the national 
Government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    For the reasons discussed above, I certify that this proposed 
regulation: (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

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


Sec.  39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Boeing: Docket 98-NM-11-AD.

    Applicability: Model 737-100, 737-200, -200C, -300, -400, and -
500 series airplanes; line numbers (L/N) 1 through 2947 inclusive; 
certified in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (i) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent skin doublers (tear straps) from delaminating from 
their skin panels, which could result in fatigue cracks in the skin 
doublers and skin panels and consequent rapid decompression of the 
airplane, accomplish the following:

Initial and Repetitive Inspections (L/N 611 through 2725 inclusive)

    (a) For airplanes having L/N 611 through 2725 inclusive: 
Accomplish the actions required by paragraphs (a)(1) and (a)(2) of 
this AD on any bonded skin panel assembly that has NOT been replaced 
with any new or serviceable bonded skin panel assembly, in 
accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 737-53-1179, Revision 2, dated October 25, 2001.

    Note 2: For the purposes of this AD, bonded skin panels consist 
of skin doublers

[[Page 39489]]

(tear straps) that are bonded to skin panels located above stringer 
S-26 from body station (BS) 259 to BS 1016 on both sides of the 
airplane.


    Note 3: If the skin panel is solid with no doublers (tear 
straps) bonded to it, the inspections required by this AD are not 
necessary for that skin panel.

    (1) Prior to the accumulation of 20,000 total flight cycles, or 
within 5,000 flight cycles after the effective date of this AD, 
whichever occurs later, accomplish paragraphs (a)(1)(i) and 
(a)(1)(ii) of this AD, in accordance with the Accomplishment 
Instructions of the service bulletin. Repeat the inspections 
thereafter at intervals not to exceed 5,000 flight cycles, until 
accomplishment of paragraph (a)(2) of this AD.
    (i) Perform an external general visual inspection of all 
affected areas NOT specified in paragraph (a)(1)(ii) of this AD to 
detect cracks or corrosion of bonded skin panels.
    (ii) Perform an external detailed inspection to detect cracks or 
corrosion of bonded skin panels at all stringers, window belts, lap 
joints, and butt splice joints.

    Note 4: For the purposes of this AD, a general visual inspection 
is defined as: ``A visual examination of an interior or exterior 
area, installation, or assembly to detect obvious damage, failure, 
or irregularity. This level of inspection is made from within 
touching distance unless otherwise specified. A mirror may be 
necessary to enhance visual access to all exposed surfaces in the 
inspection area. This level of inspection is made under normally 
available lighting conditions such as daylight, hangar lighting, 
flashlight, or droplight and may require removal or opening of 
access panels or doors. Stands, ladders, or platforms may be 
required to gain proximity to the area being checked.''


    Note 5: For the purposes of this AD, a detailed inspection is 
defined as: ``An intensive visual examination of a specific 
structural area, system, installation, or assembly to detect damage, 
failure, or irregularity. Available lighting is normally 
supplemented with a direct source of good lighting at intensity 
deemed appropriate by the inspector. Inspection aids such as mirror, 
magnifying lenses, etc., may be used. Surface cleaning and elaborate 
access procedures may be required.''

    (2) Prior to the accumulation of 50,000 total flight cycles, but 
after the accumulation of 4,500 total flight cycles; or within 
20,000 flight cycles after the effective date of this AD; whichever 
occurs later; accomplish paragraphs (a)(2)(i) and (a)(2)(ii) of this 
AD. Accomplishment of the requirements of paragraphs (a)(2)(i) and 
(a)(2)(ii) of this AD constitutes terminating action for the 
repetitive inspection requirement of paragraph (a)(1) of this AD.
    (i) For ``Zone A'' areas (as defined in the Accomplishment 
Instructions and Figure 2 of the service bulletin): Perform a one-
time internal detailed inspection to detect cracks or corrosion of 
bonded skin panels, or delamination of the skin doublers from the 
bonded skin panels.
    (ii) For ``Zone B'' areas (as defined in the Accomplishment 
Instructions and Figure 2 of the service bulletin): Perform an 
internal or external ultrasonic inspection to detect cracks or 
corrosion of bonded skin panels, or delamination of the skin 
doublers from the bonded skin panels.

Initial and Repetitive Inspections (L/N 1 through 2947 inclusive)

    (b) For airplanes having L/N 1 through 2947 inclusive, on which 
any bonded skin panel was replaced with a new or serviceable, 
Boeing-built, bonded skin panel prior to October 1, 1997: Accomplish 
the actions required by paragraphs (b)(1) and (b)(2) of this AD, in 
accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 737-53-1179, Revision 2, dated October 25, 2001.
    (1) Within 20,000 flight cycles after replacement of the bonded 
skin panel, or within 5,000 flight cycles after the effective date 
of this AD, whichever occurs later, accomplish paragraphs (b)(1)(i) 
and (b)(1)(ii) of this AD. Repeat the inspections thereafter at 
intervals not to exceed 5,000 flight cycles, until accomplishment of 
paragraph (b)(2) of this AD.
    (i) Perform an external general visual inspection of all 
affected areas NOT specified in paragraph (b)(1)(ii) to detect 
cracks or corrosion of bonded skin panels.
    (ii) Perform a detailed inspection to detect cracks or corrosion 
of bonded skin panels at all stringers, window belts, lap joints, 
and butt splice joints.
    (2) Within 50,000 flight cycles after replacement of the bonded 
skin panel, but after the accumulation of 4,500 flight cycles after 
such replacement; or within 20,000 flight cycles after the effective 
date of this AD; whichever occurs later; accomplish paragraphs 
(b)(2)(i) and (b)(2)(ii) of this AD. Accomplishment of the 
requirements of paragraphs (b)(2)(i) and (b)(2)(ii) of this AD 
constitutes terminating action for the repetitive inspection 
requirement of paragraph (b)(1) of this AD.
    (i) For ``Zone A'' areas (as defined in the Accomplishment 
Instructions and Figure 2 of the service bulletin): Perform a one-
time internal detailed inspection to detect cracks or corrosion of 
bonded skin panels or delamination of the skin doublers from the 
bonded skin panels.
    (ii) For ``Zone B'' areas (as defined in the Accomplishment 
Instructions and Figure 2 of the service bulletin): Perform an 
internal or external ultrasonic inspection to detect cracks or 
corrosion of bonded skin panels, or delamination of the skin 
doublers from the bonded skin panels.

Corrective Actions

    (c) If any crack, corrosion, or delamination is detected during 
any inspection required by paragraph (a) or (b) of this AD, prior to 
further flight, accomplish the actions required by either paragraph 
(c)(1) or (c)(2) of this AD.
    (1) Replace the cracked, corroded, or delaminated skin panel 
with a new or serviceable skin panel manufactured by Boeing on or 
after April 1, 1997, in accordance with Figure 2 and the 
Accomplishment Instructions of Boeing Service Bulletin 737-53-1179, 
Revision 2, dated October 25, 2001.
    (2) Accomplish corrective actions (including additional 
inspections and repairs) in accordance with Figure 2 and the 
``Delamination and Crack Repair'' section of the Accomplishment 
Instructions of Boeing Service Bulletin 737-53-1179, Revision 2, 
dated October 25, 2001, except as provided by paragraph (d) of this 
AD.

Exception to Repair Procedures

    (d) Where Boeing Service Bulletin 737-53-1179, Revision 2, dated 
October 25, 2001, specifies that repair of a cracked, corroded, or 
delaminated skin panel is to be accomplished in accordance with 
instructions received from Boeing, this AD requires that the repair 
be accomplished in accordance with a method approved by the Manager, 
Seattle Aircraft Certification Office (ACO), FAA; or in accordance 
with data meeting the type certification basis of the airplane 
approved by a Boeing Company Designated Engineering Representative 
who has been authorized by the Manager, Seattle ACO, to make such 
findings. For a repair method to be approved by the Manager, Seattle 
ACO, as required by this paragraph, the approval letter must 
specifically reference this AD.

Operator's Equivalent Procedures

    (e) Where Boeing Service Bulletin 737-53-1179, Revision 2, dated 
October 25, 2001, specifies that the inspections required by this AD 
may be accomplished in accordance with an ``equivalent'' procedure, 
the inspections must be accomplished in accordance with the chapter 
of the Boeing 737 Nondestructive Test Manual specified in the 
service bulletin.

Credit for Actions Accomplished Previously

    (f) Where the service bulletin refers to specific sections of 
the Boeing 737 Structural Repair Manual (SRM) for repair 
instructions, repairs accomplished before the effective date of this 
AD per those SRM sections eliminate the requirement to do the 
inspections required by this proposed AD for the repaired area only.
    (g) Internal detailed inspections of ``Zone A'' skin panels 
accomplished before the effective date of this AD in accordance with 
the original issue of Boeing Service Bulletin 737-53-1179, dated 
June 22, 1995, or Revision 1, dated September 30, 1999, are 
acceptable for compliance with paragraph (a)(2)(i) of this AD, 
provided that they were accomplished after the accumulation of 4,500 
total flight cycles.
    (h) Inspections accomplished per the Corrosion Prevention and 
Control Program established by AD 90-25-01, amendment 39-6789, are 
acceptable for compliance with the external general visual 
inspections of ``Zone A'' skin panels required by paragraphs 
(a)(1)(i) and (b)(1)(i) of this AD, provided that the inspections 
are accomplished within the applicable compliance times specified in 
paragraphs (a) and (b) of this AD.

Alternative Methods of Compliance

    (i) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle ACO. Operators shall submit 
their requests through an appropriate FAA Principal

[[Page 39490]]

Maintenance Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.

    Note 6: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (j) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on June 26, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-16693 Filed 7-1-03; 8:45 am]
BILLING CODE 4910-13-P