[Federal Register Volume 69, Number 173 (Wednesday, September 8, 2004)]
[Rules and Regulations]
[Pages 54206-54211]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-20120]



[[Page 54206]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NM-246-AD; Amendment 39-13784; AD 2004-18-06]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 737-200, -200C, -300, -400, and -500 
series airplanes, that requires repetitive inspections to find fatigue 
cracking of certain upper and lower skin panels of the fuselage, and 
follow-on and corrective actions, if necessary. This amendment also 
includes terminating action for the repetitive inspections of certain 
modified or repaired areas only. This action is necessary to find and 
fix fatigue cracking of the skin panels, which could result in sudden 
fracture and failure of the skin panels of the fuselage, and consequent 
rapid decompression of the airplane. This action is intended to address 
the identified unsafe condition.

DATES: Effective October 13, 2004.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of October 13, 2004.

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the National 
Archives and Records Administration (NARA). For information on the 
availability of this material at NARA, call (202) 741-6030, or go to: 
http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

FOR FURTHER INFORMATION CONTACT: Suzanne Lucier, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
917-6438; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 737-200, -
200C, -300, -400, and -500 series airplanes was published in the 
Federal Register on June 18, 2003 (68 FR 36515). That action proposed 
to require repetitive inspections to find fatigue cracking of certain 
upper and lower skin panels of the fuselage, and follow-on and 
corrective actions, if necessary. That action also includes terminating 
action for the repetitive inspections of certain modified or repaired 
areas only.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Agreement With Proposed Rule

    One commenter generally agrees with the proposed rule.

Request To Clarify Repetitive Eddy Current Inspections

    Several commenters request clarification of the repetitive eddy 
current inspections required by paragraph (a) of the proposed rule. The 
commenters note that the proposed rule differs from the service 
bulletin in that the proposed rule requires both external detailed and 
eddy current inspections every 4,500 flight cycles, while the service 
bulletin only specifies to repeat the detailed inspections. One 
commenter asks if the repetitive eddy current inspections are 
mandatory. Another commenter points out that no explanation is given in 
the preamble of the proposed rule in the ``Differences'' paragraph. 
Because no technical reason is given for this change, the commenter 
believes the proposed rule's intent was not to include repetitive eddy 
current inspections that are beyond the scope of the service bulletin.
    Another commenter, the manufacturer, agrees with the proposed rule 
that the eddy current inspections should be repetitive. The commenter 
states that because of recent upper row cracks found on a Model 737 
series airplane with disbonded waffle doublers, it seems prudent to use 
the more sensitive eddy current inspection at repetitive intervals of 
4,500 flight cycles. The commenter notes that only external detailed 
inspections were originally used because it was assumed that the tear 
straps were bonded and functioning to slow down the cracks until they 
could easily be detected using visual methods. The commenter states 
that in the case of a disbonded panel, it is unclear if the chem-mill 
type crack would slow down as it approaches the tear straps. The 
commenter believes that if it is assumed that tear straps do not slow 
the growth of the cracks, then the repetitive external detailed 
inspections every 4,500 flight cycles would allow more than two 
inspection opportunities to pass as cracks detectable by eddy current 
inspections become critical.
    We agree with the request to clarify the repetitive eddy current 
inspections required by paragraph (a) of the final rule. Paragraph (a) 
of the proposed rule did specify repetitive external detailed and eddy 
current inspections but stated this as ``repeat the inspections.'' 
Because the service bulletin only specifies repetitive detailed 
inspections, we should have explained the difference in the 
``Differences'' paragraph of the proposed rule for the reasons stated 
by the last commenter (i.e. because of the recent upper row cracks 
found on an airplane with disbonded waffle doublers). However the 
``Differences'' paragraph of the proposed rule is not repeated in the 
final rule. We have clarified the repetitive eddy current inspections 
by revising paragraph (a) of the final rule to state, ``Repeat the 
external detailed and eddy current inspections * * *.''

Request To Revise Text To Describe the Area of Inspection

    One commenter requests to revise the text in paragraph (a) of the 
proposed rule from ``crown area'' to ``crown area and other known areas 
of cracking.'' The commenter states that the inspections in Part 1 and 
Figure 1 of Boeing Alert Service Bulletin 737-53A1210, Revision 1, 
dated October 25, 2001 (referenced as the appropriate source of service 
information in the proposed rule), include areas of known cracking 
outside the crown. The commenter believes that since paragraph (a) of 
the proposed rule states to inspect only the ``crown area,'' then the 
areas of known cracking outside the crown as specified in the service 
bulletin may not get inspected. In addition, another commenter notes 
that it reported a crack at S12L on a Boeing Model 737-300 series 
airplane.
    The FAA agrees with the commenter that the text to describe the 
area of inspection should be revised. While the heading of Part 1 of 
the service bulletin (like the proposed rule) makes reference only to 
the crown area, Part 1 includes inspections outside that area, as 
stated by the commenter. We proposed to require all of the actions 
specified in Part 1 and Figure 1 of the service bulletin. For the 
reasons stated by that

[[Page 54207]]

commenter, we have clarified paragraph (a) of the final rule to state, 
``* * * crown area and other known areas of fuselage skin cracking, per 
Part 1 and Figure 1 * * *.'' This clarification does not expand the 
inspection locations specified in Part 1 and Figure 1.

Request To Reduce Inspection Area

    One commenter requests reducing the area of the eddy current 
inspection required by paragraph (a) of the proposed rule from body 
station (BS) 360 to BS 1016 to the area BS 460 to BS 787. The commenter 
contends that the cracking reported in the upper crown at locations 
ranging from BS 480 to BS 777, per Boeing Service Bulletin 737-53A1210, 
Revision 1, does not warrant accomplishing both a visual and an eddy 
current inspection of areas BS 360 to BS 1016. The commenter recommends 
a visual inspection for areas BS 360 to BS 1016 and an eddy current 
inspection for areas BS 460 to BS 787.
    We do not agree with the request to reduce the area of the eddy 
current inspection required by paragraph (a) of the final rule. Since 
the issuance of the service bulletin, we have received new reports of 
cracking. To address the identified unsafe condition, detailed and eddy 
current inspections are required by paragraph (a) of the final rule for 
areas BS 360 to BS 1016 identified in the service bulletin. No change 
is made to the final rule in this regard.

Request To Clarify Inspections of Chem-mill Areas

    Two commenters request clarification of inspections for chem-mill 
areas covered by FAA-approved or accepted repairs other than external 
repair doublers that extend a minimum of three rows of fasteners above 
and below the chem-mill steps. One commenter, the manufacturer, 
requests that an inspection be added to the proposed rule for areas 
that are covered by external repair doublers that do not extend a 
minimum of three rows of fasteners above and below the chem-mill steps 
because paragraph (a) of the proposed rule does not address inspecting 
these areas. The commenter states that Boeing has developed a new 
internal inspection method for chem-mill cracks under the external 
repair doublers, as specified in Boeing 737 Non-Destructive Test (NDT) 
Manual, Part 6, Subject 53-30-20. The commenter contends that this 
inspection method can be used as a substitute for the external 
inspections with no change in the proposed compliance times. The 
commenter believes that chem-mill cracks under a repair doubler that do 
not extend beyond the chem-mill step are just as critical because three 
rows are required to carry failsafe loads. However, the commenter 
believes the cracks in this area are inspected less than cracks 
addressed by the proposed rule, and that it is likely repairs have been 
installed over undetected chem-mill cracks. The other commenter 
recommends that a general visual inspection of the repair for chem-
milled areas covered by other FAA-approved or accepted repairs be added 
to the proposed rule, or that the areas be exempted from the 
inspections required by paragraphs (a) and (b) of the proposed rule.
    We agree that inspections of the chem-mill areas should be 
clarified. Inspections are not required in areas that are spanned by an 
FAA-approved repair that has a minimum of 3 rows of fasteners above and 
below the chem-milled step. If an external doubler covers the chem-
milled step, but does not span it by a minimum of 3 rows of fasteners 
above and below, operators must request an alternative method of 
compliance (AMOC) as required by section 39.17 of the Federal Aviation 
Regulations (14 CFR 39.17). In lieu of requesting an AMOC, one method 
of compliance with the inspection requirement of paragraphs (a) and (b) 
of this final rule is to inspect all chem-milled steps covered by the 
repair using internal nondestructive test (NDT) methods in accordance 
with Boeing 737 NDT Manual, Part 6, Subject 53-30-20. We have included 
new paragraph (i) of this final rule to provide inspection procedures, 
in lieu of requesting an AMOC, as one method of compliance with the 
requirements of paragraphs (a) and (b) of this final rule.

Request To Clarify Inspection Requirements in the Area of an Internal 
Doubler at the Emergency Door Surround Structure

    One commenter requests that an inspection method be specified for 
the area of the internal doubler at the emergency exit surround 
structure as shown in Figure 5 of the service bulletin, or that the 
requirement to inspect this area be removed. The commenter notes that 
inspecting the area between BS 540 and BS 727 would require a different 
inspection procedure than the Boeing 737 NDT Manual, Part 6, Subject 
53-30-18 or 53-30-19 procedures which are specified in Figure 5 of 
Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 
25, 2001.
    We agree with the commenter that there should not be a requirement 
to inspect this area because the internal doubler that extends above S-
10 stabilizes the skin in this area and eliminates this area as a 
cracking concern. However, there is not a need to clarify this in the 
final rule because the service bulletin does not specify to inspect 
this area. This area is shown with a dotted line in Figure 5 of the 
service bulletin and is excluded from the inspections in Figure 5. 
Therefore, no change to the final rule is necessary.

Request To Clarify Terminating Action for Repetitive Inspections

    Two commenters request that the terminating action for the 
repetitive inspections required by paragraph (a) of the proposed rule 
be clarified. One commenter states that the proposed rule requires to 
``Repeat the inspections at least every 4,500 flight cycles until 
paragraph (c) or (d)(1)(ii) of this AD has been done, as applicable.'' 
The commenter notes that paragraph (c) and (d)(1)(ii) of the proposed 
rule do not cover the joint cutout modification per paragraph (g) of AD 
2002-07-08, amendment 39-12702 (67 FR 17917). The commenter contends 
that the lap joint repair per paragraph (g) of AD 2002-07-08 ends the 
repetitive inspections for those lap joints, and therefore, should be 
included as a terminating action in paragraph (a) of the proposed rule. 
The other commenter questions if the statement ``Installation of the 
lap joint repair * * * is considered acceptable for compliance with * * 
*'' in paragraph (d)(1) of the proposed AD ends the repetitive 
inspections per paragraph (a) of the proposed AD for those lap joints.
    We agree with the commenters that we should clarify the terminating 
actions for the repetitive actions for the reasons stated by the first 
commenter. The lap joint modification (repair) is an alternate method 
of compliance for the repetitive requirements of paragraph (a) of the 
final rule. There is language in paragraph (d)(1) of the AD that does 
specify, ``Installation of the lap joint repair specified in paragraph 
(g) of AD 2002-07-08, amendment 39-12702, is considered acceptable for 
compliance with the corresponding action specified in this paragraph 
for the lap joint areas only.'' We have moved this language to 
paragraph (d)(1)(ii) of the final rule to clarify that modifications 
performed in accordance with paragraph (g) of AD 2002-07-08 are 
considered a terminating modification for the chem-mill step areas 
within the modified areas.

[[Page 54208]]

Request To Add New Repair Option

    One commenter requests that a new repair option be added to 
paragraph (d) of the proposed rule. Paragraph (d) of the proposed rule 
provides two options for repair if cracking is found. The commenter 
points out that general skin repairs have been added to Boeing 737 
structural repair manuals, and that these repairs meet or exceed the 
requirements as stated in paragraph (d) of the proposed rule. The 
commenter suggests adding paragraph (d)(3) to the proposed rule 
stating, ``For cracking in any area within the limitations of 737-100/
200 SRM 53-30-3 Figure 48 for -100's and -200 aircraft, 737-300 SRM 53-
00-01 Figure 229 for -300 aircraft, 737-400 SRM 53-00-01 Figure 231 for 
-400 aircraft, and 737-500 SRM 53-00-01 Figure 229 for -500 aircraft, 
cracks can be repaired per these SRM figures as applicable. 
Accomplishment of these repairs ends the repetitive inspections 
required by paragraph (b) of this AD for the repaired area only.'' The 
commenter also suggests revising the first sentence of paragraph (d) of 
the proposed rule to state, `` * * * specified in paragraphs (d)(1), 
(d)(2), and (d)(3) of this AD, as applicable * * *.'' The commenter 
points out that these SRM repairs are being used extensively within the 
industry to repair skin damage, including chem-mill cracks.
    We agree with the commenter that the new repair option should be 
added and concur with its justification. Accordingly, we have added 
paragraph (e) to the final rule as follows: ``For cracking in any area 
specified in paragraphs (d)(1) and (d)(2) of this AD within the 
limitations of Chapter 53, Subject 53-30-3, Figure 48 (for Model 737-
100 and -200 series airplanes), of the Boeing 737-100 and -200 
Structural Repair Manual (SRM); Chapter 53, Subject 53-00-01, Figure 
229 (for Model 737-300 airplanes), of the Boeing 737-300 SRM; Chapter 
53, Subject 53-00-01, Figure 231 (for Model 737-400 series airplanes), 
of the Boeing 737-400 SRM; and Chapter 53, Subject 53-00-01, Figure 229 
(for Model 737-500 series airplanes), of the Boeing 737-500 SRM; repair 
cracks per the applicable SRM. Accomplishment of the applicable repair 
terminates the repetitive inspections required by paragraphs (a) and 
(b) of this AD for the repaired area only.'' We also revised paragraphs 
(a) and (b) of the final rule to include paragraph (e) of the final 
rule as an optional terminating action for the repaired area only. In 
addition, we revised paragraphs (d)(1) and (d)(2) of the final rule by 
adding paragraph (e) of the final rule as a repair option.

Request To Revise Repair Instructions

    One commenter requests that the repair instructions in paragraph 
(d)(2) of the proposed rule be revised. The commenter notes that 
paragraph (d)(2) gives instructions to ``* * * repair per Part 2 of the 
Work Instructions of the service bulletin * * *,'' and the service 
bulletin specifies to ask Boeing for repair data. The commenter 
contends that an operator may interpret paragraph (d)(2) of the 
proposed rule as requiring them to contact Boeing for all repairs in 
the lower lobe and section 41. The commenter suggests revising 
paragraph (d)(2) of the proposed rule to state, ``For cracking of the 
lower lobe area and Section 41, repair per paragraph (d)(3) of this AD 
before further flight * * *.''
    We disagree with the commenter to revise paragraph (d)(3) of the 
final rule per its suggested wording. As stated earlier, paragraph 
(d)(2) of the final rule has been revised by adding paragraph (e) of 
the final rule as an option to the repair of the cracking of the lower 
lobe and Section 41 done per Part 2 of the Work Instructions of the 
service bulletin. Operators should note that while the service bulletin 
does specify to contact Boeing for repair, paragraph (d) of the final 
rule requires operators to contact the FAA or a Designated Engineering 
Representative (DER) if the service bulletin specifies to contact 
Boeing for repair instructions. No change is made to the final rule in 
this regard.

Request To Add Inspection Requirement

    One commenter requests that the external subsurface inspection of 
the chem-mill steps in adjacent bays per step 2 of Figure 18 of the 
service bulletin be added to paragraph (e)(2) of the proposed rule. The 
commenter notes that paragraph (e)(2) of the proposed rule requires an 
``internal eddy current inspection of the skin, tear straps, and lap 
joint * * *'' The commenter states that, while this agrees with the 
service bulletin, the service bulletin also specifies an external 
subsurface inspection of the chem-mill steps in adjacent bays. The 
commenter points out that when the time-limited repair required by 
paragraph (e) of the proposed rule is accomplished at remote sites, it 
may not be possible to do an NDT inspection of the adjacent chem-mill 
steps. The commenter states that, often times in service, the bays 
adjacent to the cracked bay will also have cracks. The commenter also 
notes that inspection of the adjacent bays within 4,000 flight cycles 
after doing the repair is recommended by the service bulletin as a 
precautionary measure.
    We agree with the commenter that the service bulletin also 
specifies external subsurface inspection of the chem-mill steps in 
adjacent bays. In our effort to describe the types of inspections 
referenced in Part 4 of the service bulletin, we inadvertently omitted 
the one mentioned by the commenter. We had no intention of deviating 
from the service bulletin. To clarify this intent, the final rule has 
been revised to track the precise wording of Part 4 of the service 
bulletin: ``Do inspections of the repaired area * * *.''

Request To Remove ``Tear Straps'' From Inspection Description

    One commenter requests that the words ``tear straps'' be removed 
from paragraph (e)(2) of the proposed rule. The commenter notes that 
the internal inspection shown in Figure 18 of the service bulletin 
looks for cracks in the skin under the tear strap and does not look for 
cracks in the tear straps.
    We agree with the commenter that the words ``tear straps'' be 
removed from paragraph (f)(2) of the final rule (specified as paragraph 
(e)(2) of the proposed rule). As stated previously, paragraph (f)(2) of 
the final rule (specified as paragraph (e)(2) of the proposed rule) has 
been changed to state, ``Do the inspections of the repaired area * * 
*.''

Request To Add Inspection for Disbonding To Terminate Repetitive Eddy 
Current Inspections

    One commenter requests that an inspection for disbonding be added 
that would terminate the repetitive eddy current inspections required 
by paragraph (a) of the proposed rule. The commenter recommends that 
the inspection for disbonding specified in Boeing Service Bulletin 737-
53-1179, Revision 2, dated October 25, 2001, be added as a terminating 
action for the repetitive eddy current inspections required by 
paragraph (a) of the proposed rule, and then only repetitive detailed 
inspections would be needed to ensure safety.
    We agree that an inspection for disbonding should be added to 
terminate the repetitive eddy current inspections required by paragraph 
(a) of the final rule. The inspection for disbonding specified in 
Boeing Service Bulletin 737-53-1179, Revision 2, dated October 25, 
2001, will verify the integrity of the doublers, and therefore, the 
repetitive eddy current inspections will no longer be required. The 
service bulletin is the source of service information for paragraphs 
(b) and (c) of

[[Page 54209]]

AD 2003-14-06, amendment 39-13225. That AD requires repetitive 
inspections for cracking of certain lap splices, and corrective action 
if necessary. We have added paragraph (g) to the final rule as follows: 
``Accomplishment of paragraph (b) or (c), as applicable, of AD 2003-14-
06, amendment 39-13225, terminates the repetitive eddy current 
inspections required by paragraph (a) of this AD; however the 
repetitive detailed inspections required by paragraph (a) of this AD 
are still required.''

Request To Exclude Appendix A From Service Bulletin References

    Two commenters request that the phrase ``including Appendix A'' in 
paragraphs (a) through (e) of the proposed rule either be removed or 
changed to ``excluding Appendix A.'' One commenter notes that Appendix 
A of the service bulletin is an optional cost benefit analysis 
worksheet that is included in the service bulletin for the benefit of 
the operators if they elect to use it and that it has no effect on the 
repair, modification, or compliance instructions of the referenced 
service bulletin. The other commenter questions why Appendix A is 
mandatory and what operators should do with it if it is not excluded 
from the proposed rule.
    We agree that Appendix A should be excluded from the service 
bulletin references for the reasons stated by the first commenter. We 
removed the wording ``including Appendix A'' from paragraphs (a) 
through (d) of the final rule and paragraph (f) of the final rule 
(specified as paragraph (e) of the proposed rule). We also removed the 
wording ``excluding Evaluation Form.''

Explanation of Editorial Changes

    We have revised certain wording regarding the compliance times of 
the repetitive inspection requirements specified in paragraphs (a), 
(b), and (f)(1) (specified as paragraph (e)(1) of the proposed rule) of 
the final rule. Instead of specifying that the repetitive inspections 
be repeated ``at least every,'' as stated in paragraphs (a), (b), and 
(e)(1) of the proposed rule, this final rule specifies that the 
inspections be repeated ``at intervals not to exceed.''

Clarification of Type of Inspection

    We have clarified one of the inspection requirements contained in 
the proposed rule. Whereas paragraph (f)(1) of the proposed rule 
specifies a general visual inspection, we have revised paragraph (f)(1) 
of the final rule to clarify that our intent is to require a detailed 
inspection, as specified in the service bulletin.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Changes to 14 CFR Part 39/Effect on the AD

    On July 10, 2002, the FAA issued a new version of 14 CFR part 39 
(67 FR 47997, July 22, 2002), which governs the FAA's airworthiness 
directives system. The regulation now includes material that relates to 
altered products, special flight permits, and alternative methods of 
compliance. However, for clarity and consistency in this final rule, we 
have retained the language of the NPRM regarding that material.

Change to Labor Rate Estimate

    We have reviewed the figures we have used over the past several 
years to calculate AD costs to operators. To account for various 
inflationary costs in the airline industry, we find it necessary to 
increase the labor rate used in these calculations from $60 per work 
hour to $65 per work hour. The cost impact information, below, reflects 
this increase in the specified hourly labor rate.

Interim Action

    This is considered to be interim action for Group 7 airplanes. 
Although the service bulletin described previously does not include the 
inspection of the crown area (upper lobe) for Group 7 airplanes, as 
specified in paragraph (a) of this final rule, the manufacturer has 
advised that it currently is developing a new service bulletin to 
address those airplanes. Once the FAA has reviewed and approved the 
service bulletin, we may consider additional rulemaking to mandate 
those inspections.

Cost Impact

    There are approximately 2,200 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 903 airplanes of U.S. 
registry will be affected by this proposed AD.
    It will take approximately 94 work hours per airplane to accomplish 
the inspections of the crown area, at an average labor rate of $65 per 
work hour. Based on these figures, the cost impact of these inspections 
on U.S. operators is estimated to be $5,517,330, or $6,110 per 
airplane, per inspection cycle.
    It will take approximately 96 work hours per airplane to accomplish 
the inspections of the lower lobe area, at an average labor rate of $65 
per work hour. Based on these figures, the cost impact of these 
inspections on U.S. operators is estimated to be $5,634,720, or $6,240 
per airplane, per inspection cycle.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the requirements of this 
AD action, and that no operator would accomplish those actions in the 
future if this 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.
    Should an operator elect to install the preventive modification, it 
will take approximately 108 work hours to accomplish, at an average 
labor rate of $65 per work hour. Based on these figures, the cost 
impact of the preventive modification is estimated to be $7,020 per 
airplane.

Regulatory Impact

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

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

[[Page 54210]]

Adoption of the Amendment

0
Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. Section 39.13 is amended by adding the following new airworthiness 
directive:

2004-18-06 Boeing: Amendment 39-13784. Docket 2001-NM-246-AD.

    Applicability: Model 737-200, -200C, -300, -400, and -500 series 
airplanes, as listed in Boeing Alert Service Bulletin 737-53A1210, 
Revision 1, dated October 25, 2001; certificated 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 (j) 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 find and fix fatigue cracking of certain upper and lower skin 
panels of the fuselage, which could result in sudden fracture and 
failure of the skin panels and consequent rapid decompression of the 
airplane, accomplish the following:

External Detailed and Eddy Current Inspections

    (a) For Groups 1 through 6 and Group 8 airplanes: Before the 
accumulation of 35,000 total flight cycles, or within 4,500 flight 
cycles after the effective date of this AD, whichever is later, do 
external detailed and eddy current inspections of the crown area and 
other known areas of fuselage skin cracking, per Part 1 and Figure 1 
of the Work Instructions of Boeing Alert Service Bulletin 737-
53A1210, Revision 1, dated October 25, 2001, except as provided by 
paragraph (i) of this AD. Repeat the external detailed and eddy 
current inspections at intervals not to exceed 4,500 flight cycles 
until paragraph (c), (d)(1)(ii), (e), (f), or (g) of this AD has 
been done, as applicable. Although paragraph 1.D. of the service 
bulletin references a reporting requirement, such reporting is not 
required by this AD.

    Note 2: 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.''

    (b) For all airplanes: Before the accumulation of 40,000 total 
flight cycles, or within 4,500 flight cycles after the effective 
date of this AD, whichever is later, do an external detailed 
inspection of the lower lobe area and section 41 of the fuselage for 
cracking, per Part 2 and Figure 2 of the Work Instructions of Boeing 
Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 
2001, except as provided by paragraph (i) of this AD. Repeat the 
inspection at intervals not to exceed 9,000 flight cycles until 
paragraph (d)(2) or (e) of this AD has been done, as applicable.

Preventive Modification

    (c) For Groups 3, 5, 6, and 8 airplanes: If no cracking is found 
during any inspection required by paragraph (a) of this AD, doing 
the preventive modification of the chem-milled pockets in the upper 
skin as specified in Part 5 of the Work Instructions of Boeing Alert 
Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001, 
ends the repetitive external detailed and eddy current inspections 
required by paragraph (a) of this AD for the modified area only.

Corrective Actions

    (d) If any cracking is found during any inspection required by 
paragraph (a) or (b) of this AD, before further flight, do the 
actions specified in paragraphs (d)(1) and (d)(2) of this AD, as 
applicable, per the Work Instructions of Boeing Alert Service 
Bulletin 737-53A1210, Revision 1, dated October 25, 2001. Where the 
service bulletin specifies to contact Boeing for repair 
instructions, before further flight, repair per a method approved by 
the Manager, Seattle Aircraft Certification Office (ACO), FAA; or 
per data meeting the type certification basis of the airplane 
approved by a Boeing Company Designated Engineering Representative 
(DER) 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.
    (1) Except as provided by paragraph (e) of this AD, for cracking 
of the crown area, do the repair specified in either paragraph 
(d)(1)(i) or (d)(1)(ii) of this AD.
    (i) Do a time-limited repair per Part 4 of the Work Instructions 
of the service bulletin, then do the actions required by paragraph 
(f) of this AD at the times specified in that paragraph.
    (ii) Do a permanent repair per Part 3 of the Work Instructions 
of the service bulletin. Installation of a permanent repair ends the 
repetitive inspections required by paragraph (a) of this AD for the 
repaired area only. Installation of the lap joint repair specified 
in paragraph (g) of AD 2002-07-08, amendment 39-12702, is considered 
acceptable for compliance with the corresponding permanent repair 
specified in this paragraph for the repaired areas only.
    (2) Except as provided by paragraph (e) of this AD, for cracking 
of the lower lobe area and Section 41, repair per Part 2 of the Work 
Instructions of the service bulletin. Accomplishment of this repair 
ends the repetitive inspections required by paragraph (b) of this AD 
for the repaired area only.

Optional Repair Method

    (e) For cracking in any area specified in paragraphs (d)(1) and 
(d)(2) of this AD within the limitations of Chapter 53, Subject 53-
30-3, Figure 48 (for Model 737-100 and -200 series airplanes), of 
the Boeing 737-100 and -200 Structural Repair Manual (SRM); Chapter 
53, Subject 53-00-01, Figure 229 (for Model 737-300 airplanes), of 
the Boeing 737-300 SRM; Chapter 53, Subject 53-00-01, Figure 231 
(for Model 737-400 series airplanes), of the Boeing 737-400 SRM; and 
Chapter 53, Subject 53-00-01, Figure 229 (for Model 737-500 series 
airplanes), of the Boeing 737-500 SRM; repair cracks per the 
applicable SRM. Accomplishment of the applicable repair terminates 
the repetitive inspections required by paragraphs (a) and (b) of 
this AD for the repaired area only.

Follow-on and Corrective Actions

    (f) If a time-limited repair is done, as specified in paragraph 
(d)(1)(i) of this AD: Do the actions specified in paragraphs (f)(1), 
(f)(2), and (f)(3) of this AD, at the times specified in paragraphs 
(f)(1), (f)(2), and (f)(3) of this AD, per the Work Instructions of 
Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 
25, 2001.
    (1) Within 3,000 flight cycles after doing the repair: Do a 
detailed inspection of the repaired area for loose fasteners per 
Part 4 of the Work Instructions of the service bulletin. If any 
loose fastener is found, before further flight, replace with a new 
fastener per the service bulletin. Then repeat the inspection at 
intervals not to exceed 3,000 flight cycles until permanent rivets 
are installed in the repaired area, which ends the repetitive 
inspections for this paragraph.
    (2) Within 4,000 flight cycles after doing the repair: Do 
inspections of the repaired area for cracking per Part 4 of the Work 
Instructions of the service bulletin. If any cracking is found, 
before further flight, repair per a method approved by the Manager, 
Seattle ACO, or per data meeting the type certification basis of the 
airplane approved by a Boeing Company DER who has been authorized by 
the FAA 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.
    (3) Within 10,000 flight cycles after doing the repair: Make the 
repair permanent per Part 4 and Figure 20 of the Work Instructions 
of the service bulletin, which ends the repetitive inspections for 
the repaired area only.

[[Page 54211]]

Optional Terminating Action for Repetitive Eddy Current Inspections

    (g) Accomplishment of paragraph (b) or (c), as applicable, of AD 
2003-14-06, amendment 39-13225, ends the repetitive eddy current 
inspections required by paragraph (a) of this AD for that skin panel 
only; however the repetitive external detailed inspections required 
by paragraph (a) of this AD are still required for all areas.

Credit for Actions Done Per Previous Service Bulletin

    (h) Inspections, repairs, and preventive modifications done 
before the effective date of this AD per Boeing Alert Service 
Bulletin 737-53A1210, dated December 14, 2000, are acceptable for 
compliance with the corresponding actions required by this AD.

Exception to Service Bulletin Procedures

    (i) For airplanes subject to the requirements of paragraphs (a) 
and (b) of this AD: Inspections are not required in areas that are 
spanned by an FAA-approved repair that has a minimum of 3 rows of 
fasteners above and below the chem-milled step. If an external 
doubler covers the chem-milled step, but does not span it by a 
minimum of 3 rows of fasteners above and below, in lieu of 
requesting approval for an alternative method of compliance (AMOC), 
one method of compliance with the inspection requirement of 
paragraphs (a) and (b) of this AD is to inspect all chemical-milled 
steps covered by the repair using internal nondestructive test (NDT) 
methods in accordance with Boeing 737 Non-Destructive Test NDT 
Manual, Part 6, Subject 53-30-20.

Alternative Methods of Compliance

    (j)(1) An alternative method of compliance (AMOC) 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 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.
    (2) AMOCs, approved previously in accordance with AD 2003-14-06, 
amendment 39-13225, for paragraphs (b) and (c) of AD 2003-14-06, are 
approved as AMOCs with paragraphs (a) and (g) of this AD for the 
applicable terminating action for the repetitive eddy current 
inspections only.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permit

    (k) 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.

Incorporation by Reference

    (l) Unless otherwise specified in this AD, the actions shall be 
done in accordance with Boeing Alert Service Bulletin 737-53A1210, 
Revision 1, dated October 25, 2001, excluding Appendix A. This 
incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from Boeing Commercial Airplanes, P.O. 
Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at 
the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., 
Renton, Washington; or at the National Archives and Records 
Administration (NARA). For information on the availability of this 
material at NARA, call (202) 741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

Effective Date

    (m) This amendment becomes effective on October 13, 2004.

    Issued in Renton, Washington, on August 26, 2004.
Kevin M. Mullin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-20120 Filed 9-7-04; 8:45 am]
BILLING CODE 4910-13-P