2013-24034. Airworthiness Directives; The Boeing Company Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule.

SUMMARY:

We are superseding airworthiness directive (AD) 2004-18-06 for certain The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes. AD 2004-18-06 required repetitive inspections to find fatigue cracking of certain upper and lower skin panels of the fuselage, and follow-on and corrective actions if necessary. AD 2004-18-06 also included a terminating action for the repetitive inspections of certain modified or repaired areas only. This new AD adds new inspections for cracking of the fuselage skin along certain chem-milled lines, and corrective actions if necessary. This new AD also reduces certain thresholds and intervals required by AD 2004-18-06. This AD was prompted by new findings of vertical cracks along chem-milled steps adjacent to the butt joints. We are issuing this AD to detect and correct 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.

DATES:

This AD is effective November 6, 2013.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in the AD as of November 6, 2013.

The Director of the Federal Register approved the incorporation by reference of a certain other publication listed in the AD as of October 13, 2004 (69 FR 54206, September 8, 2004).

ADDRESSES:

For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone [phone], extension 1; fax [phone]; Internet https://www.myboeingfleet.com. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov;​; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this AD, the regulatory evaluation, any comments received, and other information. The address for the Docket Office (phone: [phone]) is Document Management Facility, U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT:

Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue SW., Renton, Washington 98057-3356; phone: [phone]; fax: [phone]; email: [e-mail].

SUPPLEMENTARY INFORMATION:

Discussion

We issued a supplemental notice of proposed rulemaking (SNPRM) to amend 14 CFR part 39 to supersede AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004). AD 2004-18-06 applied to the specified products. The SNPRM published in the Federal Register on October 10, 2012 (77 FR 61550). We preceded the SNPRM with a notice of proposed rulemaking (NPRM) that published in the Federal Register on March 8, 2011 (76 FR 12619). The NPRM proposed to continue 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. The NPRM also included a terminating action for the repetitive inspections of certain modified or repaired areas only. The NPRM proposed to add new inspections for cracking of the fuselage skin along certain chem-milled lines, and corrective actions if necessary. The NPRM also proposed to reduce certain thresholds and intervals required by AD 2004-18-06. The SNPRM proposed to revise the NPRM by reducing the proposed repetitive inspection intervals.

Comments

We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the SNPRM (77 FR 61550, October 10, 2012) and the FAA's response to each comment.

Request To Change Certain Repetitive Inspection Intervals

Boeing asked that the repetitive inspection interval of 1,800 flight cycles or 1,800 flight hours, as specified in paragraph (r) of the SNPRM (77 FR 61550, October 10, 2012), be changed to eliminate the 1,800 flight-hour interval. Boeing stated that the longitudinal chem-milled cracks are driven primarily by hoop loading as a result of pressurization cycles, and added that the vertical chem-milled cracks are driven by both pressure and flight loads. Boeing added that the threshold and repetitive inspection intervals can be affected by this. Boeing noted that repeating the inspection at 1,800 flight cycles at the butt joints was a conservative estimate obtained from crack growth data of longitudinal chem-milled cracks; this is conservative because the stresses in the skins at the butt joints are lower than the hoop stresses, which cause the longitudinal cracks to develop and grow. Boeing concluded that a detailed analysis of the stresses on the vertical cracks compared with the horizontal cracks confirmed that repeating the inspections every 1,800 flight cycles is adequate to detect cracks before they spread and result in an unsafe condition.

We agree that eliminating the 1,800-flight-hour aspect of the repetitive inspection interval and the threshold is acceptable for the reasons provided by the commenter. We have determined that this change adequately addresses the identified unsafe condition. Therefore, we have changed paragraph (r) of this final rule accordingly.

Requests To Clarify Exception to Service Information

Boeing and Southwest Airlines (SWA) asked that we clarify the exception language identified in paragraph (o) of the SNPRM (77 FR 61550, October 10, 2012). Boeing and SWA both suggested language for changing that paragraph.

Boeing stated that the language in paragraph (o) of the SNPRM (77 FR 61550, October 10, 2012) gives relief for inspections under FAA-approved repair doublers that span the chem-milled step by a minimum of three rows of fasteners above and below the chem-milled step. Boeing added that paragraph (o) of the SNPRM does not distinguish the reason for the repair (i.e., cracks, dents, corrosion, etc.), but just specifies that a repair doubler exists and spans the chem-milled step with a sufficient number of fastener rows. Boeing asked that this same allowance be given to chem-milled steps under repairs that are accomplished according to the general skin repairs specified in paragraph (k) of the SNPRM. Boeing noted that paragraph (k) of the SNPRM already has language that terminates inspections under repairs accomplished according to paragraph (k) of the SNPRM; however, paragraph (k) of the SNPRM is for the repair of chem-milled step cracks only, so it would not terminate future chem-milled steps under a repair that is installed for some reason other than chem-milled cracking.

SWA stated certain conditions for external repairs are not stipulated in paragraph (o) of the SNPRM (77 FR 61550, October 10, 2012). SWA noted that for airplanes on which the repair does not meet these conditions, paragraph (o) of the SNPRM specifies that one option to comply with the inspections is to use the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. SWA added that the option to use an alternate inspection is given in the notes section of Tables 1 through 6 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, rather than in the Work Instructions of this service bulletin. SWA also asked that we change the language in paragraphs (p), (q), and (r) of the SNPRM for the alternate inspection given in Tables 1 through 6 of paragraph 1.E., “Compliance” of this service bulletin.

We agree that clarification of the language in paragraph (o) of this final rule is necessary to ensure that all inspection requirements are complied with as written. We have revised the language in paragraph (o) of this final rule to include the language “or repairs that have a minimum of 2 rows of fasteners above and below the chem-milled step, and have been installed in accordance with the requirements of paragraph (k) of this final rule.” We have also included language for repairs to the vertical chem-milled steps. In addition, we have revised paragraph (o) of this final rule to refer to the notes in Tables 1 through 6 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, for the inspection requirements. With this clarification added to paragraph (o) of this final rule, it is not necessary to change the language in paragraphs (p) and (q) of this final rule. We have added the exception specified in paragraph (o) of this final rule to paragraphs (r), (s), (t), and (u) of this final rule.

Request To Clarify Certain Repetitive Inspection Intervals

SWA asked that we clarify the repetitive inspection intervals required by paragraph (h) of the SNPRM (77 FR 61550, October 10, 2012). SWA stated that paragraph (h) of the SNPRM includes a new repetitive inspection interval for doing the inspections of the lower lobe and section 41, and that repeating those inspections every 4,500 flight cycles is a new requirement. SWA added that paragraph (s) of the SNPRM introduces a new repetitive inspection interval of 1,800 flight cycles for the inspections of the lower lobe and section 41, which contradicts paragraph (h) of the SNPRM.

SWA stated that paragraph (s) of the SNPRM (77 FR 61550, October 10, 2012) introduces the terminology “areas of known cracking” and “areas of no known cracking” for inspections of the lower lobe and section 41. SWA added that, for areas of known cracking, the inspections are required at the latest of the times specified in paragraphs (s)(2)(i) and (s)(2)(ii) of the SNPRM. SWA stated that paragraph (s)(2)(i) of the SNPRM specifies inspections before the accumulation of 35,000 total flight cycles; paragraph (s)(2)(ii) of the SNPRM specifies inspections within 4,500 flight cycles after the most recent inspection required by paragraph (h) of the SNPRM or within 1,800 flight cycles after the effective date of the AD, whichever is earlier. SWA noted that although paragraph (h) of the SNPRM includes the new requirement of repeating those inspections every 4,500 flight cycles, airplanes are still subject to the existing repetitive inspection interval of 9,000 flight cycles, as required by AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004). SWA added that this is a significant conflict since airplanes on which the inspection threshold specified in paragraph (s)(2)(i) of the SNPRM has been surpassed “will immediately be rendered out of compliance by paragraph (s)(2)(ii) if the most recent inspection was accomplished more than 4,500 flight cycles from the last inspection.” SWA also asked that we clarify the inspection requirements for airplanes that have accumulated more than 35,000 total flight cycles as of the effective date of the AD.

Boeing stated that paragraph (s)(2)(ii) of the SNPRM (77 FR 61550, October 10, 2012) gives a grace period to start inspections in lower lobe and section 41 for areas of known cracking for airplanes that have exceeded the threshold of 35,000 total flight cycles. Boeing added that this grace period is 4,500 flight cycles from the previous inspections done in accordance with AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), which required that those areas be re-inspected at 9,000 flight-cycle intervals. Boeing noted that, as a result of this, it is likely that many airplanes will be grounded. Boeing asked that the grace period be changed to 9,000 flight cycles.

We agree that paragraphs (h) and (s) of this final rule should be changed since the new requirements could put airplanes out of compliance. We have revised paragraph (h) of this final rule to specify a repetitive inspection interval of 9,000 flight cycles, as required by AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), and have deleted paragraphs (h)(1) and (h)(2) of this final rule to eliminate those repetitive inspection intervals.

We have also revised paragraph (s)(2) of this final rule to include the existing repetitive inspection interval of 9,000 flight cycles so that no airplanes will be out of compliance with the inspection requirements carried over from AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004).

Request To Update Structural Repair Manual (SRM) References

SWA asked that we update the SRM repair references in paragraphs (k)(2) and (k)(4) of the SNPRM (77 FR 61550, October 10, 2012). SWA stated that the references to Figure 229 for Revisions 92 and 70, both dated November 10, 2010, in those paragraphs is incorrect. SWA noted that the correct repair for those SRM revisions is Repair 31.

We agree that this final rule should refer to the latest repairs. We have determined that the SRM repair references specified in paragraphs (k)(2) and (k)(4) of the SNPRM (77 FR 61550, October 10, 2012), have been updated. The SRM repair reference in paragraph (k)(3) of the SNPRM also has been updated. Therefore, we have changed paragraphs (k)(2), (k)(3), and (k)(4) of this final rule to update the SRM references to include the appropriate repair.

Request To Clarify Terminating Action

SWA asked that we change paragraph (j)(1)(i) of the SNPRM (77 FR 61550, October 10, 2012) to reflect that the time-limited repair specified in that paragraph terminates the repetitive inspections required by paragraph (g) of the SNPRM. SWA also asked that, if we do not change that paragraph, we provide clarification that accomplishment of the repair specified in paragraph (v) of the SNPRM terminates those repetitive inspections. SWA stated that paragraph (j) of the SNPRM addresses retained corrective actions for cracking found during the inspections required by paragraphs (g), (h), (p), (q), (r), and (s) of the SNPRM. SWA added that paragraph (v) of the SNPRM specifies that accomplishment of the permanent repair specified in Part 5, or the time-limited repair specified in Part 6, of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, terminates the repetitive inspections required by paragraphs (p), (q), (r), and (s) of the SNPRM for the repaired area only. SWA noted that paragraph (j)(1)(i) of the SNPRM specifies that installation of a permanent repair terminates the repetitive inspections required by paragraph (g) of the SNPRM for the repaired area only; however, paragraph (j)(1)(i) of the SNPRM does not indicate that accomplishing the time-limited repair terminates the repetitive inspections.

We agree that clarification is necessary. Since the crack at the chem-milled step has been trimmed out during installation of the time-limited repair in accordance with Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, the inspections required by paragraph (g) of this final rule cannot be accomplished. We have changed paragraph (j)(1)(i) of this final rule to specify “Installation of a time-limited repair ends the repetitive inspections required by paragraph (g) of this final rule for the repaired area only.” We have also added a reference to paragraph (j)(1)(i) of this final rule in paragraph (g) of this final rule to specify that the actions specified in paragraph (j)(1)(i) of this final rule terminate the repetitive inspections.

Additional Changes Made to This Final Rule

We have removed paragraph (b)(2) of the SNPRM (77 FR 61550, October 10, 2012) from this final rule, because the ADs that were identified in paragraph (b)(2) of the SNPRM are not “affected” by this AD. We have also redesignated paragraph (b)(1) of the SNPRM as paragraph (b) of this final rule. These changes do not affect the intent of this AD.

We have revised the wording in paragraph (n) of this AD; this change has not changed the intent of that paragraph.

Conclusion

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously—and minor editorial changes. We have determined that these minor changes:

• Αre consistent with the intent that was proposed in the SNPRM (77 FR 61550, October 10, 2012) for correcting the unsafe condition; and
• Do not add any additional burden upon the public than was already proposed in the SNPRM (77 FR 61550, October 10, 2012).

We also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.

Costs of Compliance

We estimated that 903 airplanes of U.S. registry are affected by AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004).

The inspections of the crown area that are retained from AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), take about 94 work-hours per airplane to accomplish, at an average labor rate of $85 per work-hour. Based on these figures, the estimated cost of the retained inspections is $7,990 per airplane, per inspection cycle.

The inspections of the lower lobe area that are retained from AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), take about 96 work-hours per airplane to accomplish, at an average labor rate of $85 per work-hour. Based on these figures, the estimated cost of the retained inspections is $8,160 per airplane, per inspection cycle.

Should an operator elect to install the preventive modification specified in AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), it will take about 108 work-hours per airplane to accomplish, at an average labor rate of $85 per work-hour. Based on these figures, the estimated cost of the modification is $9,180 per airplane.

We estimate that this AD affects about 701 airplanes of U.S. registry.

The new inspections take about 27 work-hours per airplane, at an average labor rate of $85 per work-hour. Based on these figures, the estimated cost of the new actions specified in this AD for U.S. operators is $1,608,795, or $2,295 per airplane, per inspection cycle.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this AD will not have federalism implications under Executive Order 13132. This AD 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.

For the reasons discussed above, I certify that this AD:

(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),

(3) Will not affect intrastate aviation in Alaska, and

(4) 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.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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.

§ 39.13

[Amended]

2. The FAA amends § 39.13 by removing airworthiness directive (AD) 2004-18-06, Amendment 39-13784 ( 69 FR 54206, September 8, 2004), and adding the following new AD:

2013-18-08 The Boeing Company: Amendment 39-17581; Docket No. FAA-2011-0155; Directorate Identifier 2009-NM-141-AD.

(a) Effective Date

This AD is effective November 6, 2013.

(b) Affected ADs

This AD supersedes AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004).

(c) Applicability

This AD applies to The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009.

(d) Subject

Joint Aircraft System Component (JASC)/Air Transport Association (ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

This AD was prompted by new findings of vertical cracks along chem-milled steps adjacent to the butt joints. We are issuing this AD to detect and correct 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.

(f) Compliance

Comply with this AD within the compliance times specified, unless already done.

(g) Retained External Detailed and Eddy Current Inspections

This paragraph restates the requirements of paragraph (a) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), with revised service information. For Groups 1 through 5 airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001: Before the accumulation of 35,000 total flight cycles, or within 4,500 flight cycles after October 13, 2004 (the effective date of AD 2004-18-06), whichever is later, do external detailed and eddy current inspections of the crown area and other known areas of fuselage skin cracking, in accordance with Part 1 and Figure 1 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in accordance with Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009; except as provided by paragraph (o) of this AD. Repeat the external detailed and eddy current inspections at intervals not to exceed 4,500 flight cycles until paragraph (i), (j)(1)(i), (j)(1)(ii), (k), (l), or (m) of this AD has been done, as applicable. Although paragraph 1.D. of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001, references a reporting requirement, such reporting is not required by this AD. Accomplishing the actions required by paragraph (p) or (q) of this AD ends the repetitive requirements in this paragraph.

(h) Retained External Detailed Inspection With Reduced Compliance Time

This paragraph restates the requirements of paragraph (b) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), with reduced compliance time and revised service information. For all airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001: Before the accumulation of 40,000 total flight cycles, or within 4,500 flight cycles after October 13, 2004 (the effective date of AD 2004-18-06), whichever is later, do an external detailed inspection of the lower lobe area and section 41 of the fuselage for cracking, in accordance with Part 2 and Figure 2 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in accordance with Part 4 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009; except as provided by paragraph (o) of this AD. Repeat the inspection thereafter at intervals not to exceed 9,000 flight cycles until the actions specified in paragraph (j)(2) or paragraph (k), as applicable, of this AD have been done. Accomplishing the actions required by paragraph (s) of this AD ends the requirements in this paragraph.

(i) Retained Preventive Modification at Stringer 12

This paragraph restates the requirements of paragraph (c) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), with revised service information. For Groups 3 and 5 airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001: If no cracking is found during any inspection required by paragraph (g) 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; or as specified in Part 7 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as required by paragraph (x) of this AD; ends the repetitive external detailed and eddy current inspections required by paragraph (g) of this AD for the modified area only. As of the effective date of this AD, use only Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, to do the actions required by this paragraph.

(j) Retained Corrective Actions

This paragraph restates the requirements of paragraph (d) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), with revised service information. If any cracking is found during any inspection required by paragraph (g), (h), (p), (q), or (s) of this AD, before further flight, do the actions specified in paragraphs (j)(1) and (j)(2) of this AD, as applicable, in accordance with the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in accordance with the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. As of the effective date of this AD, use only Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, to do the actions required by this paragraph. Where Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009; specify to contact Boeing for repair instructions, before further flight, repair 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 if it is approved by the Boeing Commercial Airplanes Organization Designation Authorization (ODA) or any other person authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane and the approval must specifically refer to this AD.

(1) Except as provided by paragraph (k) of this AD, for cracking of the crown area, do the repair specified in either paragraph (j)(1)(i) or (j)(1)(ii) of this AD.

(i) Do a time-limited repair in accordance with Part 4 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in accordance with Part 6 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as required by paragraph (x) of this AD; then do the actions required by paragraph (l) of this AD at the times specified in that paragraph. Installation of a time-limited repair ends the repetitive inspections required by paragraph (g) of this AD for the repaired area only.

(ii) Do a permanent repair in accordance with Part 3 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in accordance with Part 5 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. Installation of a permanent repair ends the repetitive inspections required by paragraph (g) 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 (67 FR 17917, April 12, 2002), 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 (k) of this AD, for cracking of the lower lobe area and section 41, repair in accordance with Part 2 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in accordance with paragraph (j)(2)(i) or (j)(2)(ii) of this AD. Accomplishment of this repair ends the repetitive inspections required by paragraph (h) of this AD for the repaired area only. As of the effective date of this, do the repair specified in paragraph (j)(2)(i) or (j)(2)(ii) of this AD.

(i) Do a time-limited repair in accordance with Part 6 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as required by paragraph (x) of this AD, then do the actions required by paragraph (l) of this AD at the times specified in that paragraph.

(ii) Do a permanent repair in accordance with Part 5 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009.

(k) Retained Optional Repair Method

This paragraph restates the requirements of paragraph (e) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), with revised service information. For cracking in any area specified in paragraphs (j)(1) and (j)(2) of this AD within the limitations of the applicable structural repair manual (SRM) specified in paragraphs (k)(1) through (k)(4) of this AD, repair any cracks, in accordance with a method approved by the Manager, Seattle ACO; or in accordance with data meeting the type certification basis of the airplane if it is approved by the Boeing Commercial Airplanes ODA or any other person authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved the repair must meet the certification basis of the airplane and the approval must specifically refer to this AD. Accomplishment of the applicable repair terminates the repetitive inspections required by paragraphs (g) and (h) of this AD for the repaired area only. Guidance on repairing the cracking can be found in the applicable SRM specified in paragraphs (k)(1) through (k)(4) of this AD.

(1) For Model 737-100, -200 series airplanes: Figure 48, General Fuselage Skin Repair, of Subject 53-30-3, Skin Repair, of Chapter 53, Fuselage, of the Boeing 737-100/-200 SRM D6-15565, Revision 102, dated September 10, 2010.

(2) For Model 737-300 series airplanes: Repair 31, General Fuselage Skin Repairs, of Subject 53-00-01, Fuselage Skin—General, of Chapter 53, Fuselage, of the Boeing 737-300 SRM D6-37635, Revision 92, dated November 10, 2010.

(3) For Model 737-400 series airplanes: Repair 31, General Fuselage Skin Repairs, of Subject 53-00-01, Fuselage Skin—General, of Chapter 53, Fuselage, of the Boeing 737-400 SRM D6-38246, Revision 75, dated November 10, 2010.

(4) For Model 737-500 series airplanes: Repair 31, General Fuselage Skin Repairs, of Subject 53-00-01, Fuselage Skin—General, of Chapter 53, Fuselage, of the Boeing 737-500 SRM D6-38441, Revision 70, dated November 10, 2010.

(l) Retained Follow-On and Corrective Actions

This paragraph restates the requirements of paragraph (f) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), with revised service information. If a time-limited repair is done, as specified in paragraph (j)(1)(i) or (j)(2)(i) of this AD: Do the actions specified in paragraphs (l)(1), (l)(2), and (l)(3) of this AD, at the times specified in paragraphs (l)(1), (l)(2), and (l)(3) of this AD, in accordance with the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in accordance with the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009.

(1) Within 3,000 flight cycles after doing the repair: Do the actions specified in paragraph (l)(1)(i) or (l)(1)(ii) of this AD. Then repeat the applicable inspection specified in paragraph (l)(1)(i) or (l)(1)(ii) of this AD 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. As of the effective date of this AD, do only the inspections specified in paragraph (l)(1)(ii) of this AD.

(i) For repairs done before the effective date of this AD: Do a detailed inspection of the repaired area for loose fasteners in accordance with Part 4 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001, or do the actions specified in paragraph (l)(1)(ii) of this AD. If any loose fastener is found, before further flight, replace with a new fastener, in accordance with the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001.

(ii) For repairs done after the effective date of this AD: Do a detailed inspection of the repaired area for loose, damaged, and missing fasteners, in accordance with Part 6 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. If any loose, missing, or damaged fastener is found, before further flight, replace with a new fastener, in accordance with the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009.

(2) At the applicable time specified in paragraph (l)(2)(i) and (l)(2)(ii) of this AD: Do inspections of the repaired area for cracking in accordance with Part 4 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in accordance with Part 6 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. If any cracking is found, before further flight, repair in accordance with a method approved by the Manager, Seattle ACO, or in accordance with data meeting the type certification basis of the airplane if it is approved by the Boeing Commercial Airplanes ODA or any other person authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved the repair must meet the certification basis of the airplane and the approval must specifically refer to this AD.

(i) For repairs done before the effective date of this AD: Within 4,000 flight cycles after doing the repair, do the inspections.

(ii) For repairs done on or after the effective date of this AD: Within 3,000 flight cycles after doing the repair, do the inspections.

(3) At the earlier of the times specified in paragraphs (l)(3)(i) and (l)(3)(ii) of this AD: Make the repair permanent in accordance with Part 4 and Figure 20 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001, or do the permanent repair, in accordance with Part 5 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, which ends the repetitive inspections for the repaired area only. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, may be used to make the repair permanent.

(i) Within 10,000 flight cycles after doing the repair in accordance with Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001.

(ii) At the later of the times specified in paragraphs (l)(3)(ii)(A) and (l)(3)(ii)(B) of this AD.

(A) Within 6,000 flight cycles after doing the repair.

(B) Within 1,000 flight cycles after the effective date of this AD.

(m) Retained Optional Terminating Action for Repetitive Eddy Current Inspections

This paragraph restates the requirements of paragraph (g) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), with revised service information. Accomplishment of paragraph (b) or (c), as applicable, of AD 2003-14-06, Amendment 39-13225 (68 FR 42956, July 21, 2003), before the effective date of this AD ends the repetitive eddy current inspections required by paragraph (g) of this AD for that skin panel only; however, the repetitive external detailed inspections required by paragraph (g) of this AD are still required for all areas. Accomplishing paragraph (b) or (c), as applicable, of AD 2003-14-06, on or after the effective date of this AD, does not end either the repetitive detailed or eddy current inspections required by paragraph (g) of this AD.

(n) Retained Credit for Previous Actions

This paragraph restates the provisions of paragraph (h) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004). This paragraph provides credit for actions specified by paragraphs (g), (h), (i), (j), (k), and (l) of this AD, if those actions were done before October 13, 2004 (the effective date of AD 2004-18-06), using Boeing Alert Service Bulletin 737-53A1210, dated December 14, 2000 (which is not incorporated by reference in this AD).

(o) Retained Exception to Service Bulletin Procedures

This paragraph restates the provision of paragraph (i) of AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), with revised service information. For airplanes subject to the requirements of paragraphs (g) and (h) 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, or forward and aft of the chem-milled step, or repairs that have a minimum of 2 rows of fasteners above and below, or forward and aft of the chem-milled step, and have been installed in accordance with the requirements of paragraph (k) of this AD. 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, or forward and aft, or does not have a minimum of 2 rows of fasteners above and below, and have been installed in accordance with the requirements of paragraph (k) of this AD: In lieu of requesting approval for an alternative method of compliance (AMOC), one option to comply with the inspection requirement of paragraphs (g) and (h) of this AD is to inspect all chem-milled steps covered by the repair using the method specified in the notes in Tables 1 through 6 of paragraph 1.E., “Compliance,” and in accordance with the Work Instructions, of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009.

(p) For Certain Airplanes: New Repetitive External Detailed and Eddy Current Inspections of the Crown Area and Other Known Areas of Fuselage Skin Cracking, and Corrective Actions

For Groups 1 through 5 and Groups 9 through 21 airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, on which the inspections required by paragraph (g) of this AD have been done before the effective date of this AD: Within 4,500 flight cycles after doing the most recent inspection required by paragraph (g) of this AD, or within 1,800 flight cycles after the effective date of this AD, whichever is earlier; do external detailed and eddy current inspections of the crown area and other known areas of the fuselage skin cracking, in accordance with Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009; except as provided by paragraph (o) of this AD. Repeat the external detailed and eddy current inspections thereafter at intervals not to exceed 1,800 flight cycles. Accomplishing the inspections required by this paragraph ends the repetitive inspections required by paragraph (g) of this AD. Before further flight, do all applicable corrective actions as specified in paragraph (j) of this AD. For the locations specified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, in lieu of doing detailed inspections, operators may do general visual inspections, provided that the general visual inspections are done at intervals not to exceed 1,000 flight cycles.

(q) For Certain Other Airplanes: New Repetitive External Detailed and Eddy Current Inspections of the Crown Area and Other Known Areas of Fuselage Skin Cracking, and Corrective Actions

For Groups 1 through 5 and 9 through 21 airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, on which the inspections required by paragraph (g) of this AD have not been done before the effective date of this AD: Before the accumulation of 28,000 total flight cycles, or within 1,800 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, in accordance with Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as provided by paragraph (o) of this AD. Repeat the external detailed and eddy current inspections thereafter at intervals not to exceed 1,800 flight cycles. Accomplishing the inspections required by this paragraph ends the repetitive inspections required by paragraph (g) of this AD. Before further flight, do all applicable corrective actions as specified in paragraph (j) of this AD. For the locations specified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, in lieu of doing detailed inspections, operators may do general visual inspections, provided that the general visual inspections are done at intervals not to exceed 1,000 flight cycles.

(r) New Repetitive External Detailed and Eddy Current Inspections of the Fuselage Skin Along the Chem-Milled Steps of the Butt Joints, and Corrective Actions

For Groups 1 through 5, and 9 through 21 airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009: At the later of the times specified in paragraphs (r)(1) and (r)(2) of this AD, do external detailed and eddy current inspections for vertical cracks in the fuselage skin along the chem-milled steps of the butt joints, in accordance with Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as provided by paragraph (o) of this AD. Repeat the inspections thereafter at intervals not to exceed 1,800 flight cycles. If any cracking is found, before further flight, repair in accordance with Part 5 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. Doing the repair terminates the repetitive inspections specified in this paragraph for the repaired area only.

(1) Before the accumulation of 55,000 total flight cycles or 55,000 total flight hours, whichever occurs first.

(2) Within 1,800 flight cycles after the effective date of this AD.

(s) New Repetitive Detailed and Eddy Current Inspections Along the Chem-Milled Lines of the Fuselage Skin of the Lower Lobe Area and Section 41, and Corrective Actions

For Groups 1 through 21 airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009: At the applicable time specified in paragraph (s)(1) or (s)(2) of this AD, do external detailed and eddy current inspections, as applicable, for horizontal cracks along the chem-milled lines of the fuselage skin of the lower lobe area and section 41, in accordance with Part 4 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as provided by paragraphs (o) and (x) of this AD. Repeat the inspections thereafter at intervals not to exceed 1,800 flight cycles. Accomplishing the inspections required by this paragraph ends the inspections required by paragraph (h) of this AD. Before further flight, do all applicable corrective actions as specified in paragraph (j) of this AD. For the locations specified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, in lieu of doing detailed inspections, operators may do general visual inspections, provided that the general visual inspections are done at intervals not to exceed 1,000 flight cycles.

(1) Before the accumulation of 35,000 total flight cycles.

(2) Within 9,000 flight cycles after the most recent inspection required by paragraph (h) of this AD, or within 1,800 flight cycles after the effective date of this AD, whichever is earlier.

(t) For Certain Airplanes: New Repetitive External Detailed and Eddy Current Inspections Along the Chem-Milled Lines of the Fuselage Skin of the Window Belt Area, and Corrective Actions

For Groups 4, 11, and 16 airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009: Before the accumulation of 25,000 total flight cycles or within 1,800 flight cycles after the effective date of this AD, whichever is later, do external detailed and eddy current inspections for horizontal cracks along the chem-milled lines of the fuselage skin of the fuselage window belt area, in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as provided by paragraph (o) of this AD. Repeat the inspections thereafter at intervals not to exceed 1,800 flight cycles. If any cracking is found, before further flight, repair using a method approved in accordance with the procedures specified in paragraph (y) of this AD. Doing the repair terminates the repetitive inspections specified in this paragraph for the repaired area only.

(u) For Certain Other Airplanes: New Repetitive External Detailed and Eddy Current Inspections Along the Chem-Milled Lines of the Fuselage Skin of the Window Belt Area, and Corrective Actions

For Groups 3, 5, 9, 10, 12, 14, 15, 17, 18, 19, 20, and 21 airplanes identified in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009: Do the actions specified in paragraph (u)(1) or (u)(2) of this AD, as applicable. Part 7 (Figure 10) of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, specifies applying corrosion inhibiting compound (CIC) Boeing Material Specification (BMS) 3-23 to the surfaces of the repaired area. As an option to using CIC BMS 3-23, operators may use CIC BMS 3-35, which is equivalent to CIC BMS 3-23.

(1) For airplanes on which the inspections required by paragraph (g) of this AD have been done before the effective date of this AD: Within 4,500 flight cycles after doing the most recent inspection required by paragraph (g) of this AD, or within 1,800 flight cycles after the effective date of this AD, whichever is earlier, do external detailed and eddy current inspections for horizontal cracks along the chem-milled lines of the fuselage skin of the fuselage window belt area, in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as provided by paragraph (o) of this AD. Repeat the inspections thereafter at intervals not to exceed 1,800 flight cycles. If any cracking is found, before further flight, repair in accordance with Part 8 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as required by paragraph (x) of this AD.

(2) For airplanes on which the inspections required by paragraph (g) of this AD have not been done before the effective date of this AD: Before the accumulation of 25,000 total flight cycles or within 1,800 flight cycles after the effective date of this AD, whichever is later, do external detailed and eddy current inspections for horizontal cracks along the chem-milled lines of the fuselage skin of the fuselage window belt area, in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. Repeat the inspections thereafter at intervals not to exceed 1,800 flight cycles. If any cracking is found, before further flight, repair in accordance with Part 8 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as required by paragraph (x) of this AD.

(v) New Optional Repair

For airplanes on which cracking is found during any inspection required by paragraph (p), (q), (r), or (s) of this AD, as applicable, doing the repair of the chem-milled area in the skin, as specified in Part 5 or Part 6 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, ends the repetitive external detailed and eddy current inspections required by paragraph (p), (q), (r), or (s) of this AD, as applicable, for the repaired area only.

Note 1 to paragraph (v) of this AD: Part 8 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, specifies a post-repair inspection of the skin chem-milled crack repair at stringer 12; that inspection is not required by this AD. The damage tolerance inspections specified in Table 7 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, may be used in support of compliance with section 121.1109(c)(2) or 129.109(c)(2) of the Code of Federal Regulations (14 CFR 121.1109(c)(2) or 14 CFR 129.109(c)(2)).

(w) New Optional Preventive Modification at Stringer 12

For airplanes on which no cracking is found during any inspection required by paragraph (u) of this AD, doing the preventive modification of the chem-milled areas in the skin at stringer 12, as specified in Part 7 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, except as required by paragraph (x) of this AD, ends the repetitive external detailed and eddy current inspections required by paragraph (u) of this AD, for the modified areas common to stringer 12 only. Part 7 (Figure 10) of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, specifies applying CIC BMS 3-23 to the surfaces of the repaired area. As an option to using CIC BMS 3-23, operators may use CIC BMS 3-35, which is equivalent to CIC BMS 3-23.

(x) Exception to Service Information

Where Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009, specifies to contact Boeing for repair instructions, before further flight, repair using a method approved in accordance with the procedures specified in paragraph (y) of this AD.

(y) Alternative Methods of Compliance (AMOCs)

(1) The Manager, Seattle ACO, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the ACO, send it to the attention of the person identified in paragraph (z)(1) of this AD. Information may be emailed to: [e-mail].

(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office.

(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD if it is approved by the Boeing Commercial Airplanes ODA that has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD.

(4) AMOCs approved previously in accordance with AD 2004-18-06, Amendment 39-13784 (69 FR 54206, September 8, 2004), are approved as AMOCs for the corresponding provisions of this AD.

(5) Inspections and corrective actions required by paragraph (g) of AD 2009-21-01, Amendment 39-16038 (74 FR 52395, October 13, 2009), are approved as AMOCs for the corresponding provisions of paragraph(s) of this AD, but only for the areas of the lower lobe skin identified in AD 2009-21-01.

(z) Related Information

(1) For more information about this AD, contact Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue SW., Renton, Washington 98057-3356; phone: [phone]; fax: [phone]; email: [e-mail].

(2) Service information that is referenced in this AD that is not incorporated by reference in this AD may be obtained at the addresses identified in paragraphs (aa)(5) and (aa)(6) of this AD.

(aa) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference (IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) You must use this service information as applicable to do the actions required by this AD, unless the AD specifies otherwise.

(3) The following service information was approved for IBR on November 6, 2013.

(i) Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009.

(ii) Figure 48, General Fuselage Skin Repair, of Subject 53-30-3, Skin Repair, of Chapter 53, Fuselage, of the Boeing 737-100/-200 SRM D6-15565, Revision 102, dated September 10, 2010. The revision level of this document is identified in only the transmittal letter; no other page of the document contains this information.

(iii) Repair 31, General Fuselage Skin Repairs, of Subject 53-00-01, Fuselage Skin—General, of Chapter 53, Fuselage, of the Boeing 737-300 SRM D6-37635, Revision 92, dated November 10, 2010. The revision level of this document is identified in only the transmittal letter; no other page of the document contains this information.

(iv) Repair 31, General Fuselage Skin Repairs, of Subject 53-00-01, Fuselage Skin—General, of Chapter 53, Fuselage, of the Boeing 737-400 SRM D6-38246, Revision 75, dated November 10, 2010. The revision level of this document is identified in only the transmittal letter; no other page of the document contains this information.

(v) Repair 31, General Fuselage Skin Repairs, of Subject 53-00-01, Fuselage Skin—General, of Chapter 53, Fuselage, of the Boeing 737-500 SRM D6-38441, Revision 70, dated November 10, 2010. The revision level of this document is identified in only the transmittal letter; no other page of the document contains this information.

(4) The following service information was approved for IBR on October 13, 2004 (69 FR 54206, September 8, 2004).

(i) Boeing Alert Service Bulletin 737-53A1210, Revision 1, excluding Appendix A, dated October 25, 2001.

(ii) Reserved.

(5) For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone [phone], extension 1; fax [phone]; Internet https://www.myboeingfleet.com.

(6) You may view this service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For information on the availability of this material at the FAA, call 425-227-1221.

(7) You may view this service information that is incorporated by reference 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/​cfr/​ibr-locations.html.

Issued in Renton, Washington, on August 16, 2013.

Jeffrey E. Duven,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.