2012-14373. Airworthiness Directives; The Boeing Company Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule.

SUMMARY:

We are superseding two existing airworthiness directives (ADs) for certain Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. The first existing AD currently requires, for certain airplanes, repetitive inspections of the Station (STA) 348.2 frame to detect cracking under the stop fittings and intercostal flanges at stringers S-14L, S-15L, and S-16L, and corrective action if necessary. The second existing AD currently requires repetitive inspections to detect cracking of the intercostal webs, attachment clips, and stringer splice channels, and corrective action if necessary. This new AD requires that the inspection for cracking under the stop fittings be done on additional airplanes; extends the repetitive interval for certain airplanes; adds a one-time inspection to detect missing fasteners; and updates or adds certain inspection and repair instructions. This new AD also requires, for certain airplanes, repetitive inspections of the cargo barrier net fitting for cracking, and repair if necessary. This new AD also adds, for certain airplanes, repetitive inspections for cracking of the stringer S-15L aft intercostal, and repair if necessary. This AD was prompted by reports of cracking of the STA 348.2 frame above the two outboard fasteners attaching the frame inner chord and door stop fittings, and in the outboard chord at stringer S-16L. We have also received reports of missing fasteners in the STA 348.2 frame inner chord. We are issuing this AD to detect and correct fatigue cracking of the intercostals on the forward and aft sides of the forward entry door cutout, which could result in loss of the forward entry door and rapid decompression of the airplane.

DATES:

This AD is effective July 23, 2012.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in the AD as of July 23, 2012.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of September 9, 2009 (74 FR 38901, August 5, 2009).

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of November 1, 2005 (70 FR 56361, September 27, 2005).

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of June 4, 2004 (69 FR 23646, April 30, 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:

Alan Pohl, 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 notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede airworthiness directives AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004); and AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009). Those ADs apply to the specified products. The NPRM published in the Federal Register on November 28, 2011 (76 FR 72858). The NPRM proposed to retain certain requirements of AD 2004-09-09 and AD 2009-16-14. The NPRM proposed to also add airplanes to the applicability for the high frequency eddy current (HFEC) inspection for cracking of the stop fittings at the shear web at the STA 348.2 frame; extend the repetitive interval for the HFEC inspection of the STA 348.2 frame for Model 737-200C airplanes; add an inspection to detect missing fasteners of the STA 348.2 frame inner chord; and update or add certain inspection and repair instructions.

Comments

We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the proposal (76 FR 72858, November 28, 2011) and the FAA's response to each comment.

Support for NPRM (76 FR 72858, November 28, 2011)

Boeing concurs with the contents of the NPRM (76 FR 72858, November 28, 2011).

Requests To Remove or Revise Exception to Certain Service Information

Southwest Airlines (SWA) asked that paragraph (r) of the NPRM (76 FR 72858, November 28, 2011) be removed, or revised to provide clarification. SWA stated that the exception specified in paragraph (r) of the NPRM does not allow the sequence of steps in the Work Instructions of Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, to be changed. SWA added that it has serious concerns that this paragraph effectively eliminates all flexibility when accomplishing open access, the order of which locations get inspected, and close access. SWA noted that this becomes very difficult in a maintenance environment where other activities may be worked concurrently. SWA asked if the intent of the exception in paragraph (r) of the NPRM is to make removing the windscreen before the lavatory and removing the fasteners identified in Circle Note 1 prior to removing the fasteners identified in Circle Note 2 conditions of compliance. SWA understands that certain steps contained in Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, might have to be accomplished in a specific order. However, SWA noted that the umbrella restriction imposed by paragraph (r) of the NPRM goes beyond that intent and results in restrictions when performing maintenance.

Scandanavian Airlines Systems (SAS) asked that we include an option of removing the shear web before accomplishing the inspection specified in Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, as part of the access procedures specified in the NPRM (76 FR 72858, November 28, 2011). SAS stated that it has previously accomplished the inspections as an alternative method of compliance (AMOC) to AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009). SAS noted that it also received clarification from the manufacturer regarding the shear web removal step in Parts 1 and 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010. SAS stated that the shear web removal is not part of the inspection procedures specified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007.

We agree with the commenters for the reasons provided. We have revised paragraph (r) of this AD accordingly.

Request To Include Reference to Previously Approved AMOCs

SWA asked that we include a reference to AMOCs approved for AD 2005-20-03, Amendment 39-14296 (70 FR 56361, September 27, 2005) in the NPRM (76 FR 72858, November 28, 2011). SWA pointed out that paragraph (m)(4) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), stated that “AMOCs approved previously in accordance with AD 2005-20-03 are approved as AMOCs for the corresponding provisions of this AD, provided the repetitive inspection intervals (if any) do not exceed 6,000 flight cycles.” SWA specified that paragraph (t)(5) of the NPRM can be interpreted to mean that an AMOC issued for AD 2005-20-03, which was approved as an AMOC to AD 2009-16-14, will be considered as an AMOC to the NPRM.

We agree with the commenter that AMOCs approved for AD 2005-20-03, Amendment 39-14296 (70 FR 56361, September 27, 2005), as specified in paragraph (m)(4) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), are still approved for the corresponding requirements of this AD. For clarity, we have added a new paragraph (t)(5) to this AD to include that information, and we reidentified the existing paragraph (t)(5) of the NPRM (76 FR 72858, November 28, 2011) as paragraph (t)(6) in this final rule.

Explanation of Additional Changes Made to This AD

We have clarified the compliance time in paragraph (q) of this AD by adding the phrase “whichever occurs later.”

We have updated certain headings throughout this AD.

Conclusion

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

• Are consistent with the intent that was proposed in the NPRM (76 FR 72858, November 28, 2011) for correcting the unsafe condition; and
• Do not add any additional burden upon the public than was already proposed in the NPRM (76 FR 72858, November 28, 2011).

Costs of Compliance

We estimate that this AD affects 581 airplanes of U.S. registry.

We estimate the following costs to comply with this AD:

Estimated Costs

Action	Labor cost	Parts cost	Cost per product	Cost on U.S. operators
Inspections for cracking under the stop fittings and intercostal flanges [retained from AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004)]	18 work-hours × $85 per hour = $1,530 per inspection cycle	$0	$1,530 per inspection cycle	$888,930 per inspection cycle.
Inspection of areas forward of the aft entry door [retained from AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009)]	2 work-hours × $85 per hour = $170 per inspection cycle	0	$170 per inspection cycle	$98,770 per inspection cycle.
Inspection of areas aft of the forward entry door [retained from AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009)]	1 work-hour × $85 per hour = $85 per inspection cycle	0	$85 per inspection cycle	$49,385 per inspection cycle.
Inspection for missing fasteners [new action]	1 work-hour × $85 per hour = $85	476	$561	$325,941.

We estimate the following costs to do any necessary repairs that would be required based on the results of the inspections. We have no way of determining the number of aircraft that might need these repairs:

On-Condition Costs

Action	Labor cost	Parts cost	Cost per product
Repair of cracking if done in accordance with a method approved by the FAA	Unknown	Unknown	Unknown.
Repair of cracking if done in accordance with Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010	24 work-hours	$11,856	$13,896.

According to the manufacturer, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. We do not control warranty coverage for affected individuals. As a result, we have included all costs in our cost estimate.

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 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) 2004-09-09, Amendment 39-13598 ( 69 FR 23646, April 30, 2004); and AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009); and adding the following new AD:

2012-12-05 The Boeing Company: Amendment 39-17084; Docket No. FAA-2011-1255; Directorate Identifier 2010-NM-182-AD.

(a) Effective Date

This airworthiness directive (AD) is effective July 23, 2012.

(b) Affected ADs

This AD supersedes AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004); and AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009).

(c) Applicability

This AD applies to all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category.

(d) Subject

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

(e) Unsafe Condition

This AD was prompted by reports of cracking of the station (STA) 348.2 frame above the two outboard fasteners attaching the frame inner chord and door stop fittings, and in the outboard chord at stringer S-16L. We have also received reports of missing fasteners in the STA 348.2 frame inner chord. We are issuing this AD to detect and correct fatigue cracking of the intercostals on the forward and aft sides of the forward entry door cutout, which could result in loss of the forward entry door and rapid decompression of the airplane.

(f) Compliance

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

(g) Retained Initial and Repetitive Inspections at STA 348.2 for Model 737-200C Series Airplanes

This paragraph restates the requirements of paragraph (a) of AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004), with revised service information. For Model 737-200C series airplanes: Except as provided by paragraph (h) of this AD, prior to the accumulation of 46,000 total flight cycles, or within 2,250 flight cycles after June 4, 2004 (the effective date of AD 2004-09-09), whichever occurs later, do detailed and eddy current inspections of the STA 348.2 frame for cracking under the stop fittings and intercostal flanges at stringers 14L, 15L, and 16L by accomplishing paragraphs 3.A and 3.B.1 through 3.B.7 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1240, dated April 10, 2003; or by accomplishing Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010. Do the actions in accordance with Boeing Alert Service Bulletin 737-53A1240, dated April 10, 2003; or Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010. Any applicable repair must be accomplished prior to further flight. Repeat the inspections thereafter at intervals not to exceed 6,000 flight cycles. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, may be used to accomplish the actions required by this paragraph.

(h) Retained Corrective Action for Paragraph (g) of This AD

This paragraph restates the requirements of paragraph (b) of AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004), with revised service information. If any crack is found during any inspection required by paragraph (g) of this AD, and Boeing Alert Service Bulletin 737-53A1240, dated April 10, 2003; or Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010; specifies to contact Boeing for appropriate action: Before further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or using a method approved in accordance with the procedures specified in paragraph (t) of this AD.

(i) Retained Initial Compliance Time for Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

This paragraph restates the requirements of paragraph (f) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009). For all Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, as identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007: Before the accumulation of 15,000 total flight cycles, or within 4,500 flight cycles after November 1, 2005 (the effective date of AD 2005-20-03, Amendment 39-14296 (70 FR 56361, September 27, 2005)), whichever occurs later: Do the inspections required by paragraphs (k) and (l) of this AD.

(j) Retained Initial Compliance Time for Model 737-200C Series Airplanes

This paragraph restates the requirements of paragraph (g) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009). For all Model 737-200C series airplanes, as identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007: Before the accumulation of 15,000 total flight cycles, or within 4,500 flight cycles after September 9, 2009 (the effective date of AD 2009-16-14), whichever occurs later, do the inspection required by paragraph (m) of this AD.

(k) Retained Initial Inspection for Group 1 Configuration Airplanes

This paragraph restates the requirements of paragraph (h) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), with revised service information. For Group 1 airplanes identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007: Perform a detailed inspection for cracking of the intercostal web, attachment clips, and stringer splice channels; and a high frequency eddy current (HFEC) inspection for cracking of the stringer splice channels located forward and aft of the forward entry door; and do all applicable corrective actions before further flight; in accordance with Parts 1 and 2 of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003, or Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or in accordance with Parts 1, 2, 4, and 5 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010. After September 9, 2009 (the effective date of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), and until the effective date of this AD, Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010; may be used to accomplish the actions required by this paragraph. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, may be used to accomplish the actions required by this paragraph.

(l) Retained Initial Inspection for Cargo Configuration Airplanes (Forward of the Forward Entry Door)

This paragraph restates the requirements of paragraph (i) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), with revised service information. For Group 2 cargo airplanes identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007: Perform a detailed inspection for cracking of the intercostal webs and attachment clips located forward of the forward entry door, and do all applicable corrective actions before further flight, in accordance with Part 3 of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003, or Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or in accordance with Part 3 of Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010. After September 9, 2009 (the effective date of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), and until the effective date of this AD, Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010; may be used to accomplish the actions required by this paragraph. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, may be used to accomplish the actions required by this paragraph.

(m) Retained Initial Inspection for Cargo Configuration Airplanes (Aft of the Forward Entry Door)

This paragraph restates the requirements of paragraph (j) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), with revised service information. For Group 2 cargo airplanes identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007: Perform a detailed inspection for cracking of the intercostal webs and attachment clips located aft of the forward entry door, and do all applicable corrective actions before further flight, in accordance with Part 4 of the Work Instructions of Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or in accordance with Part 3 of Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, may be used to accomplish the actions required by this paragraph.

(n) Retained Repeat Inspections

This paragraph restates the requirements of paragraph (k) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009). Repeat the inspections required by paragraphs (k), (l), and (m) of this AD thereafter at intervals not to exceed 6,000 flight cycles after the previous inspection, or within 3,000 flight cycles after September 9, 2009 (the effective date of AD 2009-1614), whichever occurs later.

(o) Retained Exceptions to Boeing Special Attention Service Bulletin 737-53-1204

This paragraph restates the requirements of paragraph (l) of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), with revised service information. Do the actions required by paragraphs (i), (j), (k), (l), (m), and (n) of this AD by accomplishing all the applicable actions specified in the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003; Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010; except as provided by paragraphs (o)(1) and (o)(2) of this AD. After September 9, 2009 (the effective date of AD 2009-16-14), and until the effective date of this AD, Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010; may be used to accomplish the actions required by this paragraph. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, may be used to accomplish the actions required by this paragraph.

(1) Where Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003; Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010; specifies to contact Boeing for repair instructions: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (t) of this AD.

(2) Where Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003; or Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; specifies a compliance time relative to the date of a service bulletin, this AD requires compliance relative to September 9, 2009 (the effective date of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009). Where Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003; or Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; specifies a compliance time relative to the date of the initial release of a service bulletin, this AD requires compliance relative to November 1, 2005 (the effective date of AD 2005-20-03, Amendment 39-14296 (70 FR 56361, September 27, 2005)).

(p) New One-Time Inspection for Missing Fasteners at STA 348.2

For Groups 2 and 3 airplanes identified in Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010: Within 4,500 flight cycles after the effective date of this AD, do a detailed inspection to detect missing fasteners of the STA 348.2 frame, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, except as required by paragraph (r) of this AD. If any fastener is missing, before further flight, repair using a method approved in accordance with the procedures specified in paragraph (t) of this AD.

(q) New Initial and Repetitive Inspections at STA 348.2 for Model 737-100, -200, -300, -400, and -500 Series Airplanes

For Groups 2 and 3 airplanes identified in Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010: Before the accumulation of 15,000 total flight cycles, or within 4,500 flight cycles after the effective date of this AD, whichever occurs later, do HFEC and surface eddy current inspections for cracking of the frame, HFEC inspections for cracking of the reinforcement angle and shear web, and a detailed inspection for cracking of the STA 348.2 frame outer chord, inner chord, and reinforcement angle, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, except as required by paragraph (r) of this AD. If any crack is found during any inspection required by this paragraph, before further flight, do all applicable corrective actions in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, except as required by paragraph (r) of this AD, and except where that service bulletin specifies to contact Boeing, before further flight, repair using a method approved in accordance with the procedures specified in paragraph (t) of this AD. Repeat the inspections thereafter at intervals not to exceed 6,000 flight cycles.

(r) New Exceptions to Boeing Alert Service Bulletins 737-53A1204 and 737-53A1240

(1) Note 1 of paragraph 3.A of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, is to be disregarded when accomplishing the actions required by this AD.

(2) The access and restoration instructions identified in the Work Instructions of Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010; and Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010; are not required by this AD. Operators may perform those actions in accordance with approved maintenance procedures.

(3) The use of Boeing Drawing 65-88700 is not allowed when accomplishing the actions required by this AD in accordance with the Work Instructions of Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010; and Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010.

(s) New Initial and Repetitive Inspections of the S-15L Aft Intercostal and Cargo Barrier Net Fitting for Model 737-200C Series Airplanes

For Group 2 airplanes identified in Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010: Before the accumulation of 15,000 total flight cycles, or within 4,500 flight cycles after the effective date of this AD, whichever occurs later, do initial detailed and HFEC inspections for cracking of the S-15L aft intercostal between BS 348.2 and BS 360, and do a detailed inspection of the cargo barrier net fitting at the intercostal, in accordance with Figure 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010. If any cracking is found, before further flight repair using a method approved in accordance with the procedures specified in paragraph (t) of this AD. Repeat the inspections thereafter at intervals not to exceed 6,000 flight cycles.

(t) 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, it 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 Organization Designation Authorization (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 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004), are approved as AMOCs for the corresponding requirements of this AD.

(5) AMOCs approved previously in accordance with AD 2005-20-03, Amendment 39-14296 (70 FR 56361, September 27, 2005), are approved as AMOCs for the corresponding requirements of this AD, provided the repetitive inspection intervals (if any) do not exceed 6,000 flight cycles.

(6) AMOCs approved previously in accordance with AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), are approved as AMOCs for the corresponding requirements of this AD.

(u) Related Information

For more information about this AD, contact Alan Pohl, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 1601 Lind Avenue SW., Renton, Washington 98057-3356; phone [phone]; fax [phone]; email: [e-mail].

(v) Material Incorporated by Reference

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

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

(3) The following service information was approved for IBR on July 23, 2012.

(i) Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010.

(ii) Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010.

(4) The following service information was approved for IBR on September 9, 2009 (74 FR 38901, August 5, 2009).

(i) Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007.

(5) The following service information was approved for IBR on November 1, 2005 (70 FR 56361, September 27, 2005).

(i) Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003.

(6) The following service information was approved for IBR on June 4, 2004 (69 FR 23646, April 30, 2004).

(i) Boeing Alert Service Bulletin 737-53A1240, dated April 10, 2003.

(7) 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.

(8) 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.

(9) You may also review copies of the 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 June 4, 2012.

Michael Kaszycki,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.