2011-30603. Airworthiness Directives; The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to supersede two existing airworthiness directives (AD) that apply to 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. Since we issued those ADs, we have received 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. This proposed AD would require additional airplanes to do the inspection for cracking under the stop fittings; extend the repetitive interval for certain airplanes; add a one-time inspection to detect missing fasteners; and update or add certain inspection and repair instructions. This proposed AD would also require, for certain airplanes, repetitive inspections of the cargo barrier net fitting for cracking and repair if necessary. This proposed AD would also add, for certain airplanes, repetitive inspections for cracking of the S-15L aft intercostal, and repair if necessary. We are proposing 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:

We must receive comments on this proposed AD by January 12, 2012.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590.
• Hand Delivery: Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

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]; email [e-mail]; 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 [phone].

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 proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (phone: [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

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:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2011-1255; Directorate Identifier 2010-NM-182-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

On April 20, 2004, we issued AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004), for all Boeing Model 737-200C series airplanes. That AD requires 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. That AD resulted from a report of cracks in the STA 348.2 frame on a Boeing Model 737-200C series airplane. We issued that 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 the loss of the forward entry door and rapid decompression of the airplane.

On July 23, 2009, we issued AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), for certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD requires repetitive inspections of the intercostal webs, attachment clips, and stringer splice channels for cracks; and corrective action if necessary. That AD resulted from reports of fatigue cracks on several Boeing Model 737-200 series airplanes. We issued that AD to detect and correct fatigue cracking of the intercostals on the forward and aft sides of the forward entry door, which could result in loss of the forward entry door and rapid decompression of the airplane.

Actions Since Existing ADs Were Issued

Since we issued AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004), we have received reports of cracking above the two outboard fasteners attaching the frame inner chord and door stop fitting of the STA 348.2 frame at S-15L. The cracking was reported on seven airplanes that had accumulated between 19,185 and 64,800 flight cycles (AD 2004-09-09 applies only to Model 737-200C airplanes). Cracking has also been found in the outboard chord at S-16L. In addition, we have received reports of 10 airplanes with missing fasteners in the STA 348.2 frame inner chord at S-7L through S-15L.

In addition, the requirement to inspect the intercostal on the aft side at S-14L to S-16L is common to both 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). Service history indicates that the repetitive inspection interval of 6,000 flight cycles for that area, as required by AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), is adequate to ensure continued operational safety. The repetitive interval required by AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004), is 4,500 flight cycles.

Boeing Commercial Airplanes has received a Organization Designation Authorization (ODA). We have revised paragraph (h) of this proposed AD to delegate the authority to approve an alternative method of compliance for any repair required by this AD to the Boeing Commercial Airplanes ODA rather than a Designated Engineering Representative (DER).

Relevant Service Information

We reviewed Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010. The procedures in Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, differ from those in 737-53A1204, Revision 1, dated March 26, 2007 (the appropriate source of service information for AD 2009-16-14 (74 FR 38901, August 5, 2009)), as follows:

• Repetitive detailed and high frequency eddy current (HFEC) inspections for cracking of the S-15L aft intercostal between body station (BS) 348.2 and BS 360 and a detailed inspection of the cargo barrier net fitting at the intercostal are added for Model 737-200C airplanes.
• New repair instructions are added for cracking found at the S-14L, S-15L, and S-16L intercostals. The repair includes either doing actions specified in Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010 (described below), or, if a crack is at the S-15L aft intercostal or the damage at other intercostal locations is outside certain parameters covered in Boeing Alert Service Bulletin 737-53A1240, Revision 1, Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, specifies contacting Boeing for repair instructions.

We also reviewed Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010. The procedures in Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, differ from those in Boeing Alert Service Bulletin 737-53A1240, dated April 10, 2003 (the appropriate source of service information for AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004)), as follows:

• All Model 737-100, -200, -300, -400, and -500 series airplanes (i.e., line numbers 1 through 3132) are added to the effectivity. For these airplanes, the service bulletin specifies procedures for inspecting under the stop fitting by doing HFEC and surface eddy current inspections for cracking of the frame, HFEC inspections for cracking of the reinforcement angle and shear web, and doing a detailed inspection for cracking of the STA 348.2 frame outer chord, inner chord, and reinforcement angle, and corrective actions if necessary. The corrective actions include replacing certain cracked parts with new parts, and if a crack is found in the frame outer chord, contacting Boeing for repair instructions and doing the repair.
• For Model 737-200C airplanes, the repetitive interval for the HFEC inspection of the STA 348.2 frame is extended from 4,500 flight cycles to 6,000 flight cycles.
• For Model 737-100, -200, -300, -400, and -500 series airplanes, a one-time detailed inspection is added to detect missing fasteners of the STA 348.2 frame inner chord at S-7L through S-15L. If any fastener is missing, the service bulletin specifies to contact Boeing for repair instructions.
• For all airplanes, intercostal inspections for cracking between STA 348.2 and STA 360 are now specified in Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010. Previously, for the intercostals at S-14 through S-16L, this inspection was common to both Boeing Alert Service Bulletin 737-53A1204 and Boeing Alert Service Bulletin 737-53A1240 for Model 737-200C airplanes.
• For Group 3 airplanes, instructions are added for repair of the STA 348.2 frame inner chord, reinforcement angle, and shear web; and of the door stop intercostals at S-14L through S16L.

FAA's Determination

We are proposing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.

Proposed AD Requirements

This proposed AD would retain certain requirements of 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). This proposed AD would add airplanes to the applicability for the HFEC inspection for cracking of the stop fittings at the shear web at 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. This proposed AD would also require accomplishing the actions specified in the service information described previously.”

Changes to Existing ADs

Since those ADs were issued, the AD format has been revised, and certain paragraphs have been rearranged. As a result, the corresponding paragraph identifiers have changed in this proposed AD, as listed in the following tables:

Revised Paragraph Identifiers

Requirement in AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004)	Corresponding requirement in this proposed AD
paragraph (a)	paragraph (g)
paragraph (b)	paragraph (h)

Requirement in AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009)	Corresponding requirement in this proposed AD
paragraph (f)	paragraph (i)
paragraph (g)	paragraph (j)
paragraph (h)	paragraph (k)
paragraph (i)	paragraph (l)
paragraph (j)	paragraph (m)
paragraph (k)	paragraph (n)
paragraph (l)	paragraph (o)

Costs of Compliance

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

We estimate the following costs to comply with this proposed 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 proposed 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 proposed 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	24 work-hours	$11,856	$13,896.

According to the manufacturer, some of the costs of this proposed 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 proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify that the proposed regulation:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979),

(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

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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:

The Boeing Company: Docket No. FAA-2011-1255; Directorate Identifier 2010-NM-182-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by January 12, 2012.

Affected ADs

(b) 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).

Applicability

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

Subject

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

Unsafe Condition

(e) 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.

Compliance

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

Restatement of the Requirements of AD 2004-09-09, Amendment 39-13598 (69 FR 23646, April 30, 2004) With Revised Service Information and Extended Repetitive Intervals

Initial and Repetitive Inspections at STA 348.2 for Model 737-200C Series Airplanes

(g) 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, Amendment 39-13598 (69 FR 23646, April 30, 2004)), 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 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.

Corrective Action for Paragraph (g) of This AD

(h) 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 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.

Restatement of the Requirements of AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009) With Revised Service Information

Initial Compliance Time

(i) 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) 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, Amendment 39-15987 (74 FR 38901, August 5, 2009)), whichever occurs later, do the inspection required by paragraph (m) of this AD.

Initial Inspection for Group 1 Configuration Airplanes

(k) 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 and until the effective date of this AD, Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or Revision 2, dated June 24, 2010; may be used. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, may be used.

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

(l) 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 and until the effective date of this AD, Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or Revision 2, dated June 24, 2010; may be used. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, may be used.

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

(m) 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.

Repeat Inspections

(n) 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, whichever occurs later.

Exceptions to Boeing Special Attention Service Bulletin 737-53A1204

(o) 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, and until the effective date of this AD, Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; or Revision 2, dated June 24, 2010; may be used. As of the effective date of this AD, only Boeing Alert Service Bulletin 737-53A1204, Revision 2, dated June 24, 2010, may be used.

(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. 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 the 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)).

New Requirements of This AD

One-Time Inspection for Missing Fasteners at STA 348.2

(p) 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.

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

(q) 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, 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.

Exception to Boeing Alert Service Bulletin 737-53A1240

(r) Where Boeing Alert Service Bulletin 737-53A1240, Revision 1, dated June 29, 2010, specifies that for the instructions identified in paragraph 3.B., Work Instructions, and the Figure(s) which give the recommended sequence of steps, the sequence of the steps to do the service bulletin can be changed; the requirements in this AD do not allow the sequence of the steps to be changed.

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

(s) 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 at intervals not to exceed 6,000 flight cycles.

Alternative Methods of Compliance (AMOCs)

(t)(1) The Manager, Seattle Aircraft Certification Office (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 for 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 for AD 2009-16-14, Amendment 39-15987 (74 FR 38901, August 5, 2009), are approved as AMOCs for the corresponding requirements of this AD.

Related Information

(u) 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) 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]; email [e-mail]; 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 [phone].

Issued in Renton, Washington, on November 18, 2011.

John P. Piccola,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.