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[Federal Register Volume 77, Number 12 (Thursday, January 19, 2012)]
[Proposed Rules]
[Pages 2669-2674]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-859]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2011-1419; Directorate Identifier 2010-NM-281-AD]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to supersede an existing airworthiness directive 
(AD) that applies to certain The Boeing Company Model 737-300, -400, 
and -500 series airplanes. The existing AD currently requires 
repetitive inspections for cracking of the crown area of the fuselage 
skin, and corrective actions if necessary. Since we issued that AD, we 
received additional reports of cracking at the horizontal chem-mill 
steps away from the lap joints over the entire crown area, and vertical 
chem-mill cracks adjacent to the butt joints. This proposed AD would 
add repetitive inspections for cracking using different inspection 
methods and would inspect additional areas, and corrective actions if 
necessary. This proposed AD would also require additional repairs to 
previously repaired areas and repetitive inspections for loose 
fasteners and replacement if necessary in certain previously repaired 
areas. This proposed AD would also reduce certain compliance times and 
extend certain other compliance times. We are proposing this AD to 
detect and correct fatigue cracking of the fuselage skin, which could 
cause the fuselage skin to fracture and fail, and result in rapid 
decompression of the airplane.

DATES: We must receive comments on this proposed AD by March 5, 2012.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: (202) 493-2251.
     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 (206) 544-
5000, extension 1; fax (206) 766-5680; email me.boecom@boeing.com; 
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 proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Office (phone: (800) 647-5527) is in the 
ADDRESSES section. Comments will be available in the AD docket shortly 
after receipt.

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: (425) 917-
6447; fax: (425) 917-6590; email: wayne.lockett@faa.gov.

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-2011-1419; 
Directorate Identifier 2010-NM-281-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 June 15, 2005, we issued AD 2005-13-27, amendment 39-14164 (70 
FR 36821, June 27, 2005), for certain Boeing Model 737-300, -400, and -
500 series airplanes. That AD requires repetitive inspections for 
cracking of the crown area of the fuselage skin, and corrective actions 
if necessary. That AD resulted from a Model 737 fuselage structure test 
and fatigue analysis that indicate fuselage skin cracking could occur 
between 21,000 and 42,000 total flight cycles. We issued that AD to 
detect and correct fatigue cracking of the fuselage skin, which could 
cause the fuselage skin to fracture and fail, and result in rapid 
decompression of the airplane.

Actions Since Existing AD Was Issued

    Since we issued AD 2005-13-27, amendment 39-14164 (70 FR 36821, 
June 27, 2005), additional reports of cracking at the horizontal chem-
mill steps away from the lap joints over the entire crown area, and 
vertical chem-mill cracks adjacent to the butt joints, have been 
received. Although there were no changes to the applicability in AD 
2005-13-17, we have changed paragraph (c) of the proposed AD to refer 
to Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated 
November 24, 2010.

Relevant Service Information

    We reviewed Boeing Alert Service Bulletin 737-53A1234, Revision 2, 
dated November 24, 2010. Boeing Special Attention Service Bulletin 737-
53-1234, Revision 1, dated March 31, 2005, was referred to for 
accomplishing the actions in AD 2005-13-27, amendment 39-14164 (70 FR 
36821, June 27, 2005). Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010, describes procedures for 
repetitive non-destructive inspections (NDI) (medium

[[Page 2670]]

frequency eddy current, magneto optical imaging, C-scan, or ultrasonic 
phased array) for cracking of the fuselage skin, and corrective actions 
if necessary. The NDI inspections for cracking of the skin include:
     Inspecting for horizontal chem-mill cracking above the S-4 
and S-10 lap joints
     Inspecting for horizontal chem-mill cracking in the shear 
wrinkle areas
     Inspecting for vertical chem-mill cracking at specified 
locations
     Inspecting for horizontal chem-mill cracking in general 
pocket-to-pocket areas at specified locations.
    The corrective actions include installing a permanent repair 
(including related investigative actions and applicable corrective 
actions), installing a time-limited repair (including related 
investigative actions and applicable corrective actions), and 
contacting Boeing for repair instructions and doing the repair. For the 
temporary repair, the related investigative actions include a detailed 
inspection for cracks of the skin and a detailed inspection for 
corrosion and disbonding of the lap joint; and the corrective action is 
contacting Boeing for repair instructions and doing the repair. For the 
permanent repair, the related investigative actions include an NDI 
inspection for cracks of the skin and fastener holes and a detailed 
inspection for corrosion and disbonding of the skin; and the corrective 
action is contacting Boeing for repair instructions and doing the 
repair.
    Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated 
November 24, 2010, also describes procedures, for airplanes on which 
permanent repairs have already been done, for installing internal tear 
strap doublers.
    Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated 
November 24, 2010, also describes procedures, for airplanes on which 
time-limited repairs have already been installed, for doing repetitive 
detailed inspections for loose fasteners until the permanent repair is 
installed; and making the repair permanent (including related 
investigative actions and applicable corrective actions) by replacing 
the blind fasteners in the time-limited repair with solid rivets, and 
installing internal tear strap doublers. The related investigative 
actions include an NDI for cracks of the fastener holes and skin, a 
general visual inspection to determine if fasteners are installed 
common to the chem-milled steps, and a detailed inspection for 
corrosion and disbonding of the skin; and the corrective action is 
contacting Boeing for repair instructions and doing the repair.
    The repetitive NDI inspection intervals vary depending on the 
configuration and the inspection option. Option 1 of Boeing Alert 
Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, 
specifies doing one of the following NDI; medium frequency eddy current 
inspection, magneto optical imaging inspection, or C-scan inspection). 
Option 2 specifies doing one NDI--an external ultrasonic phased array 
inspection. The repetitive interval ranges between 500 flight cycles 
and 2,400 flight cycles. Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010, also specifies that if the 
inspection procedure is switched from Option 2 to Option 1, then the 
next Option 1 inspection must be done within the Option 2 interval; and 
that if the inspection procedure is switched from Option 1 to Option 2, 
then the next two Option 2 inspections must be done within the Option 1 
interval.
    The inspection thresholds range from 25,000 total flight cycles to 
81,000 total flight cycles, depending on the airplane configuration and 
inspection location. The grace periods range from 500 to 2,400 flight 
cycles or 1,800 flight hours, depending on the airplane configuration 
and inspection location. The repetitive inspection intervals range from 
500 to 2,400 flight cycles, or 1,800 to 2,400 flight hours, depending 
on the inspection type and airplane configuration. For airplanes on 
which a time-limited repair is done, the compliance time to do the 
permanent repair is 6,000 flight cycles after doing the time-limited 
repair.
    Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated 
November 24, 2010, also includes an exception to inspecting the chem-
mill steps under an existing external repair doubler, provided the 
conditions specified below apply:
     The repair was installed after November 24, 2010
     The repair was approved by the FAA or by a Boeing 
Commercial Airplanes Organization Designation Authorization (ODA) who 
was authorized by the FAA to make such findings
     The repair extends a minimum of three rows of fasteners on 
each side of the chem-mill step line in the circumferential direction, 
Or
     The repair was approved by the FAA or by a Boeing 
Commercial Airplanes Organization Designation Authorization (ODA) who 
was authorized by the FAA to make such findings
     The repair extends a minimum of 2 rows of \3/16\ inch 
diameter fasteners on each side of the chem-mill step in the 
circumferential direction with 5-6D fastener spacing
     The repair is similar to Figure 201, Repair 31 of Figure 
201 of Subject 53-00-01, ``Fuselage Skin--General,'' of the Boeing 737-
300, 737-400, or 737-500 Structural Repair Manual, with regard to 
fastener type, size layout and pitch; repair part thickness and 
material; and repair installation.

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 all of the requirements of AD 2005-
13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005). This proposed 
AD would add repetitive inspections for cracking using different 
inspection methods and would inspect additional areas, and corrective 
actions if necessary. This proposed AD would also require, for 
airplanes on which the existing permanent repair was done, installing 
internal tear strap doublers. This proposed AD would also require, for 
airplanes on which the existing temporary repair was done, doing 
repetitive inspections for loose fasteners and replacement if 
necessary, and installing a permanent repair. This proposed AD would 
also change (reducing some and extending others) initial compliance 
times and repetitive intervals. This proposed AD would also require 
accomplishing the actions specified in the service information 
described previously, except as discussed under ``Differences Between 
the Proposed AD and the Service Information.''

Differences Between the Proposed AD and the Service Information

    The Accomplishment Instructions in Boeing Alert Service Bulletin 
737-53A1234, Revision 2, dated November 24, 2010, do not provide a 
procedure for replacing loose fasteners; however, this proposed AD 
requires replacing any loose fastener with a new fastener of the same 
type and size as specified in Figures 6, 35 and 36, as applicable, of 
the Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1234, Revision 2, dated November 24, 2010.
    Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated 
November 24, 2010, specifies to contact the manufacturer for 
instructions on how to

[[Page 2671]]

repair certain conditions, but this proposed AD would require repairing 
those conditions in one of the following ways:
     In accordance with a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by the Boeing Commercial 
Airplanes Organization Designation Authorization (ODA) whom we have 
authorized to make those findings.

Costs of Compliance

    We estimate that this proposed AD affects 109 airplanes of U.S. 
registry.
    We estimate the following costs to comply with this proposed AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
              Action                     Labor cost          Cost per product        Cost on U.S.  operators
----------------------------------------------------------------------------------------------------------------
Inspection (retained actions from  94 work-hours x $85    $7,990 per inspection  $870,910.
 AD 2005-13-27, Amendment           per hour = $7,990.     cycle.
 39[dash]14164 (70 FR 36821, June
 27, 2005).
New NDI Inspections (medium        Up to 390 work-hours   Up to $33,150 per      Up to $3,613,350.
 frequency eddy current, magneto    x $85 per hour =       inspection cycle.
 optical imaging, C-scan, or        $33,150.
 ultrasonic phased array).
Install internal tear strap        Up to 30               Up to $2,550.........  Up to $277,950.
 doublers (for airplanes on which   work[dash]hours x
 permanent repair was already       $85 per hour =
 done).                             $2,550.
* Inspection for loose fasteners   1 work-hour x $85 per  $85..................  $9,265.
 (for airplanes on which            hour = $85.
 temporary repair was already
 done).
* Install permanent repair (for    Up to 48               Up to $4,080.........  Up to $444,720.
 airplanes on which temporary       work[dash]hours x
 repair was already done).          $85 per hour =
                                    $4,080.
* Inspection adjacent to lap       3 work-hours x $85     $255.................  $27,795.
 joint repair.                      per hour = $255.
----------------------------------------------------------------------------------------------------------------
* The cost for this action is for one typical repair only.

    We estimate the following costs to do any necessary repairs that 
would be required based on the results of the proposed inspection. 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 \1\.......................  209 work-hours x $85   None.................  $17,765.
                                    per hour = $17,765.
----------------------------------------------------------------------------------------------------------------
\1\ Repair cost estimate is for one typical repair only.

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.

Sec.  39.13  [Amended]

    2. The FAA amends Sec.  39.13 by removing airworthiness directive 
(AD) 2005-13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005), and 
adding the following new AD:

The Boeing Company: Docket No. FAA-2011-1419; Directorate Identifier 
2010-NM-281-AD.

[[Page 2672]]

(a) Comments Due Date

    The FAA must receive comments on this AD action by March 5, 
2012.

(b) Affected ADs

    This AD supersedes AD 2005-13-27, Amendment 39-14164 (70 FR 
36821, June 27, 2005).

(c) Applicability

    This AD applies to The Boeing Company Model 737-300, -400, and -
500 series airplanes, certificated in any category; as identified in 
Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated 
November 24, 2010.

(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 at the horizontal 
chem-mill steps away from the lap joints over the entire crown area, 
and vertical chem-mill cracks adjacent to the butt joints. We are 
issuing this AD to detect and correct fatigue cracking of the 
fuselage skin, which could cause the fuselage skin to fracture and 
fail, and result in rapid decompression of the airplane.

(f) Compliance

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

(g) Restatement of Requirements of AD 2005-13-27, Amendment 39-14164 
(70 FR 36821, June 27, 2005): Initial Inspections per Boeing Special 
Attention Service Bulletin 737-53-1234, Revision 1, Dated March 31, 
2005

    At the later of the times specified in paragraphs (g)(1) and 
(g)(2) of this AD, perform detailed and eddy current inspections for 
cracking of the crown area of the fuselage skin in accordance with 
Part 1, including the ``Note,'' of the Work Instructions of Boeing 
Special Attention Service Bulletin 737-53-1234, Revision 1, dated 
March 31, 2005, except as provided by paragraph (j) of this AD. 
Doing the inspections required by paragraph (m) of this AD 
terminates the inspections required by this paragraph for the 
corresponding inspection areas.
    (1) Before the accumulation of the applicable total flight 
cycles specified in the ``Threshold'' column of Table 1 of Figure 1 
of Boeing Special Attention Service Bulletin 737-53-1234, Revision 
1, dated March 31, 2005.
    (2) Within 4,500 flight cycles after August 1, 2005 (the 
effective date of AD 2005-13-27, Amendment 39-14164 (70 FR 36821, 
June 27, 2005).

(h) Repetitive Inspections per Boeing Special Attention Service 
Bulletin 737-53-1234, Revision 1, Dated March 31, 2005

    Repeat either the detailed or eddy current inspections specified 
in paragraph (g) of this AD at the applicable intervals specified in 
paragraph (h)(1) or (h)(2) of this AD until paragraph (i)(1) or 
(i)(2) of this AD has been done, as applicable. Doing the inspection 
required by paragraph (m) of this AD terminates the inspections 
required by this paragraph for the corresponding inspection area.
    (1) Repeat the detailed inspections thereafter at intervals not 
to exceed 1,200 flight cycles.
    (2) Repeat the eddy current inspections thereafter at intervals 
not to exceed 3,000 flight cycles.

(i) Permanent or Time-Limited Repair for Cracking Found During 
Inspections in Accordance With Boeing Special Attention Service 
Bulletin 737-53-1234, Revision 1, Dated March 31, 2005

    If any cracking is found during any inspection required by 
paragraph (g) or (h) of this AD, do the actions specified in 
paragraph (i)(1) or (i)(2) of this AD in accordance with Boeing 
Special Attention Service Bulletin 737-53-1234, Revision 1, dated 
March 31, 2005, except as provided by paragraphs (j) and (k) of this 
AD.
    (1) Before further flight, do a permanent repair (including 
related investigative actions and applicable corrective actions) in 
accordance with Part 2 of the Work Instructions of Boeing Special 
Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 
2005. Doing a permanent repair ends the repetitive inspections 
required by paragraph (h) of this AD for the repaired area only.
    (2) Do the actions specified in paragraphs (i)(2)(i) and 
(i)(2)(ii) of this AD at the time specified in the applicable 
paragraph. Doing a time-limited repair ends the repetitive 
inspections required by paragraph (h) of this AD for the repaired 
area only.
    (i) Before further flight, do a time-limited repair (including 
related investigative actions and applicable corrective actions) in 
accordance with Part 3 of the Work Instructions of Boeing Special 
Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 
2005.
    (ii) At the times specified in Figure 8 of Boeing Special 
Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 
2005, do the related investigative and corrective actions in 
accordance with Part 3 of the Work Instructions of Boeing Special 
Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 
2005.

(j) Contact the FAA

    Where Boeing Special Attention Service Bulletin 737-53-1234, 
Revision 1, dated March 31, 2005, specifies to contact Boeing for 
appropriate action: Before further flight, repair according to a 
method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA; or according to data meeting the certification 
basis of the airplane approved by an Authorized Representative for 
the Boeing Delegation Option Authorization Organization who has been 
authorized by the Manager, Seattle ACO, to make those findings; or 
using a method approved in accordance with the procedures specified 
in paragraph (x) of this AD. For a repair method to be approved, the 
approval must specifically reference this AD.

(k) No Reporting for Actions in Boeing Special Attention Service 
Bulletin 737-53-1234, Revision 1, Dated March 31, 2005

    Although Boeing Special Attention Service Bulletin 737-53-1234, 
Revision 1, dated March 31, 2005, specifies reporting certain 
information to Boeing, this AD does not require that action.

(l) Actions Accomplished According to Previous Issue of Service 
Bulletin

    Actions done before August 1, 2005, in accordance with Boeing 
Special Attention Service Bulletin 737-53-1234, dated June 13, 2002, 
are acceptable for compliance with the corresponding actions 
required by paragraphs (g), (h), and (i) of this AD.

(m) New Requirements of This AD: Fuselage Skin Inspections at Chem-Mill 
Steps Common to Lap Joints

    Except as provided by paragraph (v)(1) of this AD; at the 
applicable time specified in Tables 1 and 2 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010: Do a non-destructive inspection 
(NDI) (medium frequency eddy current, magneto optical imaging, C-
scan, or ultrasonic phased array) for horizontal chem-mill cracking 
above the S-4 and S-10 lap joints, in accordance with paragraph 
3.B.1.a. of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1234, Revision 2, dated November 24, 2010, except as 
provided by paragraph (r) of this AD. Repeat the applicable 
inspections thereafter at intervals not to exceed those specified in 
paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 
737-53A1234, Revision 2, dated November 24, 2010. Accomplishment of 
the inspections required by this paragraph terminates the 
requirements of paragraphs (g) and (h) of this AD for the 
corresponding inspection areas.

    Note 1:  Option 1 of Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010, specifies doing one of the 
following NDI; medium frequency eddy current inspection, magneto 
optical imaging inspection, or C-scan inspection. Option 2 specifies 
doing one NDI--an external ultrasonic phased array inspection. These 
options have different compliance times after the initial 
inspection.

 (n) Permanent or Time-Limited Repair for Cracking Found During 
Paragraph (m) Inspections

    If any cracking is found during any inspection required by 
paragraph (m) of this AD, do the actions specified in paragraph 
(n)(1) or (n)(2) of this AD.
    (1) Before further flight, do a permanent repair (including 
related investigative actions and applicable corrective actions) in 
accordance with Part 2 of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 
2010, except as provided by paragraph (v)(2) of this AD. Doing a 
permanent repair ends the repetitive inspections required by 
paragraph (m) of this AD for the repaired area only.
    (2) Do the actions specified in paragraphs (n)(2)(i), 
(n)(2)(ii), and (n)(2)(iii) of this AD at

[[Page 2673]]

the time specified in the applicable paragraph. Doing a time-limited 
repair ends the repetitive inspections required by paragraph (m) of 
this AD for the repaired area only.
    (i) Before further flight, do a time-limited repair (including 
related investigative actions and applicable corrective actions) in 
accordance with Part 4 of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 
2010, except as provided by paragraph (v)(2) of this AD.
    (ii) Within 3,000 flight cycles after the time-limited repair 
was installed as specified in paragraph (n)(2)(i) of this AD or 
within 500 flight cycles after the effective date of this AD, 
whichever occurs later, do a detailed inspection for loose 
fasteners, in accordance with Part 4 of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 
2, dated November 24, 2010. Repeat the inspection thereafter at 
intervals not to exceed 3,000 flight cycles until the permanent 
repair required by paragraph (n)(2)(iii) of this AD is done. If any 
loose fasteners are found, before further flight, replace the 
fasteners with new fasteners of the same type and size as specified 
in Figures 6, 35 and 36 of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 
2010.
    (iii) Within 6,000 flight cycles after the time-limited repair 
was installed as specified in paragraph (n)(2)(i) of this AD, do the 
permanent repair specified in paragraph (n)(1) of this AD.

(o) Fuselage Skin Inspections at Chem-mill Steps Common to Shear 
Wrinkle Areas

    Except as provided by paragraph (v)(1) of this AD; at the 
applicable time specified in Table 3 of paragraph 1.E, 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010: Do an NDI (medium frequency 
eddy current, magneto optical imaging, C-scan, or ultrasonic phased 
array) for horizontal chem-mill cracking in the shear wrinkle areas, 
in accordance with paragraph 3.B.1.b of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 
2, dated November 24, 2010. Repeat the applicable inspections 
thereafter at intervals not to exceed those specified in paragraph 
1.E., ``Compliance,'' of Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010.

(p) Fuselage Skin Inspections at Specified Vertical Chem-mill Step 
Locations

    Except as provided by paragraph (v)(1) of this AD; at the 
applicable time specified in Table 4 of paragraph 1.E, 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010: Do an NDI (medium frequency 
eddy current, magneto optical imaging, C-scan, or ultrasonic phased 
array) for vertical chem-mill cracking at locations specified in, 
and in accordance with paragraph 3.B.1.c. of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 
2, dated November 24, 2010. Repeat the applicable inspections 
thereafter at intervals not to exceed those specified in paragraph 
1.E., ``Compliance,'' of Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010.

(q) Fuselage Skin Inspections at Chem-mill Steps in General Pocket-to-
Pocket Areas

    Except as provided by paragraph (v)(1) of this AD; at the 
applicable time specified in Tables 5 and 6 of paragraph 1.E, 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010: Do an NDI (medium frequency 
eddy current, magneto optical imaging, C-scan, or ultrasonic phased 
array) for horizontal chem-mill cracking in general pocket-to-pocket 
areas at specified locations in and in accordance with paragraph 
3.B.1.d., 3.B.1.e., and 3.B.1.f., as applicable, of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1234, Revision 2, dated November 24, 2010. Repeat the applicable 
inspections thereafter at intervals not to exceed those specified in 
Tables 5 and 6 of paragraph 1.E., ``Compliance,'' of Boeing Alert 
Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010.

(r) Inspection Exception

    For inspections required by paragraph (m) of this AD: It is not 
necessary to inspect the chem-mill steps under an existing repair 
installed using Boeing Special Attention Service Bulletin 737-53-
1234, dated June 13, 2002; or Revision 1, dated March 31, 2005.

(s) Repair of Cracking Found During Inspections Required by Paragraphs 
(o) Through (q) of This AD

    If any crack is found during any inspections required by 
paragraph (o), (p), or (q) of this AD, before further flight, repair 
the crack using a method approved in accordance with the procedures 
specified in paragraph (x) of this AD.

(t) Actions for Airplanes on Which Repairs Have Been Done Using 
Previous Service Information

    (1) For airplanes on which permanent repairs have been done in 
accordance with Boeing Special Attention Service Bulletin 737-53-
1234, dated June 13, 2002, or Revision 1, dated March 31, 2005; 
except airplanes on which internal tear strap doublers were 
previously installed using a repair plan approved using the 
procedures specified in paragraph (x) of this AD: Within 6,000 
flight cycles after the effective date of this AD, install internal 
tear strap doublers, in accordance with paragraph 3.B.3. of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1234, Revision 2, dated November 24, 2010, except as provided by 
paragraph (v)(2) of this AD. Installation of internal tear strap 
doublers specified in this paragraph terminates the inspections 
required by paragraph (m) of this AD for the repaired area only.
    (2) For airplanes on which time-limited repairs have been 
installed in accordance with Boeing Special Attention Service 
Bulletin 737-53-1234, dated June 13, 2002, or Revision 1, dated 
March 31, 2005; except airplanes on which the permanent repair has 
been installed before the effective date of this AD in accordance 
with Boeing Special Attention Service Bulletin 737-53-1234, dated 
June 13, 2002, or Revision 1, dated March 31, 2005: Within 3,000 
flight cycles after the time limited repair is installed, or within 
500 flight cycles after the effective date of the AD, whichever 
occurs later, do a detailed inspection for loose fasteners, in 
accordance with paragraph 3.B.4. of the Accomplishment Instructions 
of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated 
November 24, 2010. Repeat the inspection thereafter at intervals not 
to exceed 3,000 flight cycles until the permanent repair is 
installed in accordance with paragraph (n)(1) of this AD. If any 
loose fasteners are found, before further flight, replace the 
fasteners with new fasteners of the same type and size as specified 
in Figures 6, 35, and 36, as applicable, of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 
2, dated November 24, 2010.
    (3) For airplanes on which time-limited repairs have been 
installed in accordance with Boeing Special Attention Service 
Bulletin 737-53-1234, dated June 13, 2002, or Revision 1, dated 
March 31, 2005; except airplanes on which the permanent repair has 
been installed before the effective date of this AD in accordance 
with Boeing Special Attention Service Bulletin 737-53-1234, dated 
June 13, 2002, or Revision 1, dated March 31, 2005; before the 
effective date of this AD: Within 6,000 flight cycles after the 
time-limited repair is installed, or within 1,000 flight cycles 
after the effective date of this AD, whichever occurs later, make 
the repair permanent by replacing the blind fasteners in the time-
limited repair with solid rivets, and install internal tear strap 
doublers, in accordance with paragraph 3.B.4. of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 
2, dated November 24, 2010, except as provided by paragraph (v)(2) 
of this AD.

(u) Action Not in Accomplishment Instructions

    If any crack is found after the time-limited or permanent repair 
is installed, and Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010, specifies to contact Boeing for 
appropriate action: Before further flight, repair the crack using a 
method approved in accordance with the procedures specified in 
paragraph (x) of this AD.

(v) Exceptions to Boeing Alert Service Bulletin 737-53A1234, Revision 
2, Dated November 24, 2010

    (1) Where paragraph 1.E., ``Compliance,'' of Boeing Alert 
Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, 
specifies a compliance time relative to the ``release of Revision 2 
of this service bulletin,'' this AD requires compliance within the 
specified compliance time after the effective date of this AD.
    (2) Where Boeing Alert Service Bulletin 737-53A1234, Revision 2, 
dated November 24, 2010, specifies to contact Boeing for appropriate 
action: Before further flight, repair the cracking using a method 
approved in accordance with the procedures specified in paragraph 
(x) of this AD.

[[Page 2674]]

    (3) Although Boeing Alert Service Bulletin 737-53A1234, Revision 
2, dated November 24, 2010, specifies reporting certain information 
to Boeing, this AD does not require that action.

(w) Post-Repair Inspections

    The post-repair inspection specified in Table 7 of paragraph 
1.E., ``Compliance,'' of Boeing Alert Service Bulletin 737-53A1234, 
Revision 2, dated November 24, 2010, is not required by this AD.

    Note 2:  The damage tolerance inspections specified in Table 7 
of paragraph 1.E., Compliance, of Boeing Alert Service Bulletin 737-
53A1234, Revision 2, dated November 24, 2010, may be used in support 
of compliance with section 121.1109(c)(2) or 129.109(c)(2) of the 
Federal Aviation Regulations (14 CFR 121.1109(c)(2) or 14 CFR 
129.109(c)(2)). The corresponding actions specified in the 
Accomplishment Instructions and Figures 40 and 41 of Boeing Alert 
Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, 
are not required in this AD.

(x) 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 the 
Related Information section of this AD. Information may be emailed 
to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.
    (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 2005-13-27, Amendment 39-14164 (70 FR 
36821, June 27, 2005), are approved as AMOCs for the corresponding 
requirements in this AD.

(y) 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; telephone (425) 917-6447; fax (425) 917-6590; email: 
wayne.lockett@faa.gov.
    (2) 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 
(206) 544-5000, extension 1; fax (206) 766-5680; email 
me.boecom@boeing.com; 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.

    Issued in Renton, Washington, on January 6, 2012.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-859 Filed 1-18-12; 8:45 am]
BILLING CODE 4910-13-P
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