[Federal Register Volume 76, Number 45 (Tuesday, March 8, 2011)]
[Proposed Rules]
[Pages 12619-12624]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-5159]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2011-0155; Directorate Identifier 2009-NM-141-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede an existing airworthiness 
directive (AD) that applies to certain Boeing Model 737-200, -200C, -
300, -400, and -500 series airplanes. The existing AD currently 
requires repetitive inspections to find fatigue cracking of certain 
upper and lower skin panels of the fuselage, and follow-on and 
corrective actions if necessary. The existing AD also includes a 
terminating action for the repetitive inspections of certain modified 
or repaired areas only. This proposed AD would add new inspections for 
cracking of the fuselage skin along certain chem-milled lines, and 
corrective actions if necessary. This proposed AD would also reduce 
certain thresholds and intervals required by the existing AD. This 
proposed AD results from reports of new findings of vertical cracks in 
the fuselage skin along the chem-milled steps adjacent to the butt 
joints. We are proposing this AD to detect and correct fatigue cracking 
of the skin panels, which could result in sudden fracture and failure 
of the skin panels of the fuselage, and consequent rapid decompression 
of the airplane.

DATES: We must receive comments on this proposed AD by April 22, 2011.

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: 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: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    For service information identified in this proposed 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; e-mail [email protected]; 
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 (telephone 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; telephone (425) 
917-6447; fax (425) 917-6590; e-mail: [email protected].

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-2011-0155; 
Directorate Identifier 2009-NM-141-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 August 26, 2004, we issued AD 2004-18-06, Amendment 39-13784 (69 
FR 54206, September 8, 2004), for certain Model 737-200, -200C, -300, -
400, and -500 series airplanes. That AD requires repetitive inspections 
to find fatigue cracking of certain upper and lower skin panels of the 
fuselage, and follow-on and corrective actions if necessary. That AD 
also includes a terminating action for the repetitive inspections of 
certain modified or repaired areas only. That AD resulted from reports 
indicating new findings of cracks were found along the edges of the 
chem-milled pockets in the upper skin at certain stringers. We issued 
that AD to find and fix fatigue cracking of the skin panels, which 
could result in sudden fracture and failure of the skin panels of the 
fuselage, and consequent rapid decompression of the airplane.

Actions Since Existing AD Was Issued

    Since we issued AD 2004-18-06, we have received reports of new 
findings of vertical cracks in the fuselage skin along the chem-milled 
steps adjacent to the butt joints and at certain body stations on 
airplanes with between 45,100 flight cycles (65,200 flight hours) and 
67,400 flight cycles (70,800 flight hours).
    A decompression event connected to chem-milled steps occurred in 
July 2009 (after issuance of Boeing Alert Service Bulletin 737-53A1210, 
Revision 3, dated July 16, 2009) and resulted in re-evaluation of the 
inspection thresholds and repetitive intervals. The new data and 
analysis require the repetitive intervals be reduced from those 
currently specified in Boeing Alert Service Bulletin 737-53A1210, 
Revision 3, dated July 16, 2009. These new repetitive intervals are 
defined in the differences section of the NPRM.

Explanation of Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-53A1210, 
Revision 2, dated March 3, 2009; and Boeing Alert Service Bulletin 737-
53A1210, Revision 3, dated July 16, 2009. Boeing Alert Service Bulletin 
737-53A1210, Revision 1, dated October 25, 2001, was referred to as the 
appropriate source of service information for accomplishing the actions 
in the existing AD.
    Boeing Alert Service Bulletin 737-53A1210, Revision 2, describes 
procedures for, among other things,

[[Page 12620]]

repetitive external detailed and eddy current inspections for cracking 
of the fuselage skin along certain chem-milled lines, and corrective 
actions if necessary. The corrective actions include doing a time-
limited repair or a permanent repair, as applicable. After installation 
of a time-limited repair, an external detailed inspection is done of 
the repaired area for cracks and loose or missing fasteners. For 
airplanes on which cracks are found, this service bulletin recommends 
contacting Boeing for repair instructions and repairing; and, for 
airplanes on which loose or damaged fasteners are found this service 
bulletin specifies replacing any damaged or loose fasteners. This 
service bulletin adds an optional preventive modification for Groups 3, 
5, 6, and 8 at body station (BS) 500D through BS 520 on Model 737-300 
airplanes, and BS 482B through BS 520, stringer 12, on Model 737-500 
airplanes. This service bulletin also reduces the effectivity specified 
in Revision 1, and contains editorial changes.
    Boeing Alert Service Bulletin 737-53A1210, Revision 3, clarifies 
certain work instructions. This service bulletin also specifies that 
more work is necessary for airplanes on which the actions in Boeing 
Alert Service Bulletin 737-53A1210, dated December 14, 2000; or 
Revision 1, dated October 25, 2001; were done. In addition, Revision 3 
of this service bulletin adds the airplanes that were incorrectly 
removed from the effectivity in Revision 2 of this service bulletin, 
which were not identified until after Revision 2 of this service 
bulletin was issued. Therefore, the effectivity in Revision 3 of this 
service bulletin is the same as the effectivity in Revision 1 of this 
service bulletin.
    Boeing Alert Service Bulletin 737-53A1210, Revision 3, specifies 
that the repetitive inspection interval is 4,500 flight cycles.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to develop on other airplanes of the 
same type design. For this reason, we are proposing this AD, which 
would supersede AD 2004-18-06 and would retain certain requirements of 
the existing AD. 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 
Service Information.'' This proposed AD also reduces the compliance 
time of 40,000 total flight cycles for doing certain actions in AD 
2004-18-06; this proposed AD specifies a compliance time of 35,000 
total flight cycles in paragraph (s) of this AD.

Differences Between the Proposed AD and Service Information

    Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 
16, 2009, specifies to contact the manufacturer for disposition of 
certain repair 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) that we have 
authorized to make those findings.
    Boeing Alert Service Bulletin 737-53A1210, Revision 2, dated March 
3, 2009, specifies that no airplanes were added or removed from the 
effectivity; however, the manufacturer has informed us that there were 
airplanes incorrectly removed in the ``Identification by Customer, 
Customer Code, Group and Variable Number'' section in Paragraph 1.A.1 
of Revision 2 of this service bulletin. In light of the fact that 
Revision 3 of this service bulletin includes those airplanes in its 
effectivity, and includes all the actions specified in Revision 2 of 
this service bulletin, this proposed AD would require that the new 
actions be done in accordance with Revision 3 of this service bulletin.
    Paragraph 1.E of Boeing Alert Service Bulletin 737-53A1210, 
Revision 3, specifies a repetitive inspection interval of 4,500 flight 
cycles; that interval is expected to be reduced when this service 
bulletin is revised. The manufacturer has informed us that it has re-
evaluated the inspection interval because it would not address the 
identified unsafe condition soon enough to ensure an acceptable level 
of safety for the affected fleet. In light of this fact, we find that a 
repetitive inspection interval of 1,800 flight cycles, for the actions 
specified in Tables 1 through 5, represents an appropriate interval of 
time for affected airplanes to continue to operate without compromising 
safety.
    Part 8 of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1210, Revision 3, specifies a post-repair inspection of 
the skin chem-milled crack repair at stringer 12; that inspection is 
not required by this proposed AD. The damage tolerance inspections 
specified in Table 7 of Boeing Alert Service Bulletin 737-53A1210, 
Revision 3, dated July 16, 2009, may be used in support of compliance 
with section 121.1109(c)(2) or 129.109(c)(2) of the Federal Aviation 
Regulations (14 CFR 121.1109(c)(2) or 14 CFR 129.109(c)(2)).

Explanation of Change to This Proposed AD

    Boeing Commercial Airplanes has received an Organization Delegation 
Authority (ODA), which replaces their previous designation as a 
Designated Engineering Representative (DER). We have revised paragraphs 
(j) and (l)(2) 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.

Change to Existing AD

    This proposed AD would retain certain requirements of AD 2004-18-
06. Since AD 2004-18-06 was 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 table:

                      Revised Paragraph Identifiers
------------------------------------------------------------------------
                                      Corresponding  requirement in this
    Requirement in AD 2004-18-06                 proposed AD
------------------------------------------------------------------------
             paragraph (a)                        paragraph (g)
             paragraph (b)                        paragraph (h)
             paragraph (c)                        paragraph (i)
             paragraph (d)                        paragraph (j)
             paragraph (e)                        paragraph (k)
             paragraph (f)                        paragraph (l)
             paragraph (g)                        paragraph (m)
             paragraph (h)                        paragraph (n)
             paragraph (i)                        paragraph (o)
------------------------------------------------------------------------

    We have revised paragraph (m) of this proposed AD to specify that 
doing paragraph (b) or (c), as applicable, of AD 2003-14-06, Amendment 
39-13225, after the effective date of this proposed AD does not 
terminate any of the actions required by paragraph (g) of this proposed 
AD. Recent reports of cracking have shown that a detailed inspection 
alone is not sufficient to find cracks in the fuselage skin. The 
cracking begins on the internal surface of the skin and grows outward, 
not becoming visible on the external surface until the crack is at 
least three inches in length. Actions accomplished before the effective 
date of this AD in accordance with AD 2003-14-06, which terminate 
certain requirements of paragraph (g) of this proposed AD, are 
reinstated with the new requirements specified in paragraph (p) of this 
proposed AD.

[[Page 12621]]

Costs of Compliance

    There are about 903 airplanes of U.S. registry affected by AD 2004-
18-06.
    The inspections of the crown area that are required by AD 2004-18-
06 take about 94 work hours per airplane to accomplish, at an average 
labor rate of $85 per work hour. Based on these figures, the estimated 
cost of the currently required inspections is $7,990 per airplane, per 
inspection cycle.
    The inspections of the lower lobe area that are required by AD 
2004-18-06 take about 96 work hours per airplane to accomplish, at an 
average labor rate of $85 per work hour. Based on these figures, the 
estimated cost of the currently required inspections is $8,160 per 
airplane, per inspection cycle.
    Should an operator elect to install the preventive modification 
specified in AD 2004-18-06 it will take about 108 work hours per 
airplane to accomplish, at an average labor rate of $85 per work hour. 
Based on these figures, the estimated cost of the modification is 
$9,180 per airplane.
    The new proposed inspections would affect about 701 airplanes of 
U.S. registry.
    The new proposed inspections would take about 27 work hours per 
airplane, at an average labor rate of $85 per work hour. Based on these 
figures, the estimated cost of the new actions specified in this 
proposed AD for U.S. operators is $1,608,795, or $2,295 per airplane, 
per inspection cycle.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
subtitle VII, part A, subpart III, section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We have determined that this 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 amendment 39-13784 (69 FR 
54206, September 8, 2004) and adding the following new AD:

The Boeing Company: Docket No. FAA-2011-0155; Directorate Identifier 
2009-NM-141-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by April 22, 
2011.

Affected ADs

    (b) This AD supersedes AD 2004-18-06, Amendment 39-13784. AD 
2002-07-08, Amendment 39-12702; and AD 2003-14-06, Amendment 39-
13225; affect this AD.

Applicability

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

Subject

    (d) Air Transport Association (ATA) of America Code 53: 
Fuselage.

Unsafe Condition

    (e) This AD results from new findings of vertical cracks along 
chem-milled steps adjacent to the butt joints. The Federal Aviation 
Administration is issuing this AD to detect and correct fatigue 
cracking of the skin panels, which could result in sudden fracture 
and failure of the skin panels of the fuselage, and consequent rapid 
decompression of the airplane.

Compliance

    (f) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Restatement of Certain Requirements of AD 2004-18-06, Amendment 39-
13784

External Detailed and Eddy Current Inspections

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

    Note 1:  For the purposes of this AD, a detailed inspection is 
defined as: ``An intensive visual examination of a specific 
structural area, system, installation, or assembly to detect damage, 
failure, or irregularity. Available lighting is normally 
supplemented with a direct source of good lighting at intensity 
deemed appropriate by the inspector. Inspection aids such as mirror, 
magnifying lenses, etc., may be used. Surface cleaning and elaborate 
access procedures may be required.''

    (h) For all airplanes identified in Boeing Alert Service 
Bulletin 737-53A1210, Revision 1, dated October 25, 2001, do an 
external detailed inspection of the lower lobe area and section 41 
of the fuselage for cracking, per Part 2 and Figure 2 of the Work 
Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 
1, dated October 25, 2001; or in accordance with Part 4 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1210, Revision 3,

[[Page 12622]]

dated July 16, 2009. As of the effective date of this AD, use only 
Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 
16, 2009. At the earlier of the times specified in paragraphs (h)(1) 
and (h)(2) of this AD, do the inspection specified in this paragraph 
and repeat the inspection thereafter at intervals not to exceed 
4,500 flight cycles until paragraph (j)(2) or (k) of this AD has 
been done, as applicable. Accomplishing the actions required by 
paragraph (s) of this AD ends the requirements in this paragraph.
    (1) Within 9,000 flight cycles after doing the most recent 
internal detailed inspection.
    (2) Within 4,500 flight cycles after October 13, 2004, or before 
the accumulation of 40,000 total flight cycles, whichever occurs 
later.

Preventive Modification

    (i) For Groups 3 and 5 airplanes identified in Boeing Alert 
Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001: If 
no cracking is found during any inspection required by paragraph (g) 
of this AD, doing the preventive modification of the chem-milled 
pockets in the upper skin as specified in Part 5 of the Work 
Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 
1, dated October 25, 2001; or as specified in Part 7 of the Work 
Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 
3, dated July 16, 2009, except as required by paragraph (x) of this 
AD; ends the repetitive external detailed and eddy current 
inspections required by paragraph (g) of this AD for the modified 
area only. As of the effective date of this AD, use only Boeing 
Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009.

Corrective Actions

    (j) If any cracking is found during any inspection required by 
paragraph (g), (h), (p), (q), or (s) of this AD, before further 
flight, do the actions specified in paragraphs (j)(1) and (j)(2) of 
this AD, as applicable, in accordance with the Work Instructions of 
Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 
25, 2001; or Revision 3, dated July 16, 2009. As of the effective 
date of this AD, use only Boeing Alert Service Bulletin 737-53A1210, 
Revision 3, dated July 16, 2009. Where Boeing Alert Service Bulletin 
737-53A1210, Revision 1, dated October 25, 2001; or Revision 3, 
dated July 16, 2009; specify to contact Boeing for repair 
instructions, before further flight, repair per a method approved by 
the Manager, Seattle Aircraft Certification Office (ACO), FAA; or 
per data meeting the type certification basis of the airplane if it 
is approved by the Boeing Commercial Airplanes Organization 
Designation Authorization (ODA) or any other person authorized by 
the Manager, Seattle ACO to make those findings. For a repair method 
to be approved the repair must meet the certification basis of the 
airplane and the approval must specifically refer to this AD.
    (1) Except as provided by paragraph (k) of this AD, for cracking 
of the crown area, do the repair specified in either paragraph 
(j)(1)(i) or (j)(1)(ii) of this AD.
    (i) Do a time-limited repair per Part 4 of the Work Instructions 
of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated 
October 25, 2001; or in accordance with Part 6 of the Work 
Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 
3, dated July 16, 2009, except as required by paragraph (x) of this 
AD, then do the actions required by paragraph (l) of this AD at the 
times specified in that paragraph.
    (ii) Do a permanent repair per Part 3 of the Work Instructions 
of Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated 
October 25, 2001; or in accordance with Part 5 of the Work 
Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 
3, dated July 16, 2009. Installation of a permanent repair ends the 
repetitive inspections required by paragraph (g) of this AD for the 
repaired area only. Installation of the lap joint repair specified 
in paragraph (g) of AD 2002-07-08, Amendment 39-12702, is considered 
acceptable for compliance with the corresponding permanent repair 
specified in this paragraph for the repaired areas only.
    (2) Except as provided by paragraph (k) of this AD, for cracking 
of the lower lobe area and Section 41, repair per Part 2 of the Work 
Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 
1, dated October 25, 2001; or in accordance with paragraph (j)(2)(i) 
or (j)(2)(ii) of this AD. Accomplishment of this repair ends the 
repetitive inspections required by paragraph (h) of this AD for the 
repaired area only. As of the effective date of this, do the repair 
specified in paragraph (j)(2)(i) or (j)(2)(ii) of this AD.
    (i) Do a time-limited repair in accordance with Part 6 of the 
Work Instructions of Boeing Alert Service Bulletin 737-53A1210, 
Revision 3, dated July 16, 2009, except as required by paragraph (x) 
of this AD, then do the actions required by paragraph (l) of this AD 
at the times specified in that paragraph.
    (ii) Do a permanent repair in accordance with Part 5 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1210, Revision 3, dated July 16, 2009.

Optional Repair Method

    (k) For cracking in any area specified in paragraphs (j)(1) and 
(j)(2) of this AD within the limitations of the applicable 
structural repair manual (SRM) specified in table 1 of this AD, 
repair any cracks per the applicable SRM specified in table 1 of 
this AD. Accomplishment of the applicable repair terminates the 
repetitive inspections required by paragraphs (g) and (h) of this AD 
for the repaired area only.

                                                                 Table 1--SRM References
--------------------------------------------------------------------------------------------------------------------------------------------------------
                Model                               Subject/figure               Revision                  Date                            SRM
--------------------------------------------------------------------------------------------------------------------------------------------------------
737-100, -200 series airplanes.......  53-30-3, Figure 48.....................        102  September 10, 2010.................  Boeing 737-100/-200 SRM,
                                                                                                                                 D6-15565.
737-300 series airplanes.............  53-00-01, Figure 229...................         92  November 10, 2010..................  Boeing 737-300 SRM D6-
                                                                                                                                 37635.
737-400 series airplanes.............  53-00-01, Figure 231...................         75  November 10, 2010..................  Boeing 737-400 SRM, D6-
                                                                                                                                 38246.
737-500 series airplanes.............  53-00-01, Figure 229...................         70  November 10, 2010..................  Boeing 737-500 SRM, D6-
                                                                                                                                 38441.
--------------------------------------------------------------------------------------------------------------------------------------------------------

Follow-on and Corrective Actions

    (l) If a time-limited repair is done, as specified in paragraph 
(j)(1)(i) or (j)(2)(i) of this AD: Do the actions specified in 
paragraphs (l)(1), (l)(2), and (l)(3) of this AD, at the times 
specified in paragraphs (l)(1), (l)(2), and (l)(3) of this AD, per 
the Work Instructions of Boeing Alert Service Bulletin 737-53A1210, 
Revision 1, dated October 25, 2001; or Boeing Alert Service Bulletin 
737-53A1210, Revision 3, dated July 16, 2009.
    (1) Within 3,000 flight cycles after doing the repair: Do the 
actions specified in paragraph (l)(1)(i) or (l)(1)(ii) of this AD. 
Then repeat the applicable inspection specified in paragraph 
(l)(1)(i) or (l)(1)(ii) of this AD at intervals not to exceed 3,000 
flight cycles until permanent rivets are installed in the repaired 
area, which ends the repetitive inspections for this paragraph. As 
of the effective date of this AD, do only the inspections specified 
in paragraph (l)(1)(ii) of this AD.
    (i) For repairs done before the effective date of this AD: Do a 
detailed inspection of the repaired area for loose fasteners per 
Part 4 of the Work Instructions of Boeing Alert Service Bulletin 
737-53A1210, Revision 1, dated October 25, 2001, or do the actions 
specified in paragraph (l)(1)(ii) of this AD. If any loose fastener 
is found, before further flight, replace with a new fastener per 
Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 
25, 2001.
    (ii) For repairs done after the effective date of this AD: Do a 
detailed inspection of the repaired area for loose, damaged, and 
missing fasteners in accordance with Part 6 of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 
3, dated July 16, 2009. If any loose, missing, or damaged fastener 
is found, before further flight, replace with a new fastener in 
accordance with Boeing Alert Service Bulletin 737-53A1210, Revision 
3, dated July 16, 2009.
    (2) At the applicable time specified in paragraph (l)(2)(i) and 
(l)(2)(ii) of this AD: Do inspections of the repaired area for 
cracking per Part 4 of the Work Instructions of Boeing Alert Service 
Bulletin 737-53A1210, Revision 1, dated October 25, 2001; or in

[[Page 12623]]

accordance with Part 6 of the Work Instructions of Boeing Alert 
Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. If 
any cracking is found, before further flight, repair per a method 
approved by the Manager, Seattle ACO, or per data meeting the type 
certification basis of the airplane if it is approved by the Boeing 
Commercial Airplanes ODA or any other person authorized by the 
Manager, Seattle ACO to make those findings. For a repair method to 
be approved the repair must meet the certification basis of the 
airplane and the approval must specifically refer to this AD.
    (i) For repairs done before the effective date of this AD: 
Within 4,000 flight cycles after doing the repair, do the 
inspections.
    (ii) For repairs done on or after the effective date of this AD: 
Within 3,000 flight cycles after doing the repair, do the 
inspections.
    (3) At the earlier of the times specified in paragraphs 
(l)(3)(i) and (l)(3)(ii) of this AD: Make the repair permanent per 
Part 4 and Figure 20 of the Work Instructions of Boeing Alert 
Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001, or 
do the permanent repair in accordance with Part 5 of the Work 
Instructions of Boeing Alert Service Bulletin 737-53A1210, Revision 
3, dated July 16, 2009, which ends the repetitive inspections for 
the repaired area only. As of the effective date of this AD, make 
the repair permanent in accordance with Boeing Alert Service 
Bulletin 737-53A1210, Revision 3, dated July 16, 2009.
    (i) Within 10,000 flight cycles after doing the repair in 
accordance with Boeing Alert Service Bulletin 737-53A1210, Revision 
1, dated October 25, 2001.
    (ii) At the later of the times specified in paragraphs 
(l)(3)(ii)(A) and (l)(3)(ii)(B) of this AD.
    (A) Within 6,000 flight cycles after doing the repair.
    (B) Within 1,000 flight cycles after the effective date of this 
AD.

Optional Terminating Action for Repetitive Eddy Current Inspections if 
Done Before the Effective Date of This AD

    (m) Accomplishment of paragraph (b) or (c), as applicable, of AD 
2003-14-06, Amendment 39-13225, before the effective date of this AD 
ends the repetitive eddy current inspections required by paragraph 
(g) of this AD for that skin panel only; however, the repetitive 
external detailed inspections required by paragraph (g) of this AD 
are still required for all areas. As of the effective date of this 
AD, accomplishing paragraph (b) or (c), as applicable, of AD 2003-
14-06, Amendment 39-13225, does not end the repetitive eddy current 
inspections required by paragraph (g) of this AD.

Credit for Actions Done per Previous Service Bulletin

    (n) Inspections, repairs, and preventive modifications done 
before October 13, 2004, in accordance with Boeing Alert Service 
Bulletin 737-53A1210, dated December 14, 2000, are acceptable for 
compliance with the corresponding actions required by paragraphs 
(g), (h), (i), (j), (k), and (l) of this AD.

Exception to Service Bulletin Procedures

    (o) For airplanes subject to the requirements of paragraphs (g), 
(h), (p), and (q) of this AD: Inspections are not required in areas 
that are spanned by an FAA-approved repair that has a minimum of 3 
rows of fasteners above and below the chem-milled step. If an 
external doubler covers the chem-milled step, but does not span it 
by a minimum of 3 rows of fasteners above and below, in lieu of 
requesting approval for an alternative method of compliance (AMOC), 
one option to comply with the inspection requirement of paragraphs 
(g) and (h) of this AD is to inspect all chem-milled steps covered 
by the repair using internal nondestructive test (NDT) methods in 
accordance with Part 6 of the Boeing 737 Non-Destructive Test NDT 
Manual. As of the effective date of this AD, inspect in accordance 
with Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated 
July 16, 2009.

New Requirements of This AD

Repetitive Inspections and Corrective Actions if Necessary

    (p) For Groups 1 through 5 and 9 through 21 airplanes identified 
in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 
16, 2009, on which the inspections required by paragraph (g) of this 
AD have been done before the effective date of this AD: At the 
applicable time specified in paragraph (p)(1) or (p)(2) of this AD, 
do external detailed and eddy current inspections of the crown area 
and other known areas of fuselage skin cracking in accordance with 
Part 1 of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1210, Revision 3, dated July 16, 2009; except as 
provided by paragraph (o) of this AD. Repeat the external detailed 
and eddy current inspections thereafter at intervals not to exceed 
1,800 flight cycles. Accomplishing the inspections required by this 
paragraph ends the repetitive inspections required by paragraph (g) 
of this AD. Before further flight, do all applicable corrective 
actions as specified in paragraph (j) of this AD.
    (1) For airplanes on which any action specified in paragraph 
(i), (j)(1)(ii), (k), (l), or (m) of this AD has been done: Within 
1,800 flight cycles after the effective date of this AD.
    (2) For airplanes on which actions specified in paragraphs (i), 
(j)(1)(ii), (k), (l), and (m) of this AD have not been done: Within 
4,500 flight cycles after doing the most recent inspection required 
by paragraph (g) of this AD, or within 1,800 flight cycles after the 
effective date of this AD, whichever is later.
    (q) For Groups 1 through 5 and 9 through 21 airplanes identified 
in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 
16, 2009; on which the inspections required by paragraph (g) of this 
AD have not been done before the effective date of this AD: Before 
the accumulation of 35,000 total flight cycles, or within 1,800 
flight cycles after the effective date of this AD, whichever is 
later, do external detailed and eddy current inspections of the 
crown area and other known areas of fuselage skin cracking in 
accordance with Part 1 of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. 
Repeat the external detailed and eddy current inspections thereafter 
at intervals not to exceed 1,800 flight cycles. Before further 
flight, do all applicable corrective actions as specified in 
paragraph (j) of this AD.
    (r) For Group 1 through 5 and 9 through 21 airplanes identified 
in Boeing Alert Service Bulletin 737-53A1210, Revision 3, dated July 
16, 2009: At the later of the times specified in paragraphs (r)(1) 
and (r)(2) of this AD, do external detailed and eddy current 
inspections for vertical cracks in the fuselage skin along the chem-
milled steps of the butt joints, in accordance with Part 3 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1210, Revision 3, dated July 16, 2009. Repeat the inspections 
thereafter at intervals not to exceed 1,800 flight cycles or 1,800 
flight hours, whichever occurs first. If any cracking is found, 
before further flight, repair in accordance with Part 5 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1210, Revision 3, dated July 16, 2009. Doing the repair 
terminates the repetitive inspections specified in this paragraph 
for the repaired area only.
    (1) Before the accumulation of 55,000 total flight cycles or 
55,000 total flight hours, whichever occurs first.
    (2) Within 1,800 flight cycles or 1,800 flight hours after the 
effective date of this AD, whichever occurs first.
    (s) For Groups 1 through 21 airplanes identified in Boeing Alert 
Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009: 
Before the accumulation of 35,000 total flight cycles or within 
4,500 flight cycles after the effective date of this AD, whichever 
is later, do external detailed and eddy current inspections for 
horizontal cracks along the chem-milled lines of the fuselage skin 
of the lower lobe area and section 41, in accordance with Part 4 of 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
737-53A1210, Revision 3, dated July 16, 2009; except as required by 
paragraph (u) of this AD. Repeat the inspections thereafter at 
intervals not to exceed 4,500 flight cycles. Accomplishing the 
inspections required by this paragraph ends the repetitive 
inspections required by paragraph (h) of this AD. Before further 
flight, do all applicable corrective actions as specified in 
paragraph (j) of this AD.
    (t) For Groups 4, 11, and 16 airplanes identified in Boeing 
Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009: 
Before the accumulation of 25,000 total flight cycles or within 
4,500 flight cycles after the effective date of this AD, whichever 
is later, do external detailed and eddy current inspections for 
horizontal cracks along the chem-milled lines of the fuselage skin 
of the fuselage window belt area in accordance with Part 2 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1210, Revision 3, dated July 16, 2009. Repeat the inspections 
thereafter at intervals not to exceed 4,500 flight cycles. If any 
cracking is found, before further flight, repair using a

[[Page 12624]]

method approved in accordance with paragraph (y) of this AD.
    (u) For Groups 3, 5, 9, 10, 12, 14, 15, 17, 18, 19, 20, and 21 
airplanes identified in Boeing Alert Service Bulletin 737-53A1210, 
Revision 3, dated July 16, 2009: Do the actions specified in 
paragraph (u)(1) or (u)(2) of this AD, as applicable.
    (1) For airplanes on which the inspections required by paragraph 
(g) of this AD have been done before the effective date of this AD: 
Within 4,500 flight cycles after doing the most recent inspection 
required by paragraph (g) of this AD, do external detailed and eddy 
current inspections for horizontal cracks along the chem-milled 
lines of the fuselage skin of the fuselage window belt area in 
accordance with Part 2 of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1210, Revision 3, dated July 16, 2009. 
Repeat the inspections thereafter at intervals not to exceed 4,500 
flight cycles. If any cracking is found, before further flight, 
repair in accordance with Part 8 of Boeing Alert Service Bulletin 
737-53A1210, Revision 3, dated July 16, 2009, except as required by 
paragraph (x) of this AD.
    (2) For airplanes on which the inspections required by paragraph 
(g) of this AD have not been done before the effective date of this 
AD: Before the accumulation of 25,000 total flight cycles or within 
4,500 flight cycles after the effective date of this AD, whichever 
is later, do external detailed and eddy current inspections for 
horizontal cracks along the chem-milled lines of the fuselage skin 
of the fuselage window belt area in accordance with Part 2 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1210, Revision 3, dated July 16, 2009. Repeat the inspections 
thereafter at intervals not to exceed 4,500 flight cycles. If any 
cracking is found, before further flight, repair in accordance with 
Part 8 of Boeing Alert Service Bulletin 737-53A1210, Revision 3, 
dated July 16, 2009, except as required by paragraph (x) of this AD.

Repair and Preventive Modification

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

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

    (w) For airplanes on which no cracking is found during any 
inspection required by paragraph (p) or (q) of this AD, as 
applicable, doing the preventive modification of the chem-milled 
areas in the skin at stringer S-12, as specified in Part 7 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1210, Revision 3, dated July 16, 2009, except as required by 
paragraph (x) of this AD, ends the repetitive external detailed and 
eddy current inspections required by paragraph (p) or (q) of this 
AD, as applicable, for the modified area only.

Exception to Boeing Alert Service Bulletin 737-53A1210, Revision 3

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

Alternative Methods of Compliance (AMOCs)

    (y)(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, send it to the 
attention of the person identified in the Related Information 
section of this AD. Information may be e-mailed to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD if it is approved by the 
Boeing Commercial Airplanes ODA that has been authorized by the 
Manager, Seattle ACO to make those findings. For a repair method to 
be approved, the repair must meet the certification basis of the 
airplane, and the approval must specifically refer to this AD.
    (4) AMOCs approved previously in accordance with AD 2004-18-06, 
Amendment 39-13784, are approved as AMOCs for the corresponding 
provisions of this AD.

Related Information

    (z) 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; e-mail: 
[email protected].

    Issued in Renton, Washington on February 22, 2011.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2011-5159 Filed 3-7-11; 8:45 am]
BILLING CODE 4910-13-P