[Federal Register Volume 77, Number 125 (Thursday, June 28, 2012)]
[Proposed Rules]
[Pages 38547-38552]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-15601]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0645; Directorate Identifier 2011-NM-052-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 all The Boeing Company Model 737-100, -200, -200C, 
-300, -400, and -500 series airplanes. The existing AD currently 
requires repetitive inspections to detect cracking in the web of the 
aft pressure bulkhead at body station 1016 at the aft fastener row 
attachment to the ``Y'' chord, and corrective actions if necessary. 
That AD was prompted by several reports of fatigue cracking at that 
location, which could result in rapid decompression of the fuselage. 
Since we issued that AD, we have received additional reports of cracks 
found in the aft pressure bulkhead. This proposed AD would add various 
inspections for discrepancies at the aft pressure bulkhead, and related 
investigative and corrective actions if necessary. We are proposing 
this AD to detect and correct such fatigue cracking, which could result 
in rapid decompression of the fuselage.

DATES: We must receive comments on this proposed AD by August 13, 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 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; 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: Alan Pohl, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue SW., Renton, Washington 98057-3356; phone: (425) 917-
6450; fax: (425) 917-6590; email: [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-2012-0645; 
Directorate Identifier 2011-NM-052-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 9, 1999, we issued AD 99-08-23, Amendment 39-11132 (64 FR 
19879, April 23, 1999), for all The Boeing Company Model 737-100, -200, 
-200C, -300, -400, and -500 series airplanes. That AD requires 
repetitive inspections of the web of the aft pressure bulkhead at body 
station 1016 at the aft fastener row attachment to the ``Y'' chord; and 
corrective actions, if necessary. That AD resulted from reports of 
fatigue cracking found at that location on The Boeing Company Model 737 
series airplanes. We issued that AD to detect and correct such fatigue 
cracking, which could result in rapid decompression of the fuselage.

Actions Since Existing AD Was Issued

    Since we issued AD 99-08-23, Amendment 39-11132 (64 FR 19879, April 
23, 1999), we have received reports that cracks have been found in four 
general areas of the aft pressure bulkhead: In the web at the web-to-
``Y'' chord interface, in the web at the outer circumferential tear 
strap, in the web near the dome cap, and in the ``Z'' stiffeners near 
the dome cap. Cracks have been reported in these new areas on airplanes 
that have accumulated between 21,246 and 68,000 total flight cycles, 
and between 17,500 and 61,000 total flight hours.

[[Page 38548]]

Relevant Service Information

    We reviewed Boeing Alert Service Bulletin 737-53A1214, Revision 4, 
dated December 16, 2011. The service information describes procedures 
and compliance times for various inspections for discrepancies 
(including cracking, misdrilled fastener holes, elongated fastener 
holes, corrosion, oil-cans, and existing repairs) at the aft pressure 
bulkhead, and related investigative and corrective actions if 
necessary, as follows:
     Repetitive detailed and low frequency eddy current (LFEC) 
inspections of the aft side of the upper bulkhead web, or detailed and 
high frequency eddy current (HFEC) inspections from the forward side of 
the bulkhead, to detect cracks, incorrectly drilled fastener holes, or 
elongated fastener holes; and related investigative actions, including 
HFEC and detailed inspections to detect additional cracks, incorrectly 
drilled fastener holes, or elongated fastener holes on the section of 
the web of the forward side of the bulkhead.
     Repetitive detailed, surface HFEC, and subsurface LFEC 
inspections to detect cracks, incorrectly drilled fastener holes, or 
elongated fastener holes of the lower bulkhead web from the forward or 
aft side of the bulkhead.
     A one-time LFEC inspection to detect cracks on the aft 
side of the bulkhead of the web located under the outer circumferential 
tear strap, or a one-time HFEC inspection to detect cracks from the 
forward side of the bulkhead of the web located under the outer 
circumferential tear strap.
     A detailed inspection from the aft side of the bulkhead 
for oil-canning, and related investigative actions. The related 
investigative actions include detailed and HFEC inspections for cracks, 
and a measurement of the depth and width of the oil-can. For airplanes 
on which oil-cans are found within limits, the service information 
specifies an option of doing repetitive detailed and HFEC inspections 
for cracks of the oil-canning and eventual repair. Doing the repair 
terminates the repetitive inspections.
     Repetitive eddy current inspections to detect cracks of 
the dome cap at the center of the bulkhead.
     Repetitive HFEC inspections to detect cracks of the ``Z'' 
stiffener flanges at the dome cap in the center of the bulkhead.
     A detailed inspection of the bulkhead web and of the 
stiffeners for existing repairs; and, depending on the findings, 
repetitive HFEC or LFEC inspections of the web for cracking; 
replacement of existing repairs with new repairs, and damage tolerance 
inspections.
     The corrective actions include repairing discrepancies 
(including cracking, misdrilled fastener holes, elongated fastener 
holes, corrosion, oil-cans, and existing repairs), or for certain 
discrepancies, contacting Boeing for repair instructions.
     The initial compliance times vary depending on inspection 
type and area. The earliest initial inspection is within 375 flight 
cycles after the effective date of this AD. The latest initial 
inspection is within 6,000 flight cycles or 24 months after the 
effective date of this AD, whichever occurs first.
    The compliance times for the option, for airplanes on which oil-
cans are found within limits, of doing repetitive detailed and HFEC 
inspections for cracks of the oil-canning and eventual repair are as 
follows: The initial inspections are done before further flight. The 
repetitive interval is 1,200 flight cycles. The repair must be done 
within 12,000 flight cycles after the oil-can was found.
    The repetitive inspections range from intervals not to exceed 6,000 
flight cycles to intervals not to exceed 12,000 flight cycles, 
depending on the inspection type and area.

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 requirements of AD 99-08-23, 
Amendment 39-11132 (64 FR 19879, April 23, 1999). 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.''

Changes to Existing AD

    This proposed AD would retain all requirements of AD 99-08-23, 
Amendment 39-11132 (64 FR 19879, April 23, 1999). Since AD 99-08-23 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
------------------------------------------------------------------------
    Requirement in AD 99-08-23,
 Amendment 39-11132 (64 FR 19879,    Corresponding  requirement in this
          April 23, 1999)                        proposed AD
------------------------------------------------------------------------
    paragraph (a)                      paragraph (g)
    paragraph (b)                      paragraph (h)
    paragraph (c)                      paragraph (i)
    paragraph (d)                      paragraph (j)
------------------------------------------------------------------------

    Boeing Commercial Airplanes has received an Organization 
Designation Authorization (ODA). We have revised this proposed AD to 
delegate the authority to approve an alternative method of compliance 
for any repair required by this proposed AD to the Boeing Commercial 
Airplanes ODA rather than a Designated Engineering Representative 
(DER).
    We have revised the date of the document specified in paragraph 
(j)(1) of this proposed AD (which is a restatement of paragraph (d)(1) 
of AD 99-08-23, Amendment 39-11132 (64 FR 19879, April 23, 1999)), to 
November 5, 1995, as specified in the ``Incorporation of Reference'' 
paragraph of AD 99-08-23 (paragraph (g) of AD 99-08-23).

Differences Between the Proposed AD and the Service Information

    Boeing Alert Service Bulletin 737-53A1214, Revision 4, dated 
December 16, 2011, specifies to contact the manufacturer for 
instructions on how to 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 566 airplanes of U.S. 
registry. We estimate the following costs to comply with this proposed 
AD:

[[Page 38549]]



                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
LFEC [retained actions from AD 99- 8 work-hours x $85               $0  $680...............  $384,880.
 08-23, Amendment 39-11132 (64 FR   per hour = $680.
 19879, April 23, 1999)].
Detailed visual inspection         2 work-hours x $85                0  $170...............  $96,220.
 [retained actions from AD 99-      per hour = $170.
 08[dash]23, Amendment 39-11132
 (64 FR 19879, April 23, 1999)].
Detailed, HFEC, and LFEC           Up to 60                          0  $5,100 per           $2,886,600 per
 inspections of the web at the      work[dash]hours x                    inspection cycle.    inspection cycle.
 ``Y'' chord of the bulkhead, the   $85 per hour =
 web located under the outer        $5,100 per
 circumferential tear strap, the    inspection cycle.
 ``Z'' stiffeners at the dome
 cap, and existing repairs [new
 proposed action].
----------------------------------------------------------------------------------------------------------------

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

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Detailed and HFEC inspections for               1 work-hour x $85 per hour = $85              $0             $85
 oil[dash]canning.
LFEC or HFEC inspections for cracking.........  2 work-hours x $85 per hour =                  0             170
                                                 $170.
----------------------------------------------------------------------------------------------------------------

    We have received no definitive data that would enable us to provide 
cost estimates for the crack repairs specified in this proposed AD.

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) 99-08-23, Amendment 39-11132 (64 FR 19879, April 23, 1999), and 
adding the following new AD:

The Boeing Company: Docket No. FAA-2012-0645; Directorate Identifier 
2011-NM-052-AD.

(a) Comments Due Date

    The FAA must receive comments on this AD action by August 13, 
2012.

(b) Affected ADs

    This AD supersedes AD 99-08-23, Amendment 39-11132 (64 FR 19879, 
April 23, 1999).

(c) Applicability

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

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by several reports of fatigue cracks in the 
aft pressure bulkhead. We are issuing this AD to detect and correct 
such fatigue cracking, which could result in rapid decompression of 
the fuselage.

(f) Compliance

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

(g) Retained Initial Inspection

    This paragraph restates the initial inspection required by 
paragraph (a) of AD 99-08-23, Amendment 39-11132 (64 FR 19879, April 
23, 1999). Perform either inspection specified by paragraph (g)(1) 
or

[[Page 38550]]

(g)(2) of this AD at the time specified in paragraph (h) of this AD.
    (1) Perform a low frequency eddy current (LFEC) inspection from 
the aft side of the aft pressure bulkhead to detect discrepancies 
(including cracking, misdrilled fastener holes, and corrosion) of 
the web of the upper section of the aft pressure bulkhead at body 
station 1016 at the aft fastener row attachment to the ``Y'' chord, 
from stringer 15 left to stringer 15 right, in accordance with 
Boeing 737 Nondestructive Test Manual D6-37239, Part 6, Section 53-
10-54, dated December 5, 1998.
    (2) Perform a detailed visual inspection of the aft fastener row 
attachment to the ``Y'' chord from the forward side of the aft 
pressure bulkhead to detect discrepancies (including cracking, 
misdrilled fastener holes, and corrosion) of the entire web of the 
aft pressure bulkhead at body station 1016.

(h) Retained Compliance Times

    This paragraph restates the compliance times specified in 
paragraph (b) of AD 99-08-23, Amendment 39-11132 (64 FR 19879, April 
23, 1999). Perform the inspection required by paragraph (g) of this 
AD at the time specified in paragraph (h)(1), (h)(2), or (h)(3) of 
this AD, as applicable.
    (1) For airplanes that have accumulated 40,000 or more total 
flight cycles as of May 10, 1999 (the effective date of AD 99-08-23, 
Amendment 39-11132 (64 FR 19879, April 23, 1999)): Inspect within 
375 flight cycles or 60 days after May 10, 1999, whichever occurs 
later.
    (2) For airplanes that have accumulated 25,000 or more total 
flight cycles and fewer than 40,000 total flight cycles as of May 
10, 1999 (the effective date of AD 99-08-23, Amendment 39-11132 (64 
FR 19879, April 23, 1999)): Inspect within 750 flight cycles or 90 
days after May 10, 1999, whichever occurs later.
    (3) For airplanes that have accumulated fewer than 25,000 total 
flight cycles as of May 10, 1999 (the effective date of AD 99-08-23, 
Amendment 39-11132 (64 FR 19879, April 23, 1999)): Inspect prior to 
the accumulation of 25,750 total flight cycles.

(i) Retained Repetitive Inspections

    This paragraph restates the repetitive inspections required by 
paragraph (c) of AD 99-08-23, Amendment 39-11132 (64 FR 19879, April 
23, 1999). Within 1,200 flight cycles after performing the initial 
inspection required by paragraph (g) of this AD, and thereafter at 
intervals not to exceed 1,200 flight cycles: Perform either 
inspection specified by paragraph (g)(1) or (g)(2) of this AD.

(j) Retained Corrective Actions

    This paragraph restates the corrective actions required by 
paragraph (d) of AD 99-08-23, Amendment 39-11132 (64 FR 19879, April 
23, 1999). If any discrepancy is detected during any inspection 
required by paragraph (g), (h), or (i) of this AD: Prior to further 
flight, accomplish the actions specified by paragraphs (j)(1) and 
(j)(3) of this AD, and paragraph (j)(2) of this AD, if applicable.
    (1) Perform a high frequency eddy current inspection from the 
forward side of the bulkhead to detect cracking of the web at the 
``Y'' chord attachment, around the entire periphery of the ``Y'' 
chord, in accordance with Boeing 737 Nondestructive Test Manual D6-
37239, Part 6, Section 51-00-00, Figure 23, dated November 5, 1995.
    (2) If the most recent inspection performed in accordance with 
paragraph (g) of this AD was not a detailed visual inspection: 
Accomplish the actions specified by paragraph (g)(2) of this AD. If 
the inspection was a detailed visual inspection, it is not necessary 
to repeat that inspection prior to further flight.
    (3) Repair any discrepancy such as cracking or corrosion or 
misdrilled fastener holes using a method approved in accordance with 
the procedures specified in paragraph (u) of this AD.

(k) New Requirements: Inspections of the Web at the ``Y'' Chord Upper 
Bulkhead From S-15L to S-15R

    At the later of the times specified in paragraphs (k)(1) and 
(k)(2) of this AD: Do detailed and LFEC inspections of the aft side 
of the bulkhead web, or do detailed and HFEC inspections from the 
forward side of the bulkhead, and do all applicable related 
investigative and corrective actions; in accordance with Part 1 of 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
737-53A1214, Revision 4, dated December 16, 2011, except as required 
by paragraphs (r)(1) and (r)(3) of this AD. Inspect for cracks, 
incorrectly drilled fastener holes, and elongated fastener holes. Do 
all applicable related investigative and corrective actions before 
further flight. Repeat the inspections at the applicable times 
specified in table 1 of paragraph 1.E., ``Compliance,'' of Boeing 
Alert Service Bulletin 737-53A1214, Revision 4, dated December 16, 
2011.
    (1) Prior to the accumulation of 25,000 total flight cycles.
    (2) Except as required by paragraphs (r)(2) and (r)(4) of this 
AD, at the later of the times specified in the ``Compliance Time'' 
column in table 1 of paragraph 1.E., ``Compliance,'' of Boeing Alert 
Service Bulletin 737-53A1214, Revision 4, dated December 16, 2011.

(l) New Requirements: Inspections of the Web at the ``Y'' Chord in the 
Lower Bulkhead From S-15L to S-15R

    Except as required by paragraphs (r)(2) and (r)(5) of this AD, 
at the applicable time specified in table 2 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011: Do detailed and eddy current 
inspections of the web from the forward or aft side of the bulkhead 
for cracks, incorrectly drilled fasteners, and elongated fasteners, 
in accordance with Part III of the Accomplishment Instructions of 
Boeing Alert Service Bulletin 737-53A1214, Revision 4, dated 
December 16, 2011, except as required by paragraphs (r)(1) and 
(r)(3) of this AD. If any crack, incorrectly drilled fastener, 
elongated fastener, or corrosion is found, before further flight, 
repair the web using a method approved in accordance with the 
procedures specified in paragraph (u) of this AD. Repeat the 
inspections at the applicable times specified in table 2 of 
paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 
737-53A1214, Revision 4, dated December 16, 2011.

(m) New Requirements: One-Time Inspection Under the Tear Strap

    Except as required by paragraphs (r)(2) and (r)(5) of this AD, 
at the applicable time specified in table 3 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011: Do a one-time LFEC inspection 
for cracks on the aft side of the bulkhead of the web located under 
the outer circumferential tear strap, or do a one-time HFEC 
inspection for cracks from the forward side of the bulkhead of the 
web located under the outer circumferential tear strap, in 
accordance with Part II of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1214, Revision 4, dated December 16, 
2011, except as required by paragraph (r)(1) of this AD. If any 
cracking is found, before further flight, repair the bulkhead using 
a method approved in accordance with the procedures specified in 
paragraph (u) of this AD.

(n) New Requirements: Inspection for Oil-Canning

    Except as required by paragraph (r)(2) of this AD, at the 
applicable time specified in table 4 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011: Do a detailed inspection from 
the aft side of the bulkhead for oil-canning and do all applicable 
related investigative and corrective actions, in accordance with 
Part II of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1214, Revision 4, dated December 16, 2011, except as 
required by paragraph (r)(1) of this AD. Do all related 
investigative and corrective actions before further flight. 
Thereafter, repeat the inspection at the applicable times specified 
in table 4 of paragraph 1.E., ``Compliance,'' of Boeing Alert 
Service Bulletin 737-53A1214, Revision 4, dated December 16, 2011. 
For oil-cans found within the limits specified in Part II of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1214, Revision 4, dated December 16, 2011: In lieu of installing 
the repair before further flight, at the applicable times specified 
in table 4 of paragraph 1.E., ``Compliance,'' of Boeing Alert 
Service Bulletin 737-53A1214, Revision 4, dated December 16, 2011, 
do initial and repetitive detailed and HFEC inspections for cracks 
of the oil-canning and install the repair, in accordance with the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1214, Revision 4, dated December 16, 2011. If any crack is found, 
before further flight, repair the cracking using a method approved 
in accordance with the procedures specified in paragraph (u) of this 
AD. Installing the repair terminates the repetitive inspections for 
cracks.

[[Page 38551]]

(o) New Requirements: Inspection of the Dome Cap at the Center of the 
Bulkhead

    Except as required by paragraphs (r)(2) and (r)(5) of this AD, 
at the applicable time specified in table 5 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011: Do an eddy current inspection 
to detect any cracking of the dome cap at the center of the 
bulkhead, and do all applicable corrective actions, in accordance 
with Part IV of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1214, Revision 4, dated December 16, 2011. 
Do all corrective actions before further flight. Repeat the 
inspection at the times specified in table 5 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011.

(p) New Requirements: Inspection of the Forward Flange of the ``Z'' 
Stiffeners at the Dome Cap

    Except as required by paragraphs (r)(2) and (r)(5) of this AD, 
at the applicable time specified in table 6 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011: Do an HFEC inspection to detect 
any cracking of the ``Z'' stiffener flanges at the dome cap in the 
center of the bulkhead, in accordance with Part V of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1214, Revision 4, dated December 16, 2011, except as required by 
paragraph (r)(1) of this AD. If any crack is found, before further 
flight, repair the flanges using a method approved in accordance 
with the procedures specified in paragraph (u) of this AD. Repeat 
the inspection at the applicable times specified in table 6 of 
paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 
737-53A1214, Revision 4, dated December 16, 2011.

(q) New Requirement: Inspection for Existing Repairs on the Bulkhead

    Except as required by paragraph (r)(2) of this AD, at the 
applicable time specified in table 7 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011: Do a detailed inspection of the 
bulkhead web and stiffeners for existing repairs, in accordance with 
Part VI of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1214, Revision 4, dated December 16, 2011, except as 
required by paragraph (r)(1) of this AD.
    (1) If any repair identified in the ``Condition'' column of 
table 8 of paragraph 1.E., ``Compliance,'' of Boeing Alert Service 
Bulletin 737-53A1214, Revision 4, dated December 16, 2011, is found 
and the ``Reference'' column refers to Appendix A, B, C, or D of 
that service bulletin: At the applicable times specified in table 8 
of paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 
737-53A1214, Revision 4, dated December 16, 2011, except as required 
by paragraph (r)(2) of this AD, do a HFEC inspection or a LFEC 
inspection of the web for cracking, in accordance with Appendix A, 
B, C, or D, as applicable, of Boeing Alert Service Bulletin 737-
53A1214, Revision 4, dated December 16, 2011. If any cracking is 
found, before further flight, repair using a method approved in 
accordance with the procedures specified in paragraph (u) of this 
AD. Repeat the inspections, thereafter, at the applicable intervals 
specified in table 8 of paragraph 1.E., ``Compliance,'' of Boeing 
Alert Service Bulletin 737-53A1214, Revision 4, dated December 16, 
2011.
    (2) If any repair identified in the ``Condition'' column of 
table 8 of paragraph 1.E., ``Compliance,'' of Boeing Alert Service 
Bulletin 737-53A1214, Revision 4, dated December 16, 2011, is found 
and the ``Reference'' column refers to Appendix E of that service 
bulletin: At the applicable times specified in table 8 of paragraph 
1.E., ``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011, except as required by paragraph 
(r)(2) of this AD, remove the repair and replace with a new repair, 
in accordance with Appendix E of Boeing Alert Service Bulletin 737-
53A1214, Revision 4, dated December 16, 2011.
    (3) If any non-SRM (structural repair manual) repair is found 
and the repair does not have FAA-approved damage tolerance 
inspections, except as required by paragraph (r)(2) of this AD, at 
the applicable time specified in table 7 of Paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, 
Revision 4, dated December 16, 2011: Contact the Boeing Commercial 
Airplanes Organization Designation Authorization (ODA) that has been 
authorized by the Manager, Seattle ACO, for damage tolerance 
inspections. Do those damage tolerance inspections at the times 
given using a method approved in accordance with the procedures 
specified in paragraph (u) of this AD.

(r) Exceptions to the Service Bulletin

    (1) Where Boeing Alert Service Bulletin 737-53A1214, Revision 4, 
dated December 16, 2011, specifies to contact Boeing for repair 
instructions: Before further flight, repair using a method approved 
in accordance with the procedures specified in paragraph (u) of this 
AD.
    (2) Where Boeing Alert Service Bulletin 737-53A1214, Revision 4, 
dated December 16, 2011, specifies a compliance time ``after the 
date of Revision 1 to this service bulletin,'' ``from the date of 
Revision 3 of this service bulletin,'' ``after the date of Revision 
3 to this service bulletin,'' or ``of the effective date of AD 99-
08-23,'' this AD requires compliance within the specified compliance 
time after the effective date of this AD.
    (3) Access and restoration procedures specified in the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1214, Revision 4, dated December 16, 2011, are not required by 
this AD. Operators may do those procedures following their 
maintenance practices.
    (4) Where table 1 of paragraph 1.E., ``Compliance'' of Boeing 
Alert Service Bulletin 737-53A1214, Revision 4, dated December 16, 
2011, specifies a compliance time relative to actions done ``in 
accordance with paragraph (a)(2) of AD 99-08-23,'' this AD requires 
compliance within the specified compliance time relative to actions 
specified in paragraph (g)(2) of this AD.
    (5) Where the Condition columns in tables 2, 3, 5, and 6 of 
paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 
737-53A1214, Revision 4, dated December 16, 2011, refer to total 
flight cycles, this AD applies to the airplanes with the specified 
total flight cycles as of the effective date of this AD.

(s) Terminating Action

    Accomplishment of the requirements of paragraphs (k) through (q) 
of this AD terminates the requirements of paragraphs (g) through (j) 
of this AD.

(t) Credit for Previous Actions

    This paragraph provides credit for the actions required by 
paragraphs (k) through (s) of this AD, if the actions were performed 
before the effective date of this AD using the service bulletins 
specified in paragraphs (t)(1) through (t)(4) of this AD.
    (1) Boeing Alert Service Bulletin 737-53A1214, dated June 17, 
1999.
    (2) Boeing Alert Service Bulletin 737-53A1214, Revision 1, dated 
June 22, 2000.
    (3) Boeing Alert Service Bulletin 737-53A1214, Revision 2, dated 
May 24, 2001.
    (4) Boeing Alert Service Bulletin 737-53A1214, Revision 3, dated 
January 19, 2011.

(u) 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: [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 Organization Designation Authorization 
(ODA) that has been authorized by the Manager, Seattle ACO to make 
those findings. For a repair method to be approved, the repair must 
meet the certification basis of the airplane, and the approval must 
specifically refer to this AD.
    (4) AMOCs approved previously in accordance with AD 99-08-23, 
Amendment 39-11132 (64 FR 19879, April 23, 1999), are approved as 
AMOCs for the corresponding provisions of this AD.

(v) Related Information

    (1) For more information about this AD, contact Alan Pohl, 
Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue SW., Renton, Washington 
98057-3356; phone: (425) 917-6440; fax: (425) 917-6590; email: 
[email protected].

[[Page 38552]]

    (2) 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; 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 June 18, 2012.
John P. Piccola,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-15601 Filed 6-27-12; 8:45 am]
BILLING CODE 4910-13-P