[Federal Register Volume 72, Number 20 (Wednesday, January 31, 2007)]
[Rules and Regulations]
[Pages 4419-4423]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-1396]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-24496; Directorate Identifier 2005-NM-141-AD; 
Amendment 39-14914; AD 2007-03-03]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -200C, -
300, -400, and -500 Series Airplanes

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

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series 
airplanes. This AD requires repetitive inspections to detect cracks in 
the vertical beam webs of the body station (BS) 178 bulkhead, and 
corrective actions if necessary. This AD also requires a terminating 
modification for the repetitive inspections. This AD results from 
reports of numerous cracks in the vertical beam webs. We are issuing 
this AD to prevent fatigue cracks in certain vertical beam webs, which 
could result in loss of structural integrity of the BS 178 bulkhead, 
and consequently could impair the operation of the control cables for 
the elevators, speed brakes, and landing gear, or could cause the loss 
of cabin pressure.

DATES: This AD becomes effective March 7, 2007.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in the AD as of March 7, 
2007.

ADDRESSES: You may examine the AD docket on the Internet at http://dms.dot.gov or in person at the Docket Management Facility, U.S. 
Department of Transportation, 400 Seventh Street, SW., Nassif Building, 
Room PL-401, Washington, DC.
    Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207, for service information identified in this AD.

FOR FURTHER INFORMATION CONTACT: Howard Hall, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6430; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Examining the Docket

    You may examine the airworthiness directive (AD) docket on the 
Internet at http://dms.dot.gov or in person at the Docket Management 
Facility office between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. The Docket Management Facility office 
(telephone (800) 647-5227) is located on the plaza level of the Nassif 
Building at the street address stated in the ADDRESSES section.

Discussion

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to include an AD that would apply to certain Boeing Model 
737-100, -200, -200C, -300, -400, and -500 series airplanes. That NPRM 
was published in the Federal Register on April 18, 2006 (71 FR 19835). 
That NPRM proposed to require repetitive inspections to detect cracks 
in the vertical beam webs of the body station (BS) 178 bulkhead, and 
corrective actions if necessary. That NPRM also proposed to require a 
terminating modification for the repetitive inspections.

Comments

    We provided the public the opportunity to participate in the 
development of this AD. We have considered the comments received.

Request To Extend Compliance Time Threshold

    Continental Airlines (Continental) requests that the threshold for 
the compliance times specified in Table 1 of the NPRM be aligned with 
the compliance times specified in ADs 2000-05-29, amendment 39-11639 
(65 FR 14834, March 20, 2000), and 2001-02-01, amendment 39-12085 (66 
FR 7576, January 24, 2001). Continental states that this will reduce 
the economic impact on operators from doing early inspections and will 
encourage operators to terminate those ADs at 20,000 total flight 
cycles as opposed to doing repetitive inspections.
    We do not agree. Continental provided no technical justification 
for revising the inspection threshold. In developing an appropriate 
compliance time for this action, we considered the safety implications 
and normal maintenance schedules for the timely accomplishment of the 
inspections. In consideration of these items, as well as the reports of 
numerous cracks in the vertical beam webs in service, we have 
determined that the compliance times specified in Table 1 of this AD 
will ensure an acceptable level of safety and allow the inspections to 
be done during scheduled maintenance intervals for most affected 
operators. However, according to the provisions of paragraph (m) of the 
AD, we may approve requests to adjust the compliance time if the 
request includes data that substantiate that the new compliance time 
would provide an acceptable level of safety.

Request To Include an Additional Grace Period

    The Air Transport Association (ATA), on behalf of one of its 
members, United Airlines (United), requests that the compliance time 
specified in paragraph (f)(2) of the NPRM be revised to reflect the 
intention of Boeing Service Bulletin 737-53A1225, Revision 1, dated 
April 14, 2005 (referred to in the NPRM as the appropriate source of 
service information for accomplishing the repetitive inspections and 
terminating preventative modification). United proposes that all 
airplanes should have a minimum of 4,500 flight cycles after the 
effective date of the AD to do the initial inspection required by 
paragraph (f) of the NPRM. United also states that Boeing Service 
Bulletin 737-53A1225, dated October 19, 2000, specifies an interval of 
12,000 flight cycles for the repetitive high frequency eddy current 
(HFEC) inspections. Without a grace period, United points out that 
operators doing those inspections would be grounded as of the effective 
date of the AD.
    We agree and have revised paragraph (f)(2) of this AD to provide a 
grace period of 4,500 flight cycles after the effective date of this 
AD.

Request To Include Certain Airplanes in Compliance Time Table

    Boeing requests that we revise Table 1, ``Compliance Times,'' of 
the NPRM to address airplanes inspected in accordance with Boeing 
Service Bulletin 737-53A1225, Revision 1.
    We do not agree. Operators are given credit for actions previously 
done by means of the phrase in paragraph (e) of this AD that states, 
``unless the actions have already been done.'' Therefore, in the case 
of this AD, if the required inspection specified in Boeing Service 
Bulletin 737-53A1225, Revision 1, has been done before the effective 
date of this AD, this AD does not require that it be repeated. In 
addition, if the required inspection specified in Boeing Service 
Bulletin 737-53A1225, Revision

[[Page 4420]]

1, has not been done before the effective date of this AD, this AD 
requires that inspection to be done at the applicable time specified in 
Table 1. We have made no change to the final rule in this regard.

Requests To Allow the Use of Boeing BOECOM M-7200-01-00546

    KLM Engineering & Maintenance (KLM), Southwest Airlines 
(Southwest), and United request that the procedures specified in Boeing 
BOECOM M-7200-01-00546, dated March 1, 2001 (referred to in paragraph 
(j) of the NPRM) be allowed to be used after the effective date of the 
AD as an acceptable method of compliance with the preventative 
modification specified in paragraph (i) of the NPRM. Southwest states 
that BOECOM M-7200-01-00546 describes procedures for fabricating 
replacement parts, which would result in a significant cost savings to 
operators. United states that it has modified the majority of its fleet 
using instructions equivalent to those contained BOECOM M-7200-01-
00546. KLM states that it has modified a majority of its fleet using 
Boeing Service Bulletin 737-53A1173, Revision 4, dated September 19, 
2002 (Revision 3 of Boeing Service Bulletin 737-53A1173 is referred to 
in paragraph (k) of the NPRM as the appropriate source of service 
information for accomplishing the preventative modification), together 
with the instructions specified in BOECOM M-7200-01-00546. United and 
KLM would like to continue modifying their fleets using the same 
instructions. In addition, Boeing requests that the description of 
acceptable actions in paragraph (j) of the NPRM be revised to include 
procedures done in accordance with Boeing BOECOM M-7200-01-00546 and 
approved by Boeing and the FAA after March 1, 2001.
    We partially agree. We agree that doing the replacement or 
modification specified in Boeing BOECOM M-7200-01-00546, dated March 1, 
2001, may be an acceptable means of compliance with the requirements of 
paragraph (j) of this AD. However, it is not likely that replacement or 
modification in accordance with BOECOM M-7200-01-00546 can be done 
without deviations that require further FAA approval. It has been our 
experience that work done in accordance with BOECOM M-7200-01-00546 has 
nearly always required deviations. As noted in BOECOM M-7200-01-00546, 
to obtain approval for using the BOECOM, the operator must provide an 
Authorized Representative (AR) for the Boeing Commercial Airplanes 
Delegation Option Authorization Organization with the airplane 
identification, the details of the proposed replacement, and any 
deviations. Therefore, we have determined that operators who use the 
BOECOM procedures after the effective date of this AD must get them 
approved as an alternative method of compliance (AMOC) in accordance 
with the procedures specified in paragraph (m) of this AD. We have made 
no change to the final rule in this regard.

Request To Remove Option To Repair

    Boeing requests that the word ``repair'' in paragraph (i) of the 
NPRM and in the ``Relevant Service Information'' section of the NPRM be 
deleted. Boeing did not provide a justification.
    We agree. We have re-reviewed Boeing Service Bulletin 737-53A1225, 
Revision 1. In several places in Parts II through IV of the 
Accomplishment Instructions, the service bulletin states, ``Repair or 
change the vertical beam * * * Refer to Figure 25 * * *.'' Figure 25 
refers to ``replacement'' procedures; however, it does not refer to a 
repair procedure. Therefore, we have deleted ``repair or'' in paragraph 
(i) of this AD. We have made no change to the AD in regard to the 
``Relevant Service Information'' section, because that section of the 
NPRM does not reappear in the final rule.

Request To Allow Repair Plans Approved Previously

    Southwest requests that paragraph (j) of the NPRM be revised to 
allow certain repair plans approved by an AR for the Boeing Commercial 
Airplanes Delegation Option Authorization Organization or a Boeing 
Designated Engineering Representative (DER) before the release of 
Boeing BOECOM M-7200-01-00546, dated March 1, 2001, as an acceptable 
method of compliance with the preventative modification specified in 
paragraph (i) of the NPRM. Southwest states that it has installed 
thicker vertical beam webs with such approval on some of its airplanes 
before the issuance of Boeing BOECOM M-7200-01-00546, dated March 1, 
2001.
    We do not agree with Southwest to revise paragraph (j) of this AD. 
Southwest did not provide sufficient data for us to determine if these 
earlier repairs are equivalent to those specified in Boeing BOECOM M-
7200-01-00546, dated March 1, 2001. It is possible that the review and 
approval of earlier repairs may not have taken into account the latest 
information that was used to develop the BOECOM. However, if a 
particular repair is shown to be equivalent to that specified in the 
BOECOM, paragraph (m) of the AD provides operators the opportunity to 
apply for an AMOC to address this type of repair.

Request for Clarification

    Southwest requests that paragraph (j) of the NPRM be revised to 
clarify that it is not necessary to replace certain stiffeners per step 
4 of Boeing BOECOM M-7200-01-00546, if the existing holes can be 
oversized and a new identical fastener can be installed with an 
acceptable edge distance. Step 4 indicates that certain stiffeners must 
be replaced because they are offset by the thickness of the new webs. 
Southwest believes that the intent of that step is to eliminate 
detrimental fastener over-sizing and short edge distances that can 
result from the offset.
    We do not agree with Southwest to revise paragraph (j) of this AD. 
Southwest did not provide any specific limits nor define any acceptable 
combinations of maximum over-sizing of fasteners and/or minimum 
fastener edge distance. Therefore, we are unable to provide approval at 
this time. However, under the provisions of paragraph (m) of this AD, 
we may consider requests for approval of an AMOC if sufficient data are 
submitted to substantiate that such a design change would provide an 
acceptable level of safety.

Request To Delete Concurrent Requirements

    Delta Air Lines (Delta) requests that the concurrent requirements 
of paragraphs (k) and (l) of the NPRM be deleted, and to continue to 
allow the requirements specified in paragraph (c) of ADs 2000-05-29 and 
2001-02-01 to be done separately. Delta notes that the ``Effect of 
Accomplishing Concurrent Requirements'' section in the preamble of the 
NPRM states, ``We realize that the concurrent requirements of this 
proposed AD will force some operators to do the preventative 
modifications required by AD 2001-02-01 early and to do the optional 
preventative modification specified in AD 2000-05-29. However, 
accomplishing the applicable preventative modifications together is 
necessary to avoid repeated disassembly and re-assembly of common 
parts, which increases the likelihood of additional assembly errors.'' 
Delta states that the timing of doing the preventative modification is 
an economic and operational decision, which is properly at the 
discretion of the operators, not a subject for an AD.
    We partially agree. We do not agree with Delta that the concurrent

[[Page 4421]]

requirements be deleted. We determined that mandating the previous 
optional preventative modification specified in AD 2000-05-29 in this 
AD will better ensure long-term continued operational safety of the 
affected airplanes by removing the source of the problem, rather than 
by repetitive inspections. Long-term inspections may not provide the 
degree of safety necessary for the affected airplanes. This, coupled 
with our understanding of the human factor errors associated with 
numerous repetitive inspections, has led us to consider placing less 
emphasis on special procedures and more emphasis on design 
improvements. The preventative modification required by paragraph (l) 
of this AD is consistent with these considerations. Additionally, 
accomplishing the modifications concurrently provides the most 
effective installation of these modifications and will avoid repeated 
disassembly and re-assembly of common parts of critical structure, 
which increases the likelihood of additional assembly errors. Boeing 
also has provided us with data supporting our determination.
    We somewhat agree with Delta to allow the requirements specified in 
paragraph (c) of ADs 2000-05-29 and 2001-02-01 to be done separately. 
It is acceptable to do the preventative modifications required by AD 
2001-02-01 before the requirements of paragraph (i) of this AD. 
However, paragraphs (k) and (l) of the NPRM state, ``Concurrently with 
the requirements of paragraph (i) of this AD * * *.'' Therefore, we 
have revised those paragraphs to clarify that the concurrent 
requirements must be done ``before or concurrently with the 
requirements of paragraph (i) of this AD.'' For clarification purposes, 
we also removed the phrase ``unless already done before the effective 
date of this AD'' from paragraph (k) of this AD.

Request To Supersede AD 2000-05-29

    The ATA, on behalf of one of its members, Delta, requests that AD 
2000-05-29 be superseded or revised to avoid conflicting requirements. 
Delta states that this should be done if its request in the ``Request 
To Delete Concurrent Requirements'' section of this AD is not feasible.
    We do not agree. Paragraph (k) of this AD mandates the previously 
optional preventative modification specified in paragraph (c) of AD 
2000-05-29. A mandatory requirement takes precedence over an optional 
action. Therefore, we find that no conflict exists between the 
requirements of this AD and AD 2000-05-29.
    In addition, we considered superseding ADs 2000-05-29 and AD 2001-
02-01 when developing the NPRM. We determined that doing so would have 
made this AD more complex and would have increased the consequent 
workload associated with revising maintenance record entries, because 
this AD does not affect all requirements of those ADs. This AD only 
affects paragraph (c) of those ADs. Therefore, we determined that a 
less burdensome approach for operators was not to supersede those 
existing ADs.

Request To Address Certain Airplanes

    If the concurrent requirements of the NPRM are kept, Delta further 
requests that Boeing be tasked to address airplanes on which the 
replacement of the forward pressure bulkhead web has been done and on 
which the modification of the vertical beam has not been done.
    We do not agree. We have determined that the procedures specified 
in the Accomplishment Instructions of Boeing Service Bulletin 737-
53A1225, Revision 1, dated April 14, 2005, adequately address all 
affected airplanes. Although the information mentioned by Delta may be 
helpful, the procedures specified in the service bulletin are adequate. 
Therefore, we find it inappropriate to task Boeing to revise the 
service bulletin and to delay the issuance of this AD. However, if 
additional data are presented that would justify additional actions, we 
may consider further rulemaking on this issue.

Requests To Allow AMOCs Approved Previously

    Southwest requests that paragraphs (k) and (l) of the NPRM be 
revised to allow AMOCs approved previously in accordance with ADs 2000-
05-29 and 2001-02-01, respectively. Southwest wants to avoid any issues 
as to whether or not those AMOCs must be resubmitted to us for 
approval.
    Continental requests that paragraph (k) of the NPRM be revised to 
refer to Boeing Service Bulletin 737-53A1173, Revision 4, dated 
September 19, 2002. Continental states that Revision 4 included several 
corrections and work flow improvements.
    We partially agree with both Southwest and Continental. We agree 
that approved AMOCs to paragraph (c) of ADs 2000-05-29 and 2001-02-01 
that are done before or concurrently with the requirements of paragraph 
(i) of this AD are acceptable as AMOCs for the corresponding provisions 
of paragraphs (k) and (l) of this AD, respectively. Boeing Service 
Bulletin 737-53A1173, Revision 4, is one of those AMOCs. We do not 
agree with the commenters that the paragraphs (k) and (l) should be 
revised in regard to AMOCs. The appropriate paragraph to revise is 
paragraph (m) of this AD, which is the AMOC paragraph. Therefore, we 
have revised paragraph (m) accordingly.

Request To Revise AMOC Paragraph

    Boeing requests that paragraph (m)(3) of the NPRM be changed to 
allow AR approval of modifications as well as repairs.
    We agree and have revised paragraph (m)(3) of this AD accordingly.

Requests To Revise Costs of Compliance

    The ATA, on behalf of two of its members, U.S. Airways and United, 
requests that the Costs of Compliance section in the preamble of the 
NPRM account for the work required to gain access, reassemble, complete 
post-modification checkouts, close access, etc. associated with the 
proposed inspection and preventative modification. U.S. Airways states 
that these actions represent an increase of almost 40 percent above and 
beyond the 240 work hours specified in the NPRM. United states that the 
proposed inspection and preventative modification are not normally 
accessed at any routine maintenance visit.
    We do not agree. The Costs of Compliance section describes only the 
direct costs of the specific actions required by this AD. Based on the 
best data available, the manufacturer provided the number of work hours 
(240 for preventative modification; 4 for each inspection) necessary to 
do the required actions. This number represents the time necessary to 
perform only the actions actually required by this AD. We recognize 
that, in doing the actions required by an AD, operators may incur 
incidental costs in addition to the direct costs. The cost analysis in 
AD rulemaking actions, however, typically does not include incidental 
costs such as the time required to gain access and close up, time 
necessary for planning, or time necessitated by other administrative 
actions. Those incidental costs, which may vary significantly among 
operators, are almost impossible to calculate. Therefore, we have made 
no change to this AD in this regard.

Request To Correct Typographical Error

    Boeing requests that a typographical error be fixed in paragraph 
(h) of the NPRM. The reference to ``paragraph (1) of this AD'' should 
be changed to ``paragraph (m) of this AD.''
    We agree and have changed paragraph (h) of this AD accordingly.

[[Page 4422]]

Conclusion

    We have carefully reviewed the available data, including the 
comments received, and determined that air safety and the public 
interest require adopting the AD with the changes described previously. 
We have determined that these changes will neither increase the 
economic burden on any operator nor increase the scope of the AD.

 Costs of Compliance

    There are about 3,132 airplanes of the affected design in the 
worldwide fleet. The following table provides the estimated costs for 
U.S. operators to comply with this AD.

                                                                     Estimated Costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                     Number of U.S.-
             Action               Work hours   Average labor rate per hour         Parts         Cost per airplane      registered         Fleet cost
                                                                                                                        airplanes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Inspection, per inspection                 4                           $80  None..............  $320, per           1,172............  $375,040, per
 cycle.                                                                                          inspection cycle.                      inspection
                                                                                                                                        cycle.
Preventative modification......          240                            80  Between $960 and    Between $20,160     1,172 (720         Between
                                                                             $13,620,            and $32,820,        airplanes have     $9,112,320 and
                                                                             depending on kit    depending on        had the            $14,834,640.
                                                                             purchased.          configuration.      preventative
                                                                                                                     modification
                                                                                                                     incorporated).
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Authority for This Rulemaking

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

Regulatory Findings

    We have determined that this AD will not have federalism 
implications under Executive Order 13132. This AD will not have a 
substantial direct effect on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866;
    (2) Is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and
    (3) 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this AD and placed it in the AD docket. See the ADDRESSES 
section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. The Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

2007-03-03 Boeing: Amendment 39-14914. Docket No. FAA-2006-24496; 
Directorate Identifier 2005-NM-141-AD.

Effective Date

    (a) This AD becomes effective March 7, 2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-100, -200, -200C, -300, 
-400, and -500 series airplanes, certificated in any category; as 
identified in Boeing Service Bulletin 737-53A1225, Revision 1, dated 
April 14, 2005.

Unsafe Condition

    (d) This AD results from reports of numerous cracks in the 
vertical beam webs. We are issuing this AD to prevent fatigue cracks 
in certain vertical beam webs, which could result in loss of 
structural integrity of the body station (BS) 178 bulkhead, and 
consequently could impair the operation of the control cables for 
the elevators, speed brakes, and landing gear, or could cause the 
loss of cabin pressure.

Compliance

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

Repetitive Inspections

    (f) At the applicable times specified in Table 1 of this AD, do 
a high frequency eddy current (HFEC) inspection and detailed 
inspection to detect cracks in the BS 178 vertical beam webs, in 
accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 737-53A1225, Revision 1, dated April 14, 2005.

[[Page 4423]]



                       Table 1.--Compliance Times
------------------------------------------------------------------------
                                                     And repeat the HFEC
                                                        and detailed
  For airplanes on which--          Inspect--            inspections
                                                       thereafter at--
------------------------------------------------------------------------
(1) An HFEC or a detailed     Before the            Intervals not to
 inspection specified in       accumulation of       exceed 6,000 flight
 Boeing Service Bulletin 737-  15,000 total flight   cycles.
 53A1225, dated October 19,    cycles, or within
 2000, has not been done as    4,500 flight cycles
 of the effective date of      after the effective
 this AD.                      date of this AD,
                               whichever occurs
                               later.
(2) An HFEC or detailed       Within 6,000 flight   Intervals not to
 inspection specified in       cycles since the      exceed 6,000 flight
 Boeing Service Bulletin 737-  last HFEC             cycles.
 53A1225, dated October 19,    inspection, within
 2000, has been done before    1,200 flight cycles
 the effective date of this    since the last
 AD.                           detailed
                               inspection, or
                               within 4,500 flight
                               cycles after the
                               effective date of
                               this AD, whichever
                               occurs later.
------------------------------------------------------------------------

Corrective Actions

    (g) If any crack is detected during any inspection required by 
paragraph (f) of this AD, before further flight, repair or replace 
the vertical beam web and associated parts with a new vertical beam 
web, in accordance with the Accomplishment Instructions of Boeing 
Service Bulletin 737-53A1225, Revision 1, dated April 14, 2005, 
except as provided by paragraph (h) of this AD.
    (h) If any damage is beyond the scope of the service bulletin or 
structural repair manual, before further flight, repair the damaged 
vertical beam web in accordance with a method approved by the 
Manager, Seattle Aircraft Certification Office (ACO), FAA; or using 
a method approved in accordance with paragraph (m) of this AD.

Terminating Preventative Modification

    (i) Before the accumulation of 50,000 total flight cycles, or 
within 25,000 flight cycles after the effective date of this AD, 
whichever occurs later, replace the vertical beams at buttock lines 
(BL) 5.7 and 17.0 of the BS 178 bulkhead, in accordance with the 
Accomplishment Instructions of Boeing Service Bulletin 737-53A1225, 
Revision 1, dated April 14, 2005. Accomplishing the replacement ends 
the repetitive inspections required by paragraph (f) of this AD.
    (j) Actions done before the effective date of this AD in 
accordance with Boeing BOECOM M-7200-01-00546, dated March 1, 2001, 
are acceptable for compliance with the requirements of paragraph (i) 
of this AD.

Prior to or Concurrent Requirements

    (k) For Group 1 airplanes identified in Boeing Service Bulletin 
737-53A1225, Revision 1, dated April 14, 2005: Before or 
concurrently with the requirements of paragraph (i) of this AD, do 
the preventative modifications of the center web, vertical chords, 
and side chord areas, including the side chord areas at water line 
207, of the forward pressure bulkhead, specified in paragraph (c) of 
AD 2000-05-29, amendment 39-11639 (reference Boeing Alert Service 
Bulletin 737-53A1173, Revision 3, dated May 6, 1999).
    (l) For Group 2 airplanes identified in Boeing Service Bulletin 
737-53A1225, Revision 1, dated April 14, 2005: Before or 
concurrently with the requirements of paragraph (i) of this AD, but 
no later than the time specified in AD 2001-02-01, amendment 39-
12085, do the preventative modifications of the vertical and side 
chord areas of the forward pressure bulkhead required by paragraph 
(c) of AD 2001-02-01 (reference Boeing Alert Service Bulletin 737-
53A1208, dated May 6, 1999).

Alternative Methods of Compliance (AMOCs)

    (m)(1) The Manager, Seattle ACO, FAA, has the authority to 
approve AMOCs for this AD, if requested in accordance with the 
procedures found in 14 CFR 39.19.
    (2) Before using any AMOC approved in accordance with Sec.  
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
Certificate Holding District Office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any replacement or repair required by this AD, if it is 
approved by an Authorized Representative for the Boeing Commercial 
Airplanes Delegation Option Authorization Organization who has been 
authorized by the Manager, Seattle ACO, to make those findings. For 
a replacement or repair method to be approved, the replacement or 
repair must meet the certification basis of the airplane, and the 
approval must specifically refer to this AD.
    (4) Approved AMOCs to paragraph (c) of AD 2000-05-29 done before 
or concurrently with the requirements of paragraph (i) of this AD 
are approved as AMOCs for the corresponding provisions of paragraph 
(k) of this AD.
    (5) Approved AMOCs to paragraph (c) of AD 2001-02-01 done before 
or concurrently with the requirements of paragraph (i) of this AD 
are approved as AMOCs for the corresponding provisions of paragraph 
(l) of this AD.

Material Incorporated by Reference

    (n) You must use Boeing Service Bulletin 737-53A1225, Revision 
1, dated April 14, 2005, to perform the actions that are required by 
this AD, unless the AD specifies otherwise. The Director of the 
Federal Register approved the incorporation by reference of this 
document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. 
Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207, for a copy of this service information. You 
may review copies at the Docket Management Facility, U.S. Department 
of Transportation, 400 Seventh Street SW., Room PL-401, Nassif 
Building, Washington, DC; on the Internet at http://dms.dot.gov; or 
at the National Archives and Records Administration (NARA). For 
information on the availability of this material at the NARA, call 
(202) 741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

    Issued in Renton, Washington, on January 19, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E7-1396 Filed 1-30-07; 8:45 am]
BILLING CODE 4910-13-P