Document ID: FAA-2018-0393-0014
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: The Boeing Company Airplanes
Posted Date: 2018-12-28T05:00Z

[Federal Register Volume 83, Number 248 (Friday, December 28, 2018)]
[Rules and Regulations]
[Pages 67043-67049]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-28077]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0393; Product Identifier 2018-NM-010-AD; Amendment 
39-19536; AD 2018-26-06]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for all The 
Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER 
series airplanes. This AD was prompted by reports of loose, worn, or 
missing attachment bolts for the main landing gear (MLG) center door 
assemblies. This AD requires repetitive detailed inspections of the 
forward and aft MLG center door assembly attachments for loose, 
missing, damaged, or bottomed-out attachment bolts, and any wear to the 
retention clip assemblies as applicable; and applicable on-condition 
actions. This AD also provides an

[[Page 67044]]

optional terminating action for the repetitive inspections. We are 
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective February 1, 2019.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of February 1, 
2019.

ADDRESSES: For service information identified in this final rule, 
contact Boeing Commercial Airplanes, Attention: Contractual & Data 
Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 
90740-5600; telephone 562-797-1717; internet https://www.myboeingfleet.com. You may view this service information at the 
FAA, Transport Standards Branch, 2200 South 216th St., Des Moines, WA. 
For information on the availability of this material at the FAA, call 
206-231-3195. It is also available on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2018-
0393.

Examining the AD Docket

    You may examine the AD docket on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2018-
0393; or in person at Docket Operations between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays. The AD docket contains 
this final rule, the regulatory evaluation, any comments received, and 
other information. The address for Docket Operations (phone: 800-647-
5527) is U.S. Department of Transportation, Docket Operations, M-30, 
West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, 
Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Alan Pohl, Aerospace Engineer, 
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3527; email: 
alan.pohl@faa.gov.

SUPPLEMENTARY INFORMATION: 

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 by adding an AD that would apply to all The Boeing Company 
Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. 
The NPRM published in the Federal Register on May 11, 2018 (83 FR 
21948). The NPRM was prompted by reports of loose, worn, or missing 
attachment bolts for the MLG center door assemblies. The NPRM proposed 
to require repetitive detailed inspections of the forward and aft MLG 
center door assembly attachments for loose, missing, damaged, or 
bottomed-out attachment bolts, and any wear to the retention clip 
assemblies as applicable; and applicable on-condition actions. The NPRM 
also provided an optional terminating action for the repetitive 
inspections.
    We are issuing this AD to address loose, missing, damaged, or 
bottomed-out attachment bolts, and any wear to the retention clip 
assemblies, which could result in departure of the center and inboard 
MLG door assemblies, subsequent damage to the main flap and horizontal 
stabilizer, and loss of control of the airplane.

Comments

    We gave the public the opportunity to participate in developing 
this final rule. The following presents the comments received on the 
NPRM and the FAA's response to each comment.

Support for the NPRM

    Boeing and The Air Line Pilots Association, International, each 
stated that it concurred with the intent of the NPRM.

Request for Changes to Service Information

    Alaska Airlines (Alaska) requested that changes be made to Boeing 
Special Attention Service Bulletin 737-52-1170, Revision 1, dated 
December 19, 2017 (``BSASB 737-52-1170, R1''). Alaska noted that 
operators cannot comply with the requirements specified in paragraph 
(g) of the proposed AD in cases where BSASB 737-52-1170, R1, directs 
the operator to inspect a Group 3 airplane using Figure 3 or Figure 4 
of BSASB 737-52-1170, R1, because those figures are not applicable to 
Group 3 airplanes.
    We agree with the commenter's observations concerning Figure 3 and 
Figure 4 of BSASB 737-52-1170, R1. We contacted Boeing and have 
determined that the actions for Group 2 airplanes are appropriate for 
all airplanes to comply with the requirements of paragraph (g) of this 
AD. We have revised paragraph (h) of this AD, ``Exceptions to Service 
Information Specifications,'' by adding paragraph (h)(2), which states 
that ``Where BSASB 737-52-1170, R1, limits use of Figures 3 and 4 to 
Group 2 airplanes, for the purposes of this AD, those figures apply to 
all airplane groups.''

Request for Clarification of the Requirements of Paragraph (j) of the 
Proposed AD

    Alaska requested clarification of the requirements specified in 
paragraph (j) of the proposed AD and clarification of which airplane 
groups would be affected by these requirements. Alaska asked if ``all 
actions for Group 3'' means that this paragraph is for Group 3 
airplanes only or for all airplane groups. Alaska also noted that an 
inspection of the ``door assembly'' implies an inspection of the door, 
but BSASB 737-52-1170, R1, describes procedures for inspection of the 
``door installation.''
    We agree with the commenter's request and have revised paragraph 
(j) of this AD as follows:

    As of the effective date of this AD, no person may install an 
MLG assembly or MLG center door assembly on any airplane identified 
in paragraphs (c)(1) through (c)(4) of this AD unless all actions 
for Group 3 airplanes pertaining to that MLG center door attachment, 
and identified as RC in, and in accordance with, the Accomplishment 
Instructions of BSASB 737-52-1170, R1, have been accomplished on 
that MLG assembly or MLG center door assembly within the compliance 
times specified in Tables 4, 5, and 6, as applicable, of paragraph 
1.E., ``Compliance,'' of BSASB 737-52-1170, R1. The actions for 
Group 3 airplanes apply to all airplanes for the requirement of this 
paragraph.

Request To Include Identification Method for Post-Modification Door

    American Airlines (American) requested that BSASB 737-52-1170, R1, 
be revised to include an identifying stencil or placard that could be 
placed on an affected MLG center door assembly once it has been 
modified. The commenter stated that the MLG center door assembly is a 
rotable part. However, neither the NPRM nor BSASB 737-52-1170, R1, 
addresses the issue of a post-modification MLG center door assembly 
being removed from an airplane and replaced with a pre-modification MLG 
center door assembly.
    We acknowledge the commenter's concern that BSASB 737-52-1170, R1, 
does not address the rotability of an MLG center door assembly. We 
addressed the issue of rotability in this AD in two ways. First, the 
applicability in paragraph (c) of this AD includes all Model 737-600, -
700, -700C, -800, -900, and -900ER series airplanes, not just the 
airplanes specified in the effectivity of BSASB 737-52-1170, R1. 
Second, we added paragraph (j) of this AD, ``Parts Installation 
Limitation''.
    While marking or part marking might provide some benefit for 
operator awareness and recordkeeping, the issue

[[Page 67045]]

of rotability is approached in different ways by different operators. 
When there have been similar issues regarding rotable parts, operators 
expressed a preference to not have a requirement to mark and/or part 
mark, although operators may do this at their own discretion. We also 
note that this AD addresses not only the MLG center door assembly but 
also the attachments to the MLG strut assemblies. We have not changed 
this AD in regard to this issue.

Request To Extend the Compliance Time

    Delta Air Lines (DAL) and SunExpress (SXS) requested that the 
compliance time specified in paragraph (g) of the proposed AD be 
extended. SXS requested that the compliance time for the initial 
inspection be extended from 12,000 total flight cycles to 20,000 total 
flight cycles, or from 800 flight cycles after the effective date of 
the proposed AD to 1,500 flight cycles after the effective date of the 
proposed AD, and that the interval for the repetitive inspection be 
extended from 5,500 flight cycles to 6,600 flight cycles. SXS stated 
that 41 airplanes in its fleet have exceeded 12,000 total flight 
cycles, and it would have a short period of time to perform the 
required inspection as described in BSASB 737-52-1170, R1, and it would 
have to operate some airplanes a long time without the MLG shock strut 
doors. SXS noted that performing operations without a MLG shock strut 
door incurs a fuel burn penalty, which is approximately 0.77% more fuel 
burned per flight.
    DAL stated that the compliance time for the initial inspection 
would require them to inspect approximately 80 airplanes in a 200-day 
period, requiring them to accomplish the work for most of its airplanes 
in the line environment, which increases the risk for an ``airplane on 
ground'' situation if there is a finding on the MLG structure. DAL 
noted that BSASB 737-52-1170, R1, does not provide relief for operators 
when a crack or corrosion is found in the MLG lug after removal of the 
bushing. For an MLG that requires re-work, DAL typically removes the 
MLG, replaces it with another MLG, and sends the discrepant MLG to a 
shop for repair. We infer that DAL is requesting that the compliance 
time for the initial inspection be extended.
    In addition, DAL pointed out that the procedures in BSASB 737-52-
1170, R1, would restrict an operator from dispatching an affected 
airplane until corrective is taken to repair the MLG. DAL requested 
that this situation be considered in the final rule by providing a 
limited return to service. DAL stated that if several MLG lugs are 
found with discrepancies, there is the potential of the operator 
grounding airplanes outside of a heavy maintenance check to either 
replace the MLG gear or go through its spare parts inventory.
    We do not agree with the commenters' requests. We appreciate the 
impact that the required actions and the associated compliance times 
will have on operators. However, both the FAA and Boeing have 
identified this issue as an unsafe condition, and the commenters have 
not provided substantiating data for their proposals. In addition, a 
limited return to service would not be appropriate for dispatching 
airplanes with known cracking or corrosion. As SXS has noted, airplanes 
may be operated with the MLG shock strut center and inner doors removed 
until repairs can be made.
    We have reviewed the related service information and note that 
while repair of the MLG lug parts is required for compliance (``RC''), 
certain steps are either labeled as ``RC Exempt,'' or contain technical 
instructions that are prefaced by ``Refer to.'' Paragraph (l)(4) of 
this AD and paragraph 3A., ``General Information,'' of BSASB 737-52-
1170, R1 specify the actions labeled as ``RC Exempt'' are not required 
in order to show compliance to this AD. When the words ``refer to'' are 
used within an RC step and the operator has an accepted alternative 
procedure, the accepted alternative procedure can be used. When the 
words ``in accordance with'' are included in an RC step, the procedure 
in the Boeing document must be used. In addition, for proposals that 
provide an acceptable level of safety and have substantiating data, 
operators may apply for an AMOC using the procedures specified in 
paragraph (l) of this AD. We have not changed this AD in regard to this 
issue.

Request To Allow Installation of New, Overhauled, or Serviceable MLG

    DAL requested that operators be allowed to install a new, 
overhauled, or serviceable MLG instead of repairing a damaged lug and 
installing a new bushing if excessive wear, galling, or cracking is 
found during a detailed inspection/measurement of the MLG shock strut 
bushing. DAL stated that it would have to remove the damaged MLG and 
send it to the shop for repair, and it would be easier to install a 
new, overhauled, or serviceable MLG than to wait for the damaged MLG to 
be repaired. DAL explained that installing a new, overhauled, or 
serviceable MLG provides an equivalent level of safety because the 
intent of the proposed AD is to repair and install new bushings. DAL 
observed that the damaged MLG would be repaired and then be ready for 
use on another airplane.
    We agree with the commenter's request for the reasons provided by 
the commenter. We have revised paragraph (g) of this AD to clarify that 
replacement of an entire MLG assembly within the required compliance 
time satisfies the requirements of paragraph (g), provided that the 
requirements of paragraph (j) of this AD, ``Parts Installation 
Limitation,'' are satisfied for that MLG assembly.
    Since the unsafe condition is also affected by rotability, we have 
revised paragraph (j) of this AD to clarify that an MLG assembly cannot 
be installed on any airplane identified in paragraphs (c)(1) through 
(c)(4) of this AD unless all actions for Group 3 airplanes have been 
accomplished on the MLG assembly. Paragraph (j) of this AD states that:

    As of the effective date of this AD, no person may install an 
MLG assembly or MLG center door assembly on any airplane identified 
in paragraphs (c)(1) through (c)(4) of this AD unless all actions 
for Group 3 airplanes pertaining to that MLG center door attachment, 
and identified as RC in, and in accordance with, the Accomplishment 
Instructions of BSASB 737-52-1170, R1, have been accomplished on 
that MLG assembly or MLG center door assembly within the compliance 
times specified in Tables 4, 5, and 6, as applicable, of paragraph 
1.E., ``Compliance,'' of BSASB 737-52-1170, R1. The actions for 
Group 3 airplanes apply to all airplanes for the requirement of this 
paragraph.

    In the proposed AD, paragraph (j) specified only an MLG center door 
assembly.

Request for Clarification of Intent of Parts Installation Paragraph (j)

    DAL stated that paragraph (j), ``Parts Installation Paragraph,'' of 
the proposed AD was confusing because it stated that an operator may 
not install an MLG center door assembly on an airplane unless all 
actions identified as RC in BSASB 737-52-1170, R1, are accomplished 
within the compliance times specified in Tables 4, 5, and 6, as 
applicable, of paragraph 1.E., ``Compliance,'' of BSASB 737-52-1170, 
R1. DAL observed that if an operator receives a spare door with an FAA 
Form 8130, ``Authorized Release Certificate--Airworthiness Approval 
Tag,'' attached, the tag might include the AD number but the number of 
flight cycles at the last inspection or total flight cycles of the door 
would not be provided. DAL suggested that operators ensure that the 
inspection and corrective actions are accomplished before the spare 
part is installed on the airplane. Therefore, if the flight cycles on 
the door are unknown, the operator would still be in

[[Page 67046]]

compliance with the intent of the NPRM by inspecting the door before 
installation, and that it would be an equivalent level of safety that 
meets the intent of the NPRM.
    We appreciate the commenter's concern and the opportunity to 
clarify the intent of the ``Parts Installation Limitation'' paragraph. 
The compliance times specified in Tables 4, 5, and 6, as applicable, of 
paragraph 1.E., ``Compliance,'' of BSASB 737-52-1170, R1, are in 
airplane flight cycles. There is no requirement in this AD or any 
statement in BSASB 737-52-1170, R1, that it is necessary to determine 
the flight cycles accumulated on the MLG door assembly. The compliance 
times in this AD are based on flight cycles of the airplane instead of 
the MLG door assembly. Our strategy in addressing the unsafe condition 
is to first inspect all affected airplanes, and then to address future 
possible unsafe conditions with the requirements in the ``Parts 
Installation Limitation'' paragraph.
    We have not made any changes to this AD in regard to this issue.

Request To Delay Issuance of Final Rule Until Service Information is 
Corrected

    American, subsequent to its earlier comments, requested that the 
final rule not be issued until discrepancies in BSASB 737-52-1170, R1, 
are rectified and the instructions made clearer. The commenter stated 
that operators cannot comply with the requirements specified in the 
NPRM because of discrepancies in BSASB 737-52-1170, R1. The commenter 
identified the following discrepancies.

    1. BSASB 737-52-1170, R1, has quantities listed in Figures 1 and 
2 that are double what is actually on the aircraft. Although there 
is a note that says ``The QTY numbers shown below are the number or 
parts necessary for each airplane,'' there is a Figure 1 for the 
left and a Figure 2 for the right. Each side has only one of each 
bolt, not two. Note that all of the other figures list the quantity 
of parts that is needed for only the left side or the right side, as 
applicable. Figures 1 and 2 are different than the other figures in 
this regard.
    2. In Figure 5 (and Figures 6, 7, and 8), step 6 says to remove 
three laminated shims. The airplane only has two laminated shims.
    3. In Figure 13 (and Figure 14) step #4 has you install and 
torque the bolt. However, the bolt in #4 has to go through the kept 
bracket and if you install the bolt first, you have to take it back 
out to install the bracket. Steps #4 and #5 should be reversed.
    4. In Figure 13 (and Figure 14), step #6 states to install 3 
each shims, but only 2 were removed, so do we install 3 each in the 
new configuration or just put 2 back?
    5. In Figure 13 (and Figure 14), once we installed the forward 
bolt in step 4, with the correct washers installed, the bolt 
bottomed out in the barrel nut housing, since the bolt is too long. 
New bolts are slightly longer than old. The bolt needs another thick 
washer to fix the issue. The kits that are being delivered do not 
have an adequate amount of the necessary washers.

    Alaska also noted that Figure 13 and Figure 14 of BSASB 737-52-
1170, R1, depict view C with a pre-modification installation in lieu of 
a post-modification installation.
    We acknowledge the commenters' concerns regarding the information 
in the service information that requires clarification. The amount of 
clarification needed would be overly complex for inclusion in this AD. 
We expect to work with Boeing to issue a global AMOC addressing any 
known errors as soon as possible. In addition, we have revised 
paragraph (h) of this AD, ``Exceptions to Service Information 
Specifications,'' by adding paragraph (h)(3) to provide operators with 
information regarding how to address any other issues, if needed.
    In light of the critical nature of the identified unsafe condition, 
we do not consider it warranted to delay the issuance of this final 
rule. When Boeing provides a revision to BSASB 737-52-1170, R1, we will 
review it in consideration of an AMOC to this AD or may consider future 
rulemaking action.

Request To Revise Compliance Time Specifications

    DAL noted that paragraph (h) of the proposed AD states that ``For 
purposes of determining compliance with the requirements of this AD: 
Where BSASB 737-52-1170, Revision 1, uses the phrase `the original 
issue date of this service bulletin', this AD requires using `the 
effective date of this AD'.'' DAL pointed out that in Table 4 of BSASB 
737-52-1170, R1, the compliance times for the Group 3 airplanes, states 
that the actions should be completed ``Within 800 flight cycles after 
the Revision 1 date of this service bulletin.'' DAL asked if the AD 
effective date should also replace the Revision 1 date of the service 
information. We infer that DAL is requesting a revision to paragraph 
(h) of the proposed AD to clarify that for purposes of determining 
compliance with the requirements of the final rule that the effective 
date of the AD should be used instead of the original issue date or the 
Revision 1 date of the service information.
    We agree with the commenter's request for the reasons provided by 
the commenter. We have re-designated paragraph (h) of the proposed AD 
as paragraph (h)(1) in this AD, and revised the text to state that for 
purposes of determining compliance with the requirement of this AD, 
where BSASB 737-52-1170, Revision 1, uses the phrase ``the original 
issue date of this service bulletin'' or ``the Revision 1 date of this 
service bulletin'' this AD requires using ``the effective date of this 
AD.''

Observations Regarding Service Information

    American stated that BSASB 737-52-1170, R1, is confusing and 
unnecessarily complex. American observed that BSASB 737-52-1170, R1, 
provides for 14 possible conditions, multiple options for corrective 
actions, 3 multi-page logic diagrams, and 10 different parts of 
instructions. American stated that the complexity could be simplified 
if the service information pointed the operator straight to the 
modification of the MLG center door assembly retention clip assemblies 
and, if needed, repair to the lugs and replacement of the bushings. 
American declared that the unnecessary complexity of the service 
bulletin invites non-compliance issues.
    We acknowledge the commenter's concerns regarding BSASB 737-52-
1170, R1. The reason BSASB 737-52-1170, R1, includes 14 possible 
conditions, multiple options for corrective actions, 3 multi-page logic 
diagrams, and 10 different parts of instructions is to provide a 
comprehensive set of procedures to address the unsafe condition that 
exists in the affected fleet of airplanes. We suggest that the 
commenter provide its comments regarding improvements to this document 
directly to Boeing. We have not changed this AD in regard to this 
issue.

Effect of Winglets on Accomplishment of the Proposed Actions

    Aviation Partners Boeing stated that accomplishing the Supplemental 
Type Certificate (STC) ST00830SE does not affect the ability to 
accomplish the actions specified in the NPRM.
    We concur with the commenter. We have added paragraph (c)(5) to 
this AD to state that installation of STC ST00830SE does not affect the 
ability to accomplish the actions required by this final rule. 
Therefore, for airplanes on which STC ST00830SE is installed, a 
``change in product'' alternative method of compliance (AMOC) approval 
request is not necessary to comply with the requirements of 14 CFR 
39.17.

Conclusion

    We reviewed the relevant data, considered the comments received, 
and determined that air safety and the public interest require adopting 
this final rule with the changes described

[[Page 67047]]

previously and minor editorial changes. We have determined that these 
minor changes:
     Are consistent with the intent that was proposed in the 
NPRM for addressing the unsafe condition; and
     Do not add any additional burden upon the public than was 
already proposed in the NPRM.
    We also determined that these changes will not increase the 
economic burden on any operator or increase the scope of this final 
rule.

Related Service Information Under 1 CFR Part 51

    We reviewed Boeing Special Attention Service Bulletin 737-52-1170, 
Revision 1, dated December 19, 2017. The service information describes 
procedures for repetitive detailed inspections of the forward and aft 
MLG center door assembly attachments for loose, missing, damaged, or 
bottomed-out attachment bolts, and any wear to the retention clip 
assemblies as applicable; and applicable on-condition actions. The 
service information also describes procedures for modification of the 
MLG center door assembly retention clip assemblies as an optional 
terminating action for the repetitive inspections. This service 
information is reasonably available because the interested parties have 
access to it through their normal course of business or by the means 
identified in the ADDRESSES section.

Costs of Compliance

    We estimate that this AD affects 1,814 airplanes of U.S. registry. 
We estimate the following costs to comply with this AD:

                                      Estimated Costs for Required Actions
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
           Action                    Labor cost           Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Inspection..................  2 work-hours x $85 per                $0  $170 per inspection  $308,380 per
                               hour = $170 per                           cycle.               inspection cycle.
                               inspection cycle.
----------------------------------------------------------------------------------------------------------------

                                 Estimated Costs for Optional Terminating Action
----------------------------------------------------------------------------------------------------------------
              Action                      Labor cost           Parts cost              Cost per product
----------------------------------------------------------------------------------------------------------------
Modification.....................  Up to 6 work-hours x $85          $2,900  Up to $3,410.
                                    per hour = $510.
----------------------------------------------------------------------------------------------------------------

    We have received no definitive data that would enable us to provide 
cost estimates for the on-condition actions specified in this AD.
    According to the manufacturer some of the costs of this AD may be 
covered under warranty, thereby reducing the cost impact on affected 
individuals. We do not control warranty coverage for affected 
individuals. As a result, we have included all known costs in our cost 
estimate.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII: Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701: ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.
    This AD is issued in accordance with authority delegated by the 
Executive Director, Aircraft Certification Service, as authorized by 
FAA Order 8000.51C. In accordance with that order, issuance of ADs is 
normally a function of the Compliance and Airworthiness Division, but 
during this transition period, the Executive Director has delegated the 
authority to issue ADs applicable to transport category airplanes and 
associated appliances to the Director of the System Oversight Division.

Regulatory Findings

    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),
    (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.

Adoption of the Amendment

    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 FAA amends Sec.  39.13 by adding the following new airworthiness 
directive (AD):

2018-26-06 The Boeing Company: Amendment 39-19536; Docket No. FAA-
2018-0393; Product Identifier 2018-NM-010-AD.

(a) Effective Date

    This AD is effective February 1, 2019.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all The Boeing Company Model 737-600, -700, -
700C, -800, -900, and -900ER series airplanes, certificated in any 
category, as specified in paragraphs (c)(1) through (c)(4) of this 
AD.

[[Page 67048]]

    (1) Airplanes in Group 1, and in Group 2, Configuration 1, as 
identified in Boeing Special Attention Service Bulletin 737-52-1170, 
Revision 1, dated December 19, 2017 (``BSASB 737-52-1170, R1'').
    (2) Airplanes in Group 2, Configuration 2, as identified in 
BSASB 737-52-1170, R1.
    (3) Airplanes in Group 3, as identified in BSASB 737-52-1170, 
R1, except where this service bulletin specifies the groups as line 
numbers 4275 through 6724 inclusive, and 6736, this AD specifies 
those groups as line number 4275 through any line number of an 
airplane with an original Certificate of Airworthiness or an 
original Export Certificate of Airworthiness dated on or before the 
effective date of this AD.
    (4) All Model 737-600, -700, -700C, -800, -900, and -900ER 
series airplanes with an original Certificate of Airworthiness or an 
original Export Certificate of Airworthiness dated after the 
effective date of this AD.
    (5) Installation of Supplemental Type Certificate (STC) 
ST00830SE does not affect the ability to accomplish the actions 
required by this AD. Therefore, for airplanes on which STC ST00830SE 
is installed, a ``change in product'' alternative method of 
compliance (AMOC) approval request is not necessary to comply with 
the requirements of 14 CFR 39.17.

(d) Subject

    Air Transport Association (ATA) of America Code 52, Doors.

(e) Unsafe Condition

    This AD was prompted by reports of loose, worn, or missing 
attachment bolts for the main landing gear (MLG) center door 
assemblies. We are issuing this AD to address loose, missing, 
damaged, or bottomed-out attachment bolts, and any wear to the 
retention clip assemblies, which could result in departure of the 
center and inboard MLG door assemblies, subsequent damage to the 
main flap and horizontal stabilizer, and loss of control of the 
airplane.

(f) Compliance

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

(g) Required Actions

    For airplanes identified in paragraphs (c)(1), (c)(2), or (c)(3) 
of this AD: Except as required by paragraph (h) of this AD, at the 
applicable time specified in Tables 1 through 6, as applicable, of 
paragraph 1E., ``Compliance,'' of BSASB 737-52-1170, R1, do all 
applicable actions identified as ``RC'' (required for compliance) 
in, and in accordance with, the Accomplishment Instructions of BSASB 
737-52-1170, R1. Replacement of an entire MLG assembly within the 
required compliance time satisfies the requirements of this 
paragraph, provided that the requirements of paragraph (j) of this 
AD are satisfied for that MLG assembly.

(h) Exceptions to Service Information Specifications

    (1) For purposes of determining compliance with the requirements 
of this AD: Where BSASB 737-52-1170, R1, uses the phrase ``the 
original issue date of this service bulletin'' or ``the Revision 1 
date of this service bulletin'' this AD requires using ``the 
effective date of this AD.''
    (2) Where BSASB 737-52-1170, R1, limits use of Figures 3 and 4 
to Group 2 airplanes, for the purposes of this AD, those figures 
apply to all airplane groups.
    (3) If any action(s) identified as RC in BSASB 737-52-1170, R1, 
cannot be accomplished as specified therein, those action(s) must be 
accomplished using a method approved in accordance with the 
procedures specified in paragraph (l) of this AD.

(i) Optional Terminating Action for Repetitive Inspections

    Accomplishment of the modification of the MLG center door 
retention clip assemblies specified in Part 5 of the Accomplishment 
Instructions of BSASB 737-52-1170, R1, terminates the repetitive 
inspections required by paragraph (g) of this AD for that MLG center 
door retention clip only. The requirements of paragraph (j) of this 
AD continue to apply.

(j) Parts Installation Limitation

    As of the effective date of this AD, no person may install an 
MLG assembly or MLG center door assembly on any airplane identified 
in paragraphs (c)(1) through (c)(4) of this AD unless all actions 
for Group 3 airplanes pertaining to that MLG center door attachment, 
and identified as RC in, and in accordance with, the Accomplishment 
Instructions of BSASB 737-52-1170, R1, have been accomplished on 
that MLG assembly or MLG center door assembly within the compliance 
times specified in Tables 4, 5, and 6, as applicable, of paragraph 
1.E., ``Compliance,'' of BSASB 737-52-1170, R1. The actions for 
Group 3 airplanes apply to all airplanes for the requirement of this 
paragraph.

(k) Credit for Previous Actions

    This paragraph provides credit for the actions specified in 
paragraph (g) of this AD, if those actions were performed before the 
effective date of this AD using Boeing Special Attention Service 
Bulletin 737-52-1170, dated July 29, 2014.

(l) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Seattle ACO Branch, 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 certification office, send it to the attention of the 
person identified in paragraph (m)(1) of this AD. Information may be 
emailed to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair, modification, or alteration 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 Branch, FAA, to make those findings. To be 
approved, the repair method, modification deviation, or alteration 
deviation must meet the certification basis of the airplane, and the 
approval must specifically refer to this AD.
    (4) Except as required by paragraph (h) of this AD: For service 
information that contains steps that are labeled as RC, the 
provisions of paragraphs (l)(4)(i) and (l)(4)(ii) of this AD apply.
    (i) The steps labeled as RC, including substeps under an RC step 
and any figures identified in an RC step, must be done to comply 
with the AD. If a step or substep is labeled ``RC Exempt,'' then the 
RC requirement is removed from that step or substep. An AMOC is 
required for any deviations to RC steps, including substeps and 
identified figures.
    (ii) Steps not labeled as RC may be deviated from using accepted 
methods in accordance with the operator's maintenance or inspection 
program without obtaining approval of an AMOC, provided the RC 
steps, including substeps and identified figures, can still be done 
as specified, and the airplane can be put back in an airworthy 
condition.

(m) Related Information

    (1) For more information about this AD, contact Alan Pohl, 
Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 
South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3527; 
email: alan.pohl@faa.gov.
    (2) Service information identified in this AD that is not 
incorporated by reference is available at the addresses specified in 
paragraphs (n)(3) and (n)(4) of this AD.

(n) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the service information listed 
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this service information as applicable to do 
the actions required by this AD, unless the AD specifies otherwise.
    (i) Boeing Special Attention Service Bulletin 737-52-1170, 
Revision 1, dated December 19, 2017.
    (ii) [Reserved]
    (3) For service information identified in this AD, contact 
Boeing Commercial Airplanes, Attention: Contractual & Data Services 
(C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-
5600; telephone 562-797-1717; internet https://www.myboeingfleet.com.
    (4) You may view this service information at the FAA, Transport 
Standards Branch, 2200 South 216th St., Des Moines, WA. For 
information on the availability of this material at the FAA, call 
206-231-3195.
    (5) You may view this service information that is incorporated 
by reference at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, call 202-741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr-locations.html.

[[Page 67049]]

    Issued in Des Moines, Washington, on December 18, 2018.
Michael Kaszycki,
Acting Director, System Oversight Division, Aircraft Certification 
Service.
[FR Doc. 2018-28077 Filed 12-27-18; 8:45 am]
 BILLING CODE 4910-13-P