[Federal Register Volume 88, Number 78 (Monday, April 24, 2023)]
[Rules and Regulations]
[Pages 24678-24681]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-08477]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0815; Project Identifier AD-2021-00679-T; 
Amendment 39-22401; AD 2023-06-15]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and 
-900ER series airplanes. This AD was prompted by reports of missing 
shims, a wrong type of shim, shanked fasteners, fastener head gaps, and 
incorrect hole sizes common to the left and right sides at a certain 
station (STA) frame inner chord and web. This AD requires inspecting 
for existing repairs, inspecting the area for cracking, and performing 
applicable on-condition actions. The FAA is issuing this AD to address 
the unsafe condition on these products.

DATES: This AD is effective May 30, 2023.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publications listed in this AD as of May 30, 
2023.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2022-0815; 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, any comments received, and other 
information. The address for Docket Operations 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.
    Material Incorporated by Reference:
     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; website myboeingfleet.com.
     You may view this service information at the FAA, 
Airworthiness Products Section, Operational Safety 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 at 
regulations.gov under Docket No. FAA-2022-0815.

FOR FURTHER INFORMATION CONTACT: Bill Ashforth, Aerospace Engineer, 
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone: 206-231-3520; email: [email protected].

SUPPLEMENTARY INFORMATION: 

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to certain The Boeing 
Company Model 737-600, -700, -700C, -800, -900, and -900ER series 
airplanes. The NPRM published in the Federal Register on September 9, 
2022 (87 FR 55325). The NPRM was prompted by reports of missing shims, 
a wrong type of shim, shanked fasteners, fastener head gaps, and 
incorrect hole sizes common to the left and right sides at a certain 
station (STA) frame inner chord and web. In the NPRM, the FAA proposed 
to require inspecting for existing repairs, inspecting the area for 
cracking, and performing applicable on-condition actions. The FAA is 
issuing this AD to address cracking in the left and right sides of STA 
727 frame inner chord and S-18A web before the cracking reaches a 
critical length. This condition, if not addressed, could result in 
cracks in fatigue critical baseline structure (FCBS) and the inability 
of a principal structural element (PSE) to sustain limit load, which 
could adversely affect the structural integrity of the airplane.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from six commenters, including American 
Airlines (AAL), Aviation Partners Boeing (APB), Boeing, Southwest 
Airlines (SWA), United Airlines (UAL), and one individual. The 
following presents the comments received on the NPRM and the FAA's 
response to each comment, except the comment from an individual, which 
was outside the scope of this AD.

Request To Include Revised Service Information

    SWA, UAL, and AAL noted that Boeing planned to issue Revision 1 of 
Boeing Requirements Bulletin 737-53A1402 RB, and requested 
consideration for its incorporation into the final rule.
    SWA requested that the FAA issue a global AMOC for use of Revision 
1 for the requirements.
    AAL and UAL noted that the original requirements bulletin had two 
issues of concern:
     Figures 3, 4, 5, and 6 identify fastener part number (P/N) 
BACN11E4 as a replacement part. The commenters noted that the fastener 
has been superseded, and the alternative part, P/N BACN11E4V, is not 
listed in the Boeing Structural Repair Manual.
     Figures 5 and 6 specify installing a shim regardless of 
the measured gap, but also state that a gap of 0.006 inch is acceptable 
after shimming. AAL added that the original requirements bulletin does 
not give any instructions if the gap is 0.006 inch or less prior to 
shim installation.
    The commenters noted that Revision 1 addresses both issues, and 
requested that the FAA either (1) delay issuance of the final rule 
pending release of Revision 1 or (2) revise the proposed AD to allow 
use of the alternative fasteners and forgo installation of a shim for a 
gap of 0.006 inch or less prior to shim installation.
    The FAA agrees with the request. Boeing has confirmed that P/N 
BACN11E4 is no longer available, and the new replacement P/N is 
BACN11E4V. The FAA has reviewed Boeing Alert Requirements Bulletin

[[Page 24679]]

737-53A14020 RB, Revision 1, dated January 30, 2023, which updates the 
fastener callouts and clarifies that shim installation is not required 
when the measurement of the gap without shim and fasteners installed is 
0.006 inch or less. These changes do not impose any additional work 
over that specified in the original requirements bulletin. The FAA has 
revised this AD to require accomplishment of Revision 1 of the 
requirements bulletin and to provide credit for the original 
requirements bulletin in paragraph (i)(1) of this AD.

Effects of Winglets on Accomplishment of the Proposed Actions

    APB and SWA commented regarding the installation of blended or 
split scimitar winglets per Supplemental Type Certificate (STC) 
ST00830SE and the effect of that installation on compliance with the 
proposed actions. SWA further requested a change to paragraph (c) of 
the proposed AD to clarify that the installation of STC ST00830SE does 
not affect the accomplishment of the manufacturer's service 
instructions.
    The FAA agrees to clarify that the installation of winglets per STC 
ST00830SE does not affect the accomplishment of the manufacturer's 
service instructions. Therefore, the installation of STC ST00830SE does 
not affect the ability to accomplish the actions required by this AD. 
Operators of airplanes with these winglets do not need to request a 
``change in product'' alternative method of compliance (AMOC) approval 
as specified in 14 CFR 39.17. The FAA has redesignated paragraph (c) of 
the proposed AD as paragraph (c)(1) of this AD, and added paragraph 
(c)(2) to this AD accordingly.

Request To Correct Typographical Error

    Boeing requested the correction of a typographical error in the 
``Related Service Information under 1 CFR part 51'' section of the 
preamble of the NPRM. The commenter noted that ``HFECD'' should be 
corrected to ``HFEC.''
    The FAA agrees with the request. The instance of ``HFECD'' has been 
changed to ``HFEC'' in the preamble of this AD as requested.

Request To Make Required Action Optional

    SWA requested that the initial general visual inspection (GVI) for 
existing repairs be optional for airplanes in Group 1, Configuration 2, 
on which Boeing Alert Requirements Bulletin 737-53A1385 RB, dated 
August 16, 2019, has already been accomplished. SWA noted that Table 1 
and Table 2 of Boeing Alert Requirements Bulletin 737-53A1385 RB, dated 
August 16, 2019, require the initial GVI for existing repairs, and that 
including this step in Table 3 and Table 4 of Boeing Alert Requirements 
Bulletin 737-53A1402 RB, dated July 2, 2021, would necessitate 
reporting that had already been done in Boeing Alert Requirements 
Bulletin 737-53A1385 RB, dated August 16, 2019. The commenter further 
noted that Boeing Alert Service Bulletin 737-53A1402, dated July 2, 
2021, does not require re-reporting of existing repairs for Group 1, 
Configuration 1, airplanes after the shim installation or during the 
post-repair repetitive inspections.
    The FAA partially agrees with this request. Boeing Requirements 
Bulletin 737-53A1385 RB specifies inspecting for existing repairs, 
contacting Boeing if any repair is found, and checking for a gap if no 
repair is found. The FAA agrees that reports for Boeing Alert 
Requirements Bulletin 737-53A1402 RB, dated July 2, 2021, Group 1, 
Configuration 2, need not be repeated if an inspection was previously 
done as specified in Boeing Requirements Bulletin 737-53A1385 RB. 
However, rather than making this required action optional, paragraph 
(i) has been added to this AD giving operators credit for completing 
that task before the effective date of this AD using Boeing 
Requirements Bulletin 737-53A1385 RB, dated August 16, 2019.

Request for Additional AMOC

    SWA requested that for any AMOC received with regard to AD 2015-08-
09, Amendment 39-18145 (80 FR 24195, April 30, 2015) (AD 2015-08-09), 
an AMOC to the proposed AD be included as well, to alleviate the 
requirement to obtain a revised FAA 8100-9 for any AMOC to the proposed 
AD.
    The FAA does not agree with the request. AD 2015-08-09 mandated 
Boeing Alert Service Bulletin 737-53A1325, dated December 3, 2013, and 
this AD does not supersede AD 2015-08-09; therefore, AMOCs approved for 
AD 2015-08-09 will continue to be in force and are not affected by the 
required actions of this AD.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, and determined that air safety requires adopting this AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition on these products. Except for minor editorial changes, and 
any other changes described previously, this AD is adopted as proposed 
in the NPRM. None of the changes will increase the economic burden on 
any operator.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Requirements Bulletin 737-53A1402 RB, 
Revision 1, dated January 30, 2023. This service information specifies 
procedures for a general visual inspection of the left and right sides 
of STA 727 frame inner chord at S-18A for existing repairs, an open 
hole high frequency eddy current (HFEC) inspection of the left and 
right side entire stackup of the STA 727 frame inner chord at S-18A for 
cracking (for certain configurations), a surface HFEC inspection of the 
left and right side STA 727 frame inner chord at S-18A web for 
cracking, and applicable on-condition actions. On-condition actions 
include installation of a new shim, a surface HFEC inspection of the 
STA 727 frame inner chord at S-18A for cracking, and repair. 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 ADDRESSES.

Costs of Compliance

    The FAA estimates that this AD affects 1,925 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
General visual inspection.............  2 work-hours x $85 per                $0            $170        $327,250
                                         hour = $170.
HFEC inspection and shim installation.  5 work-hours x $85 per                 0             425         818,125
                                         hour = $425.
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[[Page 24680]]

    The FAA estimates the following costs to do any necessary repairs 
or inspections that would be required based on the results of the 
inspection. The agency has no way of determining the number of aircraft 
that might need these repairs or inspections:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Inspection...................................  3 work hours x $85 per hour =                $0             $255
                                                $255.
----------------------------------------------------------------------------------------------------------------

    The FAA has received no definitive data on which to base the cost 
estimates for the on-condition repairs specified in this 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.
    The FAA is 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

    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) Will not affect intrastate aviation in Alaska, 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.

List of Subjects in 14 CFR Part 39

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

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:

2023-06-15 The Boeing Company: Amendment 39-22401; Docket No. FAA-
2022-0815; Project Identifier AD-2021-00679-T.

(a) Effective Date

    This airworthiness directive (AD) is effective May 30, 2023.

(b) Affected ADs

    None.

(c) Applicability

    (1) This AD applies to The Boeing Company Model 737-600, -700, -
700C, -800, -900, and -900ER series airplanes, certificated in any 
category, as identified in Boeing Alert Requirements Bulletin 737-
53A1402 RB, dated July 2, 2021.
    (2) 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 53, Fuselage.

 (e) Unsafe Condition

    This AD was prompted by reports of missing shims, a wrong type 
of shim, shanked fasteners, fastener head gaps, and incorrect hole 
sizes common to the left and right side station (STA) 727 frame 
inner chord and S-18A web. The FAA is issuing this AD to address 
cracking in the left and right side of STA 727 frame inner chord and 
S-18A web before it reaches a critical length. This condition, if 
not addressed, could result in cracks in fatigue critical baseline 
structure (FCBS) and the inability of a principal structural element 
(PSE) to sustain limit load, which could adversely affect the 
structural integrity of the airplane.

 (f) Compliance

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

 (g) Required Actions

    Except as specified by paragraph (h) of this AD: At the 
applicable times specified in the ``Compliance'' paragraph of Boeing 
Alert Requirements Bulletin 737-53A1402 RB, Revision 1, dated 
January 30, 2023, do all applicable actions identified in, and in 
accordance with, the Accomplishment Instructions of Boeing Alert 
Requirements Bulletin 737-53A1402 RB, Revision 1, dated January 30, 
2023.
    Note 1 to paragraph (g): Guidance for accomplishing the actions 
required by this AD can be found in Boeing Alert Service Bulletin 
737-53A1402, Revision 1, dated January 30, 2023, which is referred 
to in Boeing Alert Requirements Bulletin 737-53A1402 RB, Revision 1, 
dated January 30, 2023.

 (h) Exceptions to Service Information Specifications

    (1) Where the Compliance Time columns of the tables in the 
``Compliance'' paragraph of Boeing Alert Requirements Bulletin 737-
53A1402 RB, Revision 1, dated January 30, 2023, use the phrase ``the 
Original Issue date of the Requirements Bulletin 737-53A1402 RB,'' 
this AD requires using ``the effective date of this AD.''
    (2) Where Boeing Alert Requirements Bulletin 737-53A1402 RB, 
Revision 1, dated January 30, 2023, specifies contacting Boeing for 
repair instructions or for alternative inspections: This AD requires 
doing the repair, or doing the alternative inspections and 
applicable on-condition actions using a method approved in 
accordance with the procedures specified in paragraph (j) of this 
AD.

(i) Credit for Previous Actions

    (1) 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 Alert Requirements Bulletin 
737-53A1402 RB, dated July 2, 2021.
    (2) This paragraph provides credit for accomplishment of the 
most recent inspection and report as specified in the requirements 
of paragraph (g) of this AD, if those actions were performed before 
the

[[Page 24681]]

effective date of this AD using Boeing Alert Requirements Bulletin 
737-53A1385 RB, dated August 16, 2019.

(j) 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 responsible Flight Standards 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 (k) 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 responsible Flight Standards 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 Company 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.

(k) Related Information

    For more information about this AD, contact Bill Ashforth, 
Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 
South 216th St., Des Moines, WA 98198; phone: 206-231-3520; email: 
[email protected].

 (l) 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 Alert Requirements Bulletin 737-53A1402 RB, Revision 
1, dated January 30, 2023.
    (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; website myboeingfleet.com.
    (4) You may view this service information at the FAA, 
Airworthiness Products Section, Operational Safety 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, [email protected], or go to: www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on March 24, 2023.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-08477 Filed 4-21-23; 8:45 am]
BILLING CODE 4910-13-P