[Federal Register Volume 89, Number 22 (Thursday, February 1, 2024)]
[Rules and Regulations]
[Pages 6413-6416]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-01968]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-1041; Project Identifier AD-2022-01223-T; 
Amendment 39-22657; AD 2024-01-06]
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, 737-700, and 737-800 series 
airplanes. This AD was prompted by an evaluation by the design approval 
holder (DAH) indicating the fuselage skin repairs at the double row of 
fasteners centered on certain stringers have inadequate inspection 
requirements for continuing airworthiness following repair 
accomplishment. This AD is intended to complete certain programs to 
support the airplane reaching its limit of validity (LOV). This AD 
requires repetitive inspections for cracks of skin repairs at Stringer 
S-17, and corrective actions if necessary. The FAA is issuing this AD 
to address the unsafe condition on these products.

DATES: This AD is effective March 7, 2024.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of March 7, 
2024.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2023-1041; 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-2023-1041.

FOR FURTHER INFORMATION CONTACT: Bill Ashforth, Aviation Safety 
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; telephone 
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 (Boeing) Model 737-600, 737-700, and 737-800 series airplanes. 
The NPRM was published in the Federal Register on May 25, 2023 (88 FR 
33849). The NPRM was prompted by an evaluation by the DAH indicating 
the fuselage skin repairs at the double row of fasteners centered on 
certain stringers have inadequate inspection requirements for 
continuing airworthiness following repair accomplishment, which could 
result in fatigue cracking of the repair going undetected.
    In the NPRM, the FAA proposed to require repetitive inspections for 
cracking of the skin repairs at S-17, and corrective actions if 
necessary. The FAA is issuing this AD to address this fatigue cracking, 
which, if not addressed, could grow to a critical length and result in 
rapid decompression and loss of the airplane's structural integrity.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from the Air Line Pilots Association, 
International (ALPA) who supported the NPRM without change.
    The FAA also received comments from Aviation Partners Boeing (APB), 
Boeing, Southwest Airlines (Southwest), and SunExpress Airline 
(SunExpress).

Compliance With AMOC Procedures

    APB determined that the incorporation of supplemental type 
certificate (STC) ST00830SE for installation of split scimitar winglets 
affects compliance with the mandated actions in the proposed rule, but 
the extent of the impact to compliance is not fully known at this time. 
APB noted that paragraph (h) of the proposed AD would replace the 
provisions in Boeing Service Bulletin 737-53A1217 R1 that specify 
contacting Boeing for an alternative method of compliance (AMOC) for 
alternative inspections and corrective actions, and instead would 
require using a method approved in accordance with paragraph (i) of the 
proposed AD. APB stated that for affected airplanes with these 
winglets, approval of any alternative inspections and corrective 
actions for Zone 3 and Zone 4 repairs must be obtained from the 
Manager, AIR-520 Continued Operational Safety Branch, FAA, through the 
means described in paragraph (i)(1) of the proposed AD. APB asserted 
that Boeing does not have delegation to approve repairs in areas 
affected by the configuration of STC ST00830SE and cannot use ODA 
approval as specified in paragraph (i)(3) of the proposed AD.
    The FAA acknowledges APB's comment. Paragraph (h)(1) of this AD 
states that AMOC approval be obtained using a method approved in 
accordance with the procedures specified in ``paragraph (i)'' of this 
AD, and does not limit approvals to the provisions of paragraph (i)(1) 
or (3) of this AD. Therefore, no change to this AD is necessary.

[[Page 6414]]

Request To Correct Service Bulletin Reference

    Boeing reported that the Background section of the NPRM incorrectly 
identified the original service information as Boeing Service Bulletin 
``737-53A1217,'' but that document was not an alert service bulletin 
and should have been identified as Service Bulletin ``737-53-1217.''
    The FAA agrees; no change to the final rule is necessary because 
that reference is not used.

Request To Specify Service Bulletin Revision Level

    The NPRM's Background section explained that certain existing post-
repair inspections are inadequate to address the unsafe condition, and 
that the actions in paragraph (g) of the proposed AD would apply only 
to airplanes on which a repair has been done as specified in ``Boeing 
Alert Service Bulletin 737-53A1217.'' Boeing requested that the 
statement be clarified by adding the revision level and date of the 
service bulletin. Boeing further stated that Boeing Alert Service 
Bulletin 737-53A1217, Revision 1, dated September 8, 2022, was issued 
to add the post-repair inspections to airplanes on which a repair has 
been done.
    The FAA disagrees. In this context, the revision level and date of 
the service bulletin were intentionally omitted so the Background 
section of the NPRM would refer to any repair-including a repair done 
using a method other than the service bulletin (at any revision level). 
No change is necessary to this final rule.

Request To Revise Unsafe Condition

    Boeing requested changes to paragraph (e) of the proposed AD, which 
implied the unsafe condition is the potential for cracking. Boeing 
stated that the proposed AD would require only post-repair inspections, 
and asserted that the unsafe condition is actually the lack of post-
repair inspections because it could result in undetected post-repair 
fatigue cracks.
    The FAA agrees and has incorporated the relevant changes.

Request To Revise Compliance Time

    Southwest and SunExpress stated that Boeing Alert Service Bulletin 
737-53A1217 provides no grace period for airplanes that have exceeded 
the threshold, and requested that the proposed AD be revised to provide 
a grace period or optional threshold value.
    The FAA notes that paragraph (g) of this AD mandates only Tables 3 
through 6 of paragraph 1.E., ``Compliance,'' of Boeing Alert Service 
Bulletin 737-53A1217, Revision 1, dated September 8, 2022. For those 
actions, the service bulletin specifies a compliance time of 50,000 
total flight cycles, with a grace period of 4,000 flight cycles after 
the repair. Therefore, no change is necessary to the AD.

Request To Clarify Configuration Description

    Southwest requested clarification of the affected airplanes and 
corresponding requirements for Tables 1 through 3 of Boeing Alert 
Service Bulletin 737-53A1217, Revision 1, dated September 8, 2022. 
Southwest noted that paragraphs 1.A.1. and 1.D. define Groups 1 through 
3, Configuration 3, as ``airplanes that have installed a repair,'' but 
tables 1 through 3 of paragraph 1.E list conditions for airplanes that 
both have and have not accomplished a repair.
    The FAA provides the following clarification. The tables apply to 
any airplanes that have performed a repair, whether the repair was done 
in accordance with ``SB 737-53-1217 Original Issue'' or in accordance 
with some other method. So the condition ``Airplanes that have not 
accomplished a repair in accordance with `SB 737-53-1217 Original 
Issue' applies to airplanes that have been repaired using some method 
other than `SB 737-53-1217 Original Issue.' '' Groups 1 through 3, 
Configuration 3, include any airplane on which a repair has been 
accomplished in one of the zones specified in the service information. 
No changes to this AD are necessary as a result of this comment.

Request To Use BMS 3-35 or BMS 3-23 Compound

    Southwest noted that Boeing Alert Service Bulletin 737-53A1217, 
Revision 1, dated September 8, 2022, specifies the use of BMS 3-23 
corrosion-inhibiting compound (CIC) for repairs. Southwest requested 
that the proposed AD be revised to allow the use of BMS 3-35 CIC due to 
the faster drying time compared to BMS 3-23 CIC. Southwest stated that 
Boeing Corrosion Prevention Manual (CPM) 20-60-00 and Boeing Service 
Request (SR) SWA-SWA-10-1232-02B approve BMS 3-35 for use on all Boeing 
commercial airplanes including those no longer in production.
    The FAA agrees that either BMS 3-35 or BMS 3-23 CIC is acceptable 
because both provide an adequate level of safety. Paragraph (h)(2) of 
this AD has been added to allow use of either CIC.

Conclusion

    The FAA reviewed the relevant data, considered the received 
comments, and determined that air safety requires adopting this AD as 
proposed, with limited changes as previously stated. 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 Service Bulletin 737-53A1217, 
Revision 1, dated September 8, 2022. This service information specifies 
procedures for, among other actions, repetitive internal and external 
detailed inspections, low frequency eddy current (LFEC) inspections, 
and medium frequency eddy current (MFEC) inspections for cracks of the 
skin repair of S-17, station (STA) 360 to STA 380, and STA 888 to STA 
907, left and right sides of the airplane. Corrective actions include 
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 106 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
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                                                   Parts
            Action                Labor cost        cost         Cost per product        Cost on U.S. operators
----------------------------------------------------------------------------------------------------------------
External Post Repair           56 work-hours x          $0  $4,760 per inspection      $504,560 per inspection
 Inspection.                    $85 per hour =               cycle.                     cycle.
                                $4,760 per
                                inspection
                                cycle.

[[Page 6415]]

 
Internal Post Repair           52 work-hours x           0  $4,420 per inspection      $468,520 per inspection
 Inspections.                   $85 per hour =               cycle.                     cycle.
                                $4,420 per
                                inspection
                                cycle.
----------------------------------------------------------------------------------------------------------------

    The FAA has received no definitive data on which to base the cost 
estimates for the 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:

2024-01-06 The Boeing Company: Amendment 39-22657; Docket No. FAA-
2023-1041; Project Identifier AD-2022-01223-T.

(a) Effective Date

    This airworthiness directive (AD) is effective March 7, 2024.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 737-600, 737-700, 
and 737-800 series airplanes, certificated in any category, as 
identified in Boeing Alert Service Bulletin 737-53A1217, Revision 1, 
dated September 8, 2022.

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by an evaluation by the design approval 
holder (DAH) indicating the fuselage skin repairs at the double row 
of fasteners centered on certain stringers have inadequate 
inspection requirements for continuing airworthiness following 
repair accomplishment, which could result in fatigue cracking of the 
repair going undetected. The FAA is issuing this AD to address the 
inadequacy of post-repair inspection requirements at certain repair 
fastener locations centered on stringer S-17L and S-17R, at station 
(STA) 360 to STA 380 and at STA 888 to STA 907. Such inspection 
inadequacy could result in post-repair fatigue cracks going 
undetected. Fatigue cracking, if not addressed, could grow to a 
critical length, which could result in rapid decompression and loss 
of 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 in paragraph (h) of this AD: For Group 1 
through 3, Configuration 3 airplanes as identified in Boeing Alert 
Service Bulletin 737-53A1217, Revision 1, dated September 8, 2022, 
at the applicable times specified in Tables 3 through 6 of paragraph 
1.E., ``Compliance,'' of Boeing Alert Service Bulletin 737-53A1217, 
Revision 1, dated September 8, 2022, do all applicable actions 
identified as ``RC'' (required for compliance) in, and in accordance 
with, the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1217, Revision 1, dated September 8, 2022.

(h) Exceptions to Service Information Specifications

    (1) Where Boeing Alert Service Bulletin 737-53A1217, Revision 1, 
dated September 8, 2022, 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 (i) of this AD.
    (2) Where Boeing Alert Service Bulletin 737-53A1217, Revision 1, 
dated September 8, 2022, specifies using corrosion inhibiting 
compound (CIC) compound BMS 3-23, this AD also allows use of CIC 
compound BMS 3-35.

(i) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, AIR-520 Continued Operational Safety 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, AIR-520 Continued Operational 
Safety Branch, FAA, send it to the attention of the person 
identified in paragraph (j) 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, AIR-520 
Continued Operational Safety 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 specified by paragraph (h) of this AD: For service 
information that

[[Page 6416]]

contains steps that are labeled as Required for Compliance (RC), the 
provisions of paragraphs (i)(4)(i) and (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.

(j) Related Information

    For more information about this AD, contact Bill Ashforth, 
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 
98198; telephone 206-231-3520; email [email protected].

(k) 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 Service Bulletin 737-53A1217, Revision 1, dated 
September 8, 2022.
    (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 material at the National Archives and 
Records Administration (NARA). For information on the availability 
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].

    Issued on January 6, 2024.
Caitlin Locke,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2024-01968 Filed 1-31-24; 8:45 am]
BILLING CODE 4910-13-P