[Federal Register Volume 90, Number 103 (Friday, May 30, 2025)]
[Proposed Rules]
[Pages 22867-22870]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-09770]
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Proposed Rules
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.
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Federal Register / Vol. 90, No. 103 / Friday, May 30, 2025 / Proposed
Rules
[[Page 22867]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2025-0919; Project Identifier AD-2024-00648-T]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD)
2013-08-08, which applies to certain The Boeing Company Model 737-600
series airplanes. AD 2013-08-08 requires repetitive inspections for
cracking of the fuselage skin at certain locations at chem-mill steps,
and repair if necessary. AD 2013-08-08 also provides optional
terminating action for the repetitive inspections. Since the FAA issued
AD 2013-08-08, Boeing has reported that the compliance times are not
adequate because new fleet data indicates that crack growth is faster
and more distributed between tear straps, resulting in longer cracks
than originally observed in the test data that prompted AD 2013-08-08.
This proposed AD would continue to require the actions in AD 2013-08-
08, at reduced initial compliance times and repetitive intervals for
the inspections, and mandate post-modification inspections if the
optional modification is accomplished. The FAA is proposing this AD to
address the unsafe condition on these products.
DATES: The FAA must receive comments on this proposed AD by July 14,
2025.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to regulations.gov. Follow
the instructions for submitting comments.
Fax: 202-493-2251.
Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2025-0919; 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 NPRM, any comments received, and other
information. The street address for Docket Operations is listed above.
Material Incorporated by Reference
For the material identified in this proposed 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.
You may view this material 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-2025-0919.
FOR FURTHER INFORMATION CONTACT: Luis Cortez-Muniz, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-
231-3958; email: [email protected].
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under the ADDRESSES section. Include ``Docket No. FAA-2025-0919;
Project Identifier AD-2024-00648-T'' at the beginning of your comments.
The most helpful comments reference a specific portion of the proposal,
explain the reason for any recommended change, and include supporting
data. The FAA will consider all comments received by the closing date
and may amend this proposal because of those comments.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to
regulations.gov, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.
Confidential Business Information
CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this NPRM contain commercial
or financial information that is customarily treated as private, that
you actually treat as private, and that is relevant or responsive to
this NPRM, it is important that you clearly designate the submitted
comments as CBI. Please mark each page of your submission containing
CBI as ``PROPIN.'' The FAA will treat such marked submissions as
confidential under the FOIA, and they will not be placed in the public
docket of this NPRM. Submissions containing CBI should be sent to Luis
Cortez-Muniz, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; phone: 206-231-3958; email: [email protected]. Any commentary that the FAA receives that is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.
Background
The FAA issued AD 2013-08-08, Amendment 39-17425 (78 FR 23465,
April 19, 2013) (AD 2013-08-08), for certain The Boeing Company Model
737-600 series airplanes. AD 2013-08-08 was prompted by reports of
early fatigue cracks at chem-mill areas on the crown skin panels. AD
2013-08-08 requires repetitive inspections for cracking of the fuselage
skin at certain locations at chem-mill steps, and repair if necessary.
AD 2013-08-08 also provides an optional terminating action for the
repetitive inspections. The FAA issued AD 2013-08-08 to detect and
correct fatigue cracking of the skin panel at the specified chem-mill
step locations, which could result in rapid decompression of the
airplane.
[[Page 22868]]
Actions Since AD 2013-08-08 Was Issued
Since the FAA issued AD 2013-08-08, the FAA received reports of
suspected fuselage fatigue cracks found adjacent to non-chem-mill skin
bays on Model 737-700 airplanes with between 40,000 and 43,000 total
flight cycles--earlier than the inspection thresholds specified by AD
2013-08-08. Boeing has reported that the inspection compliance times
and repetitive intervals in Boeing Service Bulletin 737-52-1309, dated
October 20, 2011, are not adequate. The new fleet data indicates that
crack growth is faster, and there are more cracks distributed along the
chem-mill steps between the tear straps; as a result, the cracks can
initiate from multiple sites along the chem-mill step and link up,
causing a faster crack propagation than initially observed in the test
data that prompted Boeing Service Bulletin 737-52-1309, dated October
20, 2011. As a result of these findings, the FAA has determined that
earlier inspection thresholds for the chem-mill areas, as well as post
modification inspections (for airplanes on which the terminating action
is accomplished), are now necessary to address the unsafe condition.
The FAA is considering similar rulemaking for Model 737-700, -700C, -
800, and -900 series airplanes.
FAA's Determination
The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of the same type design.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Boeing Special Attention Service Bulletin 737-53-
1309, Revision 1, dated May 22, 2024. This material specifies
procedures for inspecting for cracking in the fuselage skin at certain
locations at the chem-mill steps by doing repetitive external detailed
inspections and either (1) external medium frequency eddy current
(MFEC), magneto optic imager (MOI), or C-scan inspections or (2)
external ultrasonic phased array (UTPA) inspections, and applicable on-
condition actions. On-condition actions include crack repair. This
material also specifies an optional modification that eliminates the
need for repetitive inspections, provided post modification inspections
are also performed for airplanes with the optional modification
installed.
This proposed AD would also require Boeing Service Bulletin 737-53-
1309, dated October 20, 2011, which the Director of the Federal
Register approved for incorporation by reference as of May 24, 2013 (78
FR 23465, April 19, 2013).
This material 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.
Proposed AD Requirements in This NPRM
Although this proposed AD does not explicitly restate the
requirements of AD 2013-08-08, this proposed AD would retain all of the
requirements of AD 2013-08-08. Those requirements are referenced in the
material identified previously, which, in turn, is referenced in
paragraph (g) of this proposed AD.
This proposed AD would reduce the initial compliance times and
repetitive intervals for the inspections. This proposed AD would also
mandate the optional post-modification inspections (if the operator
chooses to perform the optional modification). This proposed AD would
require accomplishing the actions specified in the material already
described, except for any differences identified as exceptions in the
regulatory text of this proposed AD.
For information on the procedures and compliance times, see this
material at regulations.gov under Docket No. FAA-2025-0919.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 6 airplanes of U.S. registry. The FAA estimates the following
costs to comply with this proposed AD:
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Cost on U.S.
Action Labor cost Parts cost Cost per product operators
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Inspection of chem-mill step 39 work-hours x $85 $0 $3,315 per $19,890 per
locations. per hour = $3,315 inspection cycle. inspection cycle.
per inspection
cycle.
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Estimated Costs for Optional Actions
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Cost per
Action Labor cost Parts cost product
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Modification................. 855 work-hours $Minimal $6,840
x $85 per hour
= $6,840.
Post-modification inspections 92 work-hours x 0 7,820
$85 per hour =
$7,820.
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The FAA has received no definitive data on which to base the cost
estimates for the on-condition actions specified in this proposed AD.
Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
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
The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would not
have a substantial direct effect on the States, on the relationship
between the national government and the States, or
[[Page 22869]]
on the distribution of power and responsibilities among the various
levels of government.
For the reasons discussed above, I certify this proposed
regulation:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
The Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
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:
0
a. Removing Airworthiness Directive (AD) 2013-08-08, Amendment 39-17425
(78 FR 23465, April 19, 2013), and
0
b. Adding the following new AD:
The Boeing Company: Docket No. FAA-2025-0919; Project Identifier AD-
2024-00648-T.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by July 14, 2025.
(b) Affected ADs
This AD replaces AD 2013-08-08, Amendment 39-17425 (78 FR 23465,
April 19, 2013) (AD 2013-08-08).
(c) Applicability
(1) This AD applies to The Boeing Company Model 737-600 series
airplanes, certificated in any category, as identified in Boeing
Special Attention Service Bulletin 737-53-1309, Revision 1, dated
May 22, 2024.
(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 early fatigue cracks at chem-
mill areas on the crown skin panels, and by the need for reduced
inspection compliance times. The FAA is issuing this AD to detect
and correct fatigue cracking of the fuselage skin at the specified
chem-mill step locations. The unsafe condition, if not addressed,
could result in rapid decompression of the airplane.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Inspections
Except as required by paragraph (j) of this AD: At the
applicable time specified in Table 1 of paragraph 1.E., Compliance,
of Boeing Special Attention Service Bulletin 737-53-1309, Revision
1, dated May 22, 2024, do an external detailed inspection and an
external nondestructive inspection (a medium frequency eddy current
(MFEC), magneto optic imager (MOI), C-scan, or ultrasonic phased
array (UTPA) inspection) for cracking in the fuselage skin along the
chem-mill steps at the locations specified in, and in accordance
with, Part 2 of the Accomplishment Instructions of Boeing Special
Attention Service Bulletin 737-53-1309, Revision 1, dated May 22,
2024. Repeat the inspections thereafter at the applicable times
specified in Table 1 of paragraph 1.E., Compliance, of Boeing
Special Attention Service Bulletin 737-53-1309, Revision 1, dated
May 22, 2024.
(h) Repair
If any cracking is found during any inspection required by
paragraph (g) of this AD, before further flight, repair the cracking
using a method approved in accordance with the procedures specified
in paragraph (k) of this AD.
(i) Optional Terminating Modification
Accomplishment of the actions specified in paragraphs (i)(1)
through (4) of this AD terminates the repetitive inspections
required by paragraph (g) of this AD for the modified area only.
(1) Do an external detailed inspection and an external
nondestructive inspection (MFEC, MOI, C-scan, or UTPA) for cracking
of the area to be modified, and if no cracking is found, do the
modification, including doing a high frequency eddy current
inspection of all existing holes for cracking, in accordance with
paragraph 3.B.3., ``Part 3: Modification'' of the Accomplishment
Instructions of Boeing Service Bulletin 737-53-1309, dated October
20, 2011, or Boeing Special Attention Service Bulletin 737-53-1309,
Revision 1, dated May 22, 2024. As of the effective date of this AD,
only Boeing Special Attention Service Bulletin 737-53-1309, Revision
1, dated May 22, 2024, may be used for performing the actions in
this paragraph.
(2) Repair, before further flight, any crack found during any
inspection specified in paragraph (i)(1) of this AD, using a method
approved in accordance with the procedures specified in paragraph
(k) of this AD.
(3) Accomplish the repetitive post-modification inspections
specified in Tables 2 and 3 of paragraph 1.E., ``Compliance,'' and
in Part 5 of the Accomplishment Instructions, of Boeing Service
Bulletin 737-53-1309, dated October 20, 2011, or Boeing Special
Attention Service Bulletin 737-53-1309, Revision 1, dated May 22,
2024. The inspections must be performed and repeated at the
applicable times specified in Tables 2 and 3 of paragraph 1.E.,
``Compliance,'' of Boeing Service Bulletin 737-53-1309, dated
October 20, 2011, or Boeing Special Attention Service Bulletin 737-
53-1309, Revision 1, dated May 22, 2024. As of the effective date of
this AD, only Boeing Special Attention Service Bulletin 737-53-1309,
Revision 1, dated May 22, 2024, may be used for performing the
actions in this paragraph.
(4) Repair, before further flight, any crack found during any
inspection specified in paragraph (i)(3) of this AD, using a method
approved in accordance with the procedures specified in paragraph
(k) of this AD.
(j) Exception to Service Information Specifications
Where the Compliance Time column of Tables 1, 2, and 3 in the
``Compliance'' paragraph of Boeing Special Attention Service
Bulletin 737-53-1309, Revision 1, dated May 22, 2024, refers to the
Revision 1 date of Boeing Special Attention Service Bulletin 737-53-
1309, this AD requires using the effective date of this AD.
(k) 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 of the certification office,
send it to the attention of the person identified in paragraph (l)
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) AMOCs approved for AD 2013-08-08 are not approved as AMOCs
for the corresponding provisions of this AD.
(l) Related Information
For more information about this AD, contact Luis Cortez-Muniz,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des
[[Page 22870]]
Moines, WA 98198; phone: 206-231-3958; email: [email protected].
(m) Material Incorporated by Reference
(1) The Director of the Federal Register approved the
incorporation by reference (IBR) of the material listed in this
paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
(2) You must use this material as applicable to do the actions
required by this AD, unless the AD specifies otherwise.
(3) The following material was approved for IBR on [DATE 35 DAYS
AFTER PUBLICATION OF THE FINAL RULE].
(i) Boeing Special Attention Service Bulletin 737-53-1309,
Revision 1, dated May 22, 2024.
(ii) [Reserved]
(4) The following material was approved for IBR on May 24, 2013
(78 FR 23465, April 19, 2013).
(i) Boeing Service Bulletin 737-53-1309, dated October 20, 2011.
(ii) [Reserved]
(5) For the Boeing material 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.
(6) You may view this material 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.
(7) 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 May 23, 2025.
Lona C. Saccomando,
Acting Deputy Director, Integrated Certificate Management Division,
Aircraft Certification Service.
[FR Doc. 2025-09770 Filed 5-29-25; 8:45 am]
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