[Federal Register Volume 90, Number 114 (Monday, June 16, 2025)]
[Proposed Rules]
[Pages 25170-25173]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-11032]
[[Page 25170]]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2025-1105; Project Identifier AD-2024-00721-T]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD)
2013-08-11, which applies to certain The Boeing Company Model 737-900
and -900ER series airplanes. AD 2013-08-11 requires repetitive
inspections for cracking of the fuselage skin along chem-mill steps at
certain crown skin and shear wrinkle areas and repair if necessary.
Since the FAA issued AD 2013-08-11, the FAA has determined that the
compliance times are not adequate. This proposed AD would continue to
require the actions in AD 2013-08-11 but at reduced compliance times
and would require post-modification inspections if an 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 31,
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-2025-1105; 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 Boeing 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-2025-1105.
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-2025-1105;
Project Identifier AD-2024-00721-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 2013-08-11, Amendment 39-17428 (78 FR 24338,
April 25, 2013) (AD 2013-08-11), for The Boeing Company Model 737-900
and -900ER series airplanes with certain line numbers. AD 2013-08-11
was prompted by reports of early fatigue cracks at chem-mill areas on
the crown skin panels. AD 2013-08-11 requires repetitive inspections
for cracking of the fuselage skin along chem-mill steps at certain
crown skin and shear wrinkle areas, as applicable, and repair if
necessary. AD 2013-08-11 requires the initial inspections before the
airplane accumulates 43,000 total flight cycles. AD 2013-08-11 also
provides modification of the inspection areas as an optional
terminating action for the repetitive inspections. The agency issued AD
2013-08-11 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.
Actions Since AD 2013-08-11 Was Issued
Since the FAA issued AD 2013-08-11, the FAA received reports of
three 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 2013-08-11. Boeing has reported that the inspection compliance
times and repetitive intervals in Boeing Service Bulletin 737-53-1312,
Revision 1, dated March 14, 2012, are not adequate. The reports
indicate that crack growth is faster and cracks are more distributed
along the chem-mill steps between the tear straps, resulting in longer
cracks than initially observed in the test data that prompted Boeing
Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012. As a
result of these findings, the FAA has determined that reduced
inspection thresholds and intervals for the chem-mill areas and the
post modification inspections (for airplanes on which the optional
terminating action is accomplished) are now necessary to address the
unsafe condition.
[[Page 25171]]
The FAA is considering superseding similar ADs for Model 737-600, -
700, -700C, and -800 series airplanes, which have crown skin panels
that are of a similar design as those on Model 737-900 and -900ER
series airplanes and may be subject to the same unsafe condition.
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-
1312, Revision 2, dated May 22, 2024. This material specifies
procedures for 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 repairing any cracks. This material also
describes procedures for installing modification doublers in certain
locations, which involves an external detailed inspection and an
external non-destructive (MFEC, MOI, C-Scan, or UTPA) inspection for
any cracking of the area to be modified prior to the doubler being
placed on that area, and a high frequency eddy current inspection of
all existing holes for cracking. This material specifies that
accomplishment of the modification terminates the repetitive
inspections provided post-modification inspections are performed for
the modified areas.
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
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-2025-1105.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 56 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
----------------------------------------------------------------------------------------------------------------
Inspections...................... 31 work-hours x $85 $0 $2,635 per $147,560 per
per hour = $2,635 inspection cycle. inspection cycle.
per inspection
cycle.
----------------------------------------------------------------------------------------------------------------
Estimated Costs for Optional Actions
----------------------------------------------------------------------------------------------------------------
Action Labor cost Parts cost Cost per product
----------------------------------------------------------------------------------------------------------------
Modification........................ 632 work-hours x $85 Minimal................. $53,720.
per hours = $53,720.
Post-modification inspection........ 50 work-hours x $85 per $0...................... $4,250 per inspection
hour = $4,250 per cycle.
inspection cycle.
----------------------------------------------------------------------------------------------------------------
The extent of cracking found during the inspections could vary
significantly from airplane to airplane. The FAA has no way of
determining which conditions may be found on each airplane, the cost to
correct or repair each airplane, or the number of airplanes that may
require repair.
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 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 2013-08-11, Amendment 39-17428
(78 FR 24338, April 25, 2013), and
0
b. Adding the following new airworthiness directive:
The Boeing Company: Docket No. FAA-2025-1105; Project Identifier AD-
2024-00721-T.
[[Page 25172]]
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by July 31, 2025.
(b) Affected ADs
This AD replaces AD 2013-08-11, Amendment 39-17428 (78 FR 24338,
April 25, 2013) (AD 2013-08-11).
(c) Applicability
(1) This AD applies to The Boeing Company Model 737-900 and -
900ER series airplanes, certificated in any category, as identified
in Boeing Special Attention Service Bulletin 737-53-1312, Revision
2, 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 fatigue cracks at chem-mill
areas on the crown skin panels and by recent reports of fuselage
fatigue cracks adjacent to non-chem-mill skin bays. The FAA is
issuing this AD to detect and correct fatigue cracking of the skin
panel 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 of Crown Skin Areas
At the applicable times specified in paragraph 1.E., Compliance,
of Boeing Special Attention Service Bulletin 737-53-1312, Revision
2, dated May 22, 2024, except as required by paragraph (k) of this
AD, 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 certain locations specified in, and in accordance
with, paragraph 3.B.2.a. of the Accomplishment Instructions of
Boeing Special Attention Service Bulletin 737-53-1312, Revision 2,
dated May 22, 2024. Repeat the inspections thereafter at the
applicable times specified in paragraph 1.E., Compliance, of Boeing
Special Attention Service Bulletin 737-53-1312, Revision 2, dated
May 22, 2024.
(h) Inspections of Shear Wrinkle Areas
For Group 1 airplanes as identified in Boeing Special Attention
Service Bulletin 737-53-1312, Revision 2, dated May 22, 2024: At the
applicable time specified in paragraph 1.E., Compliance, of Boeing
Special Attention Service Bulletin 737-53-1312, Revision 2, dated
May 22, 2024, except as required by paragraph (k) of this AD, do an
external detailed inspection and an external nondestructive
inspection (MFEC, MOI, C-scan, or UTPA) for cracking in the fuselage
skin along the chem-mill steps at certain shear wrinkle locations
specified in, and in accordance with, paragraph 3.B.2.b. of the
Accomplishment Instructions of Boeing Special Attention Service
Bulletin 737-53-1312, Revision 2, dated May 22, 2024. Repeat the
inspections thereafter at the applicable times specified in
paragraph 1.E., Compliance, of Boeing Special Attention Service
Bulletin 737-53-1312, Revision 2, dated May 22, 2024.
(i) Repair
If any cracking is found during any inspection required by
paragraph (g) or (h) of this AD, before further flight, repair the
cracking using a method approved in accordance with the procedures
specified in paragraph (m) of this AD.
(j) Optional Terminating Actions
Accomplishment of the actions in paragraphs (j)(1) through (3)
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 in Boeing Special Attention Service Bulletin 737-53-
1312, Revision 2, dated May 22, 2024.
(2) Repair, before further flight, any cracking found during any
inspection specified in paragraph (j)(1) or (3) of this AD using a
method approved in accordance with the procedures specified in
paragraph (l) of this AD.
(3) Do the post-modification repetitive inspections specified in
paragraph 1.E., Compliance, and in Part 5 of the Accomplishment
Instructions of Boeing Special Attention Service Bulletin 737-53-
1312, Revision 2, dated May 22, 2024. The inspections must be
performed and repeated at the applicable times specified in
paragraph 1.E., Compliance, of Boeing Special Attention Service
Bulletin 737-53-1312, Revision 2, dated May 22, 2024, except as
required by paragraph (k) of this AD.
(k) Exceptions to Service Bulletin Specifications
Where the Compliance Time column in the tables under the
``Compliance'' paragraph of Boeing Special Attention Service
Bulletin 737-53-1312, Revision 2, dated May 22, 2024, refer to the
Revision 2 date of Boeing Special Attention Service Bulletin 737-53-
1312, dated May 22, 2024, this AD requires using the effective date
of this AD.
(l) Credit for Previous Actions
This paragraph provides credit for the optional actions in
paragraph (j)(1) of this AD, if the modification was performed
before the effective date of this AD using Boeing Service Bulletin
737-53-1312, dated October 21, 2011, as revised by Boeing Service
Bulletin 737-53-1312, Revision 1, dated March 14, 2012.
(m) 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 (n)
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.
(n) Related Information
For more information about this AD, contact Luis Cortez-Muniz,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA
98198; phone: 206-231-3958; email: [email protected].
(o) 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.
(i) Boeing Special Attention Service Bulletin 737-53-1312,
Revision 2, dated May 22, 2024.
(ii) [Reserved]
(3) For 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.
(4) 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.
(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].
[[Page 25173]]
Issued on June 12, 2025.
Peter A. White,
Deputy Director, Integrated Certificate Management Division, Aircraft
Certification Service.
[FR Doc. 2025-11032 Filed 6-13-25; 8:45 am]
BILLING CODE 4910-13-P