
[Federal Register Volume 88, Number 184 (Monday, September 25, 2023)]
[Proposed Rules]
[Pages 65637-65640]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-20507]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-1886; Project Identifier AD-2023-00429-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) 
2009-01-02, which applies to certain Boeing Model 737-600, -700, -700C, 
-800, and -900 series airplanes. AD 2009-01-02 requires an inspection 
of frames between body station (BS) 360 and BS 907 to determine if 
certain support brackets of the air conditioning (A/C) outlet 
extrusions are installed, inspections for cracking of the frames around 
the attachment holes of the subject brackets, and repair if necessary. 
AD 2009-01-02 also requires installing new, improved fittings for all 
support brackets of the A/C outlet extrusions between BS 360 and BS 
907. Since the FAA issued AD 2009-01-02, the agency determined that 
certain repairs might develop fatigue cracks that could result in the 
inability of the frame to sustain limit load and therefore must be 
inspected. This proposed AD would continue to require the actions 
specified in AD 2009-01-02 and would also require repetitive 
inspections for cracking of certain repairs and repair if necessary. 
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 November 9, 
2023.

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-2023-1886; 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 service information identified in this NPRM, 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 by searching for and locating Docket No. FAA-2023-1886.

FOR FURTHER INFORMATION CONTACT: Owen F. Bley-Male, Aviation Safety 
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-
231-3992; 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 ADDRESSES. Include ``Docket No. FAA-2023-1886; Project Identifier 
AD-2023-00429-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 
the proposal because of those comments.
    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other

[[Page 65638]]

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 
proposed AD.

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 Owen 
F. Bley-Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des 
Moines, WA 98198; phone: 206-231-3992; 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 2009-01-02, Amendment 39-15780 (74 FR 4117, 
January 23, 2009) (AD 2009-01-02), for certain Boeing Model 737-600, -
700, -700C, -800, and -900 series airplanes. AD 2009-01-02 was prompted 
by numerous reports of multiple cracks in the frame around the 
attachment holes of the support bracket of the A/C outlet extrusion. AD 
2009-01-02 requires a one-time general visual inspection of frames 
between BS 360 and BS 907 to determine if certain support brackets of 
the A/C outlet extrusions are installed, medium- and high-frequency 
eddy current inspections for cracking of the frames around the 
attachment holes of the subject brackets, and repair if necessary. AD 
2009-01-02 also requires installing new, improved fittings for all 
support brackets of the A/C outlet extrusions between BS 360 and BS 
907. AD 2009-01-02 refers to Boeing Special Attention Service Bulletin 
737-25-1544, Revision 1, dated January 16, 2008, as the appropriate 
source of service information for accomplishing the required actions. 
The agency issued AD 2009-01-02 to prevent frame cracking, which, if 
not corrected, could lead to a severed frame that, combined with 
cracking of the skin lap splice above stringer 10, could result in 
rapid decompression of the airplane.

Actions Since AD 2009-01-02 Was Issued

    Since the FAA issued AD 2009-01-02, Boeing issued Special Attention 
Service Bulletin 737-25A1544, Revision 3, dated May 16, 2016, as an 
alternative method of compliance for AD 2009-01-02, which includes an 
alternative to making repairs using Boeing Special Attention Service 
Bulletin 737-25-1544, Revision 1, dated January 16, 2008. The FAA and 
Boeing determined that the repairs done using Boeing Special Attention 
Service Bulletin 737-25A1544, Revision 3, dated May 16, 2016, might 
develop fatigue cracks that could result in the inability of the frame 
to sustain limit load. Boeing subsequently issued Alert Service 
Bulletin 737-25A1544, Revision 4, dated February 15, 2022, which added 
damage tolerance inspections for certain BS 907 repairs done using 
Boeing Special Attention Service Bulletin 737-25A1544, Revision 3, 
dated May 16, 2016. The FAA determined that those post-repair 
inspections are necessary to address the 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.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Service Bulletin 737-25A1544, 
Revision 4, dated February 15, 2022. This service information specifies 
procedures for a one-time general visual inspection of frames between 
BS 360 and BS 907 to determine if certain support brackets of the A/C 
outlet extrusions are installed; low-, medium- and high-frequency eddy 
current inspections for cracking of the frames around the attachment 
holes of the subject brackets, and repair if necessary; and 
installation of new, improved fittings for all support brackets of the 
A/C outlet extrusions between BS 360 and BS 907. This service 
information also specifies procedures for repetitive detailed and high-
frequency eddy current inspections for cracking of certain repairs at 
BS 907 and repair if necessary.
    This AD also requires Boeing Special Attention Service Bulletin 
737-25-1544, Revision 1, dated January 16, 2008, which the Director of 
the Federal Register approved for incorporation by reference as of 
February 27, 2009 (74 FR 4117, January 23, 2009).
    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.

Proposed AD Requirements in This NPRM

    This proposed AD would require accomplishing the actions specified 
in the service information described previously, 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 service information at regulations.gov by searching for and 
locating Docket No. FAA-2023-1886.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 738 airplanes of U.S. registry. The FAA estimates the following 
costs to comply with this proposed AD:

                                                                     Estimated Costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
               Action                      Labor cost                Parts cost                 Cost per product              Cost on U.S. operators
--------------------------------------------------------------------------------------------------------------------------------------------------------
General visual inspection (retained  1 work-hour x $85 per   $0.......................  $85............................  $62,730.
 actions from AD 2009-01-02).         hour = $85.
Eddy current inspections (retained   Up to 216 work-hours x  0........................  Up to 18,360...................  Up to 13,549,680.
 actions from AD 2009-01-02).         85 per hour = Up to
                                      18,360.
Replace support fittings (retained   Up to 346 work-hours x  Up to 28,789.............  Up to 57,889...................  Up to 42,722,082.
 actions from AD 2009-01-02).         85 per hour = Up to
                                      29,410.

[[Page 65639]]

 
Post-repair Inspections (new         42 work-hours x 85 per  0........................  3,570 per inspection cycle.....  2,634,660 per inspection cycle.
 proposed action).                    hour = 3,570 per
                                      inspection cycle.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The FAA has received no definitive data on which to base the cost 
estimates for the on-condition repairs that would be required based on 
the results of the inspections 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 has 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 that the 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) 2009-01-02, Amendment 39-15780 
(74 FR 4117, January 23, 2009), and
0
b. Adding the following new AD:

The Boeing Company: Docket No. FAA-2023-1886; Project Identifier AD-
2023-00429-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) action by November 9, 2023.

(b) Affected ADs

    This AD replaces AD 2009-01-02, Amendment 39-15780 (74 FR 4117, 
January 23, 2009) (AD 2009-01-02).

(c) Applicability

    This AD applies to Boeing Model 737-600, -700, -700C, -800, and 
-900 series airplanes, certificated in any category, as identified 
in Boeing Special Attention Service Bulletin 737-25A1544, Revision 
4, dated February 15, 2022.

(d) Subject

    Air Transport Association (ATA) of America Code 25, Equipment/
Furnishing.

(e) Unsafe Condition

    This AD was prompted by numerous reports of multiple cracks in 
the frame around the attachment holes of the support bracket of the 
air conditioning (A/C) outlet extrusion. Also, the FAA determined 
that certain repairs done to comply with AD 2009-01-02 might develop 
fatigue cracks that could result in the inability of the frame to 
sustain limit load and must be inspected. The FAA is issuing this AD 
to address frame cracking, which, if not corrected, could lead to a 
severed frame that, combined with cracking of the skin lap splice 
above stringer 10, could result in rapid decompression of the 
airplane.

(f) Compliance

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

(g) Retained Inspection, With New Service Information

    This paragraph restates the requirements of paragraph (f) of AD 
2009-01-02, with new service information. Before the accumulation of 
36,000 total flight cycles, or within 72 months after February 27, 
2009 (the effective date of AD 2009-01-02), whichever occurs later, 
except as required by paragraph (i) of this AD: Do a general visual 
inspection to determine if the support brackets of the A/C outlet 
extrusions between body station (BS) 360 and BS 907 have two-rivet 
attachment fittings in accordance with Part 2 of the Accomplishment 
Instructions of Boeing Special Attention Service Bulletin 737-25-
1544, Revision 1, dated January 16, 2008, or Boeing Alert Service 
Bulletin 737-25A1544, Revision 4, dated February 15, 2022; except at 
the locations identified in the notes of Step 3.B.1 of Part 1 of the 
Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-25-1544, Revision 1, dated January 16, 2008, or Boeing 
Alert Service Bulletin 737-25A1544, Revision 4, dated February 15, 
2022. As of the effective date of this AD, only use Boeing Alert 
Service Bulletin 737-25A1544, Revision 4, dated February 15, 2022, 
for the actions required by paragraph (g) of this AD.
    (1) For any support bracket attached with three or more rivets: 
No further action is required by paragraph (g) of this AD.
    (2) For any subject support bracket having a two-rivet 
attachment fitting: Before the accumulation of 36,000 total flight 
cycles, or within 72 months after February 27, 2009 (the effective 
date of AD 2009-01-02), whichever occurs later, except as required 
by paragraph (i) of this AD, do medium- and high-frequency eddy 
current inspections for cracking of the frame around the attachment 
holes of the support bracket, in accordance with Part 2 of the 
Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-25-1544, Revision 1, dated January 16, 2008, or do low-
, medium- and high-frequency eddy current inspections for cracking 
of the frame around the attachment holes of the support bracket, in 
accordance with Part 2 of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-25A1544, Revision 4, dated February 15, 
2022. If any cracking is discovered, before further flight, repair 
the cracking in accordance with Part 3 of the Accomplishment 
Instructions of Boeing Special Attention Service Bulletin 737-25-
1544, Revision 1, dated January 16, 2008, or Boeing Alert Service 
Bulletin 737-25A1544, Revision 4, dated February 15, 2022, except

[[Page 65640]]

as required by paragraph (k)(2) of this AD. As of the effective date 
of this AD, only use Boeing Alert Service Bulletin 737-25A1544, 
Revision 4, dated February 15, 2022, for the actions required by 
paragraph (g)(2) of this AD.

(h) Retained Modification With New Service Information

    This paragraph restates the requirements of paragraph (g) of AD 
2009-01-02, with new service information. Except as required by 
paragraph (i) of this AD: Before the accumulation of 36,000 total 
flight cycles, or within 72 months after February 27, 2009 (the 
effective date of AD 2009-01-02), whichever occurs later, replace 
the support fittings of all A/C outlet extrusions between BS 360 and 
BS 907 with new, improved support fittings, in accordance with Part 
4 of the Accomplishment Instructions of Boeing Special Attention 
Service Bulletin 737-25-1544, Revision 1, dated January 16, 2008, or 
Boeing Alert Service Bulletin 737-25A1544, Revision 4, dated 
February 15, 2022. As of the effective date of this AD, only use 
Boeing Alert Service Bulletin 737-25A1544, Revision 4, dated 
February 15, 2022, for the actions required by paragraph (h) of this 
AD.

(i) Retained Compliance Time for Certain Airplanes With No Changes

    This paragraph restates the compliance time specified in 
paragraph (h) of AD 2009-01-02, with no changes. For airplanes on 
which Boeing Business Jet (BBJ) lower cabin altitude modification is 
incorporated in accordance with Supplemental Type Certificate 
ST01697SE: Before the accumulation of 18,000 total flight cycles, or 
within 72 months after February 27, 2009 (the effective date of AD 
2009-01-02), whichever occurs later, do the actions specified in 
paragraphs (g) and (h) of this AD.

(j) New Requirements of This AD

    For Groups 1 through 4 and Group 6 as identified in Boeing Alert 
Service Bulletin 737-25A1544, Revision 4, dated February 15, 2022: 
Except as specified in paragraph (k) of this AD: At the applicable 
time specified in Table 2 of the ``Compliance'' paragraph of Boeing 
Alert Service Bulletin 737-25A1544, Revision 4, dated February 15, 
2022, do a detailed inspection and a high-frequency eddy current 
inspection for cracking of the repaired area at frame BS 907, and do 
all applicable repairs before further flight, in accordance with the 
Accomplishment Instructions of in Boeing Alert Service Bulletin 737-
25A1544, Revision 4, dated February 15, 2022. Repeat the inspections 
thereafter at the applicable time specified in Table 2 of the 
``Compliance'' paragraph of Boeing Alert Service Bulletin 737-
25A1544, Revision 4, dated February 15, 2022.

(k) Exceptions to Service Information Specifications

    (1) Where the Compliance Time column of Table 2 in the 
``Compliance'' paragraph of Boeing Alert Service Bulletin 737-
25A1544, Revision 4, dated February 15, 2022, uses the phrase ``the 
Revision 4 date of this Service Bulletin,'' this AD requires using 
``the effective date of this AD.''
    (2) Where Boeing Alert Service Bulletin 737-25A1544, Revision 4, 
dated February 15, 2022, specifies contacting Boeing, this AD 
requires repair before further flight using a method approved in 
accordance with the procedures specified in paragraph (m) of this 
AD.
    (3) For airplanes on which Boeing Business Jet Lower Cabin 
Altitude Supplemental Type Certificate (STC) ST01697SE (drs.faa.gov/browse/excelExternalWindow/0812969A86AF879B8625766400600105.0001) 
(6,500 feet maximum cabin altitude in lieu of 8,000 feet) has been 
incorporated, the flight-cycle related compliance times for the 
inspections required by paragraph (j) of this AD are different from 
those specified in Table 2 of the ``Compliance'' paragraph in Boeing 
Alert Service Bulletin 737-25A1544, Revision 4, dated February 15, 
2022. All initial compliance times specified in total flight cycles 
or flight cycles must be reduced to half of those specified in Table 
2 of the ``Compliance'' paragraph in Boeing Alert Service Bulletin 
737-25A1544, Revision 4, dated February 15, 2022. All repetitive 
interval compliance times specified in flight cycles must be reduced 
to one-quarter of those specified in Table 2 of the ``Compliance'' 
paragraph in Boeing Alert Service Bulletin 737-25A1544, Revision 4, 
dated February 15, 2022.

(l) Credit for Previous Actions

    (1) This paragraph provides credit for the actions specified in 
paragraphs (g) and (h) of this AD, if those actions were performed 
before February 27, 2009 (the effective date of AD 2009-01-02) using 
Boeing Alert Service Bulletin 737-25-1544, dated October 4, 2006.
    (2) This paragraph provides credit for the actions specified in 
paragraphs (g) and (h) of this AD, if those actions were performed 
before the effective date of this AD using Boeing Special Attention 
Service Bulletin 737-25-1544, Revision 2, dated March 23, 2011, or 
Boeing Special Attention Service Bulletin 737-25-1544, Revision 3, 
dated May 16, 2016.

(m) 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 AIR-520, Continued 
Operational Safety Branch, send it to the attention of the person 
identified in paragraph (n)(1) 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 2009-01-02 are approved as AMOCs for 
the corresponding provisions of paragraphs (g) through (i) of this 
AD.

(n) Related Information

    (1) For more information about this AD, contact Owen F. Bley-
Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des 
Moines, WA 98198; phone: 206-231-3992; email: [email protected].
    (2) Service information identified in this AD that is not 
incorporated by reference is available at the addresses specified in 
paragraphs (o)(5) and (6) of this AD.

(o) 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 this AD specifies otherwise.
    (3) The following service information was approved for IBR on 
[DATE 35 DAYS AFTER PUBLICATION OF THE FINAL RULE].
    (i) Boeing Alert Service Bulletin 737-25A1544, Revision 4, dated 
February 15, 2022.
    (ii) [Reserved]
    (4) The following service information was approved for IBR on 
February 27, 2009 (74 FR 4117, January 23, 2009).
    (i) Boeing Special Attention Service Bulletin 737-25-1544, 
Revision 1, dated January 16, 2008.
    (ii) [Reserved]
    (5) 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.
    (6) 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.
    (7) 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 [email protected], or go to: www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on September 18, 2023.
Victor Wicklund,
Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-20507 Filed 9-22-23; 8:45 am]
BILLING CODE 4910-13-P


