[Federal Register Volume 86, Number 213 (Monday, November 8, 2021)]
[Rules and Regulations]
[Pages 61679-61682]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-24225]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0503; Project Identifier AD-2021-00163-T; 
Amendment 39-21769; AD 2021-21-09]
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 superseding Airworthiness Directive (AD) 2005-05-
18, which applied to certain The Boeing Company Model 737-600, -700, -
700C, -800, and -900 series airplanes. AD 2005-05-18 required 
repetitive inspections for cracking of the webs of the aft pressure 
bulkhead at a certain body station, and corrective action if necessary. 
This AD was prompted by cracking found in that inspection area on 
airplanes not identified in the applicability of AD 2005-05-18. This AD 
retains the requirements of AD 2005-05-18, revises the applicability to 
include additional airplanes, and adds an inspection for existing 
repairs on the newly added airplanes. The FAA is issuing this AD to 
address the unsafe condition on these products.

DATES: This AD is effective December 13, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of December 13, 
2021.

ADDRESSES: 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; internet https://www.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 
https://www.regulations.gov by searching for and locating Docket No. 
FAA-2021-0503.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2021-0503; 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.

FOR FURTHER INFORMATION CONTACT: Wayne Lockett, Aerospace Engineer, 
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3524; email: 
[email protected].

SUPPLEMENTARY INFORMATION:

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to supersede AD 2005-05-18, Amendment 39-14007 (70 FR 
12410, March 14, 2005) (AD 2005-05-18). AD 2005-05-18 applied to 
certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 
series airplanes. The NPRM published in the Federal

[[Page 61680]]

Register on June 30, 2021 (86 FR 34660). The NPRM was prompted by 
cracking found in an inspection area on airplanes not identified in the 
applicability of AD 2005-05-18. In the NPRM, the FAA proposed to 
continue to require repetitive inspections for cracking of the webs of 
the aft pressure bulkhead at a certain body station, and corrective 
action if necessary. The NPRM also proposed to require revising the 
applicability to include additional airplanes, and adding an inspection 
for existing repairs on the newly added airplanes. The FAA is issuing 
this AD to address fatigue cracks in the webs of the aft pressure 
bulkhead, which could result in rapid decompression of the airplane.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from United Airlines and Jack Kendrick, 
who supported the NPRM without change.
    The FAA received additional comments from two commenters, including 
Boeing and Aviation Partners Boeing. The following presents the 
comments received on the NPRM and the FAA's response to each comment.

Effects of Winglets on Accomplishment of the Proposed Actions

    Aviation Partners Boeing stated that the installation of blended or 
split scimitar winglets per Supplemental Type Certificate (STC) 
ST00830SE does not affect compliance with the proposed actions.
    The FAA agrees with the commenter 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 Clarify Service Information Description

    Boeing asked that the FAA clarify the language describing the 
inspection location and reporting requirements in the ``Related Service 
Information Under 1 CFR 51'' paragraph in the preamble of the proposed 
AD. Boeing stated that the language should identify the center dome 
apex location, and also specify reporting of any cracks found.
    The FAA agrees with the commenter's request to clarify the 
inspection location in the ``Related Service Information'' section, due 
to the vast number of web fasteners located around the bulkhead. The 
FAA has clarified that language accordingly.
    The FAA does not agree with the commenter's request to add 
reporting language to that section, because the manufacturer did not 
include a reporting requirement for this particular cracking condition 
in the service information. Therefore, the FAA has not changed this AD 
in this regard.

Request To Clarify Language in Actions Since AD 2005-05-18 Was Issued 
Section

    Boeing requested that the FAA clarify the language in the Actions 
Since AD 2005-05-18 Was Issued section of the proposed AD. Boeing 
suggested changing the sentence that begins ``During the assembly 
process on line numbers 1167 through 1755, the fasteners,'' as follows: 
``Fasteners on line numbers 1167 through 1755 in the apex dome region 
are subjected to clamp-up stresses from the assembly process and 
fatigue cycles during fuselage pressurization.'' Boeing stated that 
this change is to clarify the meaning of the language used in the 
proposed AD.
    The FAA acknowledges the commenter's request and agrees the 
proposed wording provides clarity. However, that section is not carried 
over into this final rule. Therefore, the FAA has not changed this AD 
in this regard.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, and determined that air safety requires adopting this AD as 
proposed. 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 737-53A1251, 
Revision 2, dated January 20, 2021. This service information specifies 
procedures for a general visual inspection for existing repairs, 
repetitive detailed and high frequency eddy current (HFEC) inspections 
for cracks around the web center dome apex fasteners, repetitive low 
frequency eddy current (LFEC) inspection for cracks around the hidden 
web lap splice fastener locations, and repair of cracks. 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.

Costs of Compliance

    The FAA estimates that this AD affects 744 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Detailed, HFEC, and LFEC           Up to 10 work-hours              $0  Up to $850 per       Up to $632,400 per
 inspections.                       x $85 per hour =                     inspection cycle.    inspection cycle.
                                    Up to $850 per
                                    inspection cycle.
General visual inspection (194     1 work-hour x $85                 0  $85................  $16,490.
 airplanes).                        per hour = $85.
----------------------------------------------------------------------------------------------------------------

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

[[Page 61681]]



                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
           Action                  Labor cost                Parts cost                   Cost per product
----------------------------------------------------------------------------------------------------------------
Repair......................  Up to 30 * work-     Up to $30,000 *...............  Up to $32,550.*
                               hours x $85 per
                               hour = Up to
                               $2,550.
----------------------------------------------------------------------------------------------------------------
* Repair costs will vary depending on size of the repair required.

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:
0
a. Removing Airworthiness Directive (AD) 2005-05-18, Amendment 39-14007 
(70 FR 12410, March 14, 2005); and
0
b. Adding the following new AD:

2021-21-09 The Boeing Company: Amendment 39-21769; Docket No. FAA-
2021-0503; Project Identifier AD-2021-00163-T.

(a) Effective Date

    This airworthiness directive (AD) is effective December 13, 
2021.

(b) Affected ADs

    This AD replaces AD 2005-05-18, Amendment 39-14007 (70 FR 12410, 
March 14, 2005) (AD 2005-05-18).

(c) Applicability

    (1) This AD applies to The Boeing Company Model 737-600, -700, -
700C, -800, and -900 series airplanes, certificated in any category, 
as identified in Boeing Alert Service Bulletin 737-53A1251, Revision 
2, dated January 20, 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 a report of cracks found at several of 
the fastener rows in the web lap splices at the dome apex of the aft 
pressure bulkhead, and the determination that airplanes not affected 
by AD 2005-05-18 are subject to this unsafe condition. The FAA is 
issuing this AD to address fatigue cracks in the webs of the aft 
pressure bulkhead, which could result in rapid decompression 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 paragraph 1.E., ``Compliance,'' of 
Boeing Alert Service Bulletin 737-53A1251 Revision 2, dated January 
20, 2021, do all applicable actions identified as ``RC'' (required 
for compliance) in, and in accordance with, the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1251, Revision 
2, dated January 20, 2021. For Group 1 airplanes, as defined in 
Boeing Alert Service Bulletin 737-53A1251, Revision 2, dated January 
20, 2021: Step 3.B.2. of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1251, Revision 2, dated January 20, 
2021, is an RC step, and the provisions of paragraphs (j)(5)(i) and 
(ii) of this AD apply.

(h) Exceptions to Service Information Specifications

    (1) Where Boeing Alert Service Bulletin 737-53A1251, Revision 2, 
dated January 20, 2021, uses the phrase ``the Revision 1 date of 
this service bulletin,'' this AD requires using ``the effective date 
of this AD.''
    (2) Where Boeing Alert Service Bulletin 737-53A1251, Revision 2, 
dated January 20, 2021, 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) For airplanes having line numbers 1 through 1166 inclusive: 
This paragraph provides credit for the corresponding actions of 
Boeing Alert Service Bulletin 737-53A1251, Revision 2, dated January 
20, 2021, that are required by paragraph (g) of this AD, if those 
actions were performed before the effective date of this AD using 
Boeing Service Bulletin 737-53-1251, dated June 3, 2004, which was 
incorporated by reference in AD 2005-05-18.
    (2) This paragraph provides credit for the corresponding actions 
of Boeing Alert Service Bulletin 737-53A1251, Revision 2, dated 
January 20, 2021, that are required by paragraph (g) of this AD, if 
those actions were performed before the effective date of this AD 
using Boeing Alert Service Bulletin 737-53A1251, Revision 1, dated 
September 22, 2020, which is not incorporated by reference in this 
AD.

(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

[[Page 61682]]

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)(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, 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.
    (4) AMOCs approved for AD 2005-05-18 are approved as AMOCs for 
the corresponding provisions of Boeing Alert Service Bulletin 737-
53A1251, Revision 2, dated January 20, 2021, that are required by 
paragraph (g) of this AD.
    (5) Except as specified by paragraph (h) of this AD: For service 
information that contains steps that are labeled as Required for 
Compliance (RC), the provisions of paragraphs (j)(5)(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.

(k) Related Information

    (1) For more information about this AD, contact Wayne Lockett, 
Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 
South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3524; 
email: [email protected].
    (2) Service information identified in this AD that is not 
incorporated by reference is available at the addresses specified in 
paragraphs (l)(3) and (4) of this AD.

(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 Service Bulletin 737-53A1251, Revision 2, dated 
January 20, 2021.
    (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; internet https://www.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 [email protected], or go to: https://www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on October 8, 2021.
Gaetano A. Sciortino,
Deputy Director for Strategic Initiatives, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-24225 Filed 11-5-21; 8:45 am]
BILLING CODE 4910-13-P


