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PROPOSED AD THE BOEING COMPANY: Docket No. FAA-2021-0788; Project Identifier AD-2021-489-T.
(a) COMMENTS DUE DATE

    The FAA must receive comments on this airworthiness directive (AD)  by
    November 29, 2021.

(b) AFFECTED ADS

    None.

(c) APPLICABILITY

    This AD applies to The Boeing Company Model 737-700, -800, and  -900ER
    series  airplanes, certificated  in any  category,  and  identified in
    Boeing Alert Requirements Bulletin 737-53A1384 RB, dated September 10,
    2020.

(d) SUBJECT

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

(e) UNSAFE CONDITION

    This AD was prompted by reports of incorrectly installed fuselage skin
    fasteners. The FAA is issuing this AD to address incorrectly installed
    fasteners.  This  condition,  if   not  addressed,  could  result   in
    incorrectly installed fasteners going undetected. Continuous operation
    of the  airplane with  undetected incorrectly  installed fasteners may
    generate fatigue cracking that  could adversely affect the  structural
    integrity of the airplane.

(f) COMPLIANCE

    Comply with this AD within the compliance times specified,  unless al-
    ready done.

(g) REQUIRED ACTIONS

    Except as  specified by  paragraph (h)  of this  AD: At the applicable
    times  specified  in  the  "Compliance"  paragraph  of  Boeing   Alert
    Requirements Bulletin 737-53A1384 RB, dated September 10, 2020, do all
    applicable  actions  identified  in,  and  in  accordance  with,   the
    Accomplishment Instructions of Boeing Alert Requirements Bulletin  737
    -53A1384 RB, dated September 10, 2020.

Note 1 to paragraph (g):  Guidance for accomplishing the actions  required
by this  AD can  be found  in Boeing  Alert Service  Bulletin 737-53A1384,
dated  September  10,  2020,  which   is  referred  to  in  Boeing   Alert
Requirements Bulletin 737-53A1384 RB, dated September 10, 2020.

(h) EXCEPTIONS TO SERVICE INFORMATION SPECIFICATIONS

(1) Where the "Effectivity"  paragraph  and  the  Condition and Compliance
    Time columns  of the  tables in  the "Compliance"  paragraph of Boeing
    Alert Requirements Bulletin 737-53A1384 RB,  dated September 10, 2020,
    use the phrase  "the Original Issue date of Requirements Bulletin  737
    -53A1384 RB," this AD requires using "the effective date of this AD."

(2) Where Boeing Alert Requirements Bulletin 737-53A1384 RB, dated Septem-
    ber 10, 2020, 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.

(i) 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
    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 (j)(1) of this AD. Information may be  emailed
    to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.

(2) Before using any approved AMOC,  notify your appropriate principal in-
    spector, or lacking a principal inspector,  the manager of the respon-
    sible 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.

(j) RELATED INFORMATION

(1) For more information about this AD, contact Lu Lu, Aerospace Engineer,
    Airframe Section, FAA,  Seattle ACO Branch,  2200 South 216th St., Des
    Moines, WA 98198; phone and fax: 206-231-3525; email: lu.lu@faa.gov.

(2) For service information identified in this AD,  contact Boeing Commer-
    cial 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 referenced 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.

Issued on September 9, 2021.  Lance T. Gant,  Director,  Compliance & Air-
worthiness Division, Aircraft Certification Service.

DATES: The FAA must receive comments  on this proposed AD  by November 29,
2021.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration


14 CFR Part 39

[Docket No. FAA-2021-0788; Project Identifier AD-2021-00489-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 adopt a new airworthiness directive (AD)
for certain The Boeing Company Model 737-700, -800, and -900ER series
airplanes. This proposed AD was prompted by reports of incorrectly
installed fuselage skin fasteners. This proposed AD would require a
detailed inspection of a certain body station bulkhead, between certain
stringers, for any incorrectly installed fastener common to fuselage
skin, and applicable on-condition actions. 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
29, 2021.

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 https://www.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.
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; internet https://www.myboeingfleet.com. You may
view this referenced 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-2021-0788.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0788; 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.

FOR FURTHER INFORMATION CONTACT
: Lu Lu, Aerospace Engineer, Airframe
Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA
98198; phone and fax: 206-231-3525; email: lu.lu@faa.gov.

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-2021-0788; Project Identifier
AD-2021-00489-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
https://www.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 Lu
Lu, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200
South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3525;
email: lu.lu@faa.gov. Any commentary that the FAA receives which is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.

Background

The FAA has received a report indicating incorrectly installed
fasteners were found at the station (STA) 727 bulkhead between
stringers S-22 and S-27. The fasteners, installed with a gap under the
fastener head, were found at the STA 727 bulkhead common to fuselage
skin, including the S-23 skin lap splice. Incorrectly installed
fasteners are suspected to exist on airplanes delivered within a
certain time period. The FAA has confirmed that the fastener
installation procedures were corrected on airplanes subsequently
delivered. This condition was the result of incorrect procedures used
to install affected fasteners during airplane production, which could
result in incorrectly installed fasteners going undetected. Continuous
operation of the airplane with incorrectly installed fasteners may
generate fatigue cracking that could adversely affect the structural
integrity of the airplane. Gaps under fastener heads will result in
bending loads on the bulkhead chord that could cause chord failure and
adjacent skin failure, resulting in reduced control of the airplane.

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 Requirements Bulletin 737-53A1384 RB,
dated September 10, 2020. This service information specifies procedures
for a detailed inspection for incorrectly installed fasteners at the
STA 727 bulkhead outer chord common to the fuselage skin between
stringers S-22 and S-27 on the left and right sides, and applicable on-
condition actions. In addition to repair and replacement, on-condition
actions include repetitive inspections for cracking of the fuselage
skin between stringers S-22 and S-27; an open hole high frequency eddy
current (HFEC) inspection for cracking at all incorrectly installed
fastener locations; and external and internal general visual
inspections for repairs of the STA 727 bulkhead. On-condition actions
also include repetitive HFEC and low frequency eddy current (LFEC)
inspections in unrepaired areas for cracking of the inner skin from the
wheel well; of the outer, upper, and lower chords from the wheel well;
and of the fail-safe chord from the cargo compartment.
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.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified
in the service information 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
service information at https://www.regulations.gov by searching for and
locating Docket No. FAA-2021-0788.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 78 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
Inspections 13 work-hours x $85 per hour = $1,105
$0
$1,105
$86,190

The FAA estimates the following costs to do any necessary actions
that would be required based on the results of the proposed inspection.
The agency has no way of determining the number of aircraft that might
need these on-condition actions.

On-Condition Costs

Action
Labor cost
Parts cost
Cost per product
Open hole HFEC inspections 21 work-hours x $85 per hour = $85 per inspection cycle
$0
$1,785 per inspection cycle
HFEC and LFEC inspections 36 work-hours x $85 per hour = $3,060 per inspection cycle
0
3,060 per inspection cycle

The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some or all of the costs of
this proposed AD may be covered under warranty, thereby reducing the
cost impact on affected operators.

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

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]

2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive: