[Federal Register Volume 86, Number 33 (Monday, February 22, 2021)]
[Rules and Regulations]
[Pages 10441-10444]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-01851]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0459; Product Identifier 2020-NM-049-AD; Amendment 
39-21380; AD 2021-01-04]
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 adopting a new airworthiness directive (AD) for all 
The Boeing Company Model 737 series airplanes, excluding Model 737-100, 
-200, -200C, -300, -400, and -500 series airplanes. This AD was 
prompted by reports of cracked or completely severed lugs in the upper 
aft corner stop fitting assembly of the forward entry door. This AD 
requires an inspection, a measurement, or a records check of that 
assembly to determine the part number, and replacement if a certain 
part is found. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective March 29, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of March 29, 
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 on 
the internet at https://www.regulations.gov by searching for and 
locating Docket No. FAA-2020-0459.

Examining the AD Docket

    You may examine the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-
0459; 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: Michael Bumbaugh, Aerospace Engineer, 
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3522; email: 
[email protected].

SUPPLEMENTARY INFORMATION:

Discussion

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to all The Boeing Company 
Model 737 series airplanes, excluding Model 737-100, -200, -200C, -300, 
-400, and -500 series airplanes. The NPRM published in the Federal 
Register on June 3, 2020 (85 FR 34136). The NPRM was prompted by 
reports of cracked or completely severed lugs in the upper aft corner 
stop fitting assembly of the forward entry door. Analysis of the design 
of the stop fitting assembly revealed that undersized wall thickness of 
the lug made it susceptible to fatigue cracking, which may result in 
the forward entry door being unable to sustain limit load. In the NPRM, 
the FAA proposed to require an inspection, a measurement, or a records 
check of that assembly to determine the part number, and replacement if 
a certain part-numbered assembly is installed.
    The FAA is issuing this AD to address cracked or completely severed 
lugs, which could result in reduced structural integrity of the forward 
entry door and consequent rapid decompression of the airplane.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from four commenters. The following 
presents the comments received on the NPRM and the FAA's response to 
each comment.

Effect of Winglets on Accomplishment of the Proposed Actions

    Aviation Partners Boeing stated that the installation of winglets 
per Supplemental Type Certificate (STC) ST00830SE does not affect 
compliance with the proposed actions.
    The FAA agrees that the installation of winglets per STC ST00830SE 
would not affect the ability to replace the affected stop fitting 
assembly with a newly designed stop fitting assembly as 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) accordingly.

Request for Compliance Actions at the Component Level

    Southwest Airlines (SWA) asked that the compliance actions be 
reported at the component level due to the interchangeability of the 
forward entry doors between the Model 737 NG and 737 MAX fleets.
    The FAA infers that the commenter is requesting that the AD's 
applicability point towards the component parts, rather than the 
airplane. The FAA acknowledges that the component most likely to be 
rotated is the forward entry door because doors are likely removed with 
the stop fittings intact. However, the FAA disagrees with changing the 
applicability of this AD because the unsafe condition is related to the 
stop fitting assembly and an affected stop fitting assembly may be 
installed on a forward entry door of any airplane identified in 
paragraph (c) of this AD. In addition, paragraph (i) of this AD, 
``Parts Installation Prohibition,'' states that no person may install a 
forward entry door that has a stop fitting assembly with part number 
(P/N) 141A6104-3 on any airplane. The FAA used this language because 
doors are often rotated among aircraft with the stop fitting assembly 
already installed. The FAA has therefore determined that an airplane-
level applicability is appropriate and has not changed this AD in this 
regard.

[[Page 10442]]

Request for Clarification of Compliance Time

    SWA asked for clarification of the reference in paragraph (g) of 
the proposed AD to the applicable times specified in the ``Compliance'' 
paragraph of Boeing Alert Requirements Bulletin 737-52A1180 RB, dated 
January 24, 2020. SWA asked if once it is determined that a P/N 
141A6104-3 fitting is installed on a door through records or survey, 
the fitting must be replaced before further flight or whether it can be 
replaced at a later date as long as the door is still within its 
required compliance time per the referenced service information.
    ``Table 1: Forward Entry Door Number 7 Stop Fitting Assembly 
Inspection'' of Paragraph 3., ``Compliance'' of Boeing Service Bulletin 
737-52A1180, dated January 24, 2020, gives the compliance time for 
replacing the P/N 141A6104-3 fitting if found. The compliance time is 
before 10,000 total flight cycles on the forward entry door, or within 
5,000 forward entry door flight cycles after the original issue date of 
Boeing Alert Requirements Bulletin 737-52A1180 RB, dated January 24, 
2020, whichever occurs later. However, under paragraph (h) of this AD, 
the date for determining compliance time is the effective date of this 
AD, and not the issue date of the bulletin. Therefore, the FAA 
clarifies that if the compliance time has not yet been reached, then 
the fitting does not need to be replaced before further flight. The FAA 
has not changed this AD in this regard.

Request To Change Parts Installation Prohibition Paragraph

    SWA asked that the FAA reword paragraph (i) of the proposed AD to 
require compliance with the service information before installation of 
the fitting instead of prohibiting installation of the fitting.
    The intent of paragraph (i) of this AD is to prohibit installation 
of an affected part on an airplane with a compliance time for this 
prohibition related to the airplane configuration and whether the 
actions specified in Boeing Alert Requirements Bulletin 737-52A1180 RB, 
dated January 24, 2020, must be accomplished on that airplane. The FAA 
has not made the changes requested by the commenter. However, the FAA 
has revised paragraph (i) of this AD to clarify that, for any airplane 
required to accomplish the actions required by paragraph (g) of this 
AD, the parts installation prohibition does not take effect until the 
applicable actions required by paragraph (g) of this AD have been 
accomplished on that airplane. For airplanes having an original 
airworthiness certificate or original export certificate of 
airworthiness dated after the effective date of this AD, the parts 
installation prohibition continues to be applicable as of the effective 
date of this AD.

Request for Correction of Error in Service Information

    AIRDO requested the FAA correct an error in the service information 
incorporated by reference in paragraph (g) of the proposed AD. AIRDO 
noted that page 13 of Boeing Alert Requirements Bulletin 737-52A1180 
RB, dated January 24, 2020, refers to the procedures in ``SB 747-
52A1180'' when the correct reference is ``SB 737-52A1180.''
    The FAA agrees with the commenter's request. The FAA has added 
paragraph (h)(3) of this AD to clarify the correct service information 
reference.

Request To Limit the Applicability

    American Airlines (AA) and AIRDO requested the FAA limit the 
applicability of the proposed AD to the line numbers (L/Ns) identified 
in the effectivity of Boeing Alert Service Bulletin 737-52A1180, dated 
January 24, 2020. AA stated that because the aircraft illustrated parts 
catalog (IPC) does not allow for the unsafe part to be installed on 
aircraft beyond L/N 1075, or on the door assemblies allowed to be 
installed on aircraft beyond L/N 1075, including all Model 737-600, -
700, -700C, -800, -900, and -900ER series airplanes in the 
applicability of the proposed AD is unnecessarily redundant. AIRDO 
stated Boeing has not allowed operators to install P/Ns 141A6104-3, 
141A6150-1, 141A6150-2, and 141A6100-678 on airplanes other than those 
with L/N 1-1075 per the IPC and related drawings. AIRDO also stated 
that if the fitting or the door assembly must be replaced, operators 
will check the IPC and drawing to confirm if the affected part number 
can be used on the specific airplane. AIRDO stated that based on this 
general protocol, even though the fitting and door assembly are 
physically interchangeable, a suspected fitting and door assembly 
cannot be installed on airplanes having L/N 1076 and subsequent.
    The FAA does not agree with the requests to limit the 
applicability. Both the stop fitting assemblies and the doors they are 
installed on are physically interchangeable among the airplane models 
listed in the applicability of this AD. The FAA has determined it is 
necessary to ensure these rotable parts will not be introduced on other 
airplanes by including these airplanes in the applicability of this AD. 
Therefore, the FAA has not changed this AD in this regard.

Conclusion

    The FAA reviewed the relevant data, considered the comments 
received, and determined that air safety requires adopting this AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition in these products. Except for the 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 Requirements Bulletin 737-52A1180 RB, 
dated January 24, 2020. The service information specifies procedures 
for an inspection, a measurement, or a records check of the upper aft 
corner stop fitting assembly to determine the part number, and 
applicable on-condition actions. The on-condition action is to replace 
the affected stop fitting assembly with a newly designed stop fitting 
assembly that has improved wall thickness and strength. 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 1,075 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                      Estimated Costs for Required Actions
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            Action                 Labor cost       Parts cost       Cost per product     Cost on U.S. operators
----------------------------------------------------------------------------------------------------------------
Inspection and part             Up to 4 work-             $4,640  Up to $4,980.........  Up to $5,353,500.
 replacement.                    hours x $85 per
                                 hour = Up to
                                 $340.
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[[Page 10443]]

    The FAA has included all known costs in the cost estimate. 
According to the manufacturer, however, some or all of the costs of 
this 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

    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 adding the following new airworthiness 
directive:

2021-01-04 The Boeing Company: Amendment 39-21380; Docket No. FAA-
2020-0459; Product Identifier 2020-NM-049-AD.

(a) Effective Date

    This airworthiness directive (AD) is effective March 29, 2021.

(b) Affected ADs

    None.

(c) Applicability

    (1) This AD applies to all The Boeing Company Model 737 series 
airplanes, excluding Model 737-100, -200, -200C, -300, -400, and -
500 series airplanes, certificated in any category.
    (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 52, Doors.

(e) Unsafe Condition

    This AD was prompted by reports of cracked or completely severed 
lugs in the stop fitting assembly of the forward entry door. The FAA 
is issuing this AD to address such cracking or severing, which could 
result in reduced structural integrity of the forward entry door and 
consequent rapid decompression of the airplane.

(f) Compliance

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

(g) Required Actions

    For airplanes having a date of issuance of the original 
airworthiness certificate or date of issuance of the original export 
certificate of airworthiness on or before the effective date of this 
AD: Except as specified by paragraph (h) of this AD, at the 
applicable times specified in the ``Compliance'' paragraph of Boeing 
Alert Requirements Bulletin 737-52A1180 RB, dated January 24, 2020, 
do all applicable actions identified in, and in accordance with, the 
Accomplishment Instructions of Boeing Alert Requirements Bulletin 
737-52A1180 RB, dated January 24, 2020.

    Note 1 to paragraph (g):  Guidance for accomplishing the actions 
required by this AD can be found in Boeing Alert Service Bulletin 
737-52A1180, dated January 24, 2020, which is referred to in Boeing 
Alert Requirements Bulletin 737-52A1180 RB, dated January 24, 2020.

(h) Exceptions to Service Information Specifications

    (1) Where Boeing Alert Requirements Bulletin 737-52A1180 RB, 
dated January 24, 2020, uses the phrase ``the original issue date of 
Requirements Bulletin 737-52A1180 RB,'' this AD requires using ``the 
effective date of this AD.''
    (2) Where Boeing Alert Requirements Bulletin 737-52A1180 RB, 
dated January 24, 2020, specifies contacting Boeing for repair 
instructions: This AD requires doing the repair before further 
flight using a method approved in accordance with the procedures 
specified in paragraph (j) of this AD.
    (3) Where the heading in Table 1 of the Accomplishment 
Instructions in Boeing Alert Requirements Bulletin 737-52A1180 RB, 
dated January 24, 2020, identifies ``SB 747-52A1180,'' the correct 
reference for this AD is ``SB 737-52A1180.''

(i) Parts Installation Prohibition

    No person may install a stop fitting assembly with part number 
141A6104-3 or a forward entry door that has a stop fitting assembly 
with part number 141A6104-3, on any airplane, as of the applicable 
time specified in paragraph (i)(1), (2), or (3) of this AD.
    (1) For airplanes having an original airworthiness certificate 
or original export certificate of airworthiness dated after the 
effective date of this AD: As of the effective date of this AD.
    (2) For airplanes on which it is determined a stop fitting 
assembly with part number 141A6104-3 is not installed, as required 
by paragraph (g) of this AD: After accomplishing the inspection, 
records check, or measurement required by paragraph (g) of this AD.
    (3) For airplanes on which it is determined a stop fitting 
assembly with part number 141A6104-3 is installed, as required by 
paragraph (g) of this AD: After accomplishing the replacement 
required by paragraph (g) of 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 principal inspector or local Flight Standards District 
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 local flight standards district office/certificate holding 
district 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

[[Page 10444]]

method, modification deviation, or alteration deviation must meet 
the certification basis of the airplane, and the approval must 
specifically refer to this AD.

(k) Related Information

    (1) For more information about this AD, contact Michael 
Bumbaugh, Aerospace Engineer, Airframe Section, FAA, Seattle ACO 
Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 
206-231-3522; 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 Requirements Bulletin 737-52A1180 RB, dated 
January 24, 2020.
    (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 December 28, 2020.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-01851 Filed 2-19-21; 8:45 am]
BILLING CODE 4910-13-P