DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0459; Product Identifier 2020-NM-049-AD]
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 adopt 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
proposed 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 proposed AD would require 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 proposing this AD to
address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by July 20, 2020.

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 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 NPRM, any comments received, and other information. The street
address for Docket Operations is listed above. Comments will be
available in the AD docket shortly after receipt.

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:
michael.bumbaugh@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 the ADDRESSES section. Include "Docket No. FAA-2020-0459;
Product Identifier 2020-NM-049-AD" at the beginning of your comments.
The FAA specifically invites comments on the overall regulatory,
economic, environmental, and energy aspects of this NPRM. The FAA will
consider all comments received by the closing date and may amend this
NPRM 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 FAA 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 FAA
Aerospace Engineer Michael Bumbaugh at the previously-listed contact
information. Any commentary that the FAA receives which is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.

Discussion

The FAA has received reports of cracked and completely severed lugs
in the stop fitting assembly of the forward entry door on Boeing Model
737 Next Generation (NG) airplanes. Analysis of the design of the stop
fitting assembly revealed that undersized wall thickness of the lug
made it susceptible to fatigue cracking. The FAA has determined that
the failure of the door stop fitting assembly may result in the forward
entry door being unable to sustain limit load. This condition, if not
addressed, could result in reduced structural integrity of the forward
entry door and consequent rapid decompression of the airplane.

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 describes procedures
for an inspection, a measurement, or a records check of the upper aft
corner door 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.

FAA's Determination

The FAA is proposing this AD because the agency evaluated all the
relevant information and determined the unsafe condition described
previously is likely to exist or develop in other products of the same
type design.

Proposed AD Requirements

This proposed AD would require accomplishment of the actions
identified in Boeing Alert Requirements Bulletin 737-52A1180 RB, dated
January 24, 2020, described previously, except as discussed under
"Differences Between this Proposed AD and the Service Information,"
and 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-2020-0459.

Explanation of Requirements Bulletin

The FAA worked in conjunction with industry, under the
Airworthiness Directive Implementation Aviation Rulemaking Committee
(AD ARC), to enhance the AD system. One enhancement is a process for
annotating which steps in the service information are "required for
compliance" (RC) with an AD. Boeing has implemented this RC concept
into Boeing service bulletins.

In an effort to further improve the quality of ADs and AD-related
Boeing service information, a joint process improvement initiative was
worked between the FAA and Boeing. The initiative resulted in the
development of a new process in which the service information more
clearly identifies the actions needed to address the unsafe condition
in the "Accomplishment Instructions." The new process results in a
Boeing Requirements Bulletin, which contains only the actions needed to
address the unsafe condition (i.e., only the RC actions).

Differences Between This Proposed AD and the Service Information

The effectivity of Boeing Alert Requirements Bulletin 737-52A1180
RB, dated January 24, 2020, is limited to certain Boeing Model 737-600,
-700, -700C, -800, -900, and -900ER series airplanes. However, the
applicability of this proposed AD includes all existing and future
Boeing Model 737 series airplanes, excluding Model 737-100,
-200, -200C, -300, -400, and -500 series airplanes. Because the
affected parts are rotable parts, the FAA has determined that these
parts with the unsafe design could later be installed on airplanes that
were initially delivered with acceptable parts, thereby subjecting
those airplanes to the unsafe condition.

Costs of Compliance

The FAA estimates that this proposed AD would affect 1,075
airplanes of U.S. registry. The FAA estimates the following costs to
comply with this proposed AD:

Estimated Costs for Required Actions

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

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 this proposed
regulation:

(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 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 (AD):