DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0789; Project Identifier AD-2020-00849-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)
2019-22-10, which applies to all The Boeing Company Model 737-600, -
700, -700C, -800, -900, and -900ER series airplanes. AD 2019-22-10
requires repetitive inspections for cracking of the left- and right-
hand side outboard chords of frame fittings and failsafe straps at a
certain station around eight fasteners, and repair if any cracking is
found. Since the FAA issued AD 2019-22-10, it was determined that the
initial inspection threshold and repetitive inspection interval are
inadequate to address the cracking in a timely manner. For certain
airplanes, this proposed AD would reduce the compliance time for the
initial inspection, and for all airplanes this proposed AD would reduce
the compliance time for the repetitive inspections. 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 October 23,
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 service information at the FAA, Transport Standards Branch,
2200 South 216th St., Des Moines, WA. 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-2020-0789.

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-2020-0789;
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: Greg Rutar, Aerospace Engineer,
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des
Moines, WA 98198; phone and fax: 206-231-3529; email:
Greg.Rutar@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to participate in this rulemaking by submitting
written comments, data, or views about this proposal. The most helpful
comments reference a specific portion of the proposal, explain the
reason for any recommended change, and include supporting data. To
ensure the docket does not contain duplicate comments, commenters
should submit only one copy of the comments. Send your comments to an
address listed under the ADDRESSES section. Include "Docket No.
FAA-2020-0789; Project Identifier AD-2020-00849-T" at the beginning of
your 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, as well
as a report summarizing each substantive public contact with FAA
personnel concerning this proposed rulemaking. Before acting on this
proposal, the FAA will consider all comments received by the closing
date for comments. The FAA will consider comments filed after the
comment period has closed if it is possible to do so without incurring
expense or delay. The FAA may change this NPRM because of those
comments.

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 the
person identified in the FOR FURTHER INFORMATION CONTACT section. 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 issued AD 2019-22-10, Amendment 39-19789 (84 FR 61533,
November 13, 2019) ("AD 2019-22-10"), for all The Boeing Company
Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD
2019-22-10 requires inspections for cracking of the left- and right-
hand side outboard chords of frame fittings and failsafe straps at a
certain station around eight fasteners, and repair if any cracking is
found. AD 2019-22-10 superseded AD 2019-20-02 Amendment 39-19755 (84 FR
52754, October 3, 2019) ("AD 2019-20-02"). AD 2019-22-10 resulted
from reports of cracking discovered in the left- and right-hand side
outboard chords of the station (STA) 663.75 frame fittings and failsafe
straps adjacent to the stringer S-18A straps and a determination that
the inspection area specified in AD 2019-20-02 needed to be expanded.
The FAA issued AD 2019-22-10 to address cracking in the STA 663.75
frame fitting outboard chords and failsafe straps adjacent to the
stringer S-18A straps, which could result in failure of a Principal
Structural Element (PSE) to sustain limit load. This condition could
adversely affect the structural integrity of the airplane and result in
loss of control of the airplane.

Actions Since AD 2019-22-10 Was Issued

Since the FAA issued AD 2019-22-10, it was determined by an
engineering analysis of the inspection reporting results and
metallurgical evaluation of the submitted frame fitting assemblies that
the initial inspection threshold for Model 737-900ER series airplanes,
and the repetitive inspection interval for all affected airplanes is
inadequate to address the cracking in a timely manner.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Multi-Operator Message MOM-MOM-20-0443-01B
(R1), dated June 2, 2020. This service information describes procedures
for repetitive detailed inspections for cracking of the left- and
right-hand side outboard chords of the STA 663.75 frame fittings and
failsafe straps around eight fasteners adjacent to the stringer S-18A
straps.

This proposed AD also requires Boeing Multi-Operator Message MOM-
MOM-19-0536-01B, dated September 30, 2019, which the Director of the
Federal Register approved for incorporation by reference as of October
3, 2019 (84 FR 52754, October 3, 2019).

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 requires repetitive inspections for cracking of
the left- and right-hand side outboard chords of the STA 663.75 frame
fittings and failsafe straps around eight fasteners adjacent to the
stringer S-18A straps. This proposed AD also requires repair of all
cracking using a method approved by the FAA or The Boeing Company
Organization Designation Authorization (ODA). Accomplishing the initial
inspection required by paragraph (i) of this proposed AD would
terminate the inspections originally required by paragraph (g) of AD
2019-22-10, which are retained in this proposed AD (the associated
reporting specified in paragraph (h) of AD 2019-22-10 is also retained
in this proposed AD). This proposed AD would also require sending a
report of all results of the initial inspections specified in paragraph
(i) of this proposed AD to Boeing.

Although this proposed AD does not explicitly restate the
requirements of paragraphs (i), (j), and (k) of AD 2019-22-10, this
proposed AD would retain those requirements with certain revised
compliance times. Those requirements are referenced in Boeing Multi-
Operator Message MOM-MOM-20-0443-01B (R1), dated June 2, 2020, which,
in turn, is referenced in paragraphs (i) and (l) 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-2020-0789.

Explanation of New Compliance Times for Certain Configurations

For Boeing Model 737-600, -700, -700C, -800, and -900 series
airplanes having less than 22,600 total flight cycles and on which an
inspection specified in Boeing Multi-Operator Message MOM-MOM-19-0623-
01B, dated November 5, 2019, has been done; and for Boeing Model 737-
900ER series airplanes having less than 14,000 total flight cycles and
on which an inspection specified in Boeing Multi-Operator Message MOM-
MOM-19-0623-01B, dated November 5, 2019, has been done, the compliance
times specified in Boeing Multi-Operator Message MOM-MOM-20-0443-01B
(R1), dated June 2, 2020 (which will be required by this proposed AD),
are relieving as compared to the compliance times in Boeing Multi-
Operator Message MOM-MOM-19-0623-01B, dated November 5, 2019 (which is
required by AD 2019-22-10).

For example, for a Boeing Model 737-600 series airplane on which
the inspection was done and the airplane had accumulated 15,000 total
flight cycles, the next inspection required by AD 2019-22-10 would be
at 18,500 total flight cycles (i.e., 3,500 flight cycles after the
inspection as specified in Boeing Multi-Operator Message MOM-MOM-19-
0623-01B, dated November 5, 2019).

However, as specified in Boeing Multi-Operator Message MOM-MOM-20-
0443-01B (R1), dated June 2, 2020, the next inspection for that
airplane is prior to 22,600 total flight cycles or within 1,500 flight
cycles from the last inspection in accordance with MOM-MOM-19-0623-01B,
or within 30 days from the original issue date of MOM-MOM-20-0443-01B
(R1) (which would correspond to 30 days after the effective date of the
final rule for this proposed AD), whichever occurs latest.

In conclusion, if the inspection was done early, operators do not
have to do the next inspection at the 3,500 interval required by AD
2019-22-10 after this proposed AD is a final rule; instead operators
would then do the next inspection within the new compliance times
specified in Boeing Multi-Operator Message MOM-MOM-20-0443-01B R1),
dated June 2, 2020, for their configuration.

Interim Action

The FAA considers this proposed AD interim action. The inspection
reports that are required by this proposed AD will enable the
manufacturer to obtain better insight into the nature, cause, and
extent of the cracking, and eventually to develop final action to
address the unsafe condition. Once final action has been identified,
the FAA might consider further rulemaking.

Costs of Compliance

The FAA estimates that this proposed AD affects 1,911 airplanes of
U.S. registry. The FAA estimates the following costs to comply with
this proposed AD:

Estimated Costs

The FAA has received no definitive data that would enable the
agency to provide cost estimates for the on-condition actions specified
in this proposed AD.

Paperwork Reduction Act

A federal agency may not conduct or sponsor, and a person is not
required to respond to, nor shall a person be subject to penalty for
failure to comply with a collection of information subject to the
requirements of the Paperwork Reduction Act unless that collection of
information displays a current valid OMB control number. The control
number for the collection of information required by this proposed AD
is 2120-0056. The paperwork cost associated with this proposed AD has
been detailed in the Costs of Compliance section of this document and
includes time for reviewing instructions, as well as completing and
reviewing the collection of information. Therefore, all reporting
associated with this proposed AD is mandatory. Comments concerning the
accuracy of this burden and suggestions for reducing the burden should
be directed to Information Collection Clearance Officer, Federal
Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 76177-
1524.

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) 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 removing Airworthiness Directive (AD)
2019-22-10, Amendment 39-19789 (84 FR 61533, November 13, 2019), and
adding the following new AD: