DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0789; Project Identifier AD-2020-00849-T;
Amendment 39-21519; AD 2021-09-06]
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) 2019-22-
10, which applied to all The Boeing Company Model 737-600, -700, -700C,
-800, -900, and -900ER series airplanes. AD 2019-22-10 required
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.
For certain airplanes, this AD reduces the compliance time for the
initial inspection, and for all airplanes this AD reduces the
repetitive interval. This AD was prompted by a determination that the
initial inspection threshold and repetitive inspection interval are
inadequate to address the cracking in a timely manner. The FAA is
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective June 8, 2021.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of June 8,
2021.
The Director of the Federal Register approved the incorporation by
reference of a certain other publication listed in this AD as of
November 13, 2019 (84 FR 61533, November 13, 2019).
The Director of the Federal Register approved the incorporation by
reference of a certain other publication listed in this AD as of
October 3, 2019 (84 FR 52754, October 3, 2019).

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-2020-0789.

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 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: 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:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to supersede AD 2019-22-10, Amendment 39-19789 (84 FR
61533, November 13, 2019) (AD 2019-22-10). AD 2019-22-10 applied to all
The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER
series airplanes. The NPRM published in the Federal Register on
September 8, 2020 (85 FR 55391). The NPRM was prompted by an
engineering analysis of the inspection reporting results and
metallurgical evaluation of the submitted frame fitting assemblies,
which indicated that the initial inspection threshold for Model 737-
900ER series airplanes and the repetitive inspection interval for all
affected airplanes are inadequate to address the cracking in a timely
manner. For certain airplanes, the NPRM proposed to reduce the
compliance time for the initial inspection, and for all airplanes the
NPRM proposed to reduce the repetitive inspection interval.

Comments

The FAA gave the public the opportunity to participate in
developing this AD. The following presents the comments received on the
NPRM and the FAA's response to each comment.

Request To Extend the Compliance Time for the Reporting Requirement

American Airlines (AA) asked that the compliance time for the
reporting requirements in paragraphs (h) and (k) of the proposed AD be
extended to 30 days after the date of inspection. AA stated that the
cracking of the station (STA) 663.75 fitting is now a known problem,
and Boeing has been receiving reports for almost a year. AA added that
extending the reporting requirement to 30 days would provide relief to
the operators while not decreasing safety. Hainan Airlines (HNA)
recommended that the compliance time for the reporting requirement in
paragraph (k) of the proposed AD be extended from 3 to 30 days after
the inspection or after the effective date of the proposed AD, or an
equivalent date, to alleviate the burden on operators. HNA believes
that Boeing already received a large number of inspection reporting
results for its root cause analysis over the past year.
Southwest Airlines (SWA) asked that the compliance time for the
reporting requirement be extended to 10 days. SWA stated that the 3-day
reporting requirement was developed for AD 2019-20-02, Amendment 39-
19755 (84 FR 52754, October 3, 2019). SWA added that the inspection
program has matured within Boeing and the Model 737-600, -700, -700C, -
800, -900, and -900ER operators, and the reporting requirement of
initial inspections can be relaxed from 3 to 10 days to reduce the
burden on airline operations for reporting non-crack findings.
Additionally, SWA noted that Boeing's airworthiness limitation
(Document D626A001-9-01) has a requirement to report any crack found
during these inspections to Boeing within 10 days.
AIRDO Airlines asked that the reporting requirement be changed from
3 to 7 days, since the statistical data of the inspection results for
most of the aging 737NG airplanes has been reported.
Boeing stated that it has been receiving inspection reports over
the past year and has accumulated substantial data, and asked that the
reporting requirement be extended to 10 days.
Because of the information available from the inspection findings
that have already been reported to Boeing, the FAA agrees to extend the
reporting requirements in paragraphs (h) and (k) of this AD to 10 days,
which would reduce the reporting burden on operators and would provide
an acceptable level of safety. However, Boeing and the FAA are still
relying on those inspection results both to provide repair instructions
when cracks are found and to better understand the nature, cause, and
extent of the cracking and ultimately develop a terminating action. The
FAA, therefore, does not agree to extend the reporting requirement to
30 days.

Request To Provide Credit for Previous Reporting Requirement

Boeing and AIRDO Airlines asked that reporting as specified in
paragraph (k) of the proposed AD not be required if an inspection
report was previously submitted in accordance with AD 2019-20-02 or AD
2019-22-10.
The FAA partially agrees with the commenters' request. Although
reporting per AD 2019-20-02 alone is not adequate for credit with the
reporting requirement specified in paragraph (k) of this AD, reporting
per AD 2019-22-10 meets the reporting requirement specified in
paragraph (k) of this AD. Therefore, the FAA has revised paragraph (k)
of this AD to specify that a report submitted as required in paragraph
(h) of this AD is acceptable for compliance with the requirements of
paragraph (k) of this AD.

Request To Clarify Reporting Requirement

One commenter asked that the reporting requirement in paragraph (k)
of the proposed AD be clarified. The commenter stated that inspection
report example specified in Boeing Multi-Operator Message MOM-MOM-20-
0443-01B (R1), dated June 2, 2020, has columns for repetitive
inspections. The commenter noted that reporting findings only for the
initial inspection is required by the proposed AD, and would like
conformation that reporting findings for repetitive inspections
thereafter is not required if no cracks are found.
The FAA acknowledges the commenter's concern and confirms that
paragraph (k) of this AD requires reporting findings for only the
initial inspection, and no reporting is required for any repetitive
inspection regardless of the findings.

Effects of Winglets on Accomplishment of the Proposed Actions

Aviation Partners Boeing, SWA, and HNA 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 commenters that STC ST00830SE does not
affect the accomplishment of the manufacturer's service instructions.
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 Use Figures To Accomplish the Refined Inspection

AA asked that it be allowed to use the figures for the refined
inspection areas in FAA Letter 782-19-14004. AA stated that the global
AMOC provided in FAA Letter 782-19-14004 and Boeing Multi-Operator
Message MOM-MOM-19-0536-01B, dated September 30, 2019, is referenced in
Boeing Multi-Operator Message MOM-MOM-20-0443-01B (R1), dated June 2,
2020; however, it is not mentioned in the proposed AD.
The FAA partially agrees with the commenter's request. Paragraph
(n)(5) of this AD states that AMOCs approved previously for AD 2019-22-
10, which include the referenced global AMOC, are approved as AMOCs for the
corresponding provisions of this AD. Therefore, no change to this AD is
necessary regarding this issue.

Request for Correction of Typographical Error

Boeing and HNA requested the FAA correct a typographical error for
the effective date of AD 2019-22-10, which is referenced in paragraph
(h)(1) of the proposed AD as October 3, 3019, when the correct date is
October 3, 2019.
The FAA agrees with the commenters' request. The FAA has corrected
the effective date of AD 2019-22-10 in paragraph (h)(1) of this AD
accordingly.

Conclusion

The FAA reviewed the relevant data, considered the comments
received, and determined that air safety and the public interest
require adopting this AD with the changes described previously, and
minor editorial changes. The FAA has determined that these minor
changes:
Are consistent with the intent that was proposed in the
NPRM for addressing the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.
The FAA also determined that these changes will not increase the
economic burden on any operator or increase the scope of this AD.

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 specifies procedures
for repetitive detailed inspections for cracking of the left- and
right-hand outboard chords of the STA 663.75 frame fittings and
failsafe straps around eight fasteners adjacent to the stringer S-18A
straps.
This AD also requires Boeing Multi-Operator Message MOM-MOM-19-
0623-01B, dated November 5, 2019, which the Director of the Federal
Register approved for incorporation by reference as of November 13,
2019 (84 FR 61533, November 13, 2019).
This 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.

Interim Action

The FAA considers this AD interim action. The inspection reports
that are required by this 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 AD affects 1,911 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this 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 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 AD is 2120-
0056. The paperwork cost associated with this 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 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 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.

Adoption of 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

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:

a. Removing Airworthiness Directive 2019-22-10, Amendment 39-19789 (84
FR 61533, November 13, 2019); and

b. Adding the following new airworthiness directive: