[Federal Register Volume 85, Number 142 (Thursday, July 23, 2020)]
[Rules and Regulations]
[Pages 44456-44459]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-15818]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0097; Product Identifier 2019-NM-208-AD; Amendment 
39-21157; AD 2020-14-03]
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 737-300, -400, and -500 series airplanes. This 
AD was prompted by a report that a crack indication consistent with 
fatigue cracking was found on the left nacelle support overwing fitting 
flange fastener hole during teardown of a Model 737-300 series 
airplane. This AD requires a general visual inspection of the strut to 
wing diagonal brace at a certain location for cracking. For certain 
airplanes, this AD also requires an ultrasonic inspection of the 
nacelle support overwing fitting at certain fastener locations for 
cracking. For certain other airplanes, this AD requires a magnetic 
check of the nacelle support overwing fitting at a certain location to 
determine the material composition. This AD requires applicable on-
condition actions. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective August 27, 2020.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of August 27, 
2020.

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-2020-0097.

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-
0097; 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: Wayne Ha, Aerospace Engineer, Airframe 
Section, FAA, Los Angeles ACO Branch, 3960 Paramount Boulevard, 
Lakewood, CA 90712-4137; phone: 562-627-5238; fax: 562-627-5210; 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 737-300, -400, and -500 series airplanes. The NPRM published in 
the Federal Register on February 18, 2020 (85 FR 8776). The NPRM was 
prompted by a report that a crack indication consistent with fatigue 
cracking was found on the left nacelle support overwing fitting flange 
fastener hole during teardown of a Model 737-300 series airplane. The 
NPRM proposed to require a general visual inspection of the strut to 
wing diagonal brace at a certain location for cracking. For certain 
airplanes, the NPRM also proposed to require an ultrasonic inspection 
of the nacelle support overwing fitting at certain fastener locations 
for cracking. For certain other airplanes, the NPRM proposed to require 
a magnetic check of the nacelle support overwing fitting at a certain 
location to determine the material composition. The NPRM also proposed 
to require applicable on-condition actions.
    The FAA is issuing this AD to address the potential for undetected 
cracks in the nacelle support overwing fittings or strut to wing 
diagonal brace, which could result in the inability of the structure to 
carry limit load and could adversely affect the structural integrity of 
the airplane.

Comments

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

Support for the NPRM

    Bridget Powell, Herbert Dickens, Terrance Tveit, and an anonymous 
commenter expressed support for the NPRM.

Effect of Winglets on Accomplishment of the Proposed Actions

    Aviation Partners Boeing stated that accomplishing Supplemental 
Type Certificate (STC) ST01219SE does not affect the actions specified 
in the proposed AD.
    The FAA concurs with the commenter. 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 to state that installation of STC 
ST01219SE does not affect the ability to accomplish the actions 
required by this AD. Therefore, for airplanes on which STC ST01219SE 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.

[[Page 44457]]

Request To Clarify the Focus of the Ultrasonic Inspection

    Boeing requested that the FAA clarify the focus of the ultrasonic 
inspection in the SUMMARY of the NPRM. Whereas the NPRM described the 
ultrasonic inspection of ``certain fasteners of the nacelle support 
overwing fitting at a certain location for cracking,'' Boeing stated 
that the ultrasonic inspection is ``of the nacelle support overwing 
fitting at certain fastener locations for cracking.'' Boeing explained 
that the ultrasonic inspections require an inspection of the nacelle 
support overwing fitting at certain fastener holes rather than the 
fasteners themselves.
    The FAA agrees with the commenter's request because the revision 
provides more clarification for the inspection of the nacelle support 
overwing fitting. The FAA has revised the SUMMARY and Discussion 
section of this final rule accordingly.

Requests To Clarify Inspection Opportunities

    Boeing requested that the FAA modify the description of the 
opportunities for maintenance planning document (MPD) inspections to 
detect a failed nacelle support overwing fitting in the Discussion 
section of the NPRM. Boeing requested that the FAA change the following 
sentence in the Discussion section of the NPRM from ``Existing 
maintenance planning document (MPD) inspections do not provide 
opportunities to detect a failed nacelle support overwing fitting at 
wing buttock line (WBL) 191,'' to ``Existing maintenance planning 
document (MPD) inspections do not provide adequate opportunities to 
detect a failed nacelle support overwing fitting at wing buttock line 
(WBL) 191.'' Boeing explained that the MPD does provide some inspection 
opportunities, but Boeing determined they were not adequate to maintain 
safety.
    The FAA agrees that the description provided by Boeing is more 
accurate. However, since that portion of the Discussion section does 
not reappear in the final rule, this final rule has not been changed 
regarding this issue.
    Additionally, Melanie Sturgeon noted that the Discussion section of 
the proposed AD stated that existing MPD inspections ``do not provide 
opportunities to detect a failed nacelle support overwing fitting at 
wing buttock line (WBL) 191.'' Melanie Sturgeon supposed that Boeing 
would not have quickly issued Boeing Alert Requirements Bulletin 737-
57A1345 RB, dated December 17, 2019, if the inspection findings were 
not important. Melanie Sturgeon went on to cite that, of the 158 
airplanes affected by the proposed AD, many of them are at or near 30 
years old. Melanie Sturgeon questioned why such a vital part of the 
airplane was not properly inspected throughout the course of its 
service life, presuming that the unsafe condition could have been 
easily detected. Further, Melanie Sturgeon questioned why the FAA 
continued to issue airworthiness certificates for this airplane model 
when, as she stated, inspection teams seemed to be unaware of the parts 
they are charged with approving.
    The FAA agrees to clarify. The airplane model was in compliance 
with regulatory safety standards when it was designed. The design loads 
at the failed nacelle support overwing fitting at WBL 191 might have 
been considered low from testing and analysis and was not considered 
critical structure. While the airplane model operates in-service, the 
loading encountered by in-service conditions could be higher than 
designed. Therefore, once aware of the possibility of a failed part, 
Boeing reanalyzed the part and collaborated with the FAA to determine 
an inspection plan and corrective action to ensure that the failure is 
found and repaired before the residual strength capability of the part 
is lost. The FAA has not changed this AD in this regard.

Request for Clarification of Accountability

    Melanie Sturgeon questioned if Boeing will be held accountable for 
not providing the FAA with an accurate MPD, and, by extension, will the 
FAA be held responsible for not ensuring that Boeing provided an 
accurate MPD.
    The FAA agrees to clarify. The MPD provided by Boeing was based on 
accurate information available at the time of writing the MPD and was 
approved by the FAA under those circumstances. When new information 
that necessitated an update to the MPD became available, the MPD was 
updated to reflect that new information, which the FAA then reviewed 
and approved as appropriate. The FAA has not changed this AD in this 
regard.

Request To Clarify Inspection Requirements

    Melanie Sturgeon, stated that the proposed AD fails to provide 
information about the compliance time that Boeing or operators would 
have to comply with the requirements of the proposed AD. Melanie 
Sturgeon also inquired if the proposed AD would require an inspection 
on only the left nacelle support overwing fitting flange fastener hole, 
or would the proposed AD require an inspection on the left and right 
sides.
    The FAA agrees to clarify. Paragraph (g) of the proposed AD 
references Boeing Alert Requirements Bulletin 737-57A1345 RB, dated 
December 17, 2019, in which the inspections shown in Tables 1 through 8 
in Section 3., Compliance, provide inspection requirements and 
compliance times for both left and right side nacelle support overwing 
fittings. The FAA has not changed this AD in this regard.

Request for More Frequent Inspections as an Airplane Ages

    Melanie Sturgeon requested that the FAA put the airplanes within 
the applicability of this AD on a rotating, graduated safety inspection 
schedule, meaning that the plane would be inspected more often as it 
got closer to its limit of validity (LOV). Melanie Sturgeon argued 
that, if safety is the FAA's top priority, then the FAA should take 
control of its responsibilities and rely less on the manufacturer's 
ability to classify airplanes as safe.
    The FAA does not agree with the request because the inquiry mixes 
technical criteria that are not compatible. The inspections required by 
this final rule were developed using principles of damage tolerance. 
Damage tolerance has been a regulatory requirement and the accepted 
method of ensuring structural integrity for the last 42 years. The FAA 
has a long track record of successfully managing similar structural 
service difficulties by mandating inspections based on damage tolerance 
principles. It is technically incorrect to associate repetitive 
inspections based on damage tolerance principles with the airplane LOV. 
The airplane LOV (which is measured in flight cycles, flight hours, or 
both) ensures that the airplane is retired before many cracks initiate 
concurrently which are not inspectable. The crack growth rate is tied 
more closely to airplane usage than to the age of the airplane, and 
thus changing the inspection interval as the airplane ages will not 
contribute to safety. The FAA has not changed this AD in this regard.

Request To Share Information With Another Governing Body

    Melanie Sturgeon requested that the FAA share the information from 
the proposed rule with the governing bodies of other countries or the 
International Civil Aviation Organization (ICAO). Melanie Sturgeon 
pointed out that countries around the world use this airplane model, 
and in an effort to promote worldwide aviation safety, the

[[Page 44458]]

FAA should ensure that the information in the proposed AD is 
distributed to other countries that operate these airplanes.
    The FAA agrees to clarify. The FAA does share the information from 
the proposed rule with the governing bodies of other countries as 
identified in ICAO Annex 8 (https://www.icao.int/safety/airnavigation/Pages/nationality.aspx). Furthermore, ICAO Annex 8, Airworthiness of 
Aircraft requires that civil aviation authorities of other countries 
take appropriate action in response to FAA ADs. Based on the FAA's 
determination of the unsafe condition addressed by this AD, we expect 
foreign authorities to adopt similar requirements. Typically, those 
agencies post FAA ADs with no changes and notify their operators. The 
operators will then comply with this AD per their CAA's requirements. 
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 and the public interest 
require adopting this final rule 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 final 
rule.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Requirements Bulletin 737-57A1345 RB, 
dated December 17, 2019. This service information describes procedures 
for a magnetic check to determine material composition of the nacelle 
support overwing fitting at WBL 191; ultrasonic inspections of the 
nacelle support overwing fitting at WBL 191 for cracking; general 
visual inspections of the strut to wing diagonal brace at nacelle 
station (STA) 278 for cracking; and applicable on-condition actions. 
On-condition actions include repetitive ultrasonic inspections of the 
nacelle support overwing fitting at WBL 191 for cracking, repetitive 
general visual inspections of the strut to wing diagonal brace at 
nacelle STA 278 for cracking, and repair. 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 158 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                      Estimated Costs for Required Actions
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
Magnetic Check........................  1 work-hour x $85 per                 $0             $85         $13,430
                                         hour = $85.
Ultrasonic Inspection.................  5 work-hours x $85 per                 0             425          67,150
                                         hour = $425.
General Visual Inspection.............  1 work-hour x $85 per                  0              85          13,430
                                         hour = $85.
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    The FAA estimates the following costs to do any necessary on-
condition inspections that would be required. The FAA has no way of 
determining the number of aircraft that might need these on-condition 
inspections:

                                   Estimated Costs of On-Condition Inspections
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Ultrasonic Inspections...........  5 work-hours x $85               $0  $425 per inspection  $67,150 per
                                    per hour = $425                      cycle.               inspection cycle.
                                    per inspection
                                    cycle.
General Visual Inspections.......  1 work-hour x $85                 0  $85 per inspection   $13,430 per
                                    per hour = $85 per                   cycle.               inspection cycle.
                                    inspection cycle.
----------------------------------------------------------------------------------------------------------------

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

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.

[[Page 44459]]

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

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 (AD):

2020-14-03 The Boeing Company: Amendment 39-21157; Docket No. FAA-
2020-0097; Product Identifier 2019-NM-208-AD.

(a) Effective Date

    This AD is effective August 27, 2020.

(b) Affected ADs

    None.

(c) Applicability

    (1) This AD applies to all The Boeing Company Model 737-300, -
400, and -500 series airplanes, certificated in any category.
    (2) Installation of Supplemental Type Certificate (STC) 
ST01219SE does not affect the ability to accomplish the actions 
required by this AD. Therefore, for airplanes on which STC ST01219SE 
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 57, Wings.

(e) Unsafe Condition

    This AD was prompted by a report that a crack indication 
consistent with fatigue cracking was found on the left nacelle 
support overwing fitting flange fastener hole during teardown of a 
Model 737-300 series airplane. The FAA is issuing this AD to address 
the potential for undetected cracks in the nacelle support overwing 
fittings or strut to wing diagonal brace, which could result in the 
inability of the structure to carry limit load and could adversely 
affect the structural integrity of the airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already 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 737-57A1345 RB, dated December 17, 2019, 
do all applicable actions identified in, and in accordance with, the 
Accomplishment Instructions of Boeing Alert Requirements Bulletin 
737-57A1345 RB, dated December 17, 2019. Actions identified as 
terminating actions in Boeing Alert Requirements Bulletin 737-
57A1345 RB, dated December 17, 2019, terminate the applicable 
required actions of this AD, provided the terminating action is done 
in accordance with the Accomplishment Instructions of Boeing Alert 
Requirements Bulletin 737-57A1345 RB, dated December 17, 2019.
    Note 1 to paragraph (g): Guidance for accomplishing the actions 
required by this AD can be found in Boeing Alert Service Bulletin 
737-57A1345, dated December 17, 2019, which is referred to in Boeing 
Alert Requirements Bulletin 737-57A1345 RB, dated December 17, 2019.

(h) Exceptions to Service Information Specifications

    (1) Where Boeing Alert Requirements Bulletin 737-57A1345 RB, 
dated December 17, 2019, uses the phrase ``the original issue date 
of Requirements Bulletin (RB) 737-57A1345 RB,'' this AD requires 
using ``the effective date of this AD.''
    (2) Where Boeing Alert Requirements Bulletin 737-57A1345 RB, 
dated December 17, 2019, 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 (i) of this AD.

(i) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Los Angeles 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 (j)(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, Los 
Angeles 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 Wayne Ha, 
Aerospace Engineer, Airframe Section, FAA, Los Angeles ACO Branch, 
3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-
5238; fax: 562-627-5210; email: [email protected].
    (2) Service information identified in this AD that is not 
incorporated by reference is available at the addresses specified in 
paragraphs (k)(3) and (4) of this AD.

(k) 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 737-57A1345 RB, dated 
December 17, 2019.
    (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 July 6, 2020.
Gaetano A. Sciortino,
Deputy Director for Strategic Initiatives, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2020-15818 Filed 7-22-20; 8:45 am]
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