[Federal Register Volume 84, Number 171 (Wednesday, September 4, 2019)]
[Rules and Regulations]
[Pages 46426-46429]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-19012]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0187; Product Identifier 2018-NM-172-AD; Amendment 
39-19715; AD 2019-16-12]
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) 2005-20-
01, which applied to all The Boeing Company Model 737-100, -200, -200C, 
-300, -400, and -500 series airplanes. AD 2005-20-01 required 
repetitive inspections of the vertical stiffeners at left buttock line 
(LBL) and right buttock line (RBL) 6.15 for cracks; and replacement of 
both stiffeners with new, improved stiffeners if any stiffener is found 
cracked. This new AD requires, depending on airplane configuration, 
replacing the vertical stiffeners at LBL and RBL 6.15 on the rear spar 
of the wing center section, installing angle and bonding jumpers, 
installing brackets, applying sealant, and applying paint. This AD was 
prompted by reports of cracks found in the left and right side keel 
beam upper chords when replacing vertical stiffeners. This AD was also 
prompted by possible degradation of the fault current bonding path that 
could introduce an ignition source in the fuel tank in the event of a 
fault current being imparted onto the fuel tank structure. The FAA is 
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective October 9, 2019.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of October 9, 
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, Transport Standards 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 http://www.regulations.gov by searching for and locating Docket No. FAA-2019-
0187.

Examining the AD Docket

    You may examine the AD docket on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2019-
0187; 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, the regulatory evaluation, 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: Peter Jarzomb, Aerospace Engineer, 
Airframe Section, FAA, Los Angeles ACO Branch, 3960 Paramount 
Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5234; fax: 562-627-
5210; email: Peter.Jarzomb@faa.gov.

SUPPLEMENTARY INFORMATION: 

Discussion

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to supersede AD 2005-20-01, Amendment 39-14294 (70 FR 
56358, September 27, 2005) (``AD 2005-20-01''). AD 2005-20-01 applied 
to all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -
500 series airplanes. The NPRM published in the Federal Register on 
April 1, 2019 (84 FR 12143). The NPRM was prompted by reports of cracks 
found in the left and right side keel beam upper chords when replacing 
vertical stiffeners. In addition, the FAA has determined that the 
replacement stiffener installation degraded the fault current bonding 
path that could introduce an ignition source in the fuel tank in the 
event of fault current being imparted onto the fuel tank structure. The 
NPRM proposed to require, depending on airplane configuration, 
replacing the vertical stiffeners at LBL and RBL 6.15 on the rear spar 
of the wing center section, installing angle and bonding jumpers, 
installing brackets, applying sealant, and applying paint. The FAA is 
issuing this AD to address cracks in vertical stiffeners at LBL and RBL 
6.15, which could result in damage to the keel beam structure and 
consequently reduce the capability of the airplane to sustain flight 
loads. The FAA is also issuing this AD to address a potential ignition 
source in the fuel tank due to insufficient bonding, which could lead 
to a fuel tank explosion and subsequent loss of the airplane.

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. The FAA received one 
comment that was outside the scope of this rulemaking.

Effect of Winglets on Accomplishment of the Proposed Actions

    Aviation Partners Boeing stated that accomplishing Supplemental 
Type Certificate (STC) ST01219SE does not affect compliance with the 
proposed actions.
    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''

[[Page 46427]]

alternative method of compliance (AMOC) approval request is not 
necessary to comply with the requirement of 14 CFR 39.17.

Request To Correct Service Information Reference

    Boeing requested that the ``Actions Since AD 2005-20-01 was 
Issued'' section of the NPRM be revised so that the reference to 
``Boeing Alert Service Bulletin 737-57A1339 RB'' is changed to ``Boeing 
Alert Requirements Bulletin 737-57A1339 RB''. The commenter pointed out 
that the ``RB'' designation is for a Boeing requirements bulletin and 
not a Boeing service bulletin. The commenter also noted that this 
change would be consistent with how this service information is 
referred to in the ``Differences Between This Proposed AD and the 
Service Information'' section of the NPRM.
    The FAA agrees with commenter's request for the reason provided by 
the commenter. Since the ``Actions Since AD 2005-20-01 was Issued'' 
section of the preamble does not reappear in this final rule, no change 
to this final rule is necessary.

Request for Clarification of Credit for Previous Actions

    Boeing requested that the introductory text of paragraph (k) of the 
proposed AD, ``Credit for Previous Actions,'' be revised to clarify 
that the unsafe condition caused by possible degradation of the fault 
current bonding path must be corrected in accordance with the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
57A1269, Revision 2, dated October 11, 2018. The commenter stated that 
it wanted to emphasize that credit is only provided for stiffeners 
replaced using the service information specified in paragraphs (k)(1) 
and (2) of the proposed AD and that doing the procedures in the service 
information specified in paragraph (k)(1) or (2) of the proposed AD 
does not resolve the unsafe electrical bonding condition.
    The FAA agrees with the commenter's statement that the unsafe 
electrical bonding condition can only be addressed by doing the actions 
described in the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-57A1269, Revision 2, dated October 11, 2018. However, the 
FAA disagrees with the commenter's request to revise the proposed 
credit provision. After further review of Boeing Alert Service Bulletin 
737-57A1269, Revision 2, dated October 11, 2018, and clarification from 
the commenter regarding the request, the FAA has determined that credit 
for previously accomplished actions is not needed in this AD because 
the effectivity of Boeing Alert Service Bulletin 737-57A1269, Revision 
2, dated October 11, 2018, addresses airplanes on which actions have 
already been done using the procedures described in earlier revisions 
of the service information. Therefore the FAA has removed the credit 
provision from this AD, and has redesignated the subsequent paragraphs 
accordingly.

Request To Clarify Unsafe Condition

    Boeing requested that the SUMMARY section of the NPRM be revised to 
clarify the unsafe condition regarding the electrical fault current 
bonding path. The commenter specifically requested that the sentence 
``In addition, we have determined that the replacement stiffener 
installation degraded the fault current bonding path and could 
introduce an ignition source in the fuel tank in the event of an 
electrical hot short or lightning strike,'' to ``In addition, we have 
determined that the replacement stiffener installation degraded the 
fault current bonding path and could introduce an ignition source in 
the fuel tank in the event of a fault current being imparted onto the 
fuel tank structure.'' The commenter also requested that this change be 
made to the ``Actions Since AD 2005-20-01 was Issued'' section of the 
NPRM.
    The commenter explained that an ignition source threat can 
originate from a fault current that develops from a short circuit 
internal to auxiliary hydraulic pumps installed on or attached to the 
aft spar. Furthermore, the commenter noted that electrical hot shorts 
(normally associated with clamped wire bundles, which are attached to 
fuel tank walls via cushioned clamps and brackets) and lightning strike 
ignition threats are not applicable to the installation defined in 
Boeing Alert Service Bulletin 737-57A1269, Revision 2, dated October 
11, 2018.
    The FAA agrees with the commenter's request for the reasons 
provided by the commenter. The FAA has revised the SUMMARY section of 
this final rule to include the sentence ``In addition, the FAA has 
determined that the replacement stiffener installation degraded the 
fault current bonding path that could introduce an ignition source in 
the fuel tank in the event of a fault current being imparted onto the 
fuel tank structure.'' As previously stated, the ``Actions Since AD 
2005-20-01'' section does not reappear in this final rule, so no 
further change is necessary in that regard.

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 Alert Service Bulletin 737-57A1269, 
Revision 2, dated October 11, 2018. This service information describes 
procedures for replacing the vertical stiffeners at LBL and RBL 6.15 on 
the rear spar of the wing center section with new, improved stiffeners, 
installing angle and bonding jumpers, installing brackets, applying 
sealant, and applying paint.
    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 171 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

[[Page 46428]]



                                                 Estimated Costs
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            Action                  Labor cost       Parts cost    Cost per product     Cost on U.S. operators
----------------------------------------------------------------------------------------------------------------
Stiffener replacement, angle    Up to 257 work-           $14,730  Up to $36,575...  Up to $6,254,325.
 and bonding jumper              hours x $85 per
 installation, bracket           hour = Up to
 installation, and sealant and   $21,845.
 paint application.
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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.
    This AD is issued in accordance with authority delegated by the 
Executive Director, Aircraft Certification Service, as authorized by 
FAA Order 8000.51C. In accordance with that order, issuance of ADs is 
normally a function of the Compliance and Airworthiness Division, but 
during this transition period, the Executive Director has delegated the 
authority to issue ADs applicable to transport category airplanes and 
associated appliances to the Director of the System Oversight Division.

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

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 removing Airworthiness Directive (AD) 
2005-20-01, Amendment 39-14294 (70 FR 56358, September 27, 2005), and 
adding the following new AD:

2019-16-12 The Boeing Company: Amendment 39-19715; Docket No. FAA-
2019-0187; Product Identifier 2018-NM-172-AD.

(a) Effective Date

    This AD is effective October 9, 2019.

(b) Affected ADs

    This AD replaces AD 2005-20-01, Amendment 39-14294 (70 FR 56358, 
September 27, 2005) (``AD 2005-20-01''). This AD terminates certain 
requirements of AD 2018-10-12, Amendment 39-19288 (83 FR 23775, May 
23, 2018) (``AD 2018-10-12'').

(c) Applicability

    (1) This AD applies to all The Boeing Company Model 737-100, -
200, -200C, -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 reports of cracks in the aft vertical 
stiffeners at left buttock line (LBL) and right buttock line (RBL) 
6.15 on the rear spar of the wing center section and of cracks found 
in the left and right side keel upper chords when replacing vertical 
stiffeners. This AD was also prompted by possible degradation of the 
fault current bonding path due to the replacement vertical stiffener 
installation. The FAA is issuing this AD to address cracks in 
vertical stiffeners at LBL and RBL 6.15, which could result in 
damage to the keel beam structure and consequently reduce the 
capability of the airplane to sustain flight loads. The FAA is also 
issuing this AD to address a potential ignition source in the fuel 
tank due to insufficient bonding, which could lead to a fuel tank 
explosion and subsequent loss of the airplane.

(f) Compliance

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

(g) Required Actions for Groups 1 and 3 Through 8 Airplanes

    For airplanes identified as Groups 1 and 3 through 8 in Boeing 
Alert Service Bulletin 737-57A1269, Revision 2, dated October 11, 
2018: Except as specified by paragraph (j) of this AD, at the 
applicable times specified in paragraph 1.E., ``Compliance,'' of 
Boeing Alert Service Bulletin 737-57A1269, Revision 2, dated October 
11, 2018, do all applicable actions, identified in, and in 
accordance with, the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-57A1269, Revision 2, dated October 11, 2018. 
Depending on the airplane configuration, applicable actions include 
replacing the vertical stiffeners at LBL and RBL 6.15 on the rear 
spar of the wing center section, installing angle and bonding 
jumpers, installing brackets, applying sealant, and applying paint.

(h) Required Actions for Group 2 Airplanes

    For airplanes identified as Group 2 in Boeing Alert Service 
Bulletin 737-57A1269, Revision 2, dated October 11, 2018: Within 120 
days after the effective date of this AD, do actions to correct the 
unsafe condition, using a method approved in accordance with the 
procedures specified in paragraph (k) of this AD.

(i) Terminating Action for Repetitive Inspections of Aft Vertical 
Stiffener Required by AD 2018-10-12

    Accomplishment of the stiffener replacement required by 
paragraph (g) of this AD terminates only the repetitive inspections 
of the aft vertical stiffeners required by

[[Page 46429]]

paragraph (h) of AD 2018-10-12 for that airplane only. All other 
requirements of paragraph (h) of AD 2018-10-12 remain in effect.

(j) Exceptions to Service Information Specifications

    (1) For purposes of determining compliance with the requirements 
of this AD: Where Boeing Alert Service Bulletin 737-57A1269, 
Revision 2, dated October 11, 2018, uses the phrase ``the Revision 2 
date of this service bulletin,'' this AD requires using ``the 
effective date of this AD.''
    (2) Where Boeing Alert Service Bulletin 737-57A1269, Revision 2, 
dated October 11, 2018, 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 (k) of this AD.

(k) 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 (l) of this AD. Information may 
be emailed to: 9-ANM-LAACO-AMOC-Requests@faa.gov.
    (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.

(l) Related Information

    For more information about this AD, contact Peter Jarzomb, 
Aerospace Engineer, Airframe Section, FAA, Los Angeles ACO Branch, 
3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-
5234; fax: 562-627-5210; email: Peter.Jarzomb@faa.gov.

(m) 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 Service Bulletin 737-57A1269, Revision 2, dated 
October 11, 2018.
    (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, Transport 
Standards 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, call 202-741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued in Des Moines, Washington, on August 15, 2019.
Michael Kaszycki,
Acting Director, System Oversight Division, Aircraft Certification 
Service.
[FR Doc. 2019-19012 Filed 9-3-19; 8:45 am]
 BILLING CODE 4910-13-P


