[Federal Register Volume 84, Number 62 (Monday, April 1, 2019)]
[Proposed Rules]
[Pages 12143-12146]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-06031]


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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]
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: We propose to supersede Airworthiness Directive (AD) 2005-20-
01, which applies to all The Boeing Company Model 737-100, -200, -200C, 
-300, -400, and -500 series airplanes. AD 2005-20-01 requires 
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. Since we issued AD

[[Page 12144]]

2005-20-01, we have received reports of cracks found in the left and 
right side keel beam upper chords when replacing vertical stiffeners. 
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 a lightning strike. This proposed AD would 
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. We are proposing this AD to 
address the unsafe condition on these products.

DATES: We must receive comments on this proposed AD by May 16, 2019.

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 http://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. 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 NPRM, the regulatory evaluation, any comments received, and other 
information. The street address for Docket Operations (phone: 800-647-
5527) is in the ADDRESSES section. Comments will be available in the AD 
docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Galib Abumeri, Aerospace Engineer, 
Airframe Section, FAA, Los Angeles ACO Branch, 3960 Paramount 
Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5324; fax: 562-627-
5210; email: [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite 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-2019-0187; 
Product Identifier 2018-NM-172-AD'' at the beginning of your comments. 
We specifically invite comments on the overall regulatory, economic, 
environmental, and energy aspects of this NPRM. We will consider all 
comments received by the closing date and may amend this NPRM because 
of those comments.
    We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    We issued AD 2005-20-01, Amendment 39-14294 (70 FR 56358, September 
27, 2005) (``AD 2005-20-01''), for all The Boeing Company Model 737-
100, -200, -200C, -300, -400, and -500 series airplanes. AD 2005-20-01 
requires repetitive inspections of the vertical stiffeners at LBL and 
RBL 6.15 for cracks; and replacement of both stiffeners with new, 
improved stiffeners if any stiffener is found cracked. AD 2005-20-01 
also allows replacement of both stiffeners at LBL and RBL 6.15 with 
new, improved stiffeners, which terminates the repetitive inspections. 
AD 2005-20-01 resulted from reports of cracks in the aft vertical 
stiffeners at LBL and RBL 6.15 on the rear spar of the wing center 
section. We issued AD 2005-20-01 to address cracks in the 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.

Actions Since AD 2005-20-01 Was Issued

    Since we issued AD 2005-20-01, Boeing discovered that the 
replacement stiffener installation had degraded fault current bonding 
because the existing rivets (which provide an inherent bond path for 
fault currents and ground returns) had been replaced with non-
conductive finish K-code fasteners in transition fit holes. The 
replacement fasteners are not adequate in maintaining required fault 
current bonding path and could introduce an ignition source in the fuel 
tank in the event of an electrical hot short or a lightning strike.
    In addition to the above described electrical bonding issues, we 
received a report of cracks in the left side and right side keel beam 
upper chords when the aft vertical stiffeners were replaced. Boeing 
determined that the actual stresses on aft vertical stiffeners at LBL 
and RBL 6.15 exceed those used to design the structure and can cause 
fatigue cracks in the stiffeners. If the aft vertical stiffeners have 
cracks or are severed, the fatigue damage may extend into the adjacent 
keel beam structure and could reduce the limit load capability of the 
keel beam structure. Boeing has determined the inspections described in 
Boeing Alert Service Bulletin 737-57A1269, dated December 4, 2003; and 
Revision 1, dated September 16, 2004; do not provide sufficient 
inspection intervals for timely crack detection in the aft vertical 
stiffeners. AD 2005-20-01 requires the actions specified in Boeing 
Alert Service Bulletin 737-57A1269, dated December 4, 2003; and 
Revision 1, dated September 16, 2004. As a result, Boeing issued Alert 
Service Bulletin 737-57A1339 RB, dated April 16, 2018, which describes 
procedures for inspecting the vertical stiffeners and keel beam upper 
chord structures. AD 2018-10-12, Amendment 39-19288 (83 FR 23775, May 
23, 2018) (``AD 2018-10-12'') requires the actions specified in Boeing 
Alert Service Bulletin 737-57A1339 RB, dated April 16, 2018. After we 
issued AD 2018-10-12, Boeing issued Boeing Alert Service Bulletin 737-
57A1269, Revision 2, dated October 11, 2018, which provides procedures 
for replacing the vertical stiffeners with new, improved stiffeners.
    Accomplishment of the vertical stiffener replacements at LBL and 
RBL 6.15, described in Boeing Alert Service Bulletin 737-57A1269, 
Revision 2, dated October 11, 2018, as specified in paragraph (g) of 
this proposed AD, eliminates the need to do the stiffener inspection 
described in Boeing Alert Service Bulletin 737-57A1339 RB, dated April 
16, 2018.

Related Service Information Under 1 CFR Part 51

    We reviewed Boeing Alert Service Bulletin 737-57A1269, Revision 2,

[[Page 12145]]

dated October 11, 2018. This service information describes procedures 
for replacing the vertical stiffeners at LBL and RBL 6.15 on the wing 
center section rear spar 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.

FAA's Determination

    We are proposing this AD because we 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 retain none of the requirements of AD 2005-
20-01. This proposed AD would require accomplishing the actions 
specified in the service information 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 certain airplanes, 
replacing the vertical stiffeners with new, improved stiffeners, would 
terminate the need for the repetitive inspections required by AD 2018-
10-12. For information on the procedures and compliance times, see this 
service information at http://www.regulations.gov by searching for and 
locating Docket No. FAA-2019-0187.

Differences Between This Proposed AD and the Service Information

    Boeing Alert Service Bulletin 737-57A1269, Revision 2, dated 
October 11, 2018, specifies, for certain airplanes, to do a concurrent 
action consisting of a final one-time surface high frequency eddy 
current inspection of the keel beam upper chord and general visual 
inspection of the angle at LBL 6.50 and RBL 6.50, and all related 
applicable actions, as specified in Boeing Alert Requirements Bulletin 
737-57A1339 RB, dated April 16, 2018. We have determined that action is 
already mandated by AD 2018-10-12. All requirements of AD 2018-10-12 
remain in effect.

Costs of Compliance

    We estimate that this proposed AD affects 171 airplanes of U.S. 
registry. We estimate the following costs to comply with this proposed 
AD:

                                                 Estimated Costs
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                                                   Parts
            Action                Labor cost        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 = $21,845.
 installation, and sealant
 and 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.
    We are 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 proposed 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

    We have 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) Is not a ``significant rule'' under the DOT Regulatory Policies 
and Procedures (44 FR 11034, February 26, 1979),
    (3) Will not affect intrastate aviation in Alaska, and
    (4) 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

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:

The Boeing Company: Docket No. FAA-2019-0187; Product Identifier 
2018-NM-172-AD.

(a) Comments Due Date

    The FAA must receive comments on this AD action by May 16, 2019.

(b) Affected ADs

    This AD replaces AD 2005-20-01, Amendment 39-14294 (70 FR 56358,

[[Page 12146]]

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

    This AD applies to all The Boeing Company Model 737-100, -200, -
200C, -300, -400, and -500 series airplanes, certificated in any 
category.

(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. We are 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. We are 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 Group 1 and 3 Through 8 Airplanes

    For airplanes identified as Group 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 (l) 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 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 (l) of this AD.

(k) Credit for Previous Actions

    This paragraph provides credit only for the stiffener 
replacement required by paragraph (g) of this AD, if those actions 
were performed before the effective date of this AD using the 
service information identified in paragraph (k)(1) or (k)(2) of this 
AD.
    (1) Boeing Alert Service Bulletin 737-57A1269, dated December 4, 
2003, which is not incorporated by reference in this AD.
    (2) Boeing Alert Service Bulletin 737-57A1269, Revision 1, dated 
September 16, 2004, which was incorporated by reference in AD 2005-
20-01.

(l) 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 (m)(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 Commercial Airplanes 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.

(m) Related Information

    (1) For more information about this AD, contact Galib Abumeri, 
Aerospace Engineer, Airframe Section, FAA, Los Angeles ACO Branch, 
3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-
5324; fax: 562-627-5210; email: [email protected].
    (2) 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. You may view this referenced 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.

    Issued in Des Moines, Washington, on March 22, 2019.
Michael Kaszycki,
Acting Director, System Oversight Division, Aircraft Certification 
Service.
[FR Doc. 2019-06031 Filed 3-29-19; 8:45 am]
BILLING CODE 4910-13-P