
[Federal Register Volume 80, Number 177 (Monday, September 14, 2015)]
[Proposed Rules]
[Pages 55045-55049]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-22724]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2015-3628; Directorate Identifier 2015-NM-025-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) 2012-12-
04, which applies to certain The Boeing Company Model 737-300, -400, 
and -500 series airplanes. AD 2012-12-04 currently requires repetitive 
external detailed inspections and nondestructive inspections to detect 
cracks in the fuselage skin along the chem-mill steps at stringers S-1 
and S-2R, between station (STA) 400 and STA 460, and repair if 
necessary. Since we issued AD 2012-12-04, we have determined that, for 
certain airplanes, the skin pockets adjacent to the Air Traffic Control 
(ATC) antenna are susceptible to widespread fatigue damage. This 
proposed AD would require a preventive modification of the fuselage 
skin at crown stringers S-1 and S-2R. This proposed AD would reduce 
inspection thresholds and repetitive intervals for certain airplanes. 
We are proposing this AD to detect and correct fatigue cracking of the 
fuselage skin panels at the chem-mill steps, which could result in 
sudden fracture and failure of the fuselage skin panels,

[[Page 55046]]

and consequent rapid decompression of the airplane.

DATES: We must receive comments on this proposed AD by October 29, 
2015.

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 proposed AD, contact 
Boeing Commercial Airplanes, Attention: Data & Services Management, 
P.O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone 206-544-
5000, extension 1; fax 206-766-5680; Internet https://www.myboeingfleet.com. You may view this referenced service information 
at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., 
Renton, WA. For information on the availability of this material at the 
FAA, call 425-227-1221. It is also available on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2015-
3628.

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-2015-
3628; or in person at the Docket Management Facility between 9 a.m. and 
5 p.m., Monday through Friday, except Federal holidays. The AD docket 
contains this proposed AD, the regulatory evaluation, any comments 
received, and other information. The street address for the Docket 
Office (phone: 800-647-5527) is in the ADDRESSES section. Comments will 
be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Wayne Lockett, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-6447; fax: 
425-917-6590; email: wayne.lockett@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2015-3628; 
Directorate Identifier 2015-NM-025-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD 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

    On May 31, 2012, we issued AD 2012-12-04, Amendment 39-17083 (77 FR 
36134, June 18, 2012), for certain The Boeing Company Model 737-300, -
400, and -500 series airplanes. AD 2012-12-04 requires repetitive 
external detailed inspections and nondestructive inspections to detect 
cracks in the fuselage skin along the chem-mill steps at stringers S-1 
and S-2R, between station (STA) 400 and STA 460, and repair if 
necessary. AD 2012-12-04 resulted from reports of crack findings of the 
fuselage skin at the chem-mill steps. We issued AD 2012-12-04 to detect 
and correct fatigue cracking of the fuselage skin panels at the chem-
mill steps, which could result in sudden fracture and failure of the 
fuselage skin panels, and consequent rapid decompression of the 
airplane.

Widespread Fatigue Damage

    Structural fatigue damage is progressive. It begins as minute 
cracks, and those cracks grow under the action of repeated stresses. 
This can happen because of normal operational conditions and design 
attributes, or because of isolated situations or incidents such as 
material defects, poor fabrication quality, or corrosion pits, dings, 
or scratches. Fatigue damage can occur locally, in small areas or 
structural design details, or globally. Global fatigue damage is 
general degradation of large areas of structure with similar structural 
details and stress levels. Multiple-site damage is global damage that 
occurs in a large structural element such as a single rivet line of a 
lap splice joining two large skin panels. Global damage can also occur 
in multiple elements such as adjacent frames or stringers. Multiple-
site-damage and multiple-element-damage cracks are typically too small 
initially to be reliably detected with normal inspection methods. 
Without intervention, these cracks will grow, and eventually compromise 
the structural integrity of the airplane, in a condition known as 
widespread fatigue damage (WFD). As an airplane ages, WFD will likely 
occur, and will certainly occur if the airplane is operated long enough 
without any intervention.
    The FAA's WFD final rule (75 FR 69746, November 15, 2010) became 
effective on January 14, 2011. The WFD rule requires certain actions to 
prevent structural failure due to WFD throughout the operational life 
of certain existing transport category airplanes and all of these 
airplanes that will be certificated in the future. For existing and 
future airplanes subject to the WFD rule, the rule requires that DAHs 
establish a limit of validity (LOV) of the engineering data that 
support the structural maintenance program. Operators affected by the 
WFD rule may not fly an airplane beyond its LOV, unless an extended LOV 
is approved.
    The WFD rule (75 FR 69746, November 15, 2010) does not require 
identifying and developing maintenance actions if the DAHs can show 
that such actions are not necessary to prevent WFD before the airplane 
reaches the LOV. Many LOVs, however, do depend on accomplishment of 
future maintenance actions. As stated in the WFD rule, any maintenance 
actions necessary to reach the LOV will be mandated by airworthiness 
directives through separate rulemaking actions.
    In the context of WFD, this action is necessary to enable DAHs to 
propose LOVs that allow operators the longest operational lives for 
their airplanes, and still ensure that WFD will not occur. This 
approach allows for an implementation strategy that provides 
flexibility to DAHs in determining the timing of service information 
development (with FAA approval), while providing operators with 
certainty regarding the LOV applicable to their airplanes.

Actions Since AD 2012-12-04, Amendment 39-17083 (77 FR 36134, June 18, 
2012), Was Issued

    The preamble to AD 2012-12-04, Amendment 39-17083 (77 FR 36134, 
June 18, 2012), specified that we considered the requirements ``interim 
action.'' AD 2012-12-04 explained that we might consider further 
rulemaking if final action is later identified. We now

[[Page 55047]]

have determined that it is necessary to initiate further rulemaking to 
require modification of the fuselage skin at crown stringers S-1 and S-
2R, and to reduce inspection thresholds and repetitive intervals for 
certain airplanes.

Related Service Information Under 1 CFR Part 51

    We reviewed Boeing Alert Service Bulletin 737-53A1293, Revision 3, 
dated January 23, 2015. The service information describes procedures 
for repetitive external detailed inspections and non-destructive 
inspections to detect cracks in the fuselage skin along the chem-mill 
steps at stringers S-1 and S-2R, between STA 400 and STA 460, and 
repair of any cracking. The service information also describes 
procedures for a modification of the chem-milled steps at the locations 
identified, including related investigative actions and corrective 
actions. 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 of this 
NPRM.

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

    Although this proposed AD does not explicitly restate the 
requirements of AD 2012-12-04, Amendment 39-17083 (77 FR 36134, June 
18, 2012), this proposed AD would retain all of the requirements. Those 
requirements are referenced in the service information identified 
previously, which, in turn, is referenced in this proposed AD. This 
proposed AD would require accomplishing the actions specified in the 
service information described previously, except as discussed under 
``Difference Between This Proposed AD and the Service Bulletin.'' 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-2015-3628.
    The phrase ``related investigative actions'' is used in this 
proposed AD. ``Related investigative actions'' are follow-on actions 
that (1) are related to the primary action, and (2) further investigate 
the nature of any condition found. Related investigative actions in an 
AD could include, for example, inspections.
    The phrase ``corrective actions'' is used in this proposed AD. 
``Corrective actions'' are actions that correct or address any 
condition found. Corrective actions in an AD could include, for 
example, repairs.

Explanation of Compliance Time

    The compliance time for the modification specified in this proposed 
AD for addressing WFD was established to ensure that discrepant 
structure is modified before WFD develops in airplanes. Standard 
inspection techniques cannot be relied on to detect WFD before it 
becomes a hazard to flight. We will not grant any extensions of the 
compliance time to complete any AD-mandated service bulletin related to 
WFD without extensive new data that would substantiate and clearly 
warrant such an extension.

Difference Between This Proposed AD and the Service Bulletin

    Although Boeing Alert Service Bulletin 737-53A1293, Revision 3, 
dated January 23, 2015, specifies that operators may contact the 
manufacturer for disposition of certain repair conditions, this 
proposed AD would require repairing those conditions in one of the 
following ways:
     In accordance with a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by the Boeing Commercial 
Airplanes Organization Designation Authorization (ODA) whom we have 
authorized to make those findings.

Costs of Compliance

    We estimate that this proposed AD affects 186 airplanes of U.S. 
registry.
    We estimate the following costs to comply with this proposed AD:

                                                 Estimated Costs
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                                                                                                Cost on U.S.
              Action                    Labor cost        Parts cost    Cost per product          operators
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Retained inspections from AD 2012- Between 7 and 15               $0  Between $595 and      Between $110,670 and
 12-04, Amendment 39-17083 (77 FR   work-hours x $85                   $1,275 per            $237,150 per
 36134, June 18, 2012).             per hour, depending                inspection cycle.     inspection cycle.
                                    on airplane
                                    configuration =
                                    between $595 and
                                    $1,275 per
                                    inspection cycle.
New modification.................  236 work-hours x $85        (\1\)  $20,060.............  $3,731,160.
                                    per hour = $20,060.
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\1\ We currently have no specific cost estimates associated with the parts necessary for the proposed
  modification. We cannot determine the cost of the materials because the modification parts must be sized at
  the time the modification is installed, taking into account any existing repairs in the area.

    We have received no definitive data that would enable us to provide 
a cost estimate for the on-condition actions specified in this proposed 
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.
    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.

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

[[Page 55048]]

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) 
2012-12-04, Amendment 39-17083 (77 FR 36134, June 18, 2012), and adding 
the following new AD:

The Boeing Company: Docket No. FAA-2015-3628; Directorate Identifier 
2015-NM-025-AD.

(a) Comments Due Date

    The FAA must receive comments on this AD action by October 29, 
2015.

(b) Affected ADs

    This AD replaces AD 2012-12-04, Amendment 39-17083 (77 FR 36134, 
June 18, 2012).

(c) Applicability

    This AD applies to The Boeing Company Model 737-300, -400, and -
500 series airplanes, certificated in any category, as identified in 
Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 
23, 2015.

(d) Subject

    Air Transport Association (ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

    This AD was prompted by reports of cracks found on the fuselage 
skin at the chem-mill steps, and the determination that, for certain 
airplanes, the skin pockets adjacent to the Air Traffic Control 
(ATC) antenna are susceptible to widespread fatigue damage. We are 
issuing this AD to detect and correct fatigue cracking of the 
fuselage skin panels at the chem-mill steps, which could result in 
sudden fracture and failure of the fuselage skin panels, and 
consequent rapid decompression of the airplane.

(f) Compliance

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

(g) Inspections

    At the applicable time specified in tables 1, 2, 3, and 5 of 
paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 
737-53A1293, Revision 3, dated January 23, 2015, except as required 
by paragraphs (j)(1) and (j)(2) of this AD: Do the actions specified 
in paragraphs (g)(1) and (g)(2) of this AD, in accordance with the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1293, Revision 3, dated January 23, 2015, except as required by 
paragraph (j)(3) of this AD. Repeat the applicable inspections 
thereafter at the applicable times specified in paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1293, 
Revision 3, dated January 23, 2015.
    (1) Do an external detailed inspection for cracking of the 
fuselage skin chem-mill steps.
    (2) Do an external non-destructive (medium frequency eddy 
current, magneto optical imaging, C-Scan, or ultrasonic phased 
array) inspection for cracking of the fuselage skin chem-mill steps.

(h) Preventive Modification or Repair

    If any cracking is found during any inspection required by 
paragraph (g) of this AD, do the applicable actions specified in 
paragraph (h)(1) or (h)(2) of this AD.
    (1) Repair before further flight in accordance with Part 2 of 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
737-53A1293, Revision 3, dated January 23, 2015.
    (2) At the applicable time specified in tables 1, 2, 3, and 5 of 
paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 
737-53A1293, Revision 3, dated January 23, 2015, except as required 
by paragraphs (j)(1) and (j)(2) of this AD: Do a preventive 
modification of the fuselage skin at crown stringers S-1 and S-2R, 
including all applicable related investigative actions in accordance 
with Part 9 of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015. Do 
all applicable related investigative actions concurrently with the 
modification.

(i) Post-Repair Inspections/Post-Modification Inspections

    The post-repair/post-modification inspections specified in 
tables 4 and 6 of paragraph 1.E., ``Compliance,'' of Boeing Alert 
Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, 
are not required by this AD.

    Note 1 to paragraph (h) of this AD: The post-repair/post-
modification inspections specified in tables 4 and 6 of paragraph 
1.E., ``Compliance,'' of Boeing Alert Service Bulletin 737-53A1293, 
Revision 3, dated January 23, 2015, may be used in support of 
compliance with section 121.1109(c)(2) or 129.109(c)(2) of the 
Federal Aviation Regulations (14 CFR 121.1109(c)(2) or 14 CFR 
129.109(c)(2)). The corresponding actions specified in the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1293, Revision 3, dated January 23, 2015, are not required by 
this AD.

(j) Exceptions to Service Bulletin Specifications

    (1) Where Boeing Alert Service Bulletin 737-53A1293, Revision 3, 
dated January 23, 2015, specifies a compliance time ``after the 
Revision 3 date of this service bulletin,'' this AD requires 
compliance within the specified compliance time after the effective 
date of this AD.
    (2) Where the Condition column of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1293, 
Revision 3, dated January 23, 2015, specifies a condition based on 
when an airplane has or has not been inspected, this AD bases the 
condition on whether an airplane has or has not been inspected on 
the effective date of this AD.
    (3) Where Boeing Alert Service Bulletin 737-53A1293, Revision 3, 
dated January 23, 2015, specifies to contact Boeing for repair 
instructions: Before further flight, repair using a method approved 
in accordance with the procedures specified in paragraph (k) of this 
AD.

(k) Credit for Previous Actions

    (1) This paragraph provides credit for actions required by 
paragraphs (g) and (h) of this AD, if those actions were performed 
before July 23, 2012 (the effective date of AD 2012-12-04, Amendment 
39-17083 (77 FR 36134, June 18, 2012)), using Boeing Alert Service 
Bulletin 737-53A1293, Revision 1, dated July 7, 2010, which is not 
incorporated by reference in this AD.
    (2) This paragraph provides credit for actions required by 
paragraphs (g) and (h) of this AD, if those actions were performed 
before the effective date of this AD using Boeing Alert Service 
Bulletin 737-53A1293, Revision 2, dated August 10, 2011, which was 
incorporated by reference in AD 2012-12-04, Amendment 39-17083 (77 
FR 36134, June 18, 2012).

(l) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Los Angeles Aircraft Certification Office 
(ACO), 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 ACO, send it to the 
attention of the person identified in paragraph (l)(1) 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,

[[Page 55049]]

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 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, to 
make those findings. For a repair method to be approved, the repair 
must meet the certification basis of the airplane, and the approval 
must specifically refer to this AD.
    (4) AMOCs approved for AD 2012-12-04, Amendment 39-17083 (77 FR 
36134, June 18, 2012), are approved as AMOCs for the corresponding 
provisions of paragraph (g) of this AD.

(m) Related Information

    (1) For more information about this AD, contact Wayne Lockett, 
Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 
1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-6447; 
fax: 425-917-6590; email: wayne.lockett@faa.gov.
    (2) For service information identified in this AD, contact 
Boeing Commercial Airplanes, Attention: Data & Services Management, 
P.O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone 206-544-
5000, extension 1; fax 206-766-5680; Internet https://www.myboeingfleet.com. You may view this referenced service 
information at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue SW., Renton, WA. For information on the availability of this 
material at the FAA, call 425-227-1221.

    Issued in Renton, Washington, on September 1, 2015.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2015-22724 Filed 9-11-15; 8:45 am]
 BILLING CODE 4910-13-P


