
[Federal Register Volume 81, Number 168 (Tuesday, August 30, 2016)]
[Proposed Rules]
[Pages 59541-59543]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-20673]



[[Page 59541]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-8848; Directorate Identifier 2016-NM-054-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 adopt a new airworthiness directive (AD) for 
certain The Boeing Company Model 737-300, -400, and -500 series 
airplanes. This proposed AD was prompted by an evaluation by the design 
approval holder (DAH) indicating that the fuselage skin is subject to 
widespread fatigue damage (WFD). This proposed AD would require 
modification of the lap joint, including related investigative actions 
and corrective actions if necessary. This proposed AD also would 
require repetitive post-modification inspections for cracking of the 
skin at critical fastener rows, and corrective actions if necessary. We 
are proposing this AD to detect and correct cracks at the lap joint 
skin that could link up and result in rapid decompression and loss of 
structural integrity of the airplane.

DATES: We must receive comments on this proposed AD by October 14, 
2016.

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: 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-2016-
8848.

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-2016-
8848; 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: Wade Sullivan, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office 
(ACO), 1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-
6430, fax: 425-917-6590; email: wade.sullivan@faa.gov.

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-2016-8848; 
Directorate Identifier 2016-NM-054-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

    Fatigue damage can occur locally, in small areas or structural 
design details, or globally, in widespread areas. Multiple-site damage 
is widespread damage that occurs in a large structural element such as 
a single rivet line of a lap splice joining two large skin panels. 
Widespread 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. This condition is known as widespread fatigue damage. It is 
associated with general degradation of large areas of structure with 
similar structural details and stress levels. 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.
    We have received a report indicating that a Model 737-300 series 
airplane with 20-inch spaced tear strap crown skin configuration 
experienced a rapid decompression when the lap joint at stringer S-4L 
between station (STA) 664 and STA 727 cracked and opened up. 
Investigation shows that the cracks were

[[Page 59542]]

caused by fatigue cracks in the lower skin at the lower row of 
fasteners in the S-4L lap joint. The airplane had accumulated 39,781 
total flight cycles and 48,740 total flight hours. This condition, if 
not corrected, could result in rapid decompression and loss of 
structural integrity.

Related Service Information Under 1 CFR Part 51

    We reviewed Boeing Alert Service Bulletin 737-53A1343, dated March 
25, 2016. The service information describes procedures for modification 
of the lap joint, including related investigative actions and 
corrective actions if necessary. The service information also describes 
procedures for post-modification inspections for cracking of the skin 
at critical fastener rows, and corrective actions if necessary. 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 require accomplishing the actions specified 
in the service information described previously, except as discussed 
under ``Differences Between this Proposed AD and the Service 
Information.'' 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-2016-8848.
    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 correct or address any condition found. Corrective 
actions in an AD could include, for example, repairs.

Differences Between This Proposed AD and the Service Information

    Boeing Alert Service Bulletin 737-53A1343, date March 25, 2016, 
specifies to contact the manufacturer for certain instructions, but 
this proposed AD would require accomplishment of repair methods, 
modification deviations, and alteration deviations 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.

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 new data that would substantiate and clearly warrant such 
an extension.

Costs of Compliance

    We estimate that this proposed AD affects 115 airplanes of U.S. 
registry. We estimate the following costs to comply with this proposed 
AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Lap joint skin modification......  2,142 work-hours x          $12,500  $194,570...........  $22,375,550.
                                    $85 per hour =
                                    $182,070 per
                                    modification.
Post-Modification inspection.....  102 work-hours x                 $0  $8,670 per           $997,050 per
                                    $85 per hour =                       inspection cycle.    inspection cycle.
                                    $8,670 per
                                    inspection cycle.
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    We have received no definitive data that would enable us to provide 
cost estimates 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 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 this 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.

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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 adding the following new airworthiness 
directive (AD):

The Boeing Company: Docket No. FAA-2016-8848; Directorate Identifier 
2016-NM-054-AD.

(a) Comments Due Date

    We must receive comments by October 14, 2016.

(b) Affected ADs

    This AD affects AD 2015-16-08, Amendment 39-18233 (80 FR 51450, 
August 25, 2015) (``AD 2015-16-08'').

(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 737-53A1343, dated March 25, 2016; 
except for Group 5 airplanes identified in Boeing Alert Service 
Bulletin 737-53A1343, dated March 25, 2016.

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by an evaluation by the design approval 
holder (DAH) indicating that the fuselage skin is subject to 
widespread fatigue damage (WFD). We are issuing this AD to detect 
and correct cracks at the lap joint skin that could link up and 
result in rapid decompression and loss of structural integrity of 
the airplane.

(f) Compliance

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

(g) Lap Joint Skin Modification

    Before the accumulation of 50,000 total flight cycles, or within 
3,000 flight cycles after the effective date of this AD, whichever 
occurs later: Modify the lap joint skin, including doing all 
applicable related investigative and corrective actions, in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1343, dated March 25, 2016, except as 
required by paragraph (i) of this AD. Do all applicable related 
investigative and corrective actions before further flight.

(h) Inspection of the Critical Fastener Rows

    Within 38,000 flight cycles after modifying the lap joint skin 
as required by paragraph (g) of this AD: Inspect the skin at 
critical fastener rows by doing the actions specified in paragraph 
(h)(1) or (h)(2) of this AD, in accordance with the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1343, dated 
March 25, 2016. If any crack is found during any inspection, repair 
before further flight using a method approved in accordance with the 
procedures specified in paragraph (l) of this AD. Repeat the 
inspection thereafter at intervals not to exceed 2,000 flight cycles 
in unrepaired areas.
    (1) From the inside of the airplane: Do a low frequency eddy 
current (LFEC) inspection for any crack in the skin at the critical 
fastener row, and a medium frequency eddy current (MFEC) inspection 
for any crack in the skin at the critical fastener row.
    (2) From the outside of the airplane: Do a LFEC inspection for 
any crack in the fuselage skin.

(i) Exception to Service Information Specifications

    Although Boeing Alert Service Bulletin 737-53A1343, dated March 
25, 2016, specifies to contact Boeing for repair instructions, and 
specifies that action as ``RC'' (Required for Compliance), this AD 
requires repair before further flight using a method approved in 
accordance with the procedures specified in paragraph (l) of this 
AD.

(j) AD Provisions for Part 26 Supplemental Inspections

    Table 5 of paragraph 1.E., ``Compliance,'' of Boeing Alert 
Service Bulletin 737-53A1343, dated March 25, 2016, specifies post-
modification airworthiness limitation inspections in compliance with 
14 CFR 25.571(a)(3) at the modified locations, which support 
compliance with 14 CFR 121.1109(c)(2) or 129.109(b)(2). As 
airworthiness limitations, these inspections are required by 
maintenance and operational rules. It is therefore unnecessary to 
mandate them in this AD. Deviations from these inspections require 
FAA approval, but do not require an alternative method of 
compliance.

(k) Terminating Action for AD 2015-16-08

    Accomplishing the modification required by paragraph (g) of this 
AD terminates the inspections required by paragraphs (g), (h), (i), 
(j), and (k) of AD 2015-16-08 for the modified area only.

(l) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Seattle 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 (m)(1) of this AD. 
Information may be emailed to: 9-ANM-Seattle-ACO-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 Commercial Airplanes Organization 
Designation Authorization (ODA) that has been authorized by the 
Manager, Seattle ACO, 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.
    (4) Except as required by paragraph (i) of this AD: For service 
information that contains steps that are labeled as Required for 
Compliance (RC), the provisions of paragraphs (l)(4)(i) and 
(l)(4)(ii) of this AD apply.
    (i) The steps labeled as RC, including substeps under an RC step 
and any figures identified in an RC step, must be done to comply 
with the AD. An AMOC is required for any deviations to RC steps, 
including substeps and identified figures.
    (ii) Steps not labeled as RC may be deviated from using accepted 
methods in accordance with the operator's maintenance or inspection 
program without obtaining approval of an AMOC, provided the RC 
steps, including substeps and identified figures, can still be done 
as specified, and the airplane can be put back in an airworthy 
condition.

(m) Related Information

    (1) For more information about this AD, contact Wade Sullivan, 
Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 
1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-6430, 
fax: 425-917-6590; email: wade.sullivan@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 August 16, 2016.
Dorr M. Anderson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2016-20673 Filed 8-29-16; 8:45 am]
 BILLING CODE 4910-13-P


