
[Federal Register Volume 82, Number 125 (Friday, June 30, 2017)]
[Proposed Rules]
[Pages 29792-29795]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-13773]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-0629; Directorate Identifier 2016-NM-184-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 all 
The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 
series airplanes. This proposed AD was prompted by reports of fatigue 
cracking in the frame outboard chord and in the radius of the auxiliary 
chord at a certain area. This proposed AD would require inspections to 
detect this cracking, and corrective action if necessary. We are 
proposing this AD to address the unsafe condition on these products.

DATES: We must receive comments on this proposed AD by August 14, 2017.

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; telephone 
562-797-1717; 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-2017-0629.

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-2017-
0629; 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: Alan Pohl, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue SW., Renton, Washington 98057-3356; phone: (425) 917-
6450; fax: (425) 917-6590; email: alan.pohl@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-2017-0629; 
Directorate Identifier 2016-NM-184-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

    We have received reports indicating that fatigue cracking was found 
in the frame outboard chord at BS 727 and in the radius of the 
auxiliary chord at BS 727 and S-18A on certain airplanes. Cracks in the 
outboard chord were found on airplanes having between 20,000 and 85,000 
flight cycles, and between 27,000 and 74,000 flight hours. Cracks in 
the radius of the auxiliary chord were found on airplanes having 
between 46,000 and 85,000 flight cycles, and between 41,000 and 64,000 
flight hours. The cracks were caused by fatigue, and, for certain 
airplanes, the fretting of adjacent parts contributed to the initiation 
of the fatigue damage. This condition, if not corrected, could result 
in reduced structural integrity of the outboard chord and consequent 
rapid decompression of the airplane.

Related Rulemaking

    On October 16, 2012, we issued AD 2012-23-04, Amendment 39-17260 
(77 FR 69747, November 21, 2012) (``AD 2012-23-04''), applicable to all 
The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 
series airplanes. That AD requires various inspections for cracks in 
the outboard chord of the frame at BS 727. That AD also requires 
inspections for cracks in the BS 727 frame outboard chord and the 
radius of the auxiliary chord, for certain airplanes. That AD was 
prompted by several reports of fatigue cracking in the frame outboard 
chord at BS 727 and in the radius of the auxiliary chord. The actions 
required by that AD are intended to detect and correct fatigue cracking 
of the outboard and auxiliary chords, which could result in reduced 
structural integrity of the outboard chord and consequent rapid 
decompression of the airplane.

[[Page 29793]]

    Since issuance of AD 2012-23-04, the FAA has found discrepancies in 
the requirements of that AD, as follows:
     The optional terminating action specified in paragraph (r) 
of AD 2012-23-04 allows terminating action if the preventive 
modification is installed. However, Boeing Alert Service Bulletin 737-
53A1166, Revision 2, dated May 25, 2006, allows terminating action only 
if both the BS 727 outboard chord is replaced and the preventive 
modification is installed. Consequently, for airplanes having line 
numbers 1 through 999 inclusive on which the preventive modification 
may have been installed, the outboard chord may not have been replaced. 
Additionally, paragraph (r)(2) of AD 2012-23-04 specifies replacing 
only a cracked outboard chord; however, the intent was to require 
replacement of the outboard chord whether it was cracked or not. In 
light of these factors, there could be cracking in the auxiliary chord 
combined with cracking in the outboard chord. This cracking could 
progress undetected and result in the identified unsafe condition.
     Boeing Alert Service Bulletin 737-53A1166, Revision 2, 
dated May 25, 2006, contains instructions to determine whether the 
modification should be classified as interim or permanent; a one-time 
inspection is specified after the interim modification is done. The 
instructions specified in the previous service information did not 
contain this stipulation during installation of the preventive 
modification. Therefore, the modification could have resulted in edge 
margins in the frame outboard chord that would have been classified as 
interim had the modification been done in accordance with Boeing Alert 
Service Bulletin 737-53A1166, Revision 2, dated May 25, 2006. Since 
neither Boeing Alert Service Bulletin 737-53A1166, Revision 2, dated 
May 25, 2006, nor AD 2012-23-04 contained instructions to measure edge 
margins, it is possible that an edge margin condition exists, so the 
one-time follow-on inspection must be done.
     Paragraph (r) of AD 2012-23-04 terminates the one-time 
inspection specified in Part 8 of the Accomplishment Instructions of 
Boeing Alert Service Bulletin 737-53A1166, Revision 2, dated May 25, 
2006, for airplanes that have the interim preventive modification 
installed. This inspection is referenced in paragraph (o) of AD 2012-
23-04, and should not have been terminated. Paragraph (o) of AD 2012-
23-04 was incorrectly included in the list of paragraphs with 
inspections that are terminated after accomplishing paragraph (r) of 
that AD.
    Therefore, since the discrepancies described previously provide 
inadvertent relief to operators, we find it necessary to issue 
additional, new AD rulemaking to provide additional inspection 
requirements. We have confirmed that the requirements of this AD 
correct those discrepancies and do not conflict with other requirements 
of AD 2012-23-04.

Related Service Information Under 1 CFR Part 51

    We reviewed Boeing Alert Service Bulletin 737-53A1166, Revision 2, 
dated May 25, 2006. The service information describes procedures for 
inspections for cracks of the BS 727 frame outboard chord and in the 
radius of the auxiliary chord, and repair or replacement 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 these same type 
designs.

Proposed AD Requirements

    This proposed AD would require accomplishing the actions specified 
in the service information described previously.
    This AD corrects discrepancies in the requirements for certain 
airplanes identified in AD 2012-23-04. The FAA has considered that fact 
in determining whether to issue a new AD action or to supersede AD 
2012-23-04. We have determined that a less burdensome approach is to 
issue a separate AD action applicable to the airplanes on which the 
discrepancies could have occurred. This proposed AD would not supersede 
AD 2012-23-04, and compliance with the requirements must continue for 
airplanes listed in the applicability of AD 2012-23-04. This proposed 
AD is a separate AD action, applicable only to the airplanes identified 
in paragraph (c) of this AD.

Costs of Compliance

    We estimate the following costs to comply with this proposed AD:

                                                                     Estimated Costs
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                                                                           Affected
                                                                          airplanes     Cost per
                  Action                            Labor cost             of  U.S.     product                    Cost on U.S. operators
                                                                           registry
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Detailed and High Frequency Eddy Current   6 work-hours x $85 per hour             5         $510  $2,550 per inspection cycle.
 (HFEC) inspections.                        = $510 per inspection cycle.
One-time follow-on HFEC inspection.......  9 work-hours x $85 per hour             5          765  $3,825.
                                            = $765.
HFEC inspection..........................  9 work-hours x $85 per hour           150          765  $114,750.
                                            = $765.
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    We estimate the following costs to do any necessary repairs that 
would be required based on the results of the inspections. We have no 
way of determining the number of aircraft that might need these 
repairs:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Repair of cracking of the outboard chord frame  514 work-hours x $85 per hour =          $13,586         $57,276
                                                 $43,690.
Repair of cracking of the outboard chord......  49 work-hours x $85 per hour =             4,255           8,420
                                                 $4,165.
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[[Page 29794]]

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.

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-2017-0629; Directorate Identifier 
2016-NM-184-AD.

(a) Comments Due Date

    We must receive comments by August 14, 2017.

(b) Affected ADs

    None.

(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 53, Fuselage.

(e) Unsafe Condition

    This AD was prompted by reports of fatigue cracking in the frame 
outboard chord and in the radius of the auxiliary chord at body 
station (BS) 727 and stringer (S) 18A. We are issuing this AD to 
detect and correct fatigue cracking of the outboard and auxiliary 
chords, which could result in reduced structural integrity of the 
outboard chord and consequent rapid decompression of the airplane.

(f) Compliance

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

(g) Repetitive Inspections and Corrective Action

    For airplanes identified in paragraph (h) of this AD: Within 
4,500 flight cycles or 24 months after the effective date of this 
AD, whichever occurs first, do internal detailed and High Frequency 
Eddy Current (HFEC) inspections to detect cracks in the auxiliary 
chord radius, in accordance with Part 1 of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1166, Revision 
2, dated May 25, 2006. If any crack is found during any inspection 
required by this paragraph, before further flight, repair using a 
method approved in accordance with the procedures specified in 
paragraph (l) of this AD. Repeat the inspections thereafter at 
intervals not to exceed 15,000 flight cycles. Replacement of the 
outboard chord of the frame at BS 727 concurrently with the 
installation of the preventive modification of the outboard chord in 
accordance with Part 6 of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1166, Revision 2, dated May 25, 2006, 
terminates the repetitive inspections required by this paragraph.

(h) Airplanes for Actions Specified in Paragraph (g) of This AD

    The actions specified in paragraph (g) of this AD are required 
for airplanes that meet the criteria of paragraphs (h)(1), (h)(2), 
(h)(3), and (h)(4) of this AD.
    (1) Model 737-100, -200, and -200C series airplanes, line 
numbers 1 through 999 inclusive.
    (2) Airplanes identified as Groups 1, 2, and 3 in Boeing Alert 
Service Bulletin 737-53A1166, Revision 2, dated May 25, 2006.
    (3) Airplanes on which a preventive modification has been 
installed in accordance with the method specified in paragraph 
(h)(3)(i), (h)(3)(ii), or (h)(3)(iii) of this AD.
    (i) Part 6 of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1166, Revision 2, dated May 25, 2006.
    (ii) Part II of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1166, Revision 1, dated May 25, 1995.
    (iii) Part II of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1166, dated June 30, 1994.
    (4) Airplanes on which the outboard chord has not been replaced 
in accordance with the method specified in paragraph (h)(4)(i), 
(h)(4)(ii), or (h)(4)(iii) of this AD.
    (i) Part 3 of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1166, Revision 2, dated May 25, 2006.
    (ii) Part I of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1166, Revision 1, dated May 25, 1995.
    (iii) Part I of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1166, dated June 30, 1994.

(i) Edge Margin Measurement, Related Investigative Actions, and Repair

    For Model 737-100, -200, and -200C series airplanes having line 
numbers 1 through 999 inclusive, identified as Groups 1 through 3 in 
Boeing Alert Service Bulletin 737-53A1166, Revision 2, dated May 25, 
2006, on which the preventive modification has been installed in 
accordance with Boeing Alert Service Bulletin 737-53A1166, dated 
June 30, 1994; or Boeing Alert Service Bulletin 737-53A1166, 
Revision 1, dated May 25, 1995: Within 60,000 flight cycles after 
accomplishing the preventive modification, determine if the 
modification is classified as interim or permanent by using the edge 
margin measurement and repair classification specified in Part 6 of 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
737-53A1166, Revision 2, dated May 25, 2006. In lieu of measuring on 
the airplane, a review of engineering documentation may be used to 
classify the modification if the engineering documentation was 
completed at the time of the modification and has the edge margins 
recorded.
    (1) If the modification is classified as permanent, no further 
action is required by paragraph (i) of this AD.
    (2) If the modification is classified as interim: Within 60,000 
flight cycles after accomplishment of the interim modification of 
the outboard chord of the frame at BS 727 at S-18A, but no earlier 
than 50,000 flight cycles after accomplishment of the modification, 
do a one-time follow-on open-hole eddy current inspection to detect 
cracks

[[Page 29795]]

in the modified chord, in accordance with Part 8 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1166, Revision 2, dated May 25, 2006. If any crack is found, 
before further flight, repair in accordance with Part 3 or Part 4, 
as applicable, of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1166, Revision 2, dated May 25, 2006; 
except, if the repairs cannot be installed using the identified 
procedures, repair before further flight using a method approved in 
accordance with the procedures specified in paragraph (l) of this 
AD.

(j) Follow-On Inspection for Interim Modification and Repair

    For airplanes having line numbers 1 through 3132 inclusive, on 
which an interim modification of the BS 727 outboard chord as 
defined in Part 6 of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-53A1166, Revision 2, dated May 25, 2006, has 
been accomplished: Within 60,000 flight cycles after accomplishment 
of the interim modification of the outboard chord of the frame at BS 
727 at S-18A, but no earlier than 50,000 flight cycles after 
accomplishment of the modification, do a one-time follow-on open-
hole eddy current inspection to detect cracks in the modified chord, 
in accordance with Part 8 of the Accomplishment Instructions of 
Boeing Alert Service Bulletin 737-53A1166, Revision 2, dated May 25, 
2006. If any crack is found during the inspection required by this 
paragraph, before further flight, repair in accordance with Part 3 
or Part 4, as applicable, of the Accomplishment Instructions of 
Boeing Alert Service Bulletin 737-53A1166, Revision 2, dated May 25, 
2006; except, where the repairs cannot be installed using the 
procedures identified in this service bulletin, repair before 
further flight using a method approved in accordance with the 
procedures specified in paragraph (l) of this AD.

(k) Exception to the Service Information

    Access and restoration procedures specified in the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1166, Revision 2, dated May 25, 2006, are not required by this 
AD. Operators may do those actions following their approved 
maintenance procedures.

(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.

(m) Related Information

    (1) For more information about this AD, contact Alan Pohl, 
Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue SW., Renton, Washington 
98057-3356; phone: (425) 917-6450; fax: (425) 917-6590; email: 
alan.pohl@faa.gov.
    (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; 
telephone 562-797-1717; 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 June 22, 2017.
John P. Piccola, Jr.,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2017-13773 Filed 6-29-17; 8:45 am]
BILLING CODE 4910-13-P


