[Federal Register Volume 77, Number 74 (Tuesday, April 17, 2012)]
[Proposed Rules]
[Pages 22686-22689]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-9177]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0336; Directorate Identifier 2011-NM-213-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 737-500 series airplanes. This 
proposed AD was prompted by reports of chem-mill step cracking on the 
aft lower lobe fuselage skins. This proposed AD would require 
inspections of the fuselage skin at the chem-mill steps, and repair if 
necessary. We are proposing this AD to detect and correct cracking on 
the aft lower lobe fuselage skins, which could result in decompression 
of the airplane.

DATES: We must receive comments on this proposed AD by June 1, 2012.

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, Washington 98124-2207; telephone 206-
544-5000, extension 1; fax 206-766-5680; email [email protected]; 
Internet https://www.myboeingfleet.com. You may review copies of the 
referenced service information at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue SW., Renton, Washington.

[[Page 22687]]

For information on the availability of this material at the FAA, call 
425-227-1221.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov; 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 
(ACO), 1601 Lind Avenue SW., Renton, Washington 98057-3356; phone: 425-
917-6447; fax: 425-917-6590; 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-2012-0336; 
Directorate Identifier 2011-NM-213-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

    More than 300 incidents of skin chem-mill cracks on 26 airplanes 
have been reported from body station (STA) 727 to 1016, and from 
stringer S-14 to S-25 (left and right sides). The affected airplanes 
had accumulated between 29,808 and 53,454 total flight cycles. Most of 
the skin cracks were found aft of STA 747 on the left side. Several of 
the reported cracks occurred in multiple adjacent bays. On the existing 
skin panel assembly, the doubler is chem-milled to the skin. At these 
skin panel locations on the airplanes, the loads could cause a 
condition where skin cracks could form along the longitudinal edges of 
the doubler. This condition, if not corrected, could result in 
decompression of the airplane.

Relevant Service Information

    We reviewed Boeing Special Attention Service Bulletin 737-53-1315, 
dated July 29, 2011. For information on the procedures and compliance 
times, see this service information at http://www.regulations.gov by 
searching for Docket No. FAA-2012-0336. ``Related investigative 
actions'' and ``corrective actions'' are those actions specified in the 
service information that are necessary to address the identified unsafe 
condition.

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 various repetitive inspections for 
cracking in the fuselage skin at the chem-mill steps. For airplanes on 
which cracking is found, this proposed AD would require doing one of 
the following:
     A time-limited repair, followed by related investigative 
actions (including a general visual inspection for loose or missing 
fasteners; an internal detailed inspection and a high frequency eddy 
current (HFEC) inspection for disbonding and cracks of the bonded 
doubler); corrective actions if necessary (i.e., replacing any loose or 
missing fastener, and contacting Boeing for repair instructions and 
doing the repair); and making the time-limited repair permanent; or
     A permanent repair, including a detailed inspection of the 
bonded doubler for disbonding, and an HFEC inspection for cracks in the 
bonded doubler; and repair of any cracks and disbonding. Accomplishment 
of the permanent repair would terminate the repetitive inspections 
required by this proposed AD for the area(s) of the repair only.

Difference Between the Proposed AD and the Service Information

    Boeing Special Attention Service Bulletin 737-53-1315, dated July 
29, 2011, specifies to contact the manufacturer for instructions on how 
to repair certain conditions, but 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 91 airplanes of U.S. 
registry. We estimate the following costs to comply with this proposed 
AD:

                                                 Estimated Costs
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                                                               Parts                             Cost on U.S.
              Action                      Labor cost            cost     Cost per  product        operators
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Inspections......................  23 work-hours x $85 per          $0  $1,955 per           $177,905 per
                                    hour = $1,955 per                    inspection cycle.    inspection cycle.
                                    inspection cycle.
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    We estimate the following costs to do any necessary corrective 
actions that would be required based on the results of the proposed 
inspection. We have no way of determining the number of aircraft that 
might need these corrective actions:

[[Page 22688]]



                                               On-Condition Costs
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                  Action                               Labor cost                Parts cost     Cost per product
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Inspection...............................  2 work-hours x $85 per hour =                    $0              $170
                                            $170.
Repair...................................  7 work-hours x $85 per hour =                    $0              $595
                                            $595.
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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.

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

    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]

    2. The FAA amends Sec.  39.13 by adding the following new 
airworthiness directive (AD):

The Boeing Company: Docket No. FAA-2012-0336; Directorate Identifier 
2011-NM-213-AD.

(a) Comments Due Date

    We must receive comments by June 1, 2012.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 737-500 series 
airplanes, certificated in any category, as identified in Boeing 
Special Attention Service Bulletin 737-53-1315, dated July 29, 2011.

(d) Subject

    Joint Aircraft System Component (JASC)/Air Transport Association 
(ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

    This AD was prompted by reports of chem-mill step cracking on 
the aft lower lobe fuselage skins. We are issuing this AD to detect 
and correct step cracking on the aft lower lobe fuselage skins, 
which could result in decompression of the airplane.

(f) Compliance

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

(g) Inspection

    At the applicable time specified in paragraph 1.E., 
``Compliance,'' of Boeing Special Attention Service Bulletin 737-53-
1315, dated July 29, 2011, except as required by paragraph (i)(1) of 
this AD: Do an external detailed inspection; and, as applicable, do 
an external or internal subsurface eddy current, magneto optic 
imager, or C-scan inspection; to detect cracks in the fuselage skin 
at the chem-mill steps; in accordance with the Accomplishment 
Instructions of Boeing Special Attention Service Bulletin 737-53-
1315, dated July 29, 2011. Repeat the inspections thereafter at the 
applicable times specified in paragraph 1.E., ``Compliance,'' of 
Boeing Special Attention Service Bulletin 737-53-1315, dated July 
29, 2011.

(h) Repair

    If any crack is found during any inspection required by 
paragraph (g) of this AD: At the applicable times specified in 
paragraph 1.E., ``Compliance,'' of Boeing Special Attention Service 
Bulletin 737-53-1315, dated July 29, 2011, do all the actions 
specified in either paragraph (h)(1) or (h)(2) of this AD.
    (1) Do a time-limited repair; followed by applicable related 
investigative actions, corrective actions, and making the time-
limited repair permanent; in accordance with Boeing Special 
Attention Service Bulletin 737-53-1315, dated July 29, 2011, except 
as required by paragraph (i)(2) of this AD.
    (2) Do a permanent repair, including a detailed inspection of 
the bonded doubler for disbonding and a high frequency eddy current 
inspection for cracks of the bonded doubler, in accordance with 
Boeing Special Attention Service Bulletin 737-53-1315, dated July 
29, 2011. Repair any cracks and disbonding before further flight, in 
accordance with Boeing Special Attention Service Bulletin 737-53-
1315, dated July 29, 2011, except as required by paragraph (i)(2) of 
this AD. Accomplishment of the permanent repair terminates the 
repetitive inspections required by this AD for the area(s) of the 
repair only.

(i) Exceptions to Service Bulletin Specifications

    The exceptions specified in paragraphs (i)(1) and (i)(2) of this 
AD apply to this AD.
    (1) Where Boeing Special Attention Service Bulletin 737-53-1315, 
dated July 29, 2011, specifies a compliance time after the date on 
this service bulletin, this AD requires compliance within the 
specified compliance time after the effective date of this AD.
    (2) Where Boeing Special Attention Service Bulletin 737-53-1315, 
dated July 29, 2011, specifies to contact Boeing for repair 
instructions: Before further flight, repair using a method approved 
in accordance with the procedures specified in paragraph (j) of this 
AD.

(j) 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, it may be emailed to 
[email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager

[[Page 22689]]

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, Seattle 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.

(k) Related Information

    (1) For more information about this AD, contact Wayne Lockett, 
Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft 
Certification Office (ACO), 1601 Lind Avenue SW., Renton, Washington 
98057-3356; phone: 425-917-6447; fax: 425-917-6590; email: 
[email protected].
    (2) For service information identified in this AD, contact 
Boeing Commercial Airplanes, Attention: Data & Services Management, 
P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone 
206-544-5000, extension 1; fax 206-766-5680; email 
[email protected]; Internet https://www.myboeingfleet.com. You 
may also review the referenced service information in the docket at 
www.regulations.gov (refer to Docket No. FAA-2012-0336). You may 
review copies of the referenced service information at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, 
Washington 98057-3356. For information on the availability of this 
material at the FAA, call 425-227-1221.

    Issued in Renton, Washington, on April 5, 2012.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-9177 Filed 4-16-12; 8:45 am]
BILLING CODE 4910-13-P