[Federal Register Volume 77, Number 181 (Tuesday, September 18, 2012)]
[Proposed Rules]
[Pages 57539-57541]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-22887]



[[Page 57539]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0935; Directorate Identifier 2011-NM-256-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 737-900 and -900ER series airplanes. 
This proposed AD was prompted by reports of early fatigue cracks at 
chem-mill areas on the crown skin panels. This proposed AD would 
require repetitive inspections for cracking of the fuselage skin along 
chem-mill steps at certain crown skin and shear wrinkle areas, and 
repair if necessary. We are proposing this AD to detect and correct 
fatigue cracking of the skin panel at the specified chem-mill step 
locations, which could result in rapid decompression of the airplane.

DATES: We must receive comments on this proposed AD by November 2, 
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, WA 98124-2207; telephone 206-544-
5000, extension 1; fax 206-766-5680; 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. 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, 
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-2012-0935; 
Directorate Identifier 2011-NM-256-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 received reports of early fatigue cracks near chem-mill areas on 
the crown skin panels of Model 737-300, -400, and -500 series 
airplanes. The cracks resulted from high stresses in the areas where 
chem-mill pockets are adjacent to non-chem-mill areas. Although we have 
not received any reports of this type of fuselage fatigue cracks on 
Model 737-600, -700, -700C, -800, -900, or -900ER series airplanes, a 
full-scale fatigue test article was inspected for skin cracks at 
similar structural details and two chem-mill cracks were found that 
occurred late in the testing program. This condition, if not detected 
and corrected, could result in rapid decompression of the airplane.

Relevant Service Information

    We reviewed Boeing Service Bulletin 737-53-1312, dated October 21, 
2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, 
dated March 14, 2012, for Model 737-900 and -900ER series airplanes. 
That service bulletin describes, among other things, procedures for 
doing repetitive external detailed inspections and external non-
destructive inspections (medium frequency eddy current (MFEC), magneto 
optic imager (MOI), C-scan, or ultrasonic phased array (UTPA) 
inspections) of the fuselage skin at specified locations where chem-
mill areas are adjacent to non-chem-mill areas at antenna and door 
bearstrap installations, and shear wrinkle areas at stringers 9 and 10 
between stations 500H and 500K; and repairs if necessary.
    Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as 
revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 
14, 2012, also describes procedures for installing modification 
doublers in certain locations, which involves an external detailed 
inspection and an external non-destructive (MFEC, MOI, C-Scan, or UTPA) 
inspection for any cracking of the area to be modified prior to the 
doubler being placed on that area, a high frequency eddy current 
inspection of all existing holes for cracking, and contacting Boeing if 
necessary. The service bulletin also specifies that when a modification 
is accomplished, the repetitive inspection for the area under the 
modification is no longer necessary.
    Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as 
revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 
14, 2012, specifies an initial compliance time of before 43,000 total 
flight cycles, or within 1,500 to 2,100 flight cycles (depending on 
inspection area) after the original issue date of that service 
bulletin, whichever occurs later. That service bulletin specifies a 
repetitive interval not to exceed 1,500 flight cycles, 2,100 flight 
cycles, or 2,700 flight cycles depending on inspection method and 
inspection area.
    For airplanes that have incorporated Boeing Business Jet (BBJ) 
lower cabin altitude supplemental type certificate (STC) ST010697SE, 
all initial compliance times specified in flight cycles must be reduced 
to half of those specified in Boeing Service Bulletin 737-53-1312, 
dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-
1312, Revision 1, dated March 14, 2012, and all repeat interval 
compliance times specified in flight

[[Page 57540]]

cycles must be reduced to one-quarter of those specified in that 
service bulletin.

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 the Proposed AD and the Service 
Information.''

Similar Rulemaking

    The crown skin panels on Model 737-900 and -900ER series airplanes 
are of a similar design to those on Model 737-300, -400, -500, -600, -
700, -700C, and -800 series airplanes. Therefore, all these models may 
be subject to the identified unsafe condition. We are considering 
similar rulemaking for these additional models.

Differences Between the Proposed AD and the Service Information

    Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as 
revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 
14, 2012, specifies to contact the manufacturer for disposition of 
certain repair 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.
    Tables 3 and 4 in paragraph 1.E., ``Compliance,'' of Boeing Service 
Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing 
Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012, specify 
post-modification inspections at certain chem-mill step locations, 
which 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 129.109(c)(2)). However, this NPRM does not propose 
to require those post-modification inspections. This difference has 
been coordinated with Boeing.

Costs of Compliance

    We estimate that this proposed AD affects 58 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
----------------------------------------------------------------------------------------------------------------
Inspection of chem-mill step    31 work-hours x $85     None..............  $2,635 per         $152,830 per
 locations.                      per hour = $2,635 per                       inspection cycle.  inspection
                                 inspection cycle.                                              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.

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-2012-0935; Directorate Identifier 
2011-NM-256-AD.

(a) Comments Due Date

    We must receive comments by November 2, 2012.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 737-900 and -900ER 
series airplanes, certificated in any category, as identified in 
Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as 
revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated 
March 14, 2012.

(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 early fatigue cracks at chem-
mill areas on the crown skin panels. We are issuing this AD to 
detect and correct fatigue cracking of the skin panel at the 
specified chem-mill step locations, which could result in rapid 
decompression of the airplane.

[[Page 57541]]

(f) Compliance

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

(g) Inspections of Crown Skin Areas

    At the applicable time specified in paragraph 1.E., 
``Compliance,'' of Boeing Service Bulletin 737-53-1312, dated 
October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, 
Revision 1, dated March 14, 2012, except as required by paragraph 
(k) of this AD: Do an external detailed inspection and an external 
non-destructive inspection (a medium frequency eddy current (MFEC), 
magneto optic imager (MOI), C-scan, or ultrasonic phased array 
(UTPA) inspection) for cracking in the fuselage skin along the chem-
mill steps at certain locations specified in, and in accordance 
with, Boeing Service Bulletin 737-53-1312, dated October 21, 2011, 
as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated 
March 14, 2012. Repeat the inspections thereafter at the applicable 
times specified in paragraph 1.E., ``Compliance,'' of Boeing Service 
Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing 
Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012.

(h) Inspections of Shear Wrinkle Areas

    For Group 1 airplanes as identified in Boeing Service Bulletin 
737-53-1312, dated October 21, 2011, as revised by Boeing Service 
Bulletin 737-53-1312, Revision 1, dated March 14, 2012: At the 
applicable time specified in paragraph 1.E., ``Compliance,'' of 
Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as 
revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated 
March 14, 2012, except as required by paragraph (k) of this AD, do 
an external detailed inspection and an external non-destructive 
inspection (MFEC, MOI, C-scan, or UTPA) for cracking in the fuselage 
skin along the chem-mill steps at certain shear wrinkle locations 
specified in, and in accordance with, Boeing Service Bulletin 737-
53-1312, dated October 21, 2011, as revised by Boeing Service 
Bulletin 737-53-1312, Revision 1, dated March 14, 2012. Repeat the 
inspections required by paragraph (h) of this AD thereafter at the 
applicable times specified in paragraph 1.E., ``Compliance,'' of 
Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as 
revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated 
March 14, 2012.

(i) Repair

    If any cracking is found during any inspection required by 
paragraphs (g) and (h) of this AD, before further flight, repair the 
cracking using a method approved in accordance with the procedures 
specified in paragraph (m) of this AD. Accomplishing the repair 
approved in accordance with the procedures specified in paragraph 
(m) of this AD terminates the repetitive inspection requirement for 
that area under the repair only.

(j) Optional Terminating Modification

    Modification of an inspection area specified in paragraph (g) of 
this AD, including doing an external detailed inspection and an 
external non-destructive inspection (MFEC, MOI, C-scan, or UTPA) for 
cracking of the area to be modified, and a high frequency eddy 
current inspection of all existing holes for cracking, in accordance 
with the Accomplishment Instructions of Boeing Service Bulletin 737-
53-1312, dated October 21, 2011, as revised by Boeing Service 
Bulletin 737-53-1312, Revision 1, dated March 14, 2012, terminates 
the repetitive inspections required by paragraph (g) of this AD for 
that area only. If any cracking is found during any inspection 
described by this paragraph, before further flight, repair the 
cracking using a method approved in accordance with the procedures 
specified in paragraph (m) of this AD.

(k) Service Bulletin Exception

    Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as 
revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated 
March 14, 2012, specifies compliance times ``after the original 
issue date of this service bulletin.'' However, this AD requires 
compliance within the specified compliance times ``after the 
effective date of this AD.''

(l) Post-Modification Inspections

    The post-modification inspections specified in Tables 3 and 4 of 
paragraph 1.E., ``Compliance,'' of Boeing Service Bulletin 737-53-
1312, dated October 21, 2011, as revised by Boeing Service Bulletin 
737-53-1312, Revision 1, dated March 14, 2012, are not required by 
this AD.

    Note 1 to paragraph (l) of this AD:  The damage tolerance 
inspections specified in Tables 3 and 4 of paragraph 1.E., 
``Compliance,'' of Boeing Service Bulletin 737-53-1312, dated 
October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, 
Revision 1, dated March 14, 2012, 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 actions specified in Part 5 of the 
Accomplishment Instructions and corresponding figures of Boeing 
Service Bulletin 737-53-1312, dated October 21, 2011, as revised by 
Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 
2012, are not required by this AD.

(m) 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 the Related Information 
section 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 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.

(n) Related Information

    (1) For more information about this AD, contact Wayne Lockett, 
Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft 
Certification Office, 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, WA 98124-2207; telephone 206-544-
5000, extension 1; fax 206-766-5680; 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. For information on the 
availability of this material at the FAA, call 425-227-1221.

    Issued in Renton, Washington, on September 4, 2012.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-22887 Filed 9-17-12; 8:45 am]
BILLING CODE 4910-13-P