
[Federal Register Volume 77, Number 181 (Tuesday, September 18, 2012)]
[Proposed Rules]
[Pages 57541-57544]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-22889]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0938; Directorate Identifier 2011-NM-271-AD]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain The Boeing Company Model 737-600 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 at certain 
locations at chem-mill areas, and repair if necessary. We are proposing 
this AD to detect and correct fatigue cracking of the skin panel at the 
specified chem-

[[Page 57542]]

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, WA. 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: Wayne.Lockett@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-2012-0938; 
Directorate Identifier 2011-NM-271-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 737-53-1309, dated October 20, 
2011, for Model 737-600 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 repairs if 
necessary.
    Boeing Service Bulletin 737-53-1309, dated October 20, 2011, also 
describes procedures for installing modification doublers, 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 certain modification is accomplished, the 
repetitive inspection for the area under the modification is no longer 
necessary.
    Boeing Service Bulletin 737-53-1309, dated October 20, 2011, 
specifies an initial compliance time of 43,000 total flight cycles, or 
1,500 flight cycles 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 or 2,100 flight 
cycles, depending on inspection method.

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 737-600 series airplanes are of a 
similar design to those on Model 737-300, -400, -500, -700, -700C, -
800, -900, and -900ER 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 737-53-1309, dated October 20, 2011, 
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 2 and 3 in paragraph 1.E., ``Compliance,'' of Boeing Service 
Bulletin 737-53-1309, dated October 20, 2011, 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

[[Page 57543]]

to require those post-modification inspections. This difference has 
been coordinated with Boeing.

Costs of Compliance

    We estimate that this proposed AD affects 6 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    37 work-hours x $85     None..............  $3,145 per         $18,870 per
 locations.                      per hour = $3,145 per                       inspection cycle.  inspection
                                 inspection cycle.                                              cycle.
----------------------------------------------------------------------------------------------------------------

    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-2012-0938; Directorate Identifier 
2011-NM-271-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 737-600 series 
airplanes, as identified in Boeing Service Bulletin 737-53-1309, 
dated October 20, 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 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.

(f) Compliance

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

(g) Inspections

    At the applicable time specified in paragraph 1.E., 
``Compliance,'' of Boeing Service Bulletin 737-53-1309, dated 
October 20, 2011, except as required by paragraph (j) 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 737-53-1309, dated October 20, 2011. Repeat the 
inspections required by paragraph (g) of this AD thereafter at the 
applicable times specified in paragraph 1.E., ``Compliance,'' of 
Boeing Service Bulletin 737-53-1309, dated October 20, 2011.

(h) Repair

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

(i) Optional Terminating Modification

    Modification of an inspection area, including 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 737-53-1309, dated October 20, 2011, 
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 (l) of this AD.

(j) Service Bulletin Exception

    Boeing Service Bulletin 737-53-1309, dated October 20, 2011, 
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.''

(k) Post-Modification Inspections

    The post-modification inspections specified in Tables 2 and 3 of 
paragraph 1.E., ``Compliance,'' of Boeing Service Bulletin 737-53-
1309, dated October 20, 2011, are not required by this AD.


[[Page 57544]]


    Note 1 to paragraph (k) of this AD:  The damage tolerance 
inspections specified in Tables 2 and 3 of paragraph 1.E., 
``Compliance,'' of Boeing Service Bulletin 737-53-1309, dated 
October 20, 2011, 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 737-53-1309, dated 
October 20, 2011, are not required by this AD.

(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 the Related Information 
section 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 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.

(m) 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: 
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 review copies of the 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 4, 2012.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-22889 Filed 9-17-12; 8:45 am]
BILLING CODE 4910-13-P


