[Federal Register Volume 77, Number 181 (Tuesday, September 18, 2012)]
[Proposed Rules]
[Pages 57529-57531]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-22890]



[[Page 57529]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0937; Directorate Identifier 2011-NM-270-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 737-800 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-2012-0937; 
Directorate Identifier 2011-NM-270-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 737-53-1311, dated October 21, 
2011, for Model 737-800 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 500E and 500G; and repairs 
if necessary.
    Boeing Service Bulletin 737-53-1311, dated October 21, 2011, 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 as applicable, and contacting Boeing if 
necessary. That 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 737-53-1311, dated October 21, 2011, 
specifies an initial compliance time of 43,000 total flight cycles, or 
1,500 to 2,100 flight cycles (depending on group/configuration) 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 group configuration.
    For airplanes that have incorporated Boeing Business Jet (BBJ) 
lower cabin altitude supplemental type certificate (STC) ST010697SE, 
Boeing Service Bulletin 737-53-1311, dated October 21, 2011, specifies 
that all initial compliance times specified in flight cycles must be 
reduced to half of those specified in that service bulletin, and all 
repeat interval compliance times specified in flight 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

[[Page 57530]]

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 737-800 series airplanes are of a 
similar design to those on Model 737-300, -400, -500, -600, -700, -
700C, -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 737-53-1311, dated October 21, 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 3 and 4 in paragraph 1.E., ``Compliance,'' of Boeing Service 
Bulletin 737-53-1311, dated October 21, 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 to require those 
post-modification inspections. This difference has been coordinated 
with Boeing.

Costs of Compliance

    We estimate that this proposed AD affects 441 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     30 work-hours x     None...............  $2,550 per          $1,124,550 per
 locations.                       $85 per hour =                           inspection cycle.   inspection cycle.
                                  $2,550 per
                                  inspection 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-2012-0937; Directorate Identifier 
2011-NM-270-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 737-800 series 
airplanes, certificated in any category, as identified in Boeing 
Service Bulletin 737-53-1311, dated October 21, 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.

[[Page 57531]]

(g) Inspections of Crown Skin Areas

    At the applicable time specified in paragraph 1.E., 
``Compliance,'' of Boeing Service Bulletin 737-53-1311, dated 
October 21, 2011, 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 737-53-1311, dated October 21, 2011. Repeat the 
inspections thereafter at the applicable times specified in 
paragraph 1.E., ``Compliance,'' of Boeing Service Bulletin 737-53-
1311, dated October 21, 2011.

(h) Inspections of Shear Wrinkle Areas

    For Groups 2, 5, and 6 airplanes as identified in Boeing Service 
Bulletin 737-53-1311, dated October 21, 2011: At the applicable time 
specified in paragraph 1.E., ``Compliance,'' of Boeing Service 
Bulletin 737-53-1311, dated October 21, 2011, 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 737-53-1311, dated October 21, 2011. 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 737-53-1311, dated October 21, 2011.

(i) Repairs

    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 as applicable, 
in accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 737-53-1311, dated October 21, 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 (m) of this AD.

(k) Service Bulletin Exception

    Boeing Service Bulletin 737-53-1311, dated October 21, 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.''

(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-
1311, dated October 21, 2011, 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 737-53-1311, dated 
October 21, 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 737-53-1311, dated 
October 21, 2011, 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. 2012-22890 Filed 9-17-12; 8:45 am]
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