Document ID: FAA-2009-0788-0001
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes
Posted Date: 2009-09-15T04:00Z

[Federal Register: September 15, 2009 (Volume 74, Number 177)]
[Proposed Rules]               
[Page 47148-47150]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr15se09-24]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2009-0788; Directorate Identifier 2009-NM-193-AD]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 737-300, -400, and -500 
Series 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 Boeing Model 737-300, -400, and -500 series airplanes. This 
proposed AD would require repetitive external non-destructive 
inspections to detect cracks in the fuselage skin along the chem-mill 
step at stringers S-1 and S-2 right, between station (STA) 827 and STA 
847, and repair if necessary. This proposed AD results from a report of 
a hole in the fuselage skin common to stringer S-1 and S-2 left, 
between STA 827 and STA 847 on an airplane that diverted to an 
alternate airport due to cabin depressurization. We are proposing this 
AD to detect and correct fatigue cracking of the fuselage skin panels 
at the chem-milled steps, which could result in sudden fracture and 
failure of the fuselage skin panels, and consequent rapid decompression 
of the airplane.

DATES: We must receive comments on this proposed AD by October 30, 
2009.

ADDRESSES: You may send comments 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: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, 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; e-mail me.boecom@boeing.com; 
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 or 
425-227-1152.

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 (telephone 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; telephone (425) 
917-6447; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2009-0788; 
Directorate Identifier 2009-NM-193-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 one report from an operator of a hole in the 
fuselage skin common to stringer S-1 and S-2 left, between station 
(STA) 827 and STA 847. The crack started along the chem-mill edge along 
stringer S-1. The airplane skin in the area had 20-inch tear strap 
bays, and a structural full pad up doubler provision for an emergency 
locator transmitter (ELT) antenna at this location. The airplane 
diverted to an alternate airport due to cabin depressurization and 
subsequent deployment of the oxygen masks. The airplane had accumulated 
42,569 total flight cycles. The cause of the fatigue cracking is under 
investigation. Airplanes with 10-inch tear strap bays are also 
susceptible to cracks at this location. This condition, if not 
corrected, could result in sudden fracture and failure of the fuselage 
skin panels, and consequent rapid decompression of the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-53A1301, dated 
September 3, 2009. The service bulletin describes procedures for 
repetitive external non-destructive inspections (NDI) to detect cracks 
in the fuselage skin along the chem-mill step at stringers S-1 and S-2 
right, between STA 827 and STA 847, and contacting Boeing for repair 
instructions. The NDI inspections that can be used are medium frequency 
eddy current, magneto optical imaging, or c-scan. The service bulletin 
specifies that it is not necessary to inspect the chem-mill steps under 
an existing repair doubler provided all of the following apply:
     The repair was installed after the release date of the 
service bulletin;
     The repair was approved by the FAA or by a Boeing Company 
Authorized Representative who was authorized by the FAA to make such 
findings; and
     The repair extends a minimum of three rows of fasteners on 
each side of the chem-mill line in the circumferential direction.

FAA's Determination and Requirements of This Proposed AD

    We are proposing this AD because we evaluated all relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of the same type design. 
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 Bulletin.''
    Operators should note that paragraph (i) of this AD specifies 
certain conditions for terminating the repetitive

[[Page 47149]]

inspections required by this AD for a repaired area only. One of those 
conditions is that the external repair doubler be installed after 
September 3, 2009. This is the date Boeing Service Bulletin 737-53A1301 
became available to operators to address the identified unsafe 
condition. In any case, an initial inspection, as required by paragraph 
(g) of this AD, must still be accomplished.

Differences Between the Proposed AD and the Service Bulletin

    Boeing Alert Service Bulletin 737-53A1301, dated September 3, 2009, 
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:
     Using a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by an Authorized Representative 
for the Boeing Commercial Airplanes Delegation Option Authorization 
Organization whom we have authorized to make those findings.

Interim Action

    We consider this proposed AD interim action. If final action is 
later identified, we might consider further rulemaking then.

Costs of Compliance

    We estimate that this proposed AD would affect 135 airplanes of 
U.S. registry. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD.

                                                                 Table--Estimated Costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Average                                Number of  U.S.-
                Action                   Work hours   labor rate       Cost per product          registered                    Fleet cost
                                                       per hour                                  airplanes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Inspection............................            2          $80  $160, per inspection                     135  $21,600, per inspection cycle.
                                                                   cycle.
--------------------------------------------------------------------------------------------------------------------------------------------------------

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), and
    3. 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.
    You can find our regulatory evaluation and the estimated costs of 
compliance in the AD Docket.

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 AD:

Boeing: Docket No. FAA-2009-0788; Directorate Identifier 2009-NM-
193-AD.

Comments Due Date

    (a) We must receive comments by October 30, 2009.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-300, -400, and -500 
series airplanes, certificated in any category; as identified in 
Boeing Alert Service Bulletin 737-53A1301, dated September 3, 2009.

Subject

    (d) Air Transport Association (ATA) of America Code 53: 
Fuselage.

Unsafe Condition

    (e) This AD results from a report of a hole in the fuselage skin 
common to stringer S-1 and S-2 left, between STA 827 and STA 847 on 
an airplane that diverted to an alternate airport due to cabin 
depressurization and subsequent deployment of the oxygen masks. We 
are issuing this AD to detect and correct fatigue cracking of the 
fuselage skin panels at the chem-milled steps, which could result in 
sudden fracture and failure of the fuselage skin panels, and 
consequent rapid decompression of the airplane.

Compliance

    (f) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Initial and Repetitive Inspections

    (g) Before the accumulation of 35,000 total flight cycles, or 
within 500 flight cycles after the effective date of this AD, 
whichever occurs later: Except as provided by paragraph (i) of this 
AD, do an external non-destructive inspection (NDI) to detect cracks 
in the fuselage skin along the chem-mill steps at stringers S-1 and 
S-2 right, between STA 827 and STA 847, in accordance with the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1301, dated September 3, 2009. If no cracking is found, repeat 
the inspection thereafter at intervals not to exceed 500 flight 
cycles, except as provided by paragraph (i) of this AD.

Repair

    (h) If any crack is found during any inspection required by this 
AD, and Boeing Alert Service Bulletin 737-53A1301, dated September 
3, 2009, specifies to contact Boeing for repair instructions: Before 
further flight, repair the crack using a method

[[Page 47150]]

approved in accordance with the procedures specified in paragraph 
(j) of this AD.

Optional Terminating Action for Repetitive Inspections

    (i) Installing an external repair doubler along the chem-milled 
steps at stringers S-1 and S-2 right, between STA 827 and STA 847, 
constitutes terminating action for the repetitive inspections 
required by paragraph (g) of this AD for the repaired area only, 
provided all of the conditions specified in paragraphs (i)(1), 
(i)(2), and (i)(3) of this AD are met. The initial inspection 
required by paragraph (g) of this AD must be accomplished.
    (1) The repair is installed after September 3, 2009;
    (2) The repair was approved by the FAA or by a Boeing Company 
Authorized Representative who was authorized by the FAA to make such 
findings; and
    (3) The repair extends a minimum of three rows of fasteners on 
each side of the chem-mill line in the circumferential direction.

Alternative Methods of Compliance (AMOCs)

    (j)(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. Send information to 
ATTN: Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-120S, 
FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., 
Renton, Washington 98057-3356; telephone (425) 917-6447; fax (425) 
917-6590. Or, e-mail information to 9-ANM-Seattle-ACO-AMOC-
Requests@faa.gov.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your principal maintenance inspector (PMI) or 
principal avionics inspector (PAI), as appropriate, or lacking a 
principal inspector, your local Flight Standards District Office. 
The AMOC approval letter must specifically reference this AD.
    (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 an 
Authorized Representative for the Boeing Commercial Airplanes 
Delegation Option Authorization Organization who 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.

    Issued in Renton, Washington, on September 4, 2009.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E9-22081 Filed 9-14-09; 8:45 am]

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