
[Federal Register: March 6, 2009 (Volume 74, Number 43)]
[Proposed Rules]               
[Page 9776-9778]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr06mr09-12]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0669; Directorate Identifier 2007-NM-350-AD]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 737-600, -700, and -800 
Series Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (NPRM); reopening of 
comment period.

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SUMMARY: We are revising an earlier proposed airworthiness directive 
(AD) for certain Boeing Model 737-600, -700, and -800 series airplanes. 
The original NPRM would have required an inspection of the free flange 
of the lower stringers of the wing center section for drill starts, and 
applicable related investigative and corrective actions. The original 
NPRM resulted from drill starts being found on the free flange of the 
lower stringers of the wing center section during a quality assurance 
inspection at the final assembly plant. This action revises the 
original NPRM by expanding the inspection area to include the free 
flange, the vertical web, and the fillet radius between the vertical 
web and the free flange. We are proposing this supplemental NPRM to 
prevent cracks from propagating from drill starts in the free flange, 
vertical web, and radius between the free flange and vertical web of 
the lower stringers of the wing center section lower stringers, which 
could cause a loss of structural integrity of the wing center section 
and may result in a fuel leak.

DATES: We must receive comments on this supplemental NPRM by March 31, 
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.

[[Page 9777]]

    For service information identified in this proposed AD, contact 
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-
2207; telephone 206-544-9990; fax 206-766-5682; e-mail DDCS@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: Nancy Marsh, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6440; 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-2008-0669; 
Directorate Identifier 2007-NM-350-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 issued a notice of proposed rulemaking (NPRM) (the ``original 
NPRM'') to amend 14 CFR part 39 to include an airworthiness directive 
(AD) that would apply to certain Boeing Model 737-600, -700, and -800 
series airplanes. That original NPRM was published in the Federal 
Register on June 24, 2008 (73 FR 35593). That original NPRM proposed to 
require inspecting the free flange of the lower stringers of the wing 
center section for drill starts, and applicable related investigative 
and corrective actions.

Comments

    We gave the public the opportunity to participate in developing 
this AD. We considered the comment received.

Request To Clarify Inspection Requirements

    Boeing notes that the original NPRM would have required an 
inspection of the free flange of the stringer, whereas paragraph 3.B.2. 
of the Accomplishment Instructions in Boeing Alert Service Bulletin 
737-57A1294, dated April 23, 2007, calls for inspection as given in 
Figure 1 of the service bulletin. Figure 1 specifies that the free 
flange, vertical web, and radius between the free flange and vertical 
web must be inspected. (The original NPRM referred to this service 
bulletin as the appropriate source of service information for the 
proposed actions.) The commenter requests that we clarify whether the 
inspection area is to include the free flange, vertical web, and the 
fillet radius.
    We agree that the original NPRM is unclear whether the inspection 
area includes all three parts of the stringer. The service bulletin 
does not consistently include all three parts of the stringer. The 
``Background'' section, the ``Action'' section, Paragraph 1.C., 
``Reason,'' Paragraph 1.D., ``Description,'' and Paragraph 3.B., ``Work 
Instructions,'' refer only to the free flange for the inspection. Only 
a note in Figure 1, Sheet 4, contains any reference to all three areas 
of inspection--free flange, vertical web, and the fillet radius. We 
have determined that all three areas must be inspected to adequately 
address the identified unsafe condition. We have revised paragraph (g) 
of the supplemental NRPM to explicitly state these three areas of 
inspection. We have also revised the description of the area in the 
summary and paragraph (e) of the supplemental NPRM.

Actions Since the Original NPRM Was Issued

    We have added a new paragraph (d) to this proposed AD to specify 
the Air Transport Association (ATA) of America code identifying the 
subject, and re-identified the subsequent paragraphs accordingly.

FAA's Determination and Proposed Requirements of the Supplemental NPRM

    We are proposing this supplemental NPRM because we evaluated all 
pertinent information and determined an unsafe condition exists and is 
likely to exist or develop on other products of the same type design. 
The change described above expands the scope of the original NPRM. As a 
result, we have determined that it is necessary to reopen the comment 
period to provide additional opportunity for the public to comment on 
this supplemental NPRM.

Costs of Compliance

    We estimate that this proposed AD would affect 17 airplanes of U.S. 
registry. We also estimate that it would take 7 work-hours per product 
to comply with this proposed AD. The average labor rate is $80 per 
work-hour. Based on these figures, we estimate the cost of this 
proposed AD to the U.S. operators to be $9,520, or $560 per product.

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:

[[Page 9778]]

    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-2008-0669; Directorate Identifier 2007-NM-
350-AD.

Comments Due Date

    (a) We must receive comments by March 31, 2009.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-600, -700, and -800 
series airplanes, certificated in any category, as identified in 
Boeing Alert Service Bulletin 737-57A1294, dated April 23, 2007.

Subject

    (d) Air Transport Association (ATA) of America Code 57: Wings.

Unsafe Condition

    (e) This AD results from drill starts being found on the free 
flange of the lower stringers of the wing center section during a 
quality assurance inspection at the final assembly plant. We are 
issuing this AD to prevent cracks from propagating from drill starts 
in the free flange, vertical web, and radius between the free flange 
and vertical web of the lower stringers of the wing center section 
lower stringers, which could cause a loss of structural integrity of 
the wing center section and may result in a fuel leak.

Compliance

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

Inspection and Related Investigative and Corrective Actions

    (g) Before the accumulation of 18,000 total flight cycles, or 
within 90 days after the effective date of this AD, whichever occurs 
later, do a detailed inspection of the free flange, vertical web, 
and radius between the free flange and vertical web of the lower 
stringers of the wing center section for any drill start, and do all 
applicable related investigative and corrective actions, by 
accomplishing all the applicable actions specified in paragraphs 
3.B.2 and 3.B.4 of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-57A1294, dated April 23, 2007; except as 
provided in paragraph (h) of this AD. The applicable related 
investigative and corrective actions must be done before further 
flight.
    (h) If any crack is found during any inspection required by 
paragraph (g) of this AD, and Boeing Alert Service Bulletin 737-
57A1294, dated April 23, 2007, specifies to contact Boeing for 
appropriate action: Before further flight, repair the crack using a 
method approved in accordance with the procedures specified in 
paragraph (i) of this AD.

Alternative Methods of Compliance (AMOCs)

    (i)(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: Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, 
FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., 
Renton, Washington 98057-3356; telephone (425) 917-6440; fax (425) 
917-6590.
    (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 February 20, 2009.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E9-4732 Filed 3-5-09; 8:45 am]

BILLING CODE 4910-13-P
