
[Federal Register: June 24, 2008 (Volume 73, Number 122)]
[Proposed Rules]               
[Page 35593-35594]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24jn08-13]                         

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Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of 
the proposed issuance of rules and regulations. The purpose of these 
notices is to give interested persons an opportunity to participate in 
the rule making prior to the adoption of the final rules.

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[[Page 35593]]



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: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain Boeing Model 737-600, -700, and -800 series airplanes. This 
proposed AD would require inspecting the free flange of the lower 
stringers of the wing center section for drill starts, and applicable 
related investigative and corrective actions. This proposed 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 proposing this AD to prevent cracks from 
propagating from drill starts in the free flange of the lower stringers 
of the wing center section, 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 proposed AD by August 8, 2008.

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 AD, contact Boeing 
Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

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 received reports of drill starts being found on the free flange 
of the lower stringers of the wing center during a quality assurance 
inspection at the final assembly plant. The drill starts were caused by 
a manufacturing error during wing assembly. Cracks could propagate from 
drill starts in the free flange of the lower stringers of the wing 
center section. This condition, if not corrected, could result in loss 
of structural integrity of the wing center section and may result in a 
fuel leak.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-57A1294, dated 
April 23, 2007. The service bulletin describes procedures for doing a 
detailed inspection of the free flange of the upper and lower stringers 
of the wing center section for drill starts, and applicable related 
investigative and corrective actions. The related investigative actions 
include doing high frequency eddy current (HFEC) open hole inspections 
for any cracks. The corrective actions include doing the zero-timing 
procedure at each drill start, oversizing the hole, installing new 
fasteners if the hole is within the service bulletin tolerance limits, 
and contacting Boeing for certain repair conditions, as applicable.
    Accomplishing certain actions specified in the service bulletin is 
intended to adequately address the identified unsafe condition.

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 this 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 Service Bulletin.''

Differences Between the Proposed AD and Service Bulletin

    Although Boeing Alert Service Bulletin 737-57A1294, dated April 23, 
2007, specifies a detailed inspection and applicable related 
investigative and corrective actions of the free flange of the upper 
and lower stringers of the wing center section, this proposed AD would 
require those actions for only the lower stringers of the wing center 
section. The lower stringers are the tension surface of the wing box, 
and therefore are subject to cracking. We do

[[Page 35594]]

not consider cracking of the upper surface a safety issue.
    The service bulletin 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.

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:
    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, 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 August 8, 2008.

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.

Unsafe Condition

    (d) This proposed AD results from drill starts being found on 
the free flange of the lower stringers of the wing center during a 
quality assurance inspection at the final assembly plant. We are 
proposing this AD to prevent cracks from propagating from drill 
starts in the free flange 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

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

Inspection and Related Investigative and Corrective Actions

    (f) 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 of the lower 
stringers of the wing center section for any drill start, and do any 
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 the Boeing 
Alert Service Bulletin 737-57A1294, dated April 23, 2007; except as 
provided in paragraph (g) of this AD. The applicable related 
investigative and corrective actions must be done before further 
flight.
    (g) If any crack is found during any inspection required by 
paragraph (f) 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 (h) of this AD.

Alternative Methods of Compliance (AMOCs)

    (h)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, 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 has the authority to approve AMOCs for this AD, if 
requested in accordance with the procedures found in 14 CFR 39.19.
    (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 appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.
    (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.

    Issued in Renton, Washington, on June 12, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-14185 Filed 6-23-08; 8:45 am]

BILLING CODE 4910-13-P
